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Ocean Warming Slows Coral Growth in the Central Red Sea
Abstract and Figures
Sea surface temperature (SST) across much of the tropics has increased by 0.4° to 1°C since the mid-1970s. A parallel increase
in the frequency and extent of coral bleaching and mortality has fueled concern that climate change poses a major threat to
the survival of coral reef ecosystems worldwide. Here we show that steadily rising SSTs, not ocean acidification, are already
driving dramatic changes in the growth of an important reef-building coral in the central Red Sea. Three-dimensional computed
tomography analyses of the massive coral Diploastrea heliopora reveal that skeletal growth of apparently healthy colonies has declined by 30% since 1998. The same corals responded to a
short-lived warm event in 1941/1942, but recovered within 3 years as the ocean cooled. Combining our data with climate model
simulations by the Intergovernmental Panel on Climate Change, we predict that should the current warming trend continue, this
coral could cease growing altogether by 2070.
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... Coral growth reconstructions have been conducted on a regional basis at several locations throughout the tropics, including across Australia 7-9 , Southeast Asia 10 , remote Pacific islands and atolls 11 , the South China Sea [12][13][14] , and the western Atlantic [15][16][17][18][19] . However, these studies have reported differing patterns over time: declining growth rates 7,8,20 , stable growth rates over time 9 , and even initial increases in calcification with rising SST 12,21,22 . In addition, differences in methodology have limited the reproducibility of some results 23 , especially when compounded with low replication (<10 cores in some cases 20,24 ) and inaccuracies in accounting for the complex threedimensional geometry of skeletal growth 20,25 . ...
... However, these studies have reported differing patterns over time: declining growth rates 7,8,20 , stable growth rates over time 9 , and even initial increases in calcification with rising SST 12,21,22 . In addition, differences in methodology have limited the reproducibility of some results 23 , especially when compounded with low replication (<10 cores in some cases 20,24 ) and inaccuracies in accounting for the complex threedimensional geometry of skeletal growth 20,25 . These methodological issues and overall lack of consensus regarding regional calcification trends limit our understanding of the long-term, chronic impacts of climate change on coral growth across the tropics. ...
... However, these studies have reported differing patterns over time: declining growth rates 7,8,20 , stable growth rates over time 9 , and even initial increases in calcification with rising SST 12,21,22 . In addition, differences in methodology have limited the reproducibility of some results 23 , especially when compounded with low replication (<10 cores in some cases 20,24 ) and inaccuracies in accounting for the complex threedimensional geometry of skeletal growth 20,25 . These methodological issues and overall lack of consensus regarding regional calcification trends limit our understanding of the long-term, chronic impacts of climate change on coral growth across the tropics. ...
Skeletal cores from massive, long-lived coral colonies provide a unique approach to investigating the chronic effects of climate change on coral calcification across decadal to centennial timescales. Here, we show an overall decline in calcification rates during the industrial era, broadly consistent with other studies, based on 148 skeletal cores from ten reef locations throughout the Indo-Pacific. However, these declines are region-specific, modulated by the opposing influences of density and linear extension (the product of which equals calcification), and superimposed on multi-decadal oscillations. The main drivers of declines in calcification were recent marine heatwaves that induced reductions in linear extension, rather than decreasing skeletal density. Our findings contrast with some regional studies that show growth declines beginning only in recent decades, which in some cases may be the most recent troughs of multi-decadal oscillations in calcification.
... An outstanding question, however, is to what extent adaptive responses will enable corals to fare better as ocean acidification proceeds over the coming decades, relative to the responses inferred from experiments that are often weeks-to-months and only occasionally longer than 1 yr (Comeau et al. 2019;McLachlan et al. 2022). Additionally, anthropogenic CO 2 causes warming via the greenhouse effect, and both laboratory (e.g., Schoepf et al. 2021) and field studies (e.g., Cantin et al. 2010;) point to impacts on coral calcification under rising temperatures. Together, ocean warming and acidification place reefs at risk of transitioning from net calcifying to net eroding (Eyre et al. 2018;Cornwall et al. 2021). ...
... Computed tomography (CT) has been used in more recent studies because it produces threedimensional datasets of density variations without the need for physical slicing. Bosscher (1993) first applied CT to coral skeleton blocks, and Cantin et al. (2010) later applied CT to reconstruct growth rates in skeletal cores. While CT allowed researchers to digitally cut two-dimensional slices oriented along the axis of growth (Cantin et al. 2010), measurements made on a single digital slice are still inherently two-dimensional (i.e., lacking components of growth into or out of the screen). ...
... Bosscher (1993) first applied CT to coral skeleton blocks, and Cantin et al. (2010) later applied CT to reconstruct growth rates in skeletal cores. While CT allowed researchers to digitally cut two-dimensional slices oriented along the axis of growth (Cantin et al. 2010), measurements made on a single digital slice are still inherently two-dimensional (i.e., lacking components of growth into or out of the screen). Coral colonies grow in complex three-dimensional orientations, and thus capturing three-dimensional growth with CT scans may be beneficial compared to two-dimensional slices that exclude growth directed into or out of the slice. ...
We present CoralCT, a software application for analysis of annual extension, density, and calcification in coral skeletal cores. CoralCT can be used to analyze computed tomography (CT) scans or X‐ray images of skeletal cores through a process in which observers interact with images of a core to define the locations of annual density bands. The application streamlines this process by organizing the observer‐defined banding patterns and automatically measuring growth parameters. Analyses can be conducted in two or three dimensions, and observers have the option to utilize an automatic band‐detection feature. CoralCT is linked to a server that stores the raw CT and X‐ray image data, as well as output growth rate data for hundreds of cores. Overall, this server‐based system enables broad collaborations on coral core analysis with standardized methods and—crucially—creates a pathway for implementing multiobserver analysis. We assess the method by comparing multiple techniques for measuring annual extension and density, including a corallite‐tracing approach, medical imaging software, two‐dimensional vs. three‐dimensional analyses, and between multiple observers. We recommend that CoralCT be used not only as a measurement tool but also as a platform for data archiving and conducting open, collaborative science.
... Long-term experiments have shown that most corals exhibit optimal calcification rates at SSTs ranging from 26-29°C, with calcification rates plummeting when thermal conditions become suboptimal (±2°C of mean annual SST; Clausen & Roth 1975, Jokiel & Coles 1977, Coles & Jokiel 1978, Marshall & Clode 2004, Hoegh-Guldberg et al. 2007, Veron et al. 2016. Indeed, decreasing calcification rates in different ecoregions have been linked to the continual abnormal increase in average annual SSTs over time (Wórum et al. 2007, Cooper et al. 2008, De'ath et al. 2009, Saenger et al. 2009, Tanzil et al. 2009, 2013, Cantin et al. 2010, Carricart-Ganivet et al. 2012, Tortolero-Langarica et al. 2017, Cruz-Ortega et al. 2020. ...
... The fact that female corals are more sensitive to changes in SST than male colonies is relevant in the context of climate change if the current thermal stress trends continue as predicted for all reef areas worldwide (Pandolfi et al. 2011, Alvarez-Filip et al. 2013, Manzello et al. 2017, Hughes et al. 2018. Considering that stony corals are being exposed to increasing SSTs, the first effect of this environmental stress would be a differential decrease in the calcification rate (Wórum et al. 2007, Cooper et al. 2008, De'ath et al. 2009, Saenger et al. 2009, Tanzil et al. 2009, 2013, Cantin et al. 2010, Tortolero-Langarica et al. 2017). Here, we show that a reduction in the calcification rate will be more severe in female colonies (Fig. 6). ...
