Submarine glacial landforms in Southeast Greenland fjords reveal contrasting outlet-glacier behaviour since the Last Glacial Maximum

2020 ◽  
Author(s):  
Christine Batchelor ◽  
Julian Dowdeswell ◽  
Eric Rignot ◽  
Romain Millan
Keyword(s):  
Flow Direction ◽  
Gravity Data ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Aerial Photographs ◽  
Gravity Inversion ◽  
Last Deglaciation ◽  
Outlet Glacier ◽  
The Last Deglaciation ◽  
Greenland Margin

<p>The Southeast (SE) Greenland margin, which includes the SE sector of the Greenland Ice Sheet (GIS) and the eastern Julianehåb Ice Cap (JIC), is drained by a number of fast‐flowing, marine‐terminating outlet glaciers. Although the SE Greenland margin is suggested to have been highly sensitive to past climatic changes, mountainous terrain and a lack of ice‐free areas have largely prevented analysis of the deglacial and Holocene behaviour of these outlet glaciers. Here we use bathymetric data, from multibeam echo-sounding acquired by NASA’s Earth Venture Sub‐orbital Oceans Melting Greenland (OMG) mission and from gravity inversion derived from Operation Icebridge (OIB) gravity data, from 36 fjords along the SE Greenland margin to map the distribution of more than 50 major submarine moraines. The moraines are up to 3 km long in the former ice‐flow direction, reach up to 150 m above the surrounding seafloor, and span the width of the fjord.</p><p>Inner‐fjord moraines are widespread along the SE Greenland margin, occurring in 65% of the surveyed fjords of the SE GIS and the JIC. Their locations beyond the oldest ice‐margin position where it is known from aerial photographs and correlation with prominent terrestrial moraines suggest that the inner‐fjord moraines were produced sometime during the Neoglacial (since approximately 4 ka).</p><p>Major moraine ridges are present in a midfjord setting in all of the nine fjords of the eastern JIC yet are generally absent from the deeper and wider fjords of the SE GIS. Given the distribution of published deglacial ages, we hypothesize that the midfjord moraines of the eastern JIC were formed during an ice‐margin still‐stand or advance that occurred during the early Holocene. It is possible that this still‐stand or advance had a climatic control, for example, the 8.2‐ka event that has been recorded from Greenland ice cores. The absence of midfjord moraines from the deeper and wider fjords of the SE GIS to the north suggests relatively rapid and continuous ice retreat occurred during the last deglaciation. The contrasting behaviour of the SE GIS and the eastern JIC during the last deglaciation probably reflects differences in fjord geometry and exposure to ocean heat.</p>

scholarly journals Glacial–interglacial dynamics of Antarctic firn columns: comparison between simulations and ice core air-δ<sup>15</sup>N measurements

2013 ◽  
Vol 9 (3) ◽  
pp. 983-999 ◽  
Author(s):  
E. Capron ◽  
A. Landais ◽  
D. Buiron ◽  
A. Cauquoin ◽  
J. Chappellaz ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Ice Core ◽  
Ice Cores ◽  
Detailed Comparison ◽  
Last Deglaciation ◽  
Depth Study ◽  
Dronning Maud Land ◽  
The Last Deglaciation ◽  
Correct Estimation ◽  
Lock In

Abstract. Correct estimation of the firn lock-in depth is essential for correctly linking gas and ice chronologies in ice core studies. Here, two approaches to constrain the firn depth evolution in Antarctica are presented over the last deglaciation: outputs of a firn densification model, and measurements of δ15N of N2 in air trapped in ice core, assuming that δ15N is only affected by gravitational fractionation in the firn column. Since the firn densification process is largely governed by surface temperature and accumulation rate, we have investigated four ice cores drilled in coastal (Berkner Island, BI, and James Ross Island, JRI) and semi-coastal (TALDICE and EPICA Dronning Maud Land, EDML) Antarctic regions. Combined with available ice core air-δ15N measurements from the EPICA Dome C (EDC) site, the studied regions encompass a large range of surface accumulation rates and temperature conditions. Our δ15N profiles reveal a heterogeneous response of the firn structure to glacial–interglacial climatic changes. While firn densification simulations correctly predict TALDICE δ15N variations, they systematically fail to capture the large millennial-scale δ15N variations measured at BI and the δ15N glacial levels measured at JRI and EDML – a mismatch previously reported for central East Antarctic ice cores. New constraints of the EDML gas–ice depth offset during the Laschamp event (~41 ka) and the last deglaciation do not favour the hypothesis of a large convective zone within the firn as the explanation of the glacial firn model–δ15N data mismatch for this site. While we could not conduct an in-depth study of the influence of impurities in snow for firnification from the existing datasets, our detailed comparison between the δ15N profiles and firn model simulations under different temperature and accumulation rate scenarios suggests that the role of accumulation rate may have been underestimated in the current description of firnification models.

scholarly journals Antarctic temperature and CO<sub>2</sub>: near-synchrony yet variable phasing during the last deglaciation

2019 ◽  
Vol 15 (3) ◽  
pp. 913-926 ◽  
Author(s):  
Jai Chowdhry Beeman ◽  
Léa Gest ◽  
Frédéric Parrenin ◽  
Dominique Raynaud ◽  
Tyler J. Fudge ◽  
...  
Keyword(s):  
Phase Relationship ◽  
Ice Cores ◽  
Complex Nature ◽  
Temperature Phase ◽  
Last Deglaciation ◽  
Uncertainty Range ◽  
West Antarctic ◽  
The Last Deglaciation ◽  
Temperature Records ◽  
The Individual

Abstract. The last deglaciation, which occurred from 18 000 to 11 000 years ago, is the most recent large natural climatic variation of global extent. With accurately dated paleoclimate records, we can investigate the timings of related variables in the climate system during this major transition. Here, we use an accurate relative chronology to compare temperature proxy data and global atmospheric CO2 as recorded in Antarctic ice cores. In addition to five regional records, we compare a δ18O stack, representing Antarctic climate variations with the high-resolution robustly dated WAIS Divide CO2 record (West Antarctic Ice Sheet). We assess the CO2 and Antarctic temperature phase relationship using a stochastic method to accurately identify the probable timings of changes in their trends. Four coherent changes are identified for the two series, and synchrony between CO2 and temperature is within the 95 % uncertainty range for all of the changes except the end of glacial termination 1 (T1). During the onset of the last deglaciation at 18 ka and the deglaciation end at 11.5 ka, Antarctic temperature most likely led CO2 by several centuries (by 570 years, within a range of 127 to 751 years, 68 % probability, at the T1 onset; and by 532 years, within a range of 337 to 629 years, 68 % probability, at the deglaciation end). At 14.4 ka, the onset of the Antarctic Cold Reversal (ACR) period, our results do not show a clear lead or lag (Antarctic temperature leads by 50 years, within a range of −137 to 376 years, 68 % probability). The same is true at the end of the ACR (CO2 leads by 65 years, within a range of 211 to 117 years, 68 % probability). However, the timings of changes in trends for the individual proxy records show variations from the stack, indicating regional differences in the pattern of temperature change, particularly in the WAIS Divide record at the onset of the deglaciation; the Dome Fuji record at the deglaciation end; and the EDML record after 16 ka (EPICA Dronning Maud Land, where EPICA is the European Project for Ice Coring in Antarctica). In addition, two changes – one at 16 ka in the CO2 record and one after the ACR onset in three of the isotopic temperature records – do not have high-probability counterparts in the other record. The likely-variable phasing we identify testify to the complex nature of the mechanisms driving the carbon cycle and Antarctic temperature during the deglaciation.

scholarly journals Detailed insight into Arctic climatic variability during MIS 11 at Lake El'gygytgyn, NE Russia

2012 ◽  
Vol 8 (6) ◽  
pp. 6309-6339 ◽  
Author(s):  
H. Vogel ◽  
C. Meyer-Jacob ◽  
M. Melles ◽  
J. Brigham-Grette ◽  
A. A. Andreev ◽  
...  
Keyword(s):  
Climatic Variability ◽  
Far East ◽  
Ice Cores ◽  
Precipitation Anomaly ◽  
Last Deglaciation ◽  
Lake Productivity ◽  
Lake Ice ◽  
Thermal Maximum ◽  
Lake El’Gygytgyn ◽  
The Last Deglaciation

Abstract. Here we present a detailed multiproxy record of the climate and environmental evolution at Lake El'gygytgyn/Far East Russian Arctic during the period 430–395 ka covering the Marine Isotope Stage (MIS) 12/11 transition and the thermal maximum of super interglacial MIS 11. The MIS 12/11 transition at Lake El'gygytgyn is characterized by initial warming followed by a cold reversal implying similarities to the Bølling/Allerød (B/A) to Younger Dryas (YD) pattern of the last deglaciation. Full and remarkably stable interglacial conditions with mean temperatures of warmest month (MTWM) ranging between ca. 10–15 °C, annual precipitation (PANN) ranging between ca. 300–600 mm, strong in-lake productivity, coincide with dark coniferous forests in the catchment, annual disintegration of the lake ice cover and full mixis of the water column. Such conditions persisted for ca. 27 kyrs between ca. 425–398 ka. The Lake El'gygytgyn record closely resembles the climate pattern recorded in Lake Baikal (SE Siberia) sediments and Antarctic ice cores implying strong teleconnections between Northern and Southern Hemispheres during MIS 11. A peak warm period between ca. 418–415.5 ka and a precipitation anomaly at ca. 401 ka at Lake El'gygytgyn, in contrast, appear to be an expression of more regionally confined climate variations.

scholarly journals Antarctic temperature and CO<sub>2</sub>: near-synchrony yet variable phasing during the last deglaciation

2018 ◽  
Author(s):  
Jai Chowdhry Beeman ◽  
Léa Gest ◽  
Frédéric Parrenin ◽  
Dominique Raynaud ◽  
Tyler J. Fudge ◽  
...  
Keyword(s):  
Phase Relationship ◽  
Ice Cores ◽  
Complex Nature ◽  
Temperature Phase ◽  
Last Deglaciation ◽  
The Holocene ◽  
Uncertainty Range ◽  
Major Transition ◽  
The Last Deglaciation ◽  
Temperature Proxy

Abstract. The last deglaciation, which occurred from 18,000 to 11,000 years ago, is the most recent large natural climatic variation of global extent. With accurately dated paleoclimate records, we can investigate the timings of related variables in the climate system during this major transition. Here, we use an accurate relative chronology to compare regional temperature proxy data and global atmospheric CO2 as recorded in Antarctic ice cores. We build a stack of temperature variations by averaging the records from five ice cores distributed across Antarctica, and develop a volcanic synchronization to compare it with the high-resolution, robustly dated WAIS Divide CO2 record. We assess the CO2/Antarctic temperature phase relationship using a stochastic method to accurately identify the probable timings of abrupt changes in their trends. During the large, millenial-scale changes at the onset of the last deglaciation at 18 ka and the onset of the Holocene at 11.5 ka, Antarctic temperature most likely led CO2 by several centuries. A marked event in both series around 16 ka began with a rapid rise in CO2, which stabilized synchronously with temperature. CO2 and Antarctic temperature peaked nearly synchronously at 14.4 ka, the onset of the Antarctic Cold Reversal (ACR) period. And CO2 likely led Antarctic temperature by around 250 years at the end of the ACR. The five major changes identified for both series are coherent, and synchrony is within the 2 σ uncertainty range for all of the changes except the Holocene onset. But the often-multimodal timings, centennial-scale substructures, and likely-variable phasings we identify testify to the complex nature of the two series, and of the mechanisms driving the carbon cