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Anthropogenic carbon release rate unprecedented during the past 66 million years
Abstract
Carbon release rates from anthropogenic sources reached a record high of ~10 Pg C yr−1 in 2014. Geologic analogues from past transient climate changes could provide invaluable constraints on the response of the climate system to such perturbations, but only if the associated carbon release rates can be reliably reconstructed. The Palaeocene–Eocene Thermal Maximum (PETM) is known at present to have the highest carbon release rates of the past 66 million years, but robust estimates of the initial rate and onset duration are hindered by uncertainties in age models. Here we introduce a new method to extract rates of change from a sedimentary record based on the relative timing of climate and carbon cycle changes, without the need for an age model. We apply this method to stable carbon and oxygen isotope records from the New Jersey shelf using time-series analysis and carbon cycle–climate modelling. We calculate that the initial carbon release during the onset of the PETM occurred over at least 4,000 years. This constrains the maximum sustained PETM carbon release rate to less than 1.1 Pg C yr−1. We conclude that, given currently available records, the present anthropogenic carbon release rate is unprecedented during the past 66 million years. We suggest that such a ‘no-analogue’ state represents a fundamental challenge in constraining future climate projections. Also, future ecosystem disruptions are likely to exceed the relatively limited extinctions observed at the PETM.
... Estimates of the total amount of carbon released during the PETM range from~3000 Pg to more than 13,000 Pg [2][3][4] , which span the current assessments of remaining fossil fuel reserves 5 . The PETM is considered to have the highest carbon release rates for the past 66 million years 6 , although estimates of rate are still limited by the low fidelity of records. Proposed triggers for the PETM include volcanism associated with the North Atlantic Igneous Province 4,7 , dissociation of methane hydrates (e.g., ref. 8), variations in Earth's orbit that controlled massive carbon release from permafrost melting or oceanic methane hydrates [9][10][11][12] , and an extraterrestrial impact 13,14 . ...
... The PETM CIE onset is defined by a negative shift of δ 13 C. Over the past few decades, considerable effort has been made to reconstruct the chronology of the CIE using astrochronology [17][18][19]21 , 3 He isotope measurements 22,23 , and modeling experiments 6,24 . At one extreme, the CIE onset was estimated to have spanned only 13 years based on assumed annual "bedding" couplets at a paleo-shelf section on the mid-Atlantic Coastal Plain 15 , an assumption contradicted by evidence for coring artefacts produced via biscuiting whereby the formation is fractured during coring and drilling mud is injected in between layers. ...
... At one extreme, the CIE onset was estimated to have spanned only 13 years based on assumed annual "bedding" couplets at a paleo-shelf section on the mid-Atlantic Coastal Plain 15 , an assumption contradicted by evidence for coring artefacts produced via biscuiting whereby the formation is fractured during coring and drilling mud is injected in between layers. The 13-year duration is also contradicted by evidence from foraminifer accumulation rates 25,26 , and carbon cycle/climate modeling 6,27 . At the other extreme are estimates ranging up to 20 kyr as derived from deep sea cores 28,29 . ...
The chronology of the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma) remains disputed, hampering complete understanding of the possible trigger mechanisms of this event. Here we present an astrochronology for the PETM carbon isotope excursion from Howards Tract, Maryland a paleoshelf environment, on the mid-Atlantic Coastal Plain. Statistical evaluation of variations in calcium content and magnetic susceptibility indicates astronomical forcing was involved and the PETM onset lasted about 6 kyr. The astrochronology and Earth system modeling suggest that the PETM onset occurred at an extreme in precession during a maximum in eccentricity, thus favoring high temperatures, indicating that astronomical forcing could have played a role in triggering the event. Ca content data on the paleo-shelf, along with other marine records, support the notion that a carbonate saturation overshoot followed global ocean acidification during the PETM.
... It is generally considered that the massive carbon injection into the ocean-atmosphere system caused global warming and environmental perturbations ( Pagani et al., 2006 ;Zachos et al., 2008 ). However, several studies have found that global warming and environment change precedes the carbon isotope excursion, and proposed that the initial warming may have triggered the release of the isotopically-light carbon sources ( Frieling et al., 2019 ;Handley et al., 2011 ;Harding et al., 2011 ;Kender et al., 2012 ;Sluijs et al., 2007 ;Thomas et al., 2002 ;Zeebe et al., 2016 ). Thus, despite strong correlation exists between the carbon cycle perturbation and the global warming and environment change, the exact driving mechanism between these factors still remains unclear. ...
... Based on sedimentation rates estimated from the nearby area, the time gap is about 20-25 years ( Sluijs et al., 2007 ). However, carbon cycle-climate modelling has estimated the sampling resolution of ∼40 years ( Zeebe et al., 2016 ). The exact duration between two adjacent data points is hard to be precisely quantified. ...
... It is known from other physical variables and more-detailed studies of the Earth system that climate variability itself is a function of the climate, and that the massive PETM transition, therefore, tend to be expected to involve a non-stationary transition. It has been proposed that the Millville data series are not stationary ( Zeebe et al., 2016 ). Based on Fig. 1 , it is intuitive to conclude that both the δ 13 C and δ 18 O data in Q1 and Q4 are stationary, while Q2 and Q3 (i.e., the PETM transition) are not stationary. ...
The Palaeocene-Eocene thermal maximum is a global warming period (∼56 Ma), which is marked by a sharp negative carbon isotope excursion (CIE) that caused by the injection of massive isotopically-light carbon into the ocean-atmosphere. It is generally considered that the carbon injection caused global warming. However, several studies have suggested that warming and environmental perturbations precede the onset of the CIE. Here we present Granger test to investigate the detailed mechanisms of this event. We show a shift from climate-warming driving carbon-emission scenario to a scheme in which carbon-injection causing global-warming during the CIE. The initial carbon emission might be from methane hydrates dissociation and/or permafrost thawing, possibly linked with astronomical paced warming. This change of causal direction may result from the warming feedback of the emitted carbon and additional carbon from other sources, such as volcanism, bolide impact, oxidation of marine organic matter, and wildfires burning peatlands.
... Foraminifera fossil δ 13 C records also suggest that the pre-PETM depth gradients might have been eliminated or even reversed during the PETM onset 9,13 . However, because the carbon emission rates for the PETM onset were estimated to be an order of magnitude slower than those during industrialization 8,19,20 , the PETM deep ocean might have had sufficient time to fully equilibrate to changing atmospheric CO 2 without necessarily invoking a vertical gradient reversal 8 . Nonetheless, several studies 8,11,21 suggested that relatively rapid carbon emissions could have delayed deep ocean δ 13 C-DIC excursions compared to the surface, causing a temporal reversal of the vertical δ 13 C-DIC gradient. ...
... Nonetheless, several studies 8,11,21 suggested that relatively rapid carbon emissions could have delayed deep ocean δ 13 C-DIC excursions compared to the surface, causing a temporal reversal of the vertical δ 13 C-DIC gradient. Such sensitivity indicates that the early geochemical evolution of the vertical δ 13 C-DIC gradient can provide an important constraint on the PETM onset duration, which has previously been suggested to be between 3 and 20 kyr 8,19,20 . ...
... Based on the present-day ocean model configurations (See below), we use two estimates of the early PETM atmospheric CO 2 changes following Penman and Zachos 19 and Cui et al. 8 . The two estimates are chosen because they represent both sides of the spectrum for the PETM onset period of 3-20 kyr 8,12,20,69 . In the "rapid" setup, atmospheric CO 2 linearly increases from 750 to 1500 ppm over 5 kyr according to Penman and Zachos 19 . ...
Paleoceanographic records suggest that the present-day vertical gradient in the stable carbon isotopic composition (δ13C) of dissolved inorganic carbon in the ocean was reversed during the Paleocene-Eocene Thermal Maximum, an early period of relatively rapid release of carbon into the climate system. Here we present simulations from an observationally constrained ocean model under various greenhouse gas emissions scenarios. We project a decrease in the globally averaged δ13C of dissolved inorganic carbon in the surface ocean of between −1.8 to −6.3 ‰ by 2100. This reduction is driven by oceanic absorption of anthropogenic carbon dioxide, which is depleted in carbon-13. Our findings suggest an elimination or reversal of the natural vertical gradient in the δ13C of dissolved inorganic carbon by 2100 unless anthropogenic carbon emissions are reduced soon. We conclude that the Paleocene-Eocene Thermal Maximum is a geologic analogue of future global carbon cycle perturbations under continued rapid anthropogenic carbon emissions. Uptake of 13C-depleted anthropogenic carbon dioxide in the surface ocean may eliminate or reverse the natural vertical gradient in the isotopic composition of dissolved inorganic carbon in the ocean, analogous to events at the Paleocene-Eocene Thermal Maximum, suggest ocean model simulations.
... 24 There are many important interactions, both direct and indirect, between atmospheric CO 2 concentrations and living organisms. 25 Past atmospheric conditions can be examined using Vostok ice cores from the Antarctic, since it has been shown that both CO 2 and CH 4 increase either in phase or with at most a lag of less than 1000 years at Antarctic temperatures. Studies using this method have shown that present day burdens of these gases are unprecedented over the past 420 000 years. 25 The picture is different over more extended time frames. ...
... Studies using this method have shown that present day burdens of these gases are unprecedented over the past 420 000 years. 25 The picture is different over more extended time frames. In fact, our planet's atmosphere has changed during its history gradually and over a wide range of CO 2 concentrations, from 180 ppm during the Last Glacial Maximum to 4000 to 5000 ppm 500 million years ago. ...
... In fact, an analysis shows that the current anthropogenic carbon release rate is unprecedented during the past 65 million years. 25 The fastest massive carbon release event in recent geological history was the Paleocene-Eocene Thermal Maximum (∼56 Myr [million years in the past]), when somewhat more than the total known fossil fuel reserves (1000-2000 Pg C) or 2500-4500 Pg C were released. Since this occurred over a period of at least 4000 years, the release rate was approximately 1.1 Pg C per year, or only one-tenth of the current net rate of C release (10 Pg C per year). ...
Although rarely thought of this way, in fact humankind is almost completely dependent on photosynthesis for both food and fuel. In addition to the organic carbon, newly fixed through photosynthesis, that is used as food, we also rely on photosynthesis when we use fossil fuels, which represent ancient photosynthetic products that have been stored and transformed over millions of years. More recently, biofuels, such as bioethanol and biodiesel, are now being made directly on a large scale, using recent photosynthesis. Hydrogen is an almost ideal alternative fuel, which can be produced biologically in a number of ways. Here, various processes that rely on photosynthesis as the transformative energy source behind hydrogen production are briefly introduced and discussed. These include photofermentation by purple non-sulfur photosynthetic bacteria using captured solar energy to drive H2 production from organic compounds and systems that are capable of the direct conversion of captured solar energy to hydrogen. In the most attractive system, biophotolysis, the solar energy captured by photosystem II (PSII) and photosystem I (PSI) is used to reduce ferredoxin. Subsequently, the reduced ferredoxin reduces a hydrogen-evolving enzyme. Hydrogen can also be produced by indirect biophotolysis, where photosynthetic carbon fixation occurs in the first, illuminated stage, and the stored carbohydrate is then used in a second, anaerobic, hydrogen-producing stage. Such a process thus separates in both time and space, oxygen-producing photosynthesis from the oxygen-sensitive proton reduction reaction. Here, we briefly review how these processes take place in cyanobacteria and green algae.
... The Paleocene-Eocene Thermal Maximum (PETM), occurred at approximately 56 Ma and lasted for ~150-220 kyr (Röhl et al., 2007;Westerhold et al., 2012), has received considerable attention in the last 30 years (Kennett and Stott, 1991;Bralower et al., 1995;Thomas and Shackleton, 1996;Zachos et al., 2003;Self-Trail et al., 2017). The PETM is associated with prominent global negative carbon isotope excursion (CIE, 3-6‰) and 5-9 • C warming globally (see McInerney and Wing, 2011 for a review), and shares many similarities to the ongoing climate change due to anthropogenic fossil fuel combustion (IPCC, 2013;Zeebe et al. (2016). The rate of carbon emissions during the PETM was about ten times slower than the current anthropogenic carbon release (Cui et al., 2011;Zeebe et al., 2016). ...
... The PETM is associated with prominent global negative carbon isotope excursion (CIE, 3-6‰) and 5-9 • C warming globally (see McInerney and Wing, 2011 for a review), and shares many similarities to the ongoing climate change due to anthropogenic fossil fuel combustion (IPCC, 2013;Zeebe et al. (2016). The rate of carbon emissions during the PETM was about ten times slower than the current anthropogenic carbon release (Cui et al., 2011;Zeebe et al., 2016). The estimated cumulative amount of carbon released during the PETM ranges from ~2000 to >13,000 Pg C (Panchuk et al., 2008;Cui et al., 2011;Gutjahr et al., 2017). ...
The Paleocene-Eocene Thermal Maximum (PETM) was a rapid global warming occurred 56 million years ago and has been widely viewed as an ancient analogue to the ongoing warming driven by anthropogenic CO2 emissions. The complete and continuous Paleogene shallow marine strata well preserved and outcropped in the Tarim Basin, northwestern China are ideal to study the paleoenvironmental change of the Paratethys Seaway during the PETM. To date, no high-resolution calcareous nannofossil biostratigraphy has been performed for the PETM interval in the Tarim Basin. Outcrop samples taken from the Qimugen Formation in the Kuzigongsu section contain abundant, moderately well preserved calcareous nannofossils allows for the establishment of a high-resolution biostratigraphic framework. Overall, 73 species of calcareous nannofossils from 33 genera were observed, with the dominant species including Coccolithus pelagicus, various Toweius species, Pontosphaera exilis, and Micrantholithus flos. The five calcareous nannofossil datums allow for the recognization of nannofossil Zone NP6 through Zone NP10. The common occurrence of shallow-water taxa (Micrantholithus) throughout the section suggests a middle to outer neritic setting for depositional environment of the Kuzigongsu section. The stratigraphic distribution of “excursion taxa” (Coccolithus bownii, Discoaster araneus, D. acutus, Rhomboaster spp.) is consistent with the range of negative excursion in δ¹³Ccarb and δ¹⁸Ocarb, indicating that these excursion taxa are micropaleontological means for identifying the presence of the PETM in the Paratethys Seaway. During the PETM, the deteriorated preservation and extremely low abundance of nannofossils and near-zero wt% CaCO3 values suggest that ocean acidification occurred in the shallow water of the Paratethys Seaway. In addition, a significant increase in the species Neochiastozygus junctus, which is a high productivity indicator indicates increased surface ocean productivity. Higher primary productivity may be triggered by enhanced continental weathering delivering increased nutrient through river runoff.
... On the other hand, Quaternary partial pressure of CO 2 (pCO 2 ) and temperature shifts were gradual and the overall perturbations small in magnitude (10) relative to predicted changes for the next millennia or two. Although changes in pCO 2 during the early Cenozoic warming events (foremost, the PETM) were larger in magnitude and more rapid than carbon (C) perturbations of Quaternary glacial-interglacial transitions (11,12), they occurred under a background greenhouse climate state characterized by high baseline atmospheric pCO 2 (∼1,000 ppm). Other periods of pre-Cenozoic C perturbations (13,14), such as the Cretaceous and Jurassic (Toarcian) ocean anoxic events (OAEs) (15,16), and the end-Triassic (17) and the end-Permian mass extinction events (18), also occurred during background greenhouse climates (19,20). ...
... We used the global C-cycle model Long-Term Ocean-Atmosphere-Sediment Carbon Cycle Reservoir (LOSCAR) (31) and paleosol-and stomatal-based pCO 2 estimates (21, 24) across the KGB interval to quantify the amount of C emitted, the duration of C injection, and the δ 13 C of C released that contributed to the doubling of pCO 2 and the negative C-isotope excursion. A similar methodology has been used to explore the source of the C flux during the PETM (31,32), and estimates from the LOSCAR model generally match models of greater complexity (12). To match the baseline δ 13 C carb (∼3.8&) and pCO 2 (∼350 ppm) before the KGB, we modified the default A B C D modern boundary settings (icehouse) of the LOSCAR model by adjusting the steady-state pCO 2 level, the initial δ 13 C value of weathered carbonate, and the ratio of shelf carbonate precipitated relative to deep carbonate rain (Materials and Methods). ...
Significance
Massive carbon (C) release with abrupt warming has occurred repeatedly during greenhouse states, and these events have driven episodes of ocean deoxygenation and extinction. Records from these paleo events, coupled with biogeochemical modeling, provide clear evidence that with continued warming, the modern oceans will experience substantial deoxygenation. There are, however, few constraints from the geologic record on the effects of rapid warming under icehouse conditions. We document a C-cycle perturbation that occurred under an Earth system state experiencing recurrent glaciation. A suite of proxies suggests increased seafloor anoxia during this event in step with abrupt increase in CO 2 partial pressure and a biodiversity nadir. Warming-mediated increases in marine anoxia may be more pronounced in a glaciated versus unglaciated climate state.
... It is also possible that these discrepancies have another explanation, such 74 as a greater-than-expected role for non-CO 2 forcings and feedbacks. If the paleoclimate record 75 has taught us anything, it is that the more we probe, the more we learn. 76 Past climate states were profoundly di↵erent from today. ...
... In It took the Earth ⇠ 100,000 years to recover from this perturbation (65,74). 245 Although the PETM stands out starkly in the geologic record, the rate of CO 2 release was still 246 4-10 times slower than current anthropogenic emissions (68,75). Indeed, the geological record 247 leaves no doubt that our current rate of global warming, driven by anomalous (anthropogenic) 248 forcing, is an exceptional aberration -the rate and magnitude of change far exceeds the typical 249 multi-thousand year variability that preceded it (Fig. 4). ...
The future in the past
A major cause of uncertainties in climate projections is our imprecise knowledge of how much warming should occur as a result of a given increase in the amount of carbon dioxide in the atmosphere. Paleoclimate records have the potential to help us sharpen that understanding because they record such a wide variety of environmental conditions. Tierney et al. review the recent advances in data collection, statistics, and modeling that might help us better understand how rising levels of atmospheric carbon dioxide will affect future climate.
Science , this issue p. eaay3701
... From 2000 to 2008, anthropogenic activity was responsible for the release of 9.1 Gt C yr −1 . A record high of CO 2 release was reached in 2014 with a release rate of approximately 10 Gt C yr −1 Zeebe et al. (2016). This rate of anthropogenic carbon dioxide release is unprecedented in the past 66 million years, exceeding that of the Paleocene-Eocene Thermal Maximum (PETM) which was thought the have the highest carbon release rates (Zeebe et al., 2016). ...
... A record high of CO 2 release was reached in 2014 with a release rate of approximately 10 Gt C yr −1 Zeebe et al. (2016). This rate of anthropogenic carbon dioxide release is unprecedented in the past 66 million years, exceeding that of the Paleocene-Eocene Thermal Maximum (PETM) which was thought the have the highest carbon release rates (Zeebe et al., 2016). While natural processes significantly dampen the rate of carbon accumulation in the atmosphere, there is evidence that the effectiveness of these processes is decreasing, resulting in more carbon remaining in the atmosphere (Le Quéré et al., 2009). ...
In recent years, there has been intense media attention concerning the outbreaks of devastating forest fires in Indonesia. These fires are fueled by forest wood and peat and emit large amounts of carbon to the atmosphere. Peatlands are a unique unbalanced ecosystem composed of organic-rich soils and are estimated to store approximately 600 Gt of carbon globally. Tropical peatlands are among the most space-efficient stores of carbon on Earth containing approximately 89 Gt C. Of this, 57 Gt (65%) are stored in Indonesian peatlands. Indonesian peatlands are one of the largest modern day near-surface reservoirs of terrestrial carbon, with accumulation that began as early as 22 thousand years ago and continued throughout the Pleistocene and Holocene. Despite the highly important and relevant carbon pool in peat swamp forests, they are largely neglected when modeling the past and present global carbon cycle. The forested tropical peatlands in Indonesia have been identified as a particularly crucial source of uncertainty in global carbon cycle models. In order to refine predictions of future and past climate change, this research will quantify the release of carbon from the Indonesian peatlands to better explain the effects that excess carbon has on the downstream marine ecosystems and the global carbon cycle. Currently, large-scale exploitation of land, including deforestation and drainage for the establishment of oil palm plantations, is changing the carbon balance of Indonesian peatlands, turning them from a previous sink to a source via outgassing of CO2 to the atmosphere and leakage of dissolved organic carbon (DOC) into the coastal ocean. The impacts of this perturbation to the coastal environment and the global climate are largely unknown. I use a biogeochemical box model in combination with novel observations and literature data to investigate the impact of different carbon emission scenarios on the combined ocean-atmosphere system.
... They imply that greenhouse gases released directly by LIPs can initiate global change that persists over 10 4 -10 5 years. The Paleocene-Eocene Thermal Maximum (PETM) is the largest natural climate change event of Cenozoic time, and an important yardstick for anthropogenic climate change 3,4 . During PETM initiation, release of 0.3-1.1 PgC yr -1 of carbon as greenhouse gases to the ocean-atmosphere system 4-6 drove 4-5 °C of global warming 7 over a short period (<20,000 years) 5,[8][9][10] . ...
... Thermogenic methane produced by shallow igneous sills (subhorizontal sheets of magma) and released to the atmosphere or shallow ocean through hydrothermal vents is the most likely source of the large mass of carbon (up to 13,000 PgC) 5,13 required to explain the entire PETM 17 . Environmental change records imply that carbon emissions rates reached 0.3-1.1 PgC yr -1 for several thousand years across the PETM onset [4][5][6] . Carbon emissions rates generated by representative individual NAIP sill-vent systems have not been reported. ...
Large Igneous Provinces (LIPs) are associated with the largest climate perturbations in Earth's history. The North Atlantic Igneous Province (NAIP) and Paleocene-Eocene Thermal Maximum (PETM) constitute an exemplar of this association. As yet we have no means to reconstruct the pacing of LIP greenhouse gas emissions for comparison with climate records at millennial resolution. Here, we calculate carbon-based greenhouse gas fluxes associated with the NAIP at sub-millennial resolution by linking measurements of the mantle convection process that generated NAIP magma with observations of the individual geological structures that controlled gas emissions in a Monte Carlo framework. These simulations predict peak emissions flux of 0.2-0.5 PgC yr-1 and show that the NAIP could have initiated PETM climate change. This is the first predictive model of carbon emissions flux from any proposed PETM carbon source that is directly constrained by observations of the geological structures that controlled the emissions.
... It was indeed the warmest of the Tertiary (or Cenozoic), and even beyond, at least for 100 million years (Cretaceous, Mesozoic) and lasted a little less than 220 000 years or 170 000 according to different authors. The global temperature increased from 5 ° in the tropics and from 8 to 10 ° C at high latitudes (deduced from d 18 O and Mg / Ca ratios of benthic and planktonic foraminifera ( [13], see also [4]), and massive amounts. of carbon were emitted, and estimated between ~ 3000 PgC ('P' = Peta for 10 15 ) and more than 10 000 PgC [16,17,18,19], of the same order of magnitude as current fossil carbon reserves [20,21] These carbon emissions in the ocean-atmosphere system were recorded as a negative peak (or 'excursion') of > 3 ‰ of d 13 C ( Figure 3) and cause dissolution. This event was linked to short and long cycles of eccentricity (see above). ...
... The question of EECO and especially PETM (the most extreme episode of global warming) is of great importance since this interval is considered by almost all authors as a potential analogue of the current situation [21], even if all initial conditions are not at all the same. But the chemistry of 3 He [31] has shown that warming preceded the emission of carbon in the atmosphere and the spectral analysis (astronomical forcing) from bio-and magnetostratigraphic data shows the importance of eccentricity cycles during the lower Paleogene [32,33] and their relationship with warming periods [34]. ...
The focus of this study is based on a detailed analysis of the hyperthermal events of the Paleocene / Eocene limit of 56 Ma and the lower Eocene (for the 54-52 Ma interval, Figure 1). This example will show that the Earth has experienced many times much higher temperatures than today, with warmer, sometimes more acidic oceans and an atmosphere much richer in CO2 (or CH4) than the current one. Are these past events precursors of the current situation?
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3389926
... The early Cenozoic is characterized by a series of short-lived hyper- thermals, the largest of these being the Paleocene-Eocene Thermal Maximum (PETM), considered to have been the warmest period of the Cenozoic Era ( Kennett and Stott, 1991;Zachos et al., 1993Zachos et al., , 2001; Schmitz and Pujalte, 2007;Sluijs et al., 2007;McInerney and Wing, 2011). The PETM occurred ~56 million years ago in a short period of time that spanned ~170,000 years ( Röhl et al., 2007;Westerhold et al., 2008;Charles et al., 2011;Zeebe et al., 2016) and many researchers consider it to be a good analog for ongoing climate change, as the calcu- lated rate and amount of carbon released to the atmosphere during the PETM could be similar to ongoing anthropogenic releases ( Zeebe et al., 2016). During this event, a pronounced global warming of ~5 °C of the oceans and atmosphere took place (e.g., Kennett and Stott, 1991;Koch et al., 1992;Zachos et al., 2003Zachos et al., , 2005Tripati and Elderfield, 2005;Sluijs et al., 2006;Röhl et al., 2007). ...
... The early Cenozoic is characterized by a series of short-lived hyper- thermals, the largest of these being the Paleocene-Eocene Thermal Maximum (PETM), considered to have been the warmest period of the Cenozoic Era ( Kennett and Stott, 1991;Zachos et al., 1993Zachos et al., , 2001; Schmitz and Pujalte, 2007;Sluijs et al., 2007;McInerney and Wing, 2011). The PETM occurred ~56 million years ago in a short period of time that spanned ~170,000 years ( Röhl et al., 2007;Westerhold et al., 2008;Charles et al., 2011;Zeebe et al., 2016) and many researchers consider it to be a good analog for ongoing climate change, as the calcu- lated rate and amount of carbon released to the atmosphere during the PETM could be similar to ongoing anthropogenic releases ( Zeebe et al., 2016). During this event, a pronounced global warming of ~5 °C of the oceans and atmosphere took place (e.g., Kennett and Stott, 1991;Koch et al., 1992;Zachos et al., 2003Zachos et al., , 2005Tripati and Elderfield, 2005;Sluijs et al., 2006;Röhl et al., 2007). ...
The continental Paleocene-Eocene sequence investigated in this study belongs to the Salta Group, deposited in an intracontinental rift, the Salta Basin (NW Argentina), that evolved from the lower Cretaceous to the middle Paleogene, and is subdivided into the Pirgua, the Balbuena and the Santa Barbara Subgroups. The Maíz Gordo Formation (200 m thick) is the middle unit of the Santa Bárbara Subgroup, deposited during late post-rift sedimentation. We studied the mineralogy of fine-grained horizons of this formation by X-ray diffraction and Scanning Electron Microscopy (SEM) in order to examine the connection between vertical changes in clay mineralogy in alluvial sediments and paleosols, and global paleoclimatic changes registered during the Paleogene. Paleosols vary from calcic vertisols in the lowermost levels, to inseptisols and gleysols in intermediate positions, to gleyed oxisols in the upper section, indicating increased chemical weathering through time.
Clay mineral relative abundances vary with a general increase in kaolinite content from bottom to top. However, at one site there are significant variations in kaolinite/muscovite (Kln/Ms) that define five cycles of kaolinite abundance and Kln/Ms. that indicate cyclic patterns of paleoprecipitation and paleotemperature. These are interpreted as several short-lived hyperthermals during the Paleocene-early Eocene in the Southern Hemisphere, which correlate with well-established episodes of warmth documented from the Northern Hemisphere.
... The PETM is a marked interval of climate warming (Dunkley , shoaling of oceanic 5 carbonate saturation horizons (Zachos et al., 2005) and a large global negative Carbon Isotope Excursion (CIE) in all rapidly exchangeable marine and terrestrial carbon reservoirs (McInerney and Wing, 2011). The most consistent explanation for these coupled perturbations is the release of carbon from a large shallow lithospheric reservoir, with a depleted carbon isotopic (δ 13 C) signature (~ -20 to -60 ‰), on a multi-millenial timescale (Bowen et al., 2015;Dickens et al., 1995;Gutjahr et al., 2017b;10 Kirtland Turner and Ridgwell, 2016;Zeebe et al., 2016). Although there is still no confidence on the identity of such a large (>4000 Pg C) and unstable carbon reservoir, its release and oxidation within the ocean-atmosphere system caused rising atmospheric CO 2 concentrations, warming and a range of Earth System perturbations associated with pronounced global warming (Sluijs et al., 2007). ...
... Although there is still no confidence on the identity of such a large (>4000 Pg C) and unstable carbon reservoir, its release and oxidation within the ocean-atmosphere system caused rising atmospheric CO 2 concentrations, warming and a range of Earth System perturbations associated with pronounced global warming (Sluijs et al., 2007). 15 Although considerable attention has been paid to constraining the rates of carbon release, based on deep-ocean carbonate dissolution (Panchuk et al., 2008;Zachos et al., 2005;Zeebe et al., 2009), rates of warming (Meissner et al., 2014;Zeebe et al., 2016), carbon isotope profiles (Bowen et al., 2015;Kirtland Turner and Ridgwell, 2016) and surface ocean pH (Gutjahr et al., 2017a) the mechanisms responsible for both the climatic and isotope recovery at the end of this transient event are still not well 20 ...
The response of the Earth System to greenhouse-gas driven warming is of critical importance for the future trajectory of our planetary environment. Hypethermal events – past climate transients with significant global-scale warming – can provide insights into the nature and magnitude of these responses. The largest hyperthermal of the Cenozoic was the Palaeocene-Eocene Thermal Maximum (PETM ~ 56 Ma). Here we present a new high-resolution cyclostratigraphy for the classic PETM section at Zumaia, Spain. With this new age model we are able to demonstrate that detrital sediment accumulation rates within this continental margin section increased more than four-fold during the PETM, representing a radical change in regional hydrology that drove dramatic increases in terrestrial to marine sediment flux. During the body of the PETM, orbital-scale variations in bulk sediment Si/Fe ratios are evidence for the continued orbital pacing of sediment erosion and transport processes, most likely linked to precession controls on sub-tropical hydroclimates. Most remarkable is that detrital accumulation rates remain high throughout the body of the PETM, and even reach peak values during the recovery phase of the characteristic PETM carbon isotope excursion (CIE). Using a series of Earth System Model inversions, we demonstrate that the silicate weathering feedback alone is insufficient to recover the PETM CIE, and that active organic carbon burial is required to match the observed dynamics of the CIE. Further, that the period of maximum organic carbon sequestration coincides with the peak in detrital accumulation rates observed at Zumaia. Based on these results, we hypothesize that precession controls on tropical and sub-tropical hydroclimates, and the sediment dynamics associated with this variation, play a significant role in the timing of the rapid climate and CIE recovery from peak-PETM conditions.
... A negative carbon isotope excursion of 2.5h or more ( Kennett and Stott, 1991;McInerney and Wing, 2011) coincided with a global temperature increase of 5 to 8 • C ( Zachos et al., 2003;Tripati et al., 2009;McInerney and Wing, 2011), suggesting that the PETM was caused by an extraordinary input of isotopically light C into the ocean-atmosphere system. The massive (>3,000 Pg C) input of 13 C-depleted carbon during the onset of the PETM was injected into the system over at least 4,000 yr (e.g., Zachos et al., 2005;Zeebe et al., 2016). Although the exact source of the light car* Corresponding author. ...
... As such, the PETM is considered the most important analog to the ongoing anthropogenic carbon emissions and thus has been intensively studied. The majority of the studies were focused on resolving the source and the magnitude of carbon input (onset phase) (e.g., Dickens et al., 1995;Zachos et al., 2005;Zeebe et al., 2009), as well as the duration of the emissions (onset + main phase) (e.g., Zeebe et al., 2016) or the event as a whole (e.g., Farley and Eltgroth, 2003;Murphy et al., 2010;Röhl et al., 2007), while relatively few studies were centered around the recovery-stage of the PETM ( Bowen and Zachos, 2010). Here, we primarily focus on the termination stage of the PETM and the mechanisms responsible for restoration of the earth-ocean system biogeochemistry after a major carbon perturbation. ...
Geological records reveal a major perturbation in carbon cycling during the Paleocene–Eocene Thermal Maximum (PETM, ∼56 Ma), marked by global warming of more than 5 °C and a prominent negative carbon isotope excursion of at least 2.5‰ within the marine realm. The entire event lasted about 200,000 yr and was associated with a massive release of light carbon into the ocean–atmosphere system over several thousands of years. Here we focus on the terminal stage of the PETM, during which the ocean–atmosphere system rapidly recovered from the carbon cycle perturbation. We employ a carbon-cycle box model to examine the feedbacks between surface ocean biological production, carbon, oxygen, phosphorus, and carbonate chemistry during massive CO2 release events, such as the PETM. The model results indicate that the redox-controlled carbon–phosphorus feedback is capable of producing enhanced organic carbon sequestration during large carbon emission events. The locale of carbon oxidation (ocean vs. atmosphere) does not affect the amount of carbon sequestered. However, even though the model produces trends consistent with oxygen, excess accumulation rates of organic carbon (∼1700 Pg C during the recovery stage), export production and δ¹³C data, it fails to reproduce the magnitude of change of sediment carbonate content and the CCD over-deepening during the recovery stage. The CCD and sediment carbonate content overshoot during the recovery stage is muted by a predicted increase in CaCO3 rain. Nonetheless, there are indications that the CaCO3 export remained relatively constant during the PETM. If this was indeed true, then an initial pulse of 3,000 Pg C followed by an additional, slow leak of 2,500 Pg C could have triggered an accelerated nutrient supply to the surface ocean instigating enhanced organic carbon export, consequently increasing organic carbon sequestration, resulting in an accelerated restoration of ocean–atmosphere biogeochemistry during the termination phase of the PETM.
... Up to a third of this gas is absorbed by the oceans and its dissolution is inducing the phenomenon known as ocean acidification (OA), which is characterized by changes in seawater carbonate chemistry and reduction of seawater pH. The decrease of ocean surface pH is occurring at a rate unprecedented on geological timescales (Zeebe et al., 2016). Since pre-industrial time, average pH value of shallow and surface seawaters decreased by approximately 0.1 units (IPCC, 2013), currently the average value is 8.1, while predicted global surface water pH reduction is 0.06-0.32 ...
In marine organisms, differing degree of sensitivity to ocean acidification (OA) is expected for each life stage, and disturbance at one stage can carry over into the following stage or following generation. In this study we investigated phenotypic changes of sperm and larvae of the sea urchin Paracentrotus lividus in response to different pH conditions (8.0, 7.7, 7.4) experienced by the parents during gametogenesis. In sperm from two-months exposed males, sperm motility, velocity, ATP content, ATP consumption and respiration rate were evaluated at three pH values of the activating medium (8.0, 7.7 and 7.4). Moreover, larvae from each parental group were reared at pH 8.0 and 7.7 for 20 days and larval mortality and growth were then assessed. Sperm motility and respiration rate were not affected either by exposure of males to low pH or by the post-activation pH. Sperm velocity did not differ among post-activation pH values in all sperm groups, but it decreased slower in sperm developed under acidified conditions, suggesting the presence of positive carryover effect on sperm longevity. This positive carryover effect of exposure of males to low pH values was highlighted also for the sperm ATP content, which was higher in these groups of sperm. ATP consumption rate was affected by post-activation pH with higher values at pH 8.0 in sperm from males maintained at control condition and pH 7.7 while the energy consumption appeared to be differently modulated at different experimental conditions. A negative carry over effect of OA was observed on survival of larvae from parents acclimated at pH 7.4 and additive negative effects of both parental and larval exposure to low pH can be suggested. In all groups of larvae, decreased somatic growth was observed at low rearing pH, thus larvae from parents maintained at low pH did not show an increased capability to cope with OA.
... The overwhelming majority of scientific studies agree that the natural greenhouse effect has been amplified by the increased burning of fossil fuels and the subsequent emission of potent greenhouse gas CO 2 since the Industrial Revolution (e.g. Harries et al., 2001, Feldman et al., 2015, Zeebe et al., 2016. We are in a global climate change. ...
Die weltweit größten Gebirgswellen werden an den südlichen Anden angeregt, wo sie anschließend vertikal und horizontal ins Lee propagieren und dort in der mittleren Atmosphäre ihren Impuls auf den Grundstrom übertragen. Viele Fragen im Bezug auf Anregung, genaue Ausbreitung, Wechselwirkung und Dissipation dieser Wellen sind immer noch unbeantwortet. Aus diesem Grund wurde im Auftrag des DLR in Río Grande (53, 7◦ S, 67, 7◦ W), Argentinien, ein Rayleigh Lidarsystem installiert, das vertikale Temperaturprofile aufnimmt, um Schwerewellensignaturen zu detektieren. Die Analyse des Lidar-Datensatzes, der automatisiert zwischen November 2017 und Oktober 2020 erhoben wurde, ist der Kern dieser Doktorarbeit. Neu ist hierbei nicht nur die Messung an diesem geographischen Ort, sondern auch die hohe Kadenz der Messungen. Die Messabdeckung von durchschnittlich zwei Messungen innerhalb drei Nächte ermöglicht es einen Temperaturhintergrund zu definieren, der zeitliche Skalen von 9 Tagen bis hin zu einem Jahr und vertikale Skalen ab 15 km abdeckt. Zusätzlich werden tägliche Gezeiten aus den Nachtmessungen des Lidars mit einer neuen Methodik extrahiert, die zur Validierung auch auf Reanalyse Daten des ECMWF angewandt wird. Der Vergleich zeigt gute Übereinstimmungen, wobei die Amplituden der täglichen Gezeit in den Lidardaten in der Mesosphäre größer sind und auch wesentlich stärker variieren als in den Reanalyse Daten. Zudem führt Gezeiten-Aliasing wahrscheinlich zu unerwartet kleinen/großen Amplituden in den jährlichen/halbjährlichen Schwingungen. Die untersuchten Wellenenergien sind die größten, die je in der Stratosphäre gemessen wurden und erreichen ein Sättigungslimit bei 60 km Höhe. Das Erreichen eines Sättigungslimits in derart niedrigen Höhen wurde so bisher nicht beobachtet und lässt darauf schließen, dass Wellen bereits mit sehr großen Amplituden erzeugt werden und auch während der vertikalen Propagation gute Wachstumsbedingungen vorfinden. In Zusammenhang mit der Sättigung steht auch eine beobachtete Abnahme der Schwerewellenintermittenz in der Mesosphäre. Die Entwicklung eines neuen spektralen Werkzeugs hilft bei der Bestimmung von Wellenlängen. Hierbei wird deutlich, dass etwa 50 % der Wellen vertikale Skalen von über 16,5 km aufweisen. Dies ist ein wichtiges Ergebnis, wenn man bedenkt, dass bisherige Lidar-Studien sich meist auf vertikale Wellenlängen <15 km fokussiert haben. In Einzelfällen wird ein Energiezuwachs in der Stratosphäre beobachtet, der das erwartete exponentielle Wachstum übersteigt. Dies könnte ein Hinweis darauf sein, dass die Wellen horizontal durch das Beobachtungsvolumen des Lidars hindurch propagieren. Um die Propagation der Wellen zusammen mit ihrem Anregungsmechanismus zu untersuchen, wurde eine Raytracing-Studie durchgeführt. Es wird zum einen deutlich, dass gemessene Wellenenergien in der mittleren Atmosphäre in erster Linie von den Eigenschaften der Hintergrundatmosphäre abhängen und erst in zweiter Linie von der Stärke der Anregung. Zweitens hat sich herausgestellt, dass die Anregung die Ausbreitungsrichtung der Gebirgswellen definiert. Dreht der Wind mit der Höhe, kommt es verstärkt zu lateraler Ausbreitung teilweise über mehrere 100 km leewärts. Ein horizontaler Windgradient vermag dies durch Drehung des Wellenvektors nicht zu kompensieren. Dies ist ein wichtiges Ergebnis und sollte in zukünftigen Parametrisierungs-Schemata von Klimamodellen berücksichtigt werden.
... The pace of contemporary rise in greenhouse gas concentrations is unprecedented in the climate history over the past 66 million years 37 . Current rates of greenhouse gas emissions from human activities are substantially larger than during the strong warming that marks the early Eocene. ...
Published by Future Earth and The Earth League
... The ocean is now acidifying at a rate unparalleled in the last 66 million years ( Zeebe et al 2016); since preindustrial times, ocean surface water pH has decreased on average by about 0.1 pH units, an increase in acidity of ∼26%. The saturation state of aragonite, an indicator of ocean acidification, has decreased on average by ∼0.5, or ∼17%, with substantial latitudinal variations (Feely et al 2009, IPCC 2014. ...
Recent research has quantified the contributions of CO 2 and CH 4 emissions traced to the products of major fossil fuel companies and cement manufacturers to global atmospheric CO 2 , surface temperature, and sea level rise. This work has informed societal considerations of the climate responsibilities of these major industrial carbon producers. Here, we extend this work to historical (1880–2015) and recent (1965–2015) acidification of the world’s ocean. Using an energy balance carbon-cycle model, we find that emissions traced to the 88 largest industrial carbon producers from 1880–2015 and 1965–2015 have contributed ∼55% and ∼51%, respectively, of the historical 1880–2015 decline in surface ocean pH. As ocean acidification is not spatially uniform, we employ a three-dimensional ocean model and identify five marine regions with large declines in surface water pH and aragonite saturation state over similar historical (average 1850–1859 to average 2000–2009) and recent (average 1960–1969 to average of 2000–2009) time periods. We characterize the biological and socioeconomic systems in these regions facing loss and damage from ocean acidification in the context of climate change and other stressors. Such analysis can inform societal consideration of carbon producer responsibility for current and near-term risks of further loss and damage to human communities dependent on marine ecosystems and fisheries vulnerable to ocean acidification.
... Since pre-industrial times, atmospheric CO 2 increased from 280 to 400 ppm and a further doubling is projected until the end of the century (IPCC 2013). This rate of change is unprecedented with a anthropogenic CO 2 release rate being 14,000 times faster than the natural net release of CO 2 (Zeebe et al. 2016). ...
... The Paleocene-Eocene Thermal Maximum (PETM) was the most extreme hyperthermal event of 410 the Paleogene, and probably the best ancient analog for the current rate of CO2 release. That release was 411 still a magnitude slower than modern rates however, with an initial onset of the event occurring in as little 412 as 4,000 years (Zeebe et al., 2016). Although the mechanism for carbon release is still debated, consensus severe effect on the biosphere, resulting in a major extinction of deep sea benthic foraminifera (Thomas,419 2007), a turnover of shallow water larger benthic foraminifera (Scheibner and Speijer, 2008), and a 420 collapse of coralgal reefs (Scheibner and Speijer, 2008). ...
Severe climatic and environmental changes are far more prevalent in Earth history than major extinction events, and the relationship between environmental change and extinction severity has important implications for the outcome of the ongoing anthropogenic extinction event. The response of fossilizing marine plankton to environmental change offers an interesting contrast to the overall record of marine biota, which is dominated by benthic invertebrates. Here, we summarize changes in the species diversity of planktic foraminifera and calcareous nannoplankton over the Mesozoic-Cenozoic and that of radiolarians and diatoms over the Cenozoic. We find that, aside from the Triassic-Jurassic and Cretaceous-Paleogene mass extinctions, extinction in the plankton is decoupled from that in the benthos. Extinction in the plankton appears to be driven primarily by changes in water column stratification and major climatic shifts. Changes that strongly affect the benthos, like acidification and anoxia, have little effect on the plankton, or are associated with radiation.
... Roughly one-third of all anthropogenic CO 2 (C ant ) released into the atmosphere since the beginning of the industrial revolution has been taken up by the ocean, a total of 155 ± 31 PgC as of 2010 (Khatiwala et al., 2013). Increased CO 2 levels are directly linked to an increase in free hydrogen ions causing a decrease in pH, at a rate of change that is faster than any time in the past geological record (Zeebe et al., 2016). This decrease in pH, termed ocean acidification (OA), causes detrimental effects on marine habitats by disrupting carbonate mineral saturation states affecting, for example, the growth of corals (Cohen and Holcomb, 2009;Guinotte and Fabry, 2009). ...
Ocean gliders can provide high-resolution gas observations necessary to interpret the space and time scales of highly dynamic processes such as gas uptake or outgassing in the ocean surface layer. There is a critical need to make high-resolution in situ gas measurements in the ocean for the biogeochemical community (Johnson et al., 2009). Small optical sensor, called optodes, have been used on gliders to measure dissolved oxygen in the oceans and recently optodes were modified to measure pCO2 (Atamanchuk et al., 2014). The CO2 optode is in an early prototype stage and has not undergone rigorous testing on a glider. Here we describe our approach to reference glider based O2 and pCO2 measurements to data from a vertical profiler mooring -- the SeaCycler to validate the glider data. The SeaCycler carried a Pro-Oceanus Ltd., CO2-Pro CV as part of its instrument float, an extensively tested gas analyzer, based on non-dispersive infrared refraction (NDIR), which has shown stable performance during lengthy observations (Jiang et al., 2014). We compare the glider data against the SeaCycler's O2 and CO2 measurements to compute an isopycnal-matched in-situ optode correction. We conducted further glider tests of the sensor on the Newfoundland Shelf in 2018 and further characterized the response time in profiling applications. In this thesis, we show data from both deployments to characterize the sensor performance. We also discuss the spatial and temporal structure in the Labrador Sea deployment glider data through frequency and correlation length scale analysis techniques to infer the presence of internal waves near the buoyancy frequency range. From the results of the glider missions, we present ideas to improve future glider missions into the Labrador Sea and glider based CO2 measurements.
... Finally, our observation that a fast change in sediment supply is more effective at causing a landscape response implies that anthropogenic signals are a good candidate to trigger a response in the landscape. Current climate change is occurring at a fast rate ( Zeebe et al., 2016), and, if continued for a sufficient amount of time, its signal will be transferred to stratigraphy. Likewise, sediment trapping by dams causes fast and significant changes in sediment yield (Blum & Roberts, 2009). ...
The stratigraphic record contains unique information about past landscapes and environmental change. Whether landscapes faithfully transmit signals of environmental change to stratigraphy is unknown because autogenic processes, such as river avulsion, can obscure signals prior to long‐term stratigraphic storage. We develop a theoretical framework that predicts when a sediment flux signal will be transferred from the landscape to stratigraphy. This threshold magnitude is a function of signal duration. The magnitude is set by the maximum rate of autogenic volume change of the landscape, which decreases with increasing time window. Physical delta experiments, specifically designed to test our theory, demonstrate that only sediment supply signals with a magnitude greater than the threshold are stored in stratigraphy, supporting our theory. This framework allows us to assess the fidelity of the stratigraphic record to archive past signals of environmental change and predict the short‐ and long‐term impact of current anthropogenic forcing on landscapes.
... However, for a long time, there has been a controversy about whether the dissociation of massive amounts of hydrate initially triggered the PETM warming, because there might be other multiple rapid and massive carbon inputs that seem unrelated to gas hydrates (Ruppel, 2011). In addition, even though the PETM is believed to have had the highest carbon release rate during the past 66 million years, the maximum sustained release rate of carbon was no more than 1.1 Pg C yr −1 during the PETM warming (Zeebe et al., 2016). Thus, marine-source carbon seems more likely to be oxidized in the seawater column before being released into the atmosphere. ...
In response to the accelerating processes of marine natural gas hydrate exploration and gas production from hydrate-bearing sediments, their potential impacts on the environment have been attracting extensive attention from international academia as well as from industry, especially in recent years. Methane seeps related to gas hydrate degradation on the seafloor are ubiquitous on continental slopes in both active and passive continental margins. A previous series of articles suggest that hydrate dissociation (gas release or ebullition at large scale) mainly occurs as a result of faulting or decreased lithostatic pressure triggered by many external driving forces (mainly including tectonic activities, overpressure zone, earthquake and tides), and temperature change. These frequently affect methane inputs into the atmosphere, fueling seafloor oxygen consumption or ocean acidification, and even posing submarine geohazards. Gas hydrate-related areas are usually estimated from indirect biochemical indications (cold-seep communities, element and isotopic anomalies in pore water) and geophysical indications (surface morphology, gas plumes and pathways). Therefore, appropriate application of monitoring and detection methods is of crucial significance for assessing the temporal and spatial variability of related environmental indicators in gas hydrate reservoirs. Monitoring is also as an essential support for harvesting this potential alternative energy in ways that are safer, more economical, and more environmentally friendly. Following the three structural elements of a hydrocarbon seep pumping system (gas/fluid source, fluid migration pathway, and seeping structures at or near the seafloor), this paper sets forth the significance of indicators for dynamics resulting from the destabilization of reservoirs of natural gas hydrates, reviews the corresponding monitoring or detection methods and integrated monitoring systems; and especially, expatiates the in situ observation networks regarding gas hydrate reservoirs and gas hydrate production tests. In the closing section, we discuss and draw conclusions regarding the challenges for future development of hydrate environmental monitoring and significant environmental issues requiring special attention. We intend this paper to provide references and to set the scene for future research activities about gas hydrates, so as to ignite the interest of more research groups around the world.
... This atmospheric CO 2 concentration is likely to be the highest during the last 3.4 Myr, 15 Myr, or even 34 Myr of the Earth's history (Beerling and Royer, 2011;Bijma et al., 2013;BrighamGrette et al., 2013). The current anthropogenic carbon re- lease rate (~10 Pg C yr −1 ) is nearly 10 times larger than that of the Palaeocene-Eocene Thermal Maximum (PETM), which presumably had the highest natural carbon release rate (~1.1 Pg C yr −1 ) during the past 66 Myr on Earth ( Zeebe et al., 2016). Excessive anthropogenic CO 2 production and emission, mainly due to fossil fuel combustion, deforesta- tion, and cement production, has been identified as the main cause of global climate change ( Bijma et al., 2013). ...
The global warming potential of methane (CH4) is about 30 times stronger than that of carbon dioxide (CO2) over a century timescale. Methane emission is hypothesized to have contributed to global climate change events and mass extinctions during Earth’s history. Therefore, the study of CH4 production processes is critically important to the understanding of global climate change. It has been a dogma that biogenic CH4 detectable in the oceans originates exclusively from the anaerobic metabolic activity of methanogenic archaea in hypoxic and anoxic environments, despite reports that many oxic surface and near-surface waters of the world’s oceans are CH4-supersaturated, thereby rendering net sea-to-air emissions of CH4. The phenomenon of CH4 production in oxic marine waters is referred to as the “ocean methane paradox”. Although still not totally resolved, recent studies have generated several hypotheses regarding the sources of CH4 production in oxic seawater. This review will summarize our current understanding of the importance of CH4 in the global climate and analyze the biological processes and their underpinning mechanisms that lead to the production of CH4 in oxic seawater environments. We will also tentatively explore the relationships of these microbial metabolic processes with global changes in climate and environment.
... The current carbon emission release rate is 10 times faster than at any other point in the last 66 million years [1]. It is expected to rise further due to the ongoing combustion of fossil fuels. ...
In this study we report a simple preparation technique for Ni/γ-Al2O3 catalysts for the dry reforming of methane (DRM) at 800 °C to produce CO and H2 (synthesis gas). Hard-templating with low and high surface area activated carbon was applied. The produced synthesis gas exhibited a low product ratio of H2:CO [0.04–0.12], due to reverse water-gas shift. After 75 h time on stream (TOS) minimal deactivation of the catalyst could be observed. A rather unusual activity evolution was found involving a sequence of minimum-maximum-plateau. A scheme was suggested, explaining the activity evolution based on the Ni-nanoparticle positioning from being bare or encapsulated by Al2O3. The Al2O3 shell cracks and undergoes restructuring during reaction making more active sites available for the reaction. Superior metal dispersion was achieved with average nickel nanoparticle size at 4.9 ± 1.3 nm. The sintering mechanism was also investigated. Surprisingly, hollow nickel nanoparticles were observed at 25 h TOS due to the nanoscale Kirkendall effect. This diffusion phenomenon between the core, Ni⁰, and the outer shell, NiO, (Ni²⁺) lead to pronounced structural and morphological changes of the catalyst.
... Analyses of geological ocean acidification events and modelling studies show that physico-chemical recovery from perturbations in ocean carbonate chemistry of similar magnitude to projected changes takes many thousands of years ( Zeebe and Ridgwell, 2011), due to slow rates of deep ocean mixing and of chemical equilibration with seafloor sediments. The rate of CO 2 increase today is estimated to be around 10 times faster than any natural ocean acidification event during the past 66 million years ( Honisch et al., 2012;Zeebe et al., 2016). The long-term hysteresis effects are inherent in the response of global ocean chemistry to atmospheric CO 2 forcing, and there is only very limited capacity to accelerate future recovery by actively removing CO 2 from the atmosphere ( Mathesius et al., 2015). ...
This article reviews recent scientific progress, relating to four major systems that could exhibit threshold behaviour: ice sheets, the Atlantic meridional overturning circulation (AMOC), tropical forests and ecosystem responses to ocean acidification. The focus is on advances since the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5). The most significant developments in each component are identified by synthesizing input from multiple experts from each field. For ice sheets, some degree of irreversible loss (timescales of millennia) of part of the West Antarctic Ice Sheet (WAIS) may have already begun, but the rate and eventual magnitude of this irreversible loss is uncertain. The observed AMOC overturning has decreased from 2004–2014, but it is unclear at this stage whether this is forced or is internal variability. New evidence from experimental and natural droughts has given greater confidence that tropical forests are adversely affected by drought. The ecological and socio-economic impacts of ocean acidification are expected to greatly increase over the range from today’s annual value of around 400, up to 650 ppm CO2 in the atmosphere (reached around 2070 under RCP8.5), with the rapid development of aragonite undersaturation at high latitudes affecting calcifying organisms. Tropical coral reefs are vulnerable to the interaction of ocean acidification and temperature rise, and the rapidity of those changes, with severe losses and risks to survival at 2 °C warming above pre-industrial levels. Across the four systems studied, however, quantitative evidence for a difference in risk between 1.5 and 2 °C warming above pre-industrial levels is limited.
... Oxfordshire has already suffered repeated floods, the increased incidence of which has been linked to climate change ( ). With the world emitting carbon into the atmosphere at a rate ten times faster than at any point since the dinosaurs era ( Zeebe et al., 2016), future extreme weather events are expected. Outdoor pollution is estimated to contribute to up to 40,000 deaths each year in the UK due to the burning of fossil fuels to power vehicles and generate heat and electricity, and is estimated to cost more than £20 billion per year (RCP, 2016). ...
... This is consistent with proximal to distal changes in sedimentation rates across river-influenced shelves, where shallow shelf rates can be higher than outer shelf rates [Kuehl et al., 1986;Dukat and Kuehl, 1995; Sommerfield and Nittrouer, 1999; Carlin and Dellapenna, 2014]. Therefore, the application of a 4 kyr minimum duration of the initial PETM carbon release [Zeebe et al., 2016] to the CIE onset measured in benthic foraminifera over 2.0 m results in a maximum sediment accumulation rate of 50 cm/kyr at MCBR. The foraminiferal assemblage transition from cooler, oxygenated mixed-layer conditions to warm, dysoxic, stratified conditions occurs over a 1 m interval within the CIE onset. ...
The Paleocene-Eocene Thermal Maximum (PETM) was an interval of extreme warmth that caused disruption of marine and terrestrial ecosystems on a global scale. Here we examine the sediments, flora and fauna from an expanded section at Mattawoman Creek-Billingsley Road (MCBR) in Maryland and explore the impact of warming at a nearshore shallow marine (30-100 m water depth) site in the Salisbury Embayment. Observations indicate that, at the onset of the PETM, the site abruptly shifted from an open-marine to prodelta setting with increased terrestrial and fresh water input. Changes in microfossil biota suggest stratification of the water column and low oxygen bottom water conditions in the earliest Eocene. Formation of authigenic carbonate through microbial diagenesis produced an unusually large bulk carbon isotope shift, while the magnitude of the corresponding signal from benthic foraminifera is similar to that at other marine sites. This proves that the landward increase in the magnitude of the carbon isotope excursion measured in bulk sediment is not due to a near instantaneous release of 12C-enriched CO2. We conclude that the MCBR site records nearshore marine response to global climate change that can be used as an analog for modern coastal response to global warming.
... If anthropogenic CO 2 emissions continue unabated, by the end of the 21st century the [CO 2? 3 ] of surface seawater is projected to decline to ~50% 5 of pre-industrial levels (Hoegh-Guldberg et al., 2014). This rapid change in ocean carbonate chemistry, likely unprecedented for hundreds of millions of years ( H?nisch et al., 2012;Zeebe et al., 2016), has sparked concerns for coral growth. Indeed, laboratory experiments repeatedly demonstrate that coral calcification rates decrease in response to lower [CO 2? 3 ] or [Ca 2+ ] ( Gattuso et al., 1998;Chan and Connolly, 2013;Comeau et al., 2017), leading to projections that as CO 2 levels continue to rise calcification will decline to unsustainable levels, such that there is net reef erosion (Hoegh-Guldberg et al., 2007;Pandolfi 10 et al., 2011). ...
Quantifying the saturation state of aragonite (ΩAr) within the calcifying fluid of corals is critical for understanding their biomineralisation process and sensitivity to environmental changes including ocean acidification. Recent advances in microscopy, microprobes, and isotope geochemistry allow determination of calcifying fluid pH and [CO32−], but direct quantification of ΩAr (where ΩAr =[CO32−][Ca²⁺]/Ksp) has proved elusive. Here we test a new technique for deriving ΩAr based on Raman spectroscopy. First, we analysed abiogenic aragonite crystals precipitated under a range of ΩAr from 10 to 34, and found a strong dependence of Raman peak width on ΩAr that was independent of other factors including pH, Mg/Ca partitioning, and temperature. Validation of our Raman technique for corals is difficult because there are presently no direct measurements of calcifying fluid ΩAr available for comparison. However, Raman analysis of the international coral standard JCp-1 produced ΩAr of 12.3 ± 0.3, which we demonstrate is consistent with published skeletal Sr/Ca, Mg/Ca, B/Ca, δ⁴⁴Ca, and δ¹¹B data. Raman measurements are rapid (≤ 1 s), high-resolution (Ar ±1 to 2), and require minimal sample preparation; making the technique well suited for testing the sensitivity of coral calcifying fluid ΩAr to ocean acidification and warming using samples from natural and laboratory settings. To demonstrate this, we also show a high-resolution time series of ΩAr over multiple years of growth in a Porites skeleton from the Great Barrier Reef, and we evaluate the response of ΩAr in juvenile Acropora cultured under elevated CO2 and temperature.
... This results in a ~2.5-8 ‰ negative carbon isotope excursion (CIE) in carbon-bearing substrates deposited during the PETM (McInerney and Wing, 2011;Sluijs and Dickens, 2012). The CIE has a distinct shape; a rapid " onset " (1-5 kyr; (KirtlandTurner and Ridgwell, 2016;Zeebe et al., 2016) followed by a prolonged (50-70 kyr) 10 period, the " body " , of stable low 13 C values and a recovery that lasts 42-100 kyr (Röhl et al., 2007;Abdul Aziz et al., 2008;Murphy et al., 2010) to values that remain slightly 13 C-depleted (0.5-1 ‰) relative to the latest Paleocene. This pattern is best explained by massive (>>1500 Gt) carbon input from at least 1 but likely multiple reservoirs in the shape of CO 2 and/or CH 4 ; ...
The Paleocene–Eocene Thermal Maximum (PETM, 56 Ma) was a phase of rapid
global warming associated with massive carbon input into the ocean–atmosphere
system from a 13C-depleted reservoir. Many midlatitude and high-latitude
sections have been studied and document changes in salinity, hydrology and
sedimentation, deoxygenation, biotic overturning, and migrations, but detailed
records from tropical regions are lacking. Here, we study the PETM at Ocean
Drilling Program (ODP) Site 959 in the equatorial Atlantic using a range of
organic and inorganic proxies and couple these with dinoflagellate cyst
(dinocyst) assemblage analysis. The PETM at Site 959 was previously found to
be marked by a ∼ 3.8 ‰ negative carbon
isotope excursion (CIE) and a ∼ 4 °C surface
ocean warming from the uppermost Paleocene to peak PETM, of which
∼ 1 °C occurs before the onset of the CIE. We
record upper Paleocene dinocyst assemblages that are similar to PETM
assemblages as found in extratropical regions, confirming poleward
migrations of ecosystems during the PETM. The early stages of the PETM are
marked by a typical acme of the tropical genus Apectodinium, which
reaches abundances of up to 95 %. Subsequently, dinocyst abundances
diminish greatly, as do carbonate and pyritized silicate microfossils. The
combined paleoenvironmental information from Site 959 and a close-by shelf
site in Nigeria implies the general absence of eukaryotic surface-dwelling
microplankton during peak PETM warmth in the eastern equatorial Atlantic,
most likely caused by heat stress. We hypothesize, based on a literature
survey, that heat stress might have reduced calcification in more tropical
regions, potentially contributing to reduced deep sea carbonate accumulation
rates, and, by buffering acidification, also to biological carbonate
compensation of the injected carbon during the PETM. Crucially, abundant
organic benthic foraminiferal linings imply sustained export production,
likely driven by prokaryotes. In sharp contrast, the recovery of the CIE
yields rapid (≪ 10 kyr) fluctuations in the abundance of
several dinocyst groups, suggesting extreme ecosystem and environmental
variability.
... When change is rapid, however, adaptation, migration and geophysical buffering are all challenged. Although temperatures anticipated for the end of the twenty-first century fall well below those characterizing much of Earth history, the rates at which CO 2 and, hence, temperature are increasing are unique within the past 66 million years[81]. The underlying state of the Earth system also appears to influence the biological effects of rapid environmental perturbation. ...
Extreme events can be a major driver of evolutionary change over geological and contemporary timescales. Outstanding examples are evolutionary diversification following mass extinctions caused by extreme volcanism or asteroid impact. The evolution of organisms in contemporary time is typically viewed as a gradual and incremental process that results from genetic change, environmental perturbation or both. However, contemporary environments occasionally experience strong perturbations such as heat waves, floods, hurricanes, droughts and pest outbreaks. These extreme events set up strong selection pressures on organisms, and are small-scale analogues of the dramatic changes documented in the fossil record. Because extreme events are rare, almost by definition, they are difficult to study. So far most attention has been given to their ecological rather than to their evolutionary consequences. We review several case studies of contemporary evolution in response to two types of extreme environmental perturbations, episodic (pulse) or prolonged (press). Evolution is most likely to occur when extreme events alter community composition. We encourage investigators to be prepared for evolutionary change in response to rare events during long-term field studies.
This article is part of the themed issue ‘Behavioural, ecological and evolutionary responses to extreme climatic events’.
В работе представлены результаты оценки среднемесячных и среднесуточных потоков углекислого газа на мочажинном комплексе верхового болота полевой станции «Мухрино» за летне-осенний сезон на примере самого теплого (июль), переходного (сентябрь) и холодного (октябрь) месяцев 2021 года. Данные были получены с помощью четырёх камер Li-Cor 8100-104 (LI-COR, США), измеряющих чистый экосистемный обмен (NEE) и дыхание экосистемы (Reco). Из полученных данных видно, что наибольшая активность экосистемы приходится на июль, наименьшая - на октябрь; наибольшее поглощение СО2 происходит в июле, наименьшее - в сентябре.
The paper presents the results of an assessment of the average monthly and average daily carbon dioxide fluxes in the hollow complex of the raised bog of the Mukhrino field station for the summer-autumn season, for the rise of the warmest - July, the transitional - September, and the coldest - October, the month of 2021. The data were obtained using four Li-Cor 8100-104 cameras (LI-COR, USA) measuring net ecosystem exchange (NEE) and ecosystem respiration (Reco). From the obtained data, it can be seen that: the highest activity of the ecosystem occurs in July, the lowest in October; the greatest absorption of CO2 occurs in July, the least - in September.
Keywords: CO2 STREAMS, AUTOMATIC CHAMBER METHOD, NEE, Reco, MUKHRINO FIELD STATION, WEST SIBERIA, LI-COR 8100-104
The branch of computer science that deals with the simulation of variables with the help of a computer are termed Artificial Intelligence (AI). Here we attempt to predict the pace of acidification in the Digha coast of the Bay of Bengal based on available datasets of more than three decades. The ground zero observation on the data set reveals a decreasing trend of pH since 1984 with a sudden hike in premonsoon 2020, the period coinciding with the COVID 19 lockdown phase in the Indian sub-continent.
The long‐term extent of the Earth system response to anthropogenic interference remains uncertain. However, the geologic record offers insights into this problem as Earth has previously cycled between warm and cold intervals during the Phanerozoic. We present an updated compilation of surface temperature proxies for several key time intervals to reconstruct global temperature changes during the Cenozoic. Our data synthesis indicates that Earth’s surface slowly cooled by ca. 9°C during the early Paleogene to late Neogene and that continent‐scale ice sheets developed after global temperature dropped to less than 10°C above preindustrial conditions. Slow cooling contrasts with the steep decrease in combined radiative forcing from past CO2 concentrations, solar luminosity, and ocean area, which was close to preindustrial levels even as Earth remained in a much warmer state. From this, we infer that the Earth system was less sensitive to greenhouse gas forcing for most of the Cenozoic and that sensitivity must have increased by at least a factor of 2 during the Plio‐Pleistocene. Our results imply that slow feedbacks will raise global surface temperatures by more than 3°C in the coming millennia, even if anthropogenic forcing is stabilized at the present‐day value (2 W/m²), and that their impact will diminish with further warming.
In late June 2021, western North America, and in particular the Pacific Northwest experienced a heatwave with temperatures usually only encountered in hot desert climates. Using a blend of reanalysis data and Earth System Model (ESM) simulations, we disentangle the physical drivers underlying this exceptional event. Our analysis highlights the role of the anticyclonic circulation aloft, which converted previously gained potential energy—some of which by intense latent heating thousands of kilometers upwind over the North Pacific—back into sensible heat through subsidence. We demonstrate that this upwind latent heat release did not only result in a hot troposphere above the heatwave region, but also contributed directly to escalating near‐surface temperatures. Facilitated by the mountainous terrain and dry soils in the region, deep atmospheric boundary layers were established over the course of several days, connecting the air close to Earth's surface to a massive heat reservoir many kilometers above. Anomalous soil moisture acted to raise the heatwave temperatures by 3°C in a large region during the peak of the event, with local anomalies exceeding 5°C. Overall, we conclude that this heatwave was the outcome of an intricate interplay between dynamic and thermodynamic processes. ESM experiments suggest that the same large‐scale atmospheric circulation fueled by enhanced thermodynamic drivers, such as more available moisture for condensation upwind, could enable even more extreme near‐surface temperatures, in particular in a warmer climate.
Volume I of The Cambridge History of the Pacific Ocean provides a wide-ranging survey of Pacific history to 1800. It focuses on varied concepts of the Pacific environment and its impact on human history, as well as tracing the early exploration and colonization of the Pacific, the evolution of Indigenous maritime cultures after colonization, and the disruptive arrival of Europeans. Bringing together a diversity of subjects and viewpoints, this volume introduces a broad variety of topics, engaging fully with emerging environmental and political conflicts over Pacific Ocean spaces. These essays emphasize the impact of the deep history of interactions on and across the Pacific to the present day.
The Paleocene‐Eocene Thermal Maximum (PETM) is the most pronounced global warming event of the early Paleogene related to atmospheric CO2 increases. It is characterized by negative δ¹⁸O and δ¹³C excursions recorded in sedimentary archives and a transient disruption of the marine biosphere. Sites from the U.S. Atlantic Coastal Plain show an additional small, but distinct δ¹³C excursion below the onset of the PETM, coined the “pre‐onset excursion” (POE), mimicking the PETM‐forced environmental perturbations. This study focuses on the South Dover Bridge core in Maryland, where the Paleocene‐Eocene transition is stratigraphically constrained by calcareous nannoplankton and stable isotope data, and in which the POE is well‐expressed. The site was situated in a middle neritic marine shelf setting near a major outflow of the paleo‐Potomac River system. We generated high‐resolution benthic foraminiferal assemblage, stable isotope, trace‐metal, grain‐size and clay mineralogy data. The resulting stratigraphic subdivision of this Paleocene‐Eocene transition is placed within a depth transect across the paleoshelf, highlighting that the PETM sequence is relatively expanded. The geochemical records provide detailed insights into the paleoenvironment, developing from a well‐oxygenated water column in latest Paleocene to a PETM‐ecosystem under severe biotic stress‐conditions, with shifts in food supply and temperature, and under dysoxic bottom waters in a more river‐dominated setting. Environmental changes started in the latest Paleocene and culminated atthe onset of the PETM, hinting to an intensifying trigger rather than to an instantaneous event at the Paleocene‐Eocene boundary toppling the global system.
Significance
Human-induced carbon emissions are causing global temperatures to rise and oceans to acidify. To understand how these rapid perturbations affect marine calcifying communities, we investigate a similar event in Earth’s geologic past, the Paleocene–Eocene thermal maximum (PETM). We introduce a method, isotopic filtering, to mitigate the time-averaging effects of sediment mixing on deep-sea microfossil records. Contrary to previous studies, we find that tropical planktic foraminifers in the central Pacific ocean were adversely affected by PETM conditions, as evidenced by a decrease in local diversity, extratropical migration, and impaired calcification. While these species survived the PETM through migration to cooler waters, it is unclear whether marine calcifiers can withstand the rapid changes our oceans are experiencing today.
Dry soils are known to foster hot conditions: if less water is available to evaporate, more sunlight is used to heat the air. While this interaction of land surface and atmosphere has been studied extensively at the local scale, less is known about the impacts further downwind, that is, where the winds blow to. In this thesis, a novel atmospheric heat and moisture tracking framework is developed, so that the downwind impacts of dry land can be unraveled. For the first time, droughts are shown to 'self-propagate'. Analyzing the largest droughts around the globe in recent history, it is demonstrated that through a reduction in atmospheric moistening, dry soils can cause downwind precipitation deficits, leading to the expansion of drought conditions. Moreover, reductions in moisture transport due to soil drought are accompanied by increased heat transport: upwind droughts can also fuel downwind heatwaves, which was the case for both the 2003 and 2010 mega-heatwaves in Europe. This highlights that not only local, but also upwind soil moisture anomalies are crucial for the development of compound hot–dry events. Finally, the detrimental impact of anomalous heat and moisture advection due to soil drought on the primary productivity of water-limited ecosystems is revealed. This emphasizes the far-reaching impacts of land–atmosphere interactions and their role in the downwind propagation of climatic ecosystem disturbances.
The atlantid heteropods represent the only predatory, aragonite shelled zooplankton. Atlantid shell production is likely to be sensitive to ocean acidification (OA), and yet we know little about their mechanisms of calcification, or their response to changing ocean chemistry. Here, we present the first study into calcification and gene expression effects of short-term OA exposure on juvenile atlantids across three pH scenarios: mid-1960s, ambient and 2050 conditions. Calcification and gene expression indicate a distinct response to each treatment. Shell extension and shell volume were reduced from the mid-1960s to ambient conditions, suggesting that calcification is already limited in today's South Atlantic. However, shell extension increased from ambient to 2050 conditions. Genes involved in protein synthesis were consistently upregulated, whereas genes involved in organismal development were downregulated with decreasing pH. Biomineralization genes were upregulated in the mid-1960s and 2050 conditions, suggesting that any deviation from ambient carbonate chemistry causes stress, resulting in rapid shell growth. We conclude that atlantid calcification is likely to be negatively affected by future OA. However, we also found that plentiful food increased shell extension and shell thickness, and so synergistic factors are likely to impact the resilience of atlantids in an acidifying ocean.
Ongoing ocean warming can release methane (CH4) currently stored in ocean sediments as free gas and gas hydrates. Once dissolved in ocean waters, this CH4 can be oxidized to carbon dioxide (CO2). While it has been hypothesized that the CO2 produced from aerobic CH4 oxidation could enhance ocean acidification, a previous study conducted in Hudson Canyon shows that CH4 oxidation has a small short‐term influence on ocean pH and dissolved inorganic radiocarbon. Here we expand upon that investigation to assess the impact of widespread CH4 seepage on CO2 chemistry and possible accumulation of this carbon injection along 234 km of the U.S. Mid‐Atlantic Bight. Consistent with the estimates from Hudson Canyon, we demonstrate that a small fraction of ancient CH4‐derived carbon is being assimilated into the dissolved inorganic radiocarbon (mean fraction of 0.5 ± 0.4%). The areas with the highest fractions of ancient carbon coincide with elevated CH4 concentration and active gas seepage. This suggests that aerobic CH4 oxidation has a greater influence on the dissolved inorganic pool in areas where CH4 concentrations are locally elevated, instead of displaying a cumulative effect downcurrent from widespread groupings of CH4 seeps. A first‐order approximation of the input rate of ancient‐derived dissolved inorganic carbon (DIC) into the waters overlying the northern U.S. Mid‐Atlantic Bight further suggests that oxidation of ancient CH4‐derived carbon is not negligible on the global scale and could contribute to deepwater acidification over longer time scales.
Diversification rates vary over time, yet the factors driving these variations remain unclear. Temporal declines in speciation rates have often been interpreted as the effect of ecological limits, competition, and diversity dependence, emphasising the role of biotic factors. Abiotic factors, such as climate change, are also supposed to have affected diversification rates over geological time scales, yet direct tests of these presumed effects have mainly been limited to few clades well represented in the fossil record. If warmer climatic periods have sustained faster speciation, this could explain slowdowns in speciation during the Cenozoic climate cooling. Here, we apply state‐of‐the art diversity‐dependent and temperature‐dependent phylogenetic models of diversification to 218 tetrapod families, along with constant rate and time‐dependent models. We confirm the prevalence of diversification slowdowns, and find as much support for temperature‐dependent than diversity‐dependent models. These results call for a better integration of these two processes in studies of diversification dynamics.
Premise:
Although polyploidy commonly occurs in angiosperms, not all polyploidization events lead to successful lineages, and environmental conditions could influence cytotype dynamics and polyploid success. Low soil nitrogen and/or phosphorus concentrations often limit ecosystem primary productivity, and changes in these nutrients might differentially favor some cytotypes over others, thereby influencing polyploid establishment.
Methods:
We grew diploid, established tetraploid, and neotetraploid Chamerion angustifolium (fireweed) in a greenhouse under low and high soil nitrogen and phosphorus conditions and different competition treatments and measured plant performance (height, biomass, flower production, and root bud production) and insect damage responses. By comparing neotetraploids to established tetraploids, we were able to examine traits and responses that might directly arise from polyploidization before they are modified by natural selection and/or genetic drift.
Results:
We found that (1) neopolyploids were the least likely to survive and flower and experienced the most herbivore damage, regardless of nutrient conditions; (2) both neo- and established tetraploids had greater biomass and root bud production under nutrient-enriched conditions, whereas diploid biomass and root bud production was not significantly affected by nutrients; and (3) intra-cytotype competition more negatively affected diploids and established tetraploids than it did neotetraploids.
Conclusions:
Following polyploidization, biomass and clonal growth might be more immediately affected by environmental nutrient availabilities than plant survival, flowering, and/or responses to herbivory, which could influence competitive dynamics. Specifically, polyploids might have competitive and colonizing advantages over diploids under nutrient-enriched conditions favoring their establishment, although establishment may also depend upon the density and occurrences of other related cytotypes in a population.
In this paper, numerical simulation of motion and dispersion of pollutant emissions into the atmosphere under real atmospheric conditions were considered. To solve this problem, a system of Reynolds-averaged Navier–Stokes equations was used, and the standard k-epsilon and SST k-omega turbulence models were used to close this system of equations. Moreover, the test problem was solved numerically to verify the mathematical model and numerical algorithm. The obtained numerical results were compared with the experimental data and modeling results of well-known authors. A proven mathematical model and numerical algorithm was used to describe the process of pollutant emissions from Ekibastuz SDPP (Ekibastuz State District power plant) chimneys and the spread of CO2 in the air flow field under real atmospheric conditions. For this problem, four different speed regimes (the first—0.5 m/s and 1 m/s, the second—1 m/s and 1.5 m/s, the third—2 m/s and 4 m/s, and the fourth—4 m/s and 5 m/s), as well as three different temperature regimes (constant temperature, decrease temperature, and temperature inversion) were considered.
Las actividades antropogénicas han ocasionado un incremento en la concentración de CO2
de la atmósfera, ocasionando el calentamiento global y con ello el cambio climático. Las
plantaciones forestales tienen el potencial para reducir el calentamiento global porque los
árboles capturan y almacenan carbono, pero es necesario generar información, para conocer
el beneficio. Por ello, el objetivo del trabajo fue determinar la cantidad de carbono
almacenado en la biomasa aérea de plantaciones de Pinus patula y de Pinus ayacahuite
localizadas en el municipio de Amanalco, Estado de México. Se realizó un censo en cada
plantación, se midió la altura total (m), diámetro normal (cm) y la densidad de madera de los
árboles (kg m-3). Con estos datos se calculó el coeficiente mórfico, volumen fustal (m3),
biomasa fustal (kg), biomasa de ramas (kg) y carbono almacenado (Mg ha-1). La biomasa de
las ramas se calculó con ecuaciones alométricas generadas previamente. Para comparar las
especies, se generaron ecuaciones (modelos cuadráticos) de volumen y de biomasa en
función del diámetro normal. De acuerdo con los resultados, el número de individuos
censados fue de 658 para P. patula (1.3 ha) y 262 para P. ayacahuite (0.5 ha). La densidad
de la madera fue de 507 kg m-3 para P. patula y 492 kg m-3 para P. ayacahuite. El mayor
porcentaje (57.8%) de árboles para P. patula se concentró en la categoría diamétrica > 25 ≤
40, para P. ayacahuite el mayor porcentaje (59.2%) de árboles se concentró en la categoría >
10 ≤ 25. El almacén de carbono para P. patula fue de 84.7 Mg ha-1 y 28.5 Mg ha-1 para P.
ayacahuite. Bajo las mismas condiciones de crecimiento, P. patula tienen mayor potencial de
captura y de almacén de carbono que P. ayacahuite.
Climate change is projected to change the ecosystems on land and in the sea at rates that are unprecedented for millions of years. The most commonly used approach to derive projections of how ecosystems will look in the future are experiments on living organisms. By their nature, experiments are unlike the real world and cannot capture the ability of organisms to migrate, select and evolve. They are often limited to a select few species and drivers of environmental change and hence cannot represent the complexity of interactions in ‘real’ ecosystems. The fossil record is an archive of responses to climate change at a global ecosystem scale. If, and only if, fossil assemblage variation is combined with independent information of environmental changes, sensitives of species or higher taxa to a specific magnitude of change of an environmental driver can be determined and used to inform future vulnerabilities of this species to the same driver. While records are often fragmented, there are time intervals which, when thoroughly analysed with quantitative data, can provide valuable insights into the future of biodiversity on this planet. This review provides an overview of projected impacts on marine ecosystems including: (1) the range of neontological methods, observations and their challenges; and (2) the complementary information that palaeontologists can contribution to this global challenge. I advocate that, in collaborations with other disciplines, we should aim for a strong visibility of our field and the knowledge it can provide for policy relevant assessments of the future.
The stable carbon isotopes of fossil plants are a reflection of the atmosphere and environment in which they grew. Fossil plant remains have thus stored information about the isotopic composition and concentration of atmospheric carbon dioxide (pCO2) and possibly pO2 through time. Studies to date, utilizing extant plants, have linked changes in plant stable carbon isotopes (δ¹³Cp) or carbon isotope discrimination (Δ¹³C) to changes in pCO2 and/or pO2. These studies have relied heavily on angiosperm representatives, a phylogenetic group only present in the fossil record post-Early Cretaceous (∼140 million years ago (mya)), whereas gymnosperms, monilophytes and lycophytes dominated terrestrial ecosystems prior to this time. The aim of this study was to expand our understanding of carbon isotope discrimination in all vascular plant groups of C3 plants including lycophytes, monilophytes, gymnosperms and angiosperms, under elevated CO2 and sub-ambient O2 to explore their utility as paleo-atmospheric proxies. To achieve this goal, plants were grown in controlled environment chambers under a range of O2:CO2 ratio treatments. Results reveal a strong phylogenetic dependency on Δ¹³C, where spore-bearing (lycophytes and monilophytes) have significantly higher ¹³C discrimination than seed plants (gymnosperms and angiosperms) by ∼5‰. We attribute this strong phylogenetic signal to differences in Ci/Ca likely mediated by fundamental differences in how spore and seed bearing plants control stomatal aperture. Decreasing O2:CO2 ratio in general resulted in increased carbon isotope discrimination in all plant groups. Notably, while all plant groups respond unidirectionally to elevated atmospheric CO2 (1900 ppm and ambient O2), they do not respond equally to sub-ambient O2 (16%). We conclude that (1) Δ¹³C has a strong phylogenetic or ‘reproductive grade’ bias, whereby Δ¹³C of spore reproducing plants is significantly different to seed reproducing taxa. (2) Δ¹³C increases with decreasing O2:CO2 ratios (where significant) but is more likely a result of mechanistically uncoupled responses to elevated pCO2 and sub-ambient O2; and (3) due to this response we find δ¹³Ca cannot be calculated from δ¹³Cp unless environmental influences such as O2:CO2 ratio can be independently constrained. Therefore, interpretations of trends in fossil plant δ¹³Cp to reconstruct paleoatmospheric CO2 concentration should include cross calibration based on a nearest living relative, appropriate nearest living equivalent, or utilizing the phylogenetic corrections produced from this study.
Chemical weathering consumes atmospheric carbon dioxide through the breakdown of silicate minerals and is thought to stabilize Earth’s long-term climate. However, the potential influence of silicate weathering on atmospheric pCO2 levels on geologically short timescales (10^3–10^5 years) remains poorly constrained. Here we focus on the record of a transient interval of severe climatic warming across the Toarcian Oceanic Anoxic Event or T-OAE from an open ocean sedimentary succession from western North America. Paired osmium isotope data and numerical modelling results suggest that weathering rates may have increased by 215% and potentially up to 530% compared to the pre-event baseline, which would have resulted in the sequestration of significant amounts of atmospheric CO2. This process would have also led to increased delivery of nutrients to the oceans and lakes stimulating bioproductivity and leading to the subsequent development of shallow-water anoxia, the hallmark of the T-OAE. This enhanced bioproductivity and anoxia would have resulted in elevated rates of organic matter burial that would have acted as an additional negative feedback on atmospheric pCO2 levels. Therefore, the enhanced weathering modulated by initially increased pCO2 levels would have operated as both a direct and indirect negative feedback to end the T-OAE.
On geological time-scales, the production and degree of recycling of biogenic carbon in the marine realm and ultimately its removal to sediments, exerts a dominant control on atmospheric CO2 and hence variability in climate. This is a highly complex system involving a myriad of inter-connected biological, chemical, and physical processes. For this reason alone, linking observations, often highly abstracted in the form of proxies, to the primary processes involved and ultimately to explanatory hypotheses for specific geological events and transitions, is challenging. The past few decades has seen a progressive improvement in theoretical and process-based understanding of the various components that make up the marine carbon cycle and hand-in-hand with this, the development of numerical model representations of the complete system. Models have also been designed and/or adapted with paleoclimate questions in mind and applied to quantitatively explore the role of the marine carbon cycle in both perturbations and long-term geologic evolutionary trends in global climate, and possible feedbacks between them. However, we must ask whether paleoclimate models incorporate sufficiently appropriate representations of the dynamics and sensitivities of the marine carbon cycle, and indeed, whether in the geological context, we really know what these dynamics are.
The integration of fossils, phylogeny, and geochronology has resulted in an increasingly well-resolved timetable of evolution. Life appears to have taken root before the earliest known minimally metamorphosed sedimentary rocks were deposited, but for a billion years or more, evolution played out beneath an essentially anoxic atmosphere. Oxygen concentrations in the atmosphere and surface oceans first rose in the Great Oxygenation Event (GOE) 2.4 billion years ago, and a second increase beginning in the later Neoproterozoic Era [Neoproterozoic Oxygenation Event (NOE)] established the redox profile of modern oceans. The GOE facilitated the emergence of eukaryotes, whereas the NOE is associated with large and complex multicellular organisms. Thus, the GOE and NOE are fundamental pacemakers for evolution. On the time scale of Earth’s entire 4 billion–year history, the evolutionary dynamics of the planet’s biosphere appears to be fast, and the pace of evolution is largely determined by physical changes of the planet. However, in Phanerozoic ecosystems, interactions between new functions enabled by the accumulation of characters in a complex regulatory environment and changing biological components of effective environments appear to have an important influence on the timing of evolutionary innovations. On the much shorter time scale of transient environmental perturbations, such as those associated with mass extinctions, rates of genetic accommodation may have been limiting for life.
The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO<sub>3</sub> dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. LOSCAR's configuration of ocean geometry is flexible and allows for easy switching between modern and paleo-versions. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, p CO<sub>2</sub> sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.
Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and
their redistribution among the atmosphere, ocean, and terrestrial biosphere
is important to better understand the global carbon cycle, support the
development of climate policies, and project future climate change. Here we
describe data sets and a methodology to quantify all major components of the
global carbon budget, including their uncertainties, based on the combination
of a range of data, algorithms, statistics, and model estimates and their
interpretation by a broad scientific community. We discuss changes compared
to previous estimates as well as consistency within and among components, alongside
methodology and data limitations. CO2 emissions from fossil fuels and
industry (EFF) are based on energy statistics and cement production
data, while emissions from land-use change (ELUC),
mainly deforestation, are based on combined evidence from land-cover-change
data, fire activity associated with deforestation, and models. The global
atmospheric CO2 concentration is measured directly and its rate of
growth (GATM) is computed from the annual changes in concentration.
The mean ocean CO2 sink (SOCEAN) is based on observations from
the 1990s, while the annual anomalies and trends are estimated with ocean
models. The variability in SOCEAN is evaluated with data products
based on surveys of ocean CO2 measurements. The global residual
terrestrial CO2 sink (SLAND) is estimated by the difference of
the other terms of the global carbon budget and compared to results of
independent dynamic global vegetation models forced by observed climate,
CO2, and land-cover change (some including nitrogen–carbon interactions).
We compare the mean land and ocean fluxes and their variability to estimates
from three atmospheric inverse methods for three broad latitude bands. All
uncertainties are reported as ±1σ, reflecting the current
capacity to characterise the annual estimates of each component of the global
carbon budget. For the last decade available (2005–2014), EFF was
9.0 ± 0.5 GtC yr−1, ELUC was
0.9 ± 0.5 GtC yr−1, GATM was
4.4 ± 0.1 GtC yr−1, SOCEAN was
2.6 ± 0.5 GtC yr−1, and SLAND was
3.0 ± 0.8 GtC yr−1. For the year 2014 alone, EFF grew to
9.8 ± 0.5 GtC yr−1, 0.6 % above 2013, continuing the growth
trend in these emissions, albeit at a slower rate compared to the average
growth of 2.2 % yr−1 that took place during 2005–2014. Also, for
2014, ELUC was 1.1 ± 0.5 GtC yr−1, GATM was
3.9 ± 0.2 GtC yr−1, SOCEAN was
2.9 ± 0.5 GtC yr−1, and SLAND was 4.1 ±
0.9 GtC yr−1. GATM was lower in 2014 compared to the past
decade (2005–2014), reflecting a larger SLAND for that year. The
global atmospheric CO2 concentration reached 397.15 ± 0.10 ppm
averaged over 2014. For 2015, preliminary data indicate that the growth in
EFF will be near or slightly below zero, with a projection of −0.6
[range of −1.6 to +0.5] %, based on national emissions projections
for China and the USA, and projections of gross domestic product corrected for
recent changes in the carbon intensity of the global economy for the rest of
the world. From this projection of EFF and assumed constant
ELUC for 2015, cumulative emissions of CO2 will reach about
555 ± 55 GtC (2035 ± 205 GtCO2) for 1870–2015, about
75 % from EFF and 25 % from ELUC. This living
data update documents changes in the methods and data sets used in this new
carbon budget compared with previous publications of this data set (Le
Quéré et al., 2015, 2014, 2013). All observations presented here can
be downloaded from the Carbon Dioxide Information Analysis Center
(doi:10.3334/CDIAC/GCP_2015).
The onset of the Paleocene/Eocene thermal maximum (PETM) and associated carbon isotope excursion (CIE; about 56 million years ago) was geologically abrupt but it is debated whether it took thousands of years or was effectively instantaneous. A significant new record of the onset of the CIE was published by Wright and Schaller (2013) who claimed that it could be resolved across 13 annual layers in a drill core through the Marlboro Clay at Millville, New Jersey (Ocean Drilling Program Leg 174X). Supporting evidence of similar layering was also reported from another New Jersey drill site, Wilson Lake B, and a photograph of the Marlboro Clay in outcrop. Such a short duration would imply an instantaneous perturbation of the atmosphere and surface ocean, and the impact of a comet or asteroid as the likely cause. However it was suggested by Pearson and Nicholas (2014) from the published photographs that the layers in the Marlboro Clay could be artifacts of drilling disturbance (so-called "biscuiting", wherein the formation is fractured into layers or "biscuits" and drilling mud is injected in between). Here we report new observations on the cores which support that interpretation, including concentric grooves on the surfaces of the biscuits caused by spinning in the bit, micro-fracturing at their edges, and injected drilling mud. We re-interpret the outcrop evidence as showing joints rather than sedimentary layers. We argue that foraminifer concentrations in the sediments are far too high for the layers to be annually deposited in turbid waters at depths of 40–70 m, indicating that the onset of the CIE in the Marlboro Clay likely took on the order of millennia, not years. Re-coring of Millville to minimize drilling disturbance and allow a higher resolution study of the carbon isotope excursion is highly desirable.
The Earth’s climate abruptly warmed by 5–8 degrees C during the Palaeocene–Eocene thermal maximum (PETM), about 55.5 million years ago. This warming was associated with a massive addition of carbon to the ocean–atmosphere system, but estimates of the Earth system response to this perturbation are complicated by widely varying estimates of the duration of carbon release, which range from less than a year to tens of thousands of years. In addition the source of the carbon, and whether it was released as a single injection
or in several pulses, remains the subject of debate. Here we present a new high-resolution carbon isotope record from terrestrial deposits in the Bighorn Basin (Wyoming, USA) spanning the PETM, and interpret the record using a carbon-cycle box model of the ocean–atmosphere–biosphere system. Our record shows that the beginning of the PETM is characterized by not one but two distinct carbon release events, separated by a recovery to background values. To reproduce this pattern, our model requires two discrete pulses of carbon released directly to the atmosphere, at average rates exceeding 0.9 Pg C per year, with the first pulse lasting fewer than 2,000 years. We thus conclude that the PETM involved one or more reservoirs capable of repeated, catastrophic carbon release, and that rates of carbon release during the PETM were more similar to those associated with modern anthropogenic emissions5 than previously suggested.
Many palaeoclimate studies have quantified pre-anthropogenic climate change to calculate climate sensitivity (equilibrium temperature change in response to radiative forcing change), but a lack of consistent methodologies produces a wide range of estimates and hinders comparability of results. Here we present a stricter approach, to improve intercomparison of palaeoclimate sensitivity estimates in a manner compatible with equilibrium projections for future climate change.Over the past 65 millionyears, this reveals a climate sensitivity (in K W-1m2) of 0.3–1.9 or 0.6–1.3 at 95% or 68% probability, respectively. The latter implies a warming of 2.2–4.8K per doubling of atmospheric CO2, which agrees with IPCC estimates.
Over the next few centuries, with unabated emissions of anthropogenic carbon dioxide (CO2), a total of 5000 Pg C may enter the atmosphere, causing CO2 concentrations to rise to approximately 2000 ppmv, global temperature to warm by more than 8(°)C and surface ocean pH to decline by approximately 0.7 units. A carbon release of this magnitude is unprecedented during the past 56 million years-and the outcome accordingly difficult to predict. In this regard, the geological record may provide foresight to how the Earth system will respond in the future. Here, we discuss the long-term legacy of massive carbon release into the Earth's surface reservoirs, comparing the Anthropocene with a past analogue, the Palaeocene-Eocene Thermal Maximum (PETM, approx. 56 Ma). We examine the natural processes and time scales of CO2 neutralization that determine the atmospheric lifetime of CO2 in response to carbon release. We compare the duration of carbon release during the Anthropocene versus PETM and the ensuing effects on ocean acidification and marine calcifying organisms. We also discuss the conundrum that the observed duration of the PETM appears to be much longer than predicted by models that use first-order assumptions. Finally, we comment on past and future mass extinctions and recovery times of biotic diversity.
Significance
Calcium carbonate and carbon isotope records from the rhythmically bedded Marlboro Clay, deposited during the onset of the PETM CIE, show that the massive release of isotopically light carbon was instantaneous, providing important constraints for the magnitude of carbon released and potential mechanisms.
Increasing concentrations of carbon dioxide in sea water are driving a progressive acidification of the ocean. Although the associated changes in the carbonate chemistry of surface and deep waters may adversely affect marine calcifying organisms, current experiments do not always produce consistent results for a given species. Ocean sediments record past biological responses to transient greenhouse warming and ocean acidification. During the Palaeocene-Eocene thermal maximum, for example, the biodiversity of benthic calcifying organisms decreased markedly, whereas extinctions of surface dwellers were very limited. Here we use the Earth system model GENIE-1 to simulate and compare directly past and present environmental changes in the marine realm. In our simulation of future ocean conditions, we find an undersaturation with respect to carbonate in the deep ocean that exceeds that experienced during the Palaeocene-Eocene thermal maximum and could endanger calcifying organisms. Furthermore, our simulations show higher rates of environmental change at the surface for the future than the Palaeocene-Eocene thermal maximum, which could potentially challenge the ability of plankton to adapt. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints
The Palaeocene-Eocene Thermal Maximum (about 55Myrago) represents a
possible analogue for the future and thus may provide insight into
climate system sensitivity and feedbacks. The key feature of this event
is the release of a large mass of 13C-depleted carbon into
the carbon reservoirs at the Earth's surface, although the source
remains an open issue. Concurrently, global surface temperatures rose by
5-9∘C within a few thousand years. Here we use published
palaeorecords of deep-sea carbonate dissolution and stable carbon
isotope composition along with a carbon cycle model to constrain the
initial carbon pulse to a magnitude of 3,000PgC or less, with an
isotopic composition lighter than -50‰. As a result, atmospheric
carbon dioxide concentrations increased during the main event by less
than about 70% compared with pre-event levels. At accepted values for
the climate sensitivity to a doubling of the atmospheric CO2
concentration, this rise in CO2 can explain only between 1
and 3.5∘C of the warming inferred from proxy records. We
conclude that in addition to direct CO2 forcing, other
processes and/or feedbacks that are hitherto unknown must have caused a
substantial portion of the warming during the Palaeocene-Eocene Thermal
Maximum. Once these processes have been identified, their potential
effect on future climate change needs to be taken into account.
In the New Jersey Coastal Plain, a silty to clayey sedimentary unit (the Marlboro Formation) represents deposition during the Paleocene-Eocene thermal maximum (PETM). This interval is remarkably different from the glauconitic sands and silts of the underlying Paleocene Vincentown and overlying Eocene Manasquan Formation. We integrate new and published stable isotope, biostratigraphic, lithostratigraphic and ecostratigraphic records, constructing a detailed time frame for the PETM along a depth gradient at core sites Clayton, Wilson Lake, Ancora and Bass River (updip to downdip). The onset of the PETM, marked by the base of the carbon isotope excursion (CIE), is within the gradual transition from glauconitic silty sands to silty clay, and represented fully at the updip sites (Wilson Lake and Clayton). The CIE "core" interval is expanded at the updip sites, but truncated. The CIE "core" is complete at the Bass River and Ancora sites, where the early part of the recovery is present (most complete at Ancora). The extent to which the PETM is expressed in the sediments is highly variable between sites, with a significant unconformity at the base of the overlying lower Eocene sediments. Our regional correlation framework provides an improved age model, allowing better understanding of the progression of environmental changes during the PETM. High-resolution benthic foraminiferal data document the change from a sediment-starved shelf setting to a tropical, river-dominated mud-belt system during the PETM, probably due to intensification of the hydrologic cycle. The excellent preservation of foraminifera during the PETM and the lack of severe benthic extinction suggest there was no extreme ocean acidification in shelf settings.
During the Paleocene-Eocene Thermal Maximum (PETM), ∼â̂ 56 Mya, thousands of petagrams of carbon were released into the ocean-atmosphere system with attendant changes in the carbon cycle, climate, ocean chemistry, and marine and continental ecosystems. The period of carbon release is thought to have lasted <20 ka, the duration of the whole event was ∼ 200 ka, and the global temperature increase was 5-8°C. Terrestrial and marine organisms experienced large shifts in geographic ranges, rapid evolution, and changes in trophic ecology, but few groups suffered major extinctions with the exception of benthic foraminifera. The PETM provides valuable insights into the carbon cycle, climate system, and biotic responses to environmental change that are relevant to long-term future global changes.
Isotopic records across the "Latest Paleocene Thermal Maximum' (LPTM) indicate that bottom water temperature increased by more than 4°C during a brief time interval (<104 years) of the latest Paleocene (~55.6 Ma). There also was a coeval -2 to -3‰ excursion in the δ13C of the ocean/atmosphere inorganic carbon reservoir. A rapid δ13C shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere. However, a direct consequence of warming bottom water temperature from 11 to 15°C over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic CH4 hydrate at locations with intermediate water depths. In terms of the present-day oceanic CH4 hydrate reservoir, thermal dissociation of oceanic CH4 hydrate during the LPTM could have released greater than 1.1 to 2.1 × 1018 g of carbon with a δ13C of approximately -60‰. -from Authors
Recent studies have focused on the short-term contribution of the Greenland ice sheet to sea-level rise, yet little is known about its long-term stability. The present best estimate of the threshold in global temperature rise leading to complete melting of the ice sheet is 3.1°C (1.9-5.1°C, 95% confidence interval) above the preindustrial climate, determined as the temperature for which the modelled surface mass balance of the present-day ice sheet turns negative. Here, using a fully coupled model, we show that this criterion systematically overestimates the temperature threshold and that the Greenland ice sheet is more sensitive to long-term climate change than previously thought. We estimate that the warming threshold leading to a monostable, essentially ice-free state is in the range of 0.8-3.2°C, with a best estimate of 1.6°C. By testing the ice sheet's ability to regrow after partial mass loss, we find that at least one intermediate equilibrium state is possible, though for sufficiently high initial temperature anomalies, total loss of the ice sheet becomes irreversible. Crossing the threshold alone does not imply rapid melting (for temperatures near the threshold, complete melting takes tens of millennia). However, the timescale of melt depends strongly on the magnitude and duration of the temperature overshoot above this critical threshold.
Abstract Assessments of global coal, oil, and natural gas occurrences usually focus on conventional hydrocarbon reserves, i.e. those occurrences that can be exploited with current technology and present market conditions. The focus on reserves seriously underestimates long-term global hydrocarbon availability. Greenhouse gas emissions based on these estimates may convey the message that the world is running out of fossil fuels, and as a result, emissions would be reduced automatically. If the vast unconventional hydrocarbon occurrences are included in the resource estimates and historically observed rates of technology change are applied to their mobilization, the potential accessibility of fossil sources increases dramatically with long-term production costs that are not significantly higher than present market prices. Although the geographical hydrocarbon resource distribution varies significantly, a regional breakdown for 11 world regions indicates that neither hydrocarbon resource availability nor costs are likely to become forces that automatically would help wean the global energy system from the use of fossil fuel during the next century.
Improving observations of ocean heat content show that Earth is absorbing
more energy from the sun than it is radiating to space as heat, even during the
recent solar minimum. The inferred planetary energy imbalance, 0.59 \pm 0.15
W/m2 during the 6-year period 2005-2010, confirms the dominant role of the
human-made greenhouse effect in driving global climate change. Observed surface
temperature change and ocean heat gain together constrain the net climate
forcing and ocean mixing rates. We conclude that most climate models mix heat
too efficiently into the deep ocean and as a result underestimate the negative
forcing by human-made aerosols. Aerosol climate forcing today is inferred to be
1.6 \pm 0.3 W/m2, implying substantial aerosol indirect climate forcing via
cloud changes. Continued failure to quantify the specific origins of this large
forcing is untenable, as knowledge of changing aerosol effects is needed to
understand future climate change. We conclude that recent slowdown of ocean
heat uptake was caused by a delayed rebound effect from Mount Pinatubo aerosols
and a deep prolonged solar minimum. Observed sea level rise during the Argo
float era is readily accounted for by ice melt and ocean thermal expansion, but
the ascendency of ice melt leads us to anticipate acceleration of the rate of
sea level rise this decade.
The impacts of the Paleocene-Eocene thermal maximum (PETM) (∼55 Ma), one of the most rapid and extreme warming events in Earth history, are well characterized in open marine and terrestrial environments but are less so on continental margins, a major carbon sink. Here, we present stable isotope, carbonate content, organic matter content, and C:N ratio records through the PETM from new outcrop sections in California and from cores previously drilled on the New Jersey margin. Foraminifer δ18O data suggest that midlatitude shelves warmed by a similar magnitude as the open ocean (5°C–8°C), while the carbon isotope excursion (CIE), recorded both in carbonate and organic matter δ13C records, is slightly larger (3.3–4.5‰) than documented in open ocean records. Sediment accumulation rates increase dramatically during the CIE in marked contrast to the open ocean sites. In parallel, mass accumulation rates of both organic and inorganic carbon also increased by an order of magnitude. The estimated total mass of accumulated carbon in excess of pre-CIE rates suggests that continental margins, at least along North America, became carbon sinks during the CIE, mainly because of weathering feedbacks and rising sea level. This result is significant because it implies that the negative feedback role of carbon burial on continental margins was greater than previously recognized.
Changes in sea surface temperature (SST) during the Paleocene-Eocene
Thermal Maximum (PETM) have been estimated primarily from oxygen isotope
and Mg/Ca records generated from deep-sea cores. Here we present a
record of sea surface temperature change across the Paleocene-Eocene
boundary for a nearshore, shallow marine section located on the eastern
margin of North America. The SST record, as inferred from
TEX86 data, indicates a minimum of 8 °C of warming, with
peak temperatures in excess of 33 °C. Similar SSTs are estimated
from planktonic foraminifer oxygen isotope records, although the
excursion is slightly larger. The slight offset in the oxygen isotope
record may reflect on seasonally higher runoff and lower salinity.
The Paleocene-Eocene thermal maximum (PETM) has been attributed to the rapid release of approximately 2000 x 10(9) metric tons of carbon in the form of methane. In theory, oxidation and ocean absorption of this carbon should have lowered deep-sea pH, thereby triggering a rapid (<10,000-year) shoaling of the calcite compensation depth (CCD), followed by gradual recovery. Here we present geochemical data from five new South Atlantic deep-sea sections that constrain the timing and extent of massive sea-floor carbonate dissolution coincident with the PETM. The sections, from between 2.7 and 4.8 kilometers water depth, are marked by a prominent clay layer, the character of which indicates that the CCD shoaled rapidly (<10,000 years) by more than 2 kilometers and recovered gradually (>100,000 years). These findings indicate that a large mass of carbon (>2000 x 10(9) metric tons of carbon) dissolved in the ocean at the Paleocene-Eocene boundary and that permanent sequestration of this carbon occurred through silicate weathering feedback.
Identifying and quantifying planetary boundaries that must not be transgressed could help prevent human activities from causing unacceptable environmental change, argue Johan Rockström and colleagues.
Since 65 million years ago (Ma), Earth's climate has undergone a significant and complex evolution, the finer details of which
are now coming to light through investigations of deep-sea sediment cores. This evolution includes gradual trends of warming
and cooling driven by tectonic processes on time scales of 105to 107 years, rhythmic or periodic cycles driven by orbital processes with 104- to 106-year cyclicity, and rare rapid aberrant shifts and extreme climate transients with durations of 103 to 105 years. Here, recent progress in defining the evolution of global climate over the Cenozoic Era is reviewed. We focus primarily
on the periodic and anomalous components of variability over the early portion of this era, as constrained by the latest generation
of deep-sea isotope records. We also consider how this improved perspective has led to the recognition of previously unforeseen
mechanisms for altering climate.
Most carbon dioxide released into the atmosphere as a result of the burning of fossil fuels will eventually be absorbed by the ocean, with potentially adverse consequences for marine biota. Here we quantify the changes in ocean pH that may result from this continued release of CO2 and compare these with pH changes estimated from geological and historical records. We find that oceanic absorption of CO2 from fossil fuels may result in larger pH changes over the next several centuries than any inferred from the geological record of the past 300 million years, with the possible exception of those resulting from rare, extreme events such as bolide impacts or catastrophic methane hydrate degassing.
The Palaeocene-Eocene thermal maximum (PETM) is characterized by a global negative carbon isotope excursion (CIE) and widespread dissolution of seafloor carbonate sediments. The latter feature supports the hypothesis that the PETM and CIE were caused by the rapid release of a large mass (greater than 2000Gt C) of 12C-enriched carbon. The source of this carbon, however, remains a mystery. Possible sources include volcanically driven thermal combustion of organic-rich sediment, dissociation of seafloor methane hydrates and desiccation and oxidation of soil/sediment organics. A key constraint on the source(s) is the rate at which the carbon was released. Fast rates would be consistent with a catastrophic event, e.g. massive methane hydrate dissociation, whereas slower rates might implicate other processes. The PETM carbon flux is currently constrained by high-resolution marine and terrestrial records of the CIE. In pelagic bulk carbonate records, the onset of the CIE is often expressed as a single- or multiple-step excursion extending over 10(4) years. Individual planktonic shell records, in contrast, always show a single-step CIE, with either pre-excursion or excursion isotope values, but no transition values. Benthic foraminifera records, which are less complete owing to extinction and diminutive assemblages, show a delayed excursion. Here, we compile and evaluate the individual planktonic shell isotope data from several localities. We find that the most expanded records consistently show a bimodal isotope distribution pattern regardless of location, water depth or depositional facies. This suggests one of several possibilities: (i) the isotopic composition of the surface ocean/atmosphere declined in a geologic instant (<500yr), (ii) that during the onset of the CIE, most shells of mixed-layer planktonic foraminifera were dissolved, or (iii) the abundances or shell production of these species temporarily declined, possibly due to initial pH changes.
The start of the Palaeocene/Eocene thermal maximum—
a period of exceptional global warming about 55 million years ago—
is marked by a prominent negative carbon isotope excursion that reflects a massive input of 13C-depleted ('light') carbon to the ocean–atmosphere system1. It is often assumed2 that this carbon injection initiated the rapid increase in global surface temperatures and environmental change that characterize the climate perturbation3, 4, 5, 6, 7, but the exact sequence of events remains uncertain. Here we present chemical and biotic records of environmental change across the Palaeocene/Eocene boundary from two sediment sections in New Jersey that have high sediment accumulation rates. We show that the onsets of environmental change (as recorded by the abundant occurrence ('acme') of the dinoflagellate cyst Apectodinium) and of surface-ocean warming (as evidenced by the palaeothermometer TEX86) preceded the light carbon injection by several thousand years. The onset of the Apectodinium acme also precedes the carbon isotope excursion in sections from the southwest Pacific Ocean8 and the North Sea, indicating that the early onset of environmental change was not confined to the New Jersey shelf. The lag of 3,000 years between the onset of warming in New Jersey shelf waters and the carbon isotope excursion is consistent with the hypothesis that bottom water warming caused the injection of 13C-depleted carbon by triggering the dissociation of submarine methane hydrates1, 9, 10, but the cause of the early warming remains uncertain.
Past episodes of greenhouse warming provide insight into the coupling of climate and the carbon cycle and thus may help to predict the consequences of unabated carbon emissions in the future.
Avoiding environmental damage from ocean acidification requires reductions in carbon dioxide emissions regardless of climate
change.
Policy makers have generally agreed that the average global temperature rise caused by greenhouse gas emissions should not exceed 2 °C above the average global temperature of pre-industrial times. It has been estimated that to have at least a 50 per cent chance of keeping warming below 2 °C throughout the twenty-first century, the cumulative carbon emissions between 2011 and 2050 need to be limited to around 1,100 gigatonnes of carbon dioxide (Gt CO2). However, the greenhouse gas emissions contained in present estimates of global fossil fuel reserves are around three times higher than this, and so the unabated use of all current fossil fuel reserves is incompatible with a warming limit of 2 °C. Here we use a single integrated assessment model that contains estimates of the quantities, locations and nature of the world's oil, gas and coal reserves and resources, and which is shown to be consistent with a wide variety of modelling approaches with different assumptions, to explore the implications of this emissions limit for fossil fuel production in different regions. Our results suggest that, globally, a third of oil reserves, half of gas reserves and over 80 per cent of current coal reserves should remain unused from 2010 to 2050 in order to meet the target of 2 °C. We show that development of resources in the Arctic and any increase in unconventional oil production are incommensurate with efforts to limit average global warming to 2 °C. Our results show that policy makers' instincts to exploit rapidly and completely their territorial fossil fuels are, in aggregate, inconsistent with their commitments to this temperature limit. Implementation of this policy commitment would also render unnecessary continued substantial expenditure on fossil fuel exploration, because any new discoveries could not lead to increased aggregate production.
We integrate published stable isotopic, chemical, mineralogical and biotic data from the onset of the Paleocene Eocene thermal maximum (PETM) at Site 690, Maud Rise in the Southern Ocean. The integrated dataset documents a sequence of environmental steps including warming of the ocean from the surface downwards, and modification of its thermal and nutrient structure, acidification of the deep ocean and the onset of continental weathering. The age of the events with respect to the onset of the PETM is calibrated with three different age models. The relative and absolute timing of the steps are compared with simulated temperature, salinity, calcite saturation, and dissolved PO4 and O2, at different depths in the ocean, generated with the UVic Earth System Climate Model of intermediate complexity. The simulation supports the top to bottom transfer of heat and carbon, and generally agrees with age models in terms of the durations of leads and lags in temperature, C-isotope and biotic responses. Moreover, the simulation shows that stratification increased and the nutricline strengthened at the onset of the PETM. These environmental changes explain the abundance of deep dwelling nannoplankton and foraminifera during the early part of the event. The modelled calcite saturation is consistent with a harsh deep sea habitat at the time of the benthic foraminiferal extinction.
Climate sensitivity measures the response of Earth's surface temperature to changes in forcing. The response depends on various climate processes that feed back on the initial forcing on different timescales. Understanding climate sensitivity is fundamental to reconstructing Earth's climatic history as well as predicting future climate change. On timescales shorter than centuries, only fast climate feedbacks including water vapor, lapse rate, clouds, and snow/sea ice albedo are usually considered. However, on timescales longer than millennia, the generally higher Earth system sensitivity becomes relevant, including changes in ice sheets, vegetation, ocean circulation, biogeochemical cycling, etc. Here, I introduce the time-dependent climate sensitivity, which unifies fast-feedback and Earth system sensitivity. I show that warming projections, which include a time-dependent climate sensitivity, exhibit an enhanced feedback between surface warming and ocean CO2 solubility, which in turn leads to higher atmospheric CO2 levels and further warming. Compared with earlier studies, my results predict a much longer lifetime of human-induced future warming (23,000-165,000 y), which increases the likelihood of large ice sheet melting and major sea level rise. The main point regarding the legacy of anthropogenic greenhouse gas emissions is that, even if the fast-feedback sensitivity is no more than 3 K per CO2 doubling, there will likely be additional long-term warming from slow climate feedbacks. Time-dependent climate sensitivity also helps explaining intense and prolonged warming in response to massive carbon release as documented for past events such as the Paleocene-Eocene Thermal Maximum.
Feedback analysis is a powerful tool for studying the Earth system. It provides a formal framework for evaluating the relative importance of different interactions in a dynamical system. As such, its application is essential for a predictive or even a mechanistic understanding of the complex interplay of processes on the Earth. This paper reviews the basic principles of feedback analysis and tries to highlight the importance of the technique for the interpretation of physical systems. The need for clear and consistent definitions when comparing different interactions is emphasized. It is also demonstrated that feedback analyses can shed light on how uncertainty in physical processes translates into uncertainty in system response, and that the strength of the feedbacks has a very tight connection to the dynamical response time of the system.
A continuous age model for the brief climate excursion at the Paleocene–Eocene boundary has been constructed by assuming a constant flux of extraterrestrial 3He (3HeET) to the seafloor. 3HeET measurements from ODP Site 690 provide quantitative evidence for the rapid onset (<few kyr) and short duration (<120 kyr) of global warming and of the associated disturbance to the Earth’s surficial carbon budget at this time. These observations support astronomically calibrated age models indicating extremely rapid release of isotopically light carbon, possibly from seafloor methane hydrate, as the proximal cause of the event. However, the 3HeET technique indicates a previously unrecognized and extreme increase in sedimentation rate coincident with the return of climate proxies to pre-event values. The 3HeET-based age model thus suggests a far more rapid recovery from the climatic perturbation than previously proposed or predicted on the basis of the modern carbon cycle, and so may indicate additional or accelerated mechanisms of carbon removal from the ocean–atmosphere system during this period. 3HeET was also measured at ODP Site 1051 to test the validity of the Site 690 chronology. Comparison of these data sets seems to require removal of several tens of kyr of sediment within the climatic excursion at Site 1051, an observation consistent with sediment structures and previous age modeling efforts. The Site 1051 age model shows a ∼30 kyr period in which climate proxies return toward pre-event values, after which they remain invariant for ∼80 kyr. If this rise represents the recovery interval identified at Site 690, then the 3HeET-based age models of the two sites are in good agreement. However, alternative interpretations are possible, and work on less disrupted sites is required to evaluate the reliability of the proposed new chronology of the climate excursion. Regardless of these details, this work shows that the 3HeET technique can provide useful independent evidence for the development and testing of astronomically calibrated age models.
In the deep-sea, the Paleocene–Eocene Thermal Maximum (PETM) is often marked by clay-rich condensed intervals caused by dissolution of carbonate sediments, capped by a carbonate-rich interval. Constraining the duration of both the dissolution and subsequent cap-carbonate intervals is essential to computing marine carbon fluxes and thus testing hypotheses for the origin of this event. To this end, we provide new high-resolution h