The density banding patterns of the skeletons of massive reef-building corals can be used as historical records of their growth, life history, and environmental conditions. By analyzing these patterns, it is possible to estimate growth parameters such as skeletal density, extension rate, and calcification rate. The responses of stony corals to environmental stress depend on the amount of energy available for high-energetic metabolic processes, including skeletal calcification and sexual reproduction. The sex of a colony may also influence its calcification rate and resistance to environmental stressors like thermal anomalies. Here, we review and summarize the literature that focuses on sex-associated differences in coral calcification rates between male and female colonies and then we examine their differential responses to changes in sea surface temperature (SST) in Porites panamensis, P. lobata, Pavona gigantea, Siderastrea siderea, Montastraea cavernosa, Dicho-coenia stokesi, and Dengrogyra cylindrus from the eastern Pacific and Caribbean regions through a reanalysis of published data. Differences in the calcification rates between sexes were due to the energy available for calcification and the strategy employed for skeletal growth. Female corals exhibited lower calcification rates than male colonies in all coral species. The results reveal that overall, the calcification rate was negatively related to SST when the data of both sexes were pooled. However, when data were analyzed separately by sex, only the calcification rate of females was significantly dependent on SST. These findings highlight the implications for paleoenviron-mental reconstructions using coral skeletons and the potential disparities in the populations of gonochoric corals.
... To ensure that DSM in international waters is carried out for the benefit of humankind as a whole over time, the ISA needs to identify the net benefit to humankind as a whole over time from DSM. This can be achieved only through a full cost-benefit analysis of both regulatory and contractual arrangements governing DSM applications [23][24]. ...
There are many challenges, not least health inequities, global warming, and a rush for growth and economic development. Personalized, precision, and preventative medicine, bringing the latest omics techniques—genomics, transcriptomics, and metabolomics—for individuals allied to personalized prescription and care should help health equity. Digital technologies and artificial intelligence (AI) can help in an understanding of disease processes and in drug development. A holistic approach to the relationship between technology and the environment and clarity about both the positive benefits and negative harms resulting from using digital tools is necessary. We need to focus on the complete human-environmental interface and not just on climate change and carbon. It will be a measure of collaborative civilization if digital technology, omics techniques, and education can be used to promote global equity. Education linking diversities and performance throughout the world will be crucial.
... The Eastern Mediterranean and Red Sea were two of the first marine regions to be systematically sampled during the 1890s by the Austro-Hungarian "Pola" expeditions (Luksch, 1901;Wernand, 2010). These marginal seas have warmed at a rapid rate during the last few decades (Nykjaer, 2009;Cantin et al., 2010;Raitsos et al., 2010Raitsos et al., , 2011Sisma-Ventura et al., 2014;Chaidez et al., 2017;Mohamed et al., 2019;Pastor et al., 2020;Pisano et al., 2020), however, there is limited work performed on trends in phytoplankton abundance since the 19 th century, widely used as the start of anthropogenic climate change. This work therefore provides an important opportunity to investigate potential changes to the base of these ecosystems over the last 120 years. ...
The world’s oceans and seas are changing rapidly due to several natural and anthropogenic reasons. Among these, the largest and likely most threatening to marine life being the climate crisis and rising sea temperatures. Studying the dominant primary producers of most marine ecosystems, phytoplankton, and their response to these alterations is challenging, yet essential due to the critical role phytoplankton play in both the oceans and wider biosphere. Satellites are a crucial tool used to study phytoplankton but lack the timespan needed to accurately observe abundance patterns in response to climate change. Historical oceanographic data are increasingly being used to understand changes in the abundance of phytoplankton over the last century. Here, we retrace Secchi depth and Forel-Ule colour scale surveys performed during the “Pola” expeditions between 1890-1898 using contemporary satellite data, to assess changes in water colour and clarity (and by extension phytoplankton abundance) in the Red Sea and the Eastern Mediterranean Sea over the past century. The results show a significant greening of both regions investigated as well as a decrease in water clarity. The Red Sea Forel-Ule colour increased by 0.83 (± 0.08) with an average decrease in Secchi depth of 5.07 m (± 0.44). The Forel-Ule colour in the Eastern Mediterranean increased by 0.50 (± 0.07) and the historic Secchi depth readings were an average of 8.85 m (± 0.47) deeper than present day. Changes in Secchi depth between periods were greater than that which may have been caused by differences in the size of the Secchi disk used on the “Pola” expeditions, estimated using traditional Secchi depth theory. There was no clear change in seasonality of phytoplankton abundance and blooms, although winter months saw many of the largest changes in both measured variables. We discuss potential drivers for this change and the challenges and limitations of combining historical and modern datasets of water clarity and colour.
... Its distal region from the open ocean (Indian Ocean), namely the cooler northern Red Sea, is considered a coral refuge under the ongoing climate change projections [10]. In particular, in the central and southern Red Sea, not only does ocean warming slow down coral growth, thus endangering coral reef recovery [11], but it also results in coral bleaching in the southern and central Red Sea [12,13]. Bleaching occurs when the seawater temperatures exceed their average maximum for a prolonged amount of time, causing a mutualistic interaction between the corals and their algal symbionts within their tissues to break down [14]. ...
The northeastern Red Sea (Saudi Arabia) is currently being transformed to become a global hub of economic activity and tourism. This transformation requires the development of pristine coastal areas into populated and dynamic settlements. At the same time, the northern Red Sea is considered a climate refuge for corals in changing climate conditions, and efforts to preserve and protect marine biodiversity are being proposed. Accordingly, foraminifers are an efficient tool to assess and monitor their associated coral reefs’ health. This study reports a modern-day health assessment of the corals of Shushah Island (Saudi Arabia) in the northeastern Red Sea as a reference for future monitoring as inferred by applying the FoRAM Index method. In general, our results revealed healthy conditions conducive to coral growth, yet some precautions and regular assessments are recommended.
Aims
Artificial reefs play a vital role in restoring and creating new habitats for marine species by providing suitable substrates, especially in areas where natural substrates have been degraded or lost due to declining water quality, destructive fishing practices, and coral diseases. Artificial reef restoration aimed at coral larval settlement is gaining prominence and initially depends on the development of biofilms on reef surfaces. In this study, we hypothesized that different artificial reef materials selectively influence the composition of biofilm bacterial communities, which in turn affected coral larval settlement and the overall success of coral rehabilitation efforts. To test this hypothesis, we evaluated the impact of six different reef made materials (porcelain, granite, coral-skeleton, calcium-carbonate, shell-cement, and cement) on the development of biofilm bacterial communities and their potential to support coral larval settlement.
Methods and results
The biofilm bacterial communities were developed on different artificial reef materials and studied using 16S rRNA gene amplicon sequencing and analysis. The bacterial species richness and evenness were significantly (P < 0.05) low in the seawater, while these values were high in the reef materials. At the phylum level, the biofilm bacterial composition of all materials and seawater was majorly composed of Pseudomonadota, Cyanobacteria, and Bacteroidetes, however, significantly (P < 0.05) low Bacteroidetes were found in the seawater. At the genus level, Thalassomonas, Glaciecola, Halomicronema, Lewinella, Hyphomonas, Thalassospira, Polaribacter, and Tenacibaculum were significantly (P < 0.05) low in the coral-skeleton and seawater, compared to the other reef materials. The genera Pseudoaltermonas and Thalassomonas (considered potential inducers of coral larval settlement) were highly abundant in the shell-cement biofilm, while low values were found in the biofilm of the other materials.
Conclusion
The biofilm bacterial community composition can be selective for different substrate materials, such as shell-cement exhibited higher abundances of bacteria known to facilitate coral larval settlement, highlighting their potential in enhancing restoration outcomes.
The 1997/1998 El Niño event caused mass coral bleaching and mortality in many tropical and subtropical regions, including corals on Green Island, Taiwan, in the northwestern Pacific Ocean. This study analyzed coral carbon isotope ratios (δ¹³C), oxygen isotope ratios (δ¹⁸O), and Sr/Ca ratios for 29 years, including the 1997/1998 El Niño period, to examine how high water temperature events are recorded in coral geochemical indicators. Sr/Ca ratios in coral skeletons from Green Island show the lowest peak, means the highest temperature during the 1997/1998 El Niño period. However, we couldn’t observe high-temperature events on δ¹⁸O. Furthermore, a negative δ¹³C shift was observed after El Niño events. The regime shift of δ¹³C might have been caused by temporal bleaching and/or a decrease in symbiotic algae due to high water temperature stress under the continuous decrease in δ¹³C in DIC due to the Suess effect.
Supplementary Information
The online version contains supplementary material available at 10.1038/s41598-024-74219-5.
Global climate change, resulting from natural processes, external forces, and human activities, poses a significant threat to human well-being and development. Rising sea levels and temperatures are making various regions increasingly uninhabitable, with marine ecosystems facing substantial risks, particularly from coral bleaching events. The Red Sea a young oceanic zone formed by the divergence of the Arabian and African tectonic plates, spans approximately 2,250 km in length and 355 km in width, reaching depths of up to 2,200 m. This region is characterized by arid landscapes and mountainous terrain. One of the significant concerns for the Red Sea is the presence of black sand along its coast in Egypt. This sand is rich in dark-colored minerals such as magnetite, ilmenite, and hematite, whose composition includes silica, iron oxide, and titanium oxide. Techniques like X-ray fluorescence (XRF) and X-ray diffraction (XRD) have been utilized to analyze its composition. The albedo effect of black sand, characterized by its low ability to reflect solar radiation, contributes to higher heat absorption and localized warming. This warming influences the Red Sea surface temperatures, which are affected by factors such as air-sea interactions and dust storms. The environmental implications of black sand mining are profound, with risks including habitat destruction and pollution. These activities emphasize the need for comprehensive studies and sustainable management practices in the Red Sea region. Addressing the environmental impacts associated with black sand mining is crucial for conserving the Red Sea ecosystem.
Furthermore, international collaboration and sustainable practices are vital in protecting the Red Sea ecosystem from the adverse effects of climate change. By understanding the interplay between climate change and human activities, such as black sand mining, and implementing effective conservation strategies, we can work towards mitigating the negative impacts on this unique and vital marine environment.
Sea surface temperature (SST) is an important parameter affecting global climate, weather disasters, and marine
resources. Acquiring SST data that covers large areas and spans over long periods is one of the most essential
tasks for various scientific research. During the past decades, meteorological satellites (e.g., the Himawari 8)
have been able to provide large-scale, high-resolution continuous observations (via a number of visible, nearinfrared,
and infrared bands), but have always been affected by active atmospheric activities (i.e., clouds). A
detailed literature review on SST analysis or estimation shows that limitations or challenges associated with the
existing tools and the state-of-the-art approaches have not been fully resolved yet. Through integrating the
knowledge from interdisciplinary domains, hence, we proposed a physically-informed machine learning
approach (i.e., a physically-consistent, virtual-gauge approach in the machine learning framework) to elegantly
reconstruct daily SSTs under both cloud and cloud-free areas. By this central idea, we developed the TS-RBFNN
(i.e., Temporal-Spatial Radial Basis Function Neural Network) and suggested an adequate procedure (with
artificial clouds) for model assessment since the data in the cloudy region was unavailable. A systematic study in
terms of model implication (i.e., the meaning of network architecture), model validation (i.e., the performance of
learning and generalization), and model applications (i.e., in open ocean and coastal seas with different cloud
coverage over the four seasons) was conducted. In particular, a pattern similarity analysis (examining SST distributions
for several selected sections) and a daily-based error analysis (presenting the variations and distributions
of RMSEs for each season) were carried out to clarify the relationship between varying cloud conditions
and model performances (inferenced by sunny areas). Overall, the TS-RBFNN would better perform full SST
reconstruction with significant improvement up to 60%, compared to the DINEOF (i.e., Data Interpolation
Empirical Orthogonal Function). Currently, the TS-RBFNN model is being implemented into the operational
system of Taiwan’s Central Weather Administration to provide all-weather SST products. In the near future, a
long-term societal impact would be expected as the reconstructed SST data could be broadly employed in various
scientific applications.
The sources and mechanisms of inorganic carbon transport for scleractinian coral calcification and photosynthesis were studied using a double labelling technique with H14 CO3 and 45 Ca. Clones of Stylophora pistillata that had developed into microcolonies were examined. Compartmental and pharmacological analyses of the distribution of 45 Ca and H14 CO3 in the coelenteron, tissues and skeleton were performed in dark or light conditions or in the presence of various seawater HCO3− concentrations.
For calcification, irrespective of the lighting conditions, the major source of dissolved inorganic carbon (DIC) is metabolic CO2 (70–75 % of total CaCO3 deposition), while only 25–30 % originates from the external medium (seawater carbon pool). These results are in agreement with the observation that metabolic CO2 production in the light is at least six times greater than is required for calcification. This source is dependent on carbonic anhydrase activity because it is sensitive to ethoxyzolamide. Seawater DIC is transferred from the external medium to the coral skeleton by two different pathways: from sea water to the coelenteron, the passive paracellular pathway is largely sufficient, while a DIDS-sensitive transcellular pathway appears to mediate the flux across calicoblastic cells. Irrespective of the source, an anion exchanger performs the secretion of DIC at the site of calcification. Furthermore, a fourfold light-enhanced calcification of Stylophora pistillata microcolonies was measured. This stimulation was only effective after a lag of 10 min. These results are discussed in the context of light-enhanced calcification.
Characterisation of the DIC supply for symbiotic dinoflagellate photosynthesis demonstrated the presence of a DIC pool within the tissues. The size of this pool was dependent on the lighting conditions, since it increased 39-fold after 3 h of illumination. Passive DIC equilibration through oral tissues between sea water and the coelenteric cavity is insufficient to supply this DIC pool, suggesting that there is an active transepithelial absorption of inorganic carbon sensitive to DIDS, ethoxyzolamide and iodide. These results confirm the presence of CO2-concentrating mechanisms in coral cells. The tissue pool is not, however, used as a source for calcification since no significant lag phase in the incorporation of external seawater DIC was measured.
Seawater carbonate chemistry of the mixed layer of the oceans is changing rapidly in response to increases in atmospheric CO 2. The formation and dissolution of calcium car-bonate is now known to be strongly affected by these changes, but many questions remain about other controls on biocalcification and inorganic cementation that confound our attempts to make accurate predictions about the effects on both coral reef organisms and reefs themselves. This chapter overviews the current knowledge of the relationship between seawater carbonate chemistry and coral reef calcification, identifies the hurdles in our understanding of the two, and presents a strategy for overcoming those hurdles.
are likewise exceptional for chronometric purposes, and even the terrestrial 14C timescale has now been calibrated against coral 230Th/234U. Corals also represent a testing ground for basic ideas about mineralogy and geochemistry. The shapes, sizes, and organization of skeletal crystals have been attributed to factors as diverse as mineral supersaturation levels and organic mediation of crystal growth. The coupling between calcification and photosynthesis in symbiotic corals is likewise attributed to everything from photosynthetic alkalinization of the water, to efforts by the coral to prevent photosynthetic alkalinization. Corals also leave a significant geochemical imprint on the oceans. Their aragonite skeletons accept about 10 times more strontium than does calcite, hence the proportion of marine aragonite precipitation affects the oceanic chemical balance. Biological carbonates represent the biosphere's largest carbon reservoir, hence calcareous organisms affect the ocean's pH, CO2 content, and ultimately global temperatures through the greenhouse gas connection. Finally, corals present some geochemical puzzles for ecology and conservation. How do symbiotic corals obtain nutrients in some of the most nutrient deficient parts of the planet? Are global geochemical changes partially responsible for the widespread declines in coral reefs during recent decades? We will address many of these issues, but will concentrate on coral skeletal structure and calcification mechanism. These topics bear most directly on the biomineralization process and generally affect the choice of skeletal materials and analytical techniques used in geochemical investigations. The coral reef is probably the planet's most spectacular biomineralization product. These grand and complex ecosystems build on the accumulated skeletal debris of countless generations of organisms, especially calcareous algae and symbiotic foraminifera and corals. The algae produce much of the reef mass and help to cement it together, while the corals build much of the erosion-resistant framework. Coral reefs dominate much of the world's tropical coastline and cover abut 15% of the seabed shallower than 30 m (Smith 1978).
Several negative feedback mechanisms have been proposed by others to explain the stability of maximum sea surface temperature (SST) in the western Pacific warm pool (WPWP). If these ``ocean thermostat'' mechanisms effectively suppress warming in the future, then coral reefs in this region should be less exposed to conditions that favor coral reef bleaching. In this study we look for regional differences in reef exposure and sensitivity to increasing SSTs by comparing reported coral reef bleaching events with observed and modeled SSTs of the last fifty years. Coral reefs within or near the WPWP have had fewer reported bleaching events relative to reefs in other regions. Analysis of SST data indicate that the warmest parts of the WPWP have warmed less than elsewhere in the tropical oceans, which supports the existence of thermostat mechanisms that act to depress warming beyond certain temperature thresholds.
The population dynamics of five species of foliaceous corals (Agaricia agaricites forma purpurea, A. lamarcki, Leptoseris cucullata, Montastrea annularis, and Porites astreoides) was followed on Jamaican reefs using annual photographic censuses. Overall, population cover, size frequencies, and number of colonies were stable over the monitored period from 1977 to 1980. However, individual colonies were in turmoil: of the original 883 colonies, 315 were killed outright and 499 suffered partial colony mortality (injury) at least once during the 3 yr. Partial mortality generated an additional 189 colonies by fission, while larval recruitment added another 201, and fusion subtracted 40 colonies. The net result was a decrease of
The effect of rising greenhouse-gas emissions on climate is not uniform across the globe. An analysis of the mechanisms behind model-projected changes in ocean temperature gives greater confidence in the pattern of tropical warming and its potential impacts.
Observations of sea surface and land-near-surface merged temperature anomalies are used to monitor climate variations and to evaluate climate simulations; therefore, it is important to make analyses of these data as accurate as possible. Analysis uncertainty occurs because of data errors and incomplete sampling over the historical period. This manuscript documents recent improvements in NOAA's merged global surface temperature anomaly analysis, monthly, in spatial 5° grid boxes. These improvements allow better analysis of temperatures throughout the record, with the greatest improvements in the late nineteenth century and since 1985. Improvements in the late nineteenth century are due to improved tuning of the analysis methods. Beginning in 1985, improvements are due to the inclusion of bias-adjusted satellite data. The old analysis (version 2) was documented in 2005, and this improved analysis is called version 3.
Early in 2002, satellites of the U.S. National Oceanic and Atmospheric Administration (NOAA) detected anomalously high sea surface temperatures (SST) developing in the western Coral Sea, midway along Australia's Great Barrier Reef (GBR). This was the beginning of what was to become the most significant GBR coral bleaching event on record [Wilkinson, 2002]. During this time, NOAA's National Environmental Satellite, Data, and Information Service (NESDIS) provided satellite data as part of ongoing collaborative work on coral reef health with the Australian Institute of Marine Science (AIMS) and the Great Barrier Reef Marine Park Authority (GBRMPA). These data proved invaluable to AIMS and GBRMPA as they monitored and assessed the development and evolution of SSTs throughout the austral summer, enabling them to keep stakeholders, government, and the general public informed and up to date.
The temperature and degree of carbonate mineral supersaturation
(CO3-2 ion concentration) of seawater are the two
most likely controlling variables on the compositions of recent marine
carbonate cements. The relative importance of these variables is
difficult to assess in nature because they have similar trends with
depth (0 1500 m) and latitude in modern oceans. We carried out
laboratory experiments to investigate the relative growth rates of
calcite, Mg calcite, and aragonite in seawater as functions of both
temperature (5, 25, and 37 °C) and of carbonate ion concentration
(2.5 to 15 times supersaturated with respect to calcite). The
precipitation rates of aragonite relative to those of calcite increase
strongly with increasing temperature and are not affected greatly by
changes in saturation state. At 5 °C, calcite precipitation rates
are nearly equivalent to those of aragonite, regardless of the degree of
saturation. At both 25 and 37 °C, aragonite precipitation rates are
much more rapid than those of calcite (up to a factor of 4), except at
very low saturation states. Calcite compositions vary from less than 5
mol% MgCO3 at 5 °C to 14 mol% MgCO3 at 37
°C. Our results suggest that the well-documented shift toward
precipitation of lower mol% Mg calcite and the decrease in abundance of
aragonite cements with increasing oceanic depth and latitude can be
attributed largely to lower temperatures.