March 2017
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50 Reads
High-resolution 10Be concentrations in the NGRIP, EDC, EDML and Vostok ice cores and high-resolution dD data in Vostok (5G) during the Laschamp excursion
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March 2017
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50 Reads
High-resolution 10Be concentrations in the NGRIP, EDC, EDML and Vostok ice cores and high-resolution dD data in Vostok (5G) during the Laschamp excursion
March 2017
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578 Reads
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35 Citations
Using new high-resolution 10Be measurements in the NGRIP, EDML and Vostok ice cores, together with previously published data from EDC, we present an improved synchronization between Greenland and Antarctic ice cores during the Laschamp geomagnetic excursion ∼ 41 kyr ago. We estimate the precision of this synchronization to be ±20 years, an order of magnitude better than previous work. We discuss the implications of this new synchronization for making improved estimates of the depth difference between ice and enclosed gas of the same age (Δdepth), difference between age of ice and enclosed gas at the same depth (Δage) in the EDC and EDML ice cores, spectral properties of the 10Be profiles and phasing between Dansgaard–Oeschger-10 (in NGRIP) and AIM-10 (in EDML and EDC).
July 2016
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359 Reads
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2 Citations
Climate of the Past Discussions
Using new high resolution 10Be measurements in the NGRIP, EDML and Vostok ice cores, together with previously published data from EDC, we present an improved synchronization between Greenland and Antarctic ice cores 20 during the Laschamp geomagnetic excursion ~41 ky ago. We estimate the precision of this synchronization to be ± 20 years, an order of magnitude better than our previous work. We discuss the implications of this new synchronization for making improved estimates of the difference between ice and enclosed gas of the same age (delta depth), difference between age of ice and enclosed gas at the same depth (delta age) in the EDC and EDML ice cores, spectral properties of the 10Be profiles and phasing between Dansgaard/Oeschger-10 (in NGRIP) and AIM-10 (in EDML and EDC).
December 2014
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43 Reads
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22 Citations
Annals of Glaciology
Continuous good-quality deep ice cores provide excellent scientific data with which to reconstruct a past climate record for >800 ka. At depths starting from ∼100 m using an electromechanical drill, a drilling liquid is essential for successful recovery of the very high-quality ice cores demanded by modern scientific analysis techniques (e.g. continuous flow analysis). Finding a suitable drill fluid for use at deep ice-coring drill sites is not an easy task. Temperatures vary greatly not just from site to site, but also at a site where the average mean temperature from surface to bedrock can vary from –55°C to –2.75°C. In the past 60 years, many fluids have been used, with varying degrees of success, but for various reasons are either unavailable, are now considered unsafe and dangerous or are too environmentally damaging to be permitted. Here we report on our pre-season investigation into possible candidate drill fluids, with specific information concerning ESTISOL™ 240 and COASOL™, the rationale behind the redesign of our drill successfully used at NorthGRIP, Greenland, and EPICA DML, Antarctica, the knock-on effect of those changes, and our field experience in Greenland at Flade Isblink in 2006 and at NEEM in 2009–10.
November 2014
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1,389 Reads
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342 Citations
Quaternary Science Reviews
November 2014
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3,473 Reads
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1,982 Citations
Quaternary Science Reviews
Due to their outstanding resolution and well-constrained chronologies, Greenland ice-core records provide a master record of past climatic changes throughout the Last Interglacial–Glacial cycle in the North Atlantic region. As part of the INTIMATE (INTegration of Ice-core, MArine and TErrestrial records) project, protocols have been proposed to ensure consistent and robust correlation between different records of past climate. A key element of these protocols has been the formal definition and ordinal numbering of the sequence of Greenland Stadials (GS) and Greenland Interstadials (GI) within the most recent glacial period. The GS and GI periods are the Greenland expressions of the characteristic Dansgaard–Oeschger events that represent cold and warm phases of the North Atlantic region, respectively. We present here a more detailed and extended GS/GI template for the whole of the Last Glacial period. It is based on a synchronization of the NGRIP, GRIP, and GISP2 ice-core records that allows the parallel analysis of all three records on a common time scale. The boundaries of the GS and GI periods are defined based on a combination of stable-oxygen isotope ratios of the ice (δ18O, reflecting mainly local temperature) and calcium ion concentrations (reflecting mainly atmospheric dust loading) measured in the ice. The data not only resolve the well-known sequence of Dansgaard–Oeschger events that were first defined and numbered in the ice-core records more than two decades ago, but also better resolve a number of short-lived climatic oscillations, some defined here for the first time. Using this revised scheme, we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the Last Glacial period that are represented in the Greenland ice records. The final product constitutes an extended and better resolved Greenland stratotype sequence, against which other proxy records can be compared and correlated. It also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations.
January 2014
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90 Reads
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28 Citations
October 2013
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356 Reads
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99 Citations
Rapid Communications in Mass Spectrometry
The equilibrium fractionation factors govern the relative change in the isotopic composition during phase transitions of water. The commonly used results, which were published more than 40 years ago, are limited to a minimum temperature of -33°C. This limits the reliability in cold regions. With recent instrumental developments it is now possible to test the accuracy of the earlier results as well as extend the temperature range. Novel measurements were made of the ice-vapor equilibrium fractionation factor α between 0°C and -40°C, from a unique experimental setup using both a Picarro cavity ringdown spectrometer and a TC/EA IRMS system. Using both systems allows for continuous monitoring of the equilibrium state of the system as well as testing for reproducibility. The results of the experiments show fractionation factors for δ(2) H and δ(18) O values, with a temperature dependency in accordance with theory for equilibrium fractionation. We obtain the following expressions for the temperature dependency of the fractionation coefficients: lnαδ2H=0.2133-203.10T+48888T2lnαδ18O=0.0831-49.192T+8312.5T2 Compared with previous experimental work, a significantly larger α for δ(2) H is obtained while, for δ(18) O, α is larger for temperatures below -20°C and slightly lower for temperatures above this. Using the new values for α, a Rayleigh distillation model shows significant changes in both magnitude and shape of an annual deuterium excess signal in Greenland. This emphasizes the importance of a well-defined value of α for accurate studies of the processes in the hydrological cycle and underlines the significance of the differences between the results of this work and earlier work. Copyright © 2013 John Wiley & Sons, Ltd.
April 2013
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50 Reads
The last glacial period (110 - 15 ka) has been marked by millennial scale climate variations, the trigger of which is still under debate. Such variations have been recorded in marine, ice and continental records over most of the world, but especially in the Northern Hemisphere. We first investigate the high-resolution δ18O and dust records from Greenland ice, indicating important variations in the respective moisture and dust source areas. We show that the dust concentration decrease associated with the Dansgaard-Oeschger (DO) warming events 17 to 2 happened on average within about 50 years, and that δ18O reached peak DO interstadial values faster than dust, suggesting a lag in the continental response to the abrupt warming. The individual analyzed interstadial phases lasted between 200 and 4200 years. In European eolian sequences, the different duration of the interstadials is expressed by different types of paleosols observed along a west-east transect at 50° latitude North. Discussing the paleodust cycle variations during the last climate cycle, we propose a link between European loess sequences, Chinese ones, dust records in Greenland and the variations of the North Atlantic sea ice extent and surface temperature. Changes in the dust sources are discussed (present-day deserts, but also emerged continental shelves due to sea-level lowering, dried river beds, glaciogenic dust sources along the ice-sheet edges, areas exposed to eolian erosion due to a scarce vegetation in cold climate conditions), as well as in the transport pathways in the stadial versus interstadial phases.
March 2013
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1,555 Reads
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98 Citations
The Toba eruption that occurred some 74 kyr ago in Sumatra, Indonesia, is among the largest volcanic events on Earth over the last 2 million years. Tephra from this eruption has been spread over vast areas in Asia where it constitutes a major time marker close to the Marine Isotope Stage 4/5 boundary. As yet, no tephra associated with Toba has been identified in Greenland or Antarctic ice cores. Based on new accurate dating of Toba tephra from Malaysia and on accurately dated European stalagmites the Toba event is known to occur between the onsets of Greenland Interstadials (GI) 19 and 20. Furthermore, the existing linking of Greenland and Antarctic ice cores by gas records and by the bipolar seesaw hypothesis suggests that the Antarctic counterpart is situated between Antarctic Isotope Maxima (AIM) 19 and 20. In this work we suggest a direct synchronization of Greenland (NGRIP) and Antarctic (EDML) ice cores at the Toba eruption based on matching of a pattern of bipolar volcanic spikes. Annual layer counting between volcanic spikes in both cores allows for a unique match. We first demonstrate this bipolar matching technique at the already synchronized Laschamp geomagnetic excursion (41 kyr BP) before we apply it to the suggested Toba interval. The Toba synchronization pattern covers some 2000 yr in GI-20 and AIM 19/20 and includes nine acidity peaks that are recognized in both ice cores. The suggested bipolar Toba synchronization has decadal precision. It thus allows a determination of the exact phasing of inter-hemispheric climate in a time interval of poorly constrained ice core records, and it allows for a discussion of the climatic impact of the Toba eruption in a global perspective. Furthermore, our bipolar match provides a way to place paleo-environmental records other than ice cores into a precise climatic context.
... The similarity of Van-IC8 to Greenland isotope data, Uk37 index of Lake Van, and sea surface tempera- ture data (Figure 3 and Figure 4) allows us to state that it reflects the paleo-temperature variability for the region. Using the Greenland δ 18 O record as a paleothermome- ter is a subject of debate (see Brook (2013), Vinther and Johnsen (2013) and references therein). However, it re- mains the only commonly used high resolution hemispheric paleo-temperature proxy. ...
January 2013
... So far, excluding the 12,350 bc event 41 , ESPEs have been found only in Holocene subfossil trees. Solar variability beyond the Holocene remains terra incognita, although existing tree-ring 14 C data and ice-core 10 Be and 36 Cl are seen to exhibit high-frequency structures 46,[84][85][86] . Extending the solar record beyond the Holocene will require dedicated efforts to find relatively rare subfossil trees from Glacial and Late Glacial periods. ...
March 2017
... The lower lake levels, attributed to a continuous shift to drier conditions and weaker monsoon intensity at Lake Nam Co from *9.5 to *7.7 cal ka BP (Fig. 4), confirm previous results on less moisture supply at Lake Nam Co for the period from 8.1 to 7.8 cal ka BP . The drop in TOC after *8.3 cal ka BP (Fig. 4) is possibly related to the 8.2 ka cold event, detectable in oxygen isotope data from the GRIP ice core (Andersen et al. 2007). A prominent cold and dry period after 9.0 cal ka BP at Lake Chen Co (Zhu et al. 2009), 8.8 cal ka BP at Lake Cuoe (Wu et al. 2006), 8.7 cal ka BP at Lake Zigetang (Herzschuh et al. 2006), 8.5 cal ka BP at Lake Qinghai (Shen et al. 2005), 8.1 cal ka BP at Lake Naleng (Kramer et al. 2010a, b), and 7.9 cal ka BP at Lake Ximencuo (Mischke and Zhang 2010) points to the occurrence of discrete time intervals (\1,000 a) of reduced moisture availability and lower temperatures on the central, northern, and eastern TP (Fig. 4). ...
January 2007
... H: Krakovo Forest (Sršen 2019), the wider region between Novo Mesto and Krško (Šafanda et al. 2007), and southeastern Slovenia (Čufar et al. 2008). p p. 23 Figure 5: A summary of apparent palaeoclimatic data from the Slovenian territory, accompanied by the NGRIP curve (Andersen et al. 2007) and major climatic events (red arrows for major global periods/events -warm events; blue arrows for major global periods/events -cold events (Racine et al. 2022) Major floods in Lake Bohinj at 3.9 ka, 3.7-3.55 ka, and 2.3-2.2 ...
January 2007
... The analytical uncertainty (1σ) is 0.1‰ for δ 18 O, 0.5‰ for δ 2 H, and 0.9‰ for d-excess. These discrete samples were compared with the continuous samples shown in Figure S1 in Supporting Information S1, and show a water concentration effect in the continuous measurements that alters the isotopic composition (similar to what is experienced in relatively dry water vapor isotopic measurements-e.g., Steen-Larsen et al., 2013), likely caused by variations in flow through the membrane as salt builds up on the membrane surface. We applied a water vapor concentration correction (Kopec et al., 2022) based on this difference to all continuous samples shown in this study (see Supporting Information S1). ...
January 2013
Atmospheric Chemistry and Physics
... Values of cumulative mean water molecule diffusion, known as "diffusion lengths", can be estimated for windows of time or depth along a water isotope signal by evaluating dampened sections of its high-frequency spectrum Hughes et al., 2020;Johnsen et al., 2000;Jones et al., 2017b;Jones et al. 2018;Jones et al. 2023;Kahle et 160 al., 2021;Simonsen et al., 2011). Diffusion lengths are equivalent to the estimated standard deviation (i.e. ...
March 2011
... This involved employing both Wavelength Scanned -Cavity Ring-Down Spectroscopy (WS-CRDS) and Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) LAS techniques. Notably, the precision of hydrogen and oxygen isotope measurements with WS-CRDS was found to be comparable to the previously utilized Isotope-Ratio Mass Spectrometry (IRMS) Gkinis et al., 2011;Maselli et al., 2013), leading to WS-CRDS being extensively adopted in combination with CFA as a cost-effective and time-efficient alternative to IRMS. Concurrently, the first introduction of Optical Feedback Cavity Enhanced Absorption Spectroscopy (OF-CEAS) marked a milestone, as its deployment in polar field settings interfaced with Continuous Flow Analysis systems provided continuous methane (CH 4 ) records, further expanding the scope of ice core research (Chappellaz et al., 2013). ...
November 2011
... The different structures of HS and Bond events should be addressed with caution when building a bipolar climate correlation, as the midpoint of abrupt climate transitions is often applied as a reference. Hence, at least two modes of bipolar climate correlations should be used, and a consistent lead/lag relationship between interhemispheric climates still needs to be validated, as suggested by Neukom et al. (2014) and Raisbeck et al. (2017). 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 -300 -200 -100 0 100 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 ...
July 2016
Climate of the Past Discussions
... Changes in the elemental composition of the core measured with an XRF core scanner, with (E) the calcium to aluminium ratio (Ca/Al) in black and (F) terrigenous elements in black (titanium), red (iron), and orange (aluminium) in counts per seconds (cps). Light blue shading represents the estuarine period of the basin, yellow shadings represent periods of human occupation corresponding to the Lapita and Erueti phase in the archaeological record, brown shading indicates the peat part of the core, grey area indicates the possible location of the Kuwae volcanic tephra (1452 or 1453 CE) 99 . Ca/Al ratio (Fig. 2). ...
August 2012
Journal of Geophysical Research Atmospheres
... The lowermost two units (635e600 cm and 600e595 cm; 20,000e19,500 cal yr BP, not shown in Fig. 3) were deposited directly after the last glacial maximum (LGM), in the Late Pleniglacial period (~GS-2.1; Rasmussen et al., 2014). The sediment is grey clayey silt with frequent black, seemingly burnt layers. ...
January 2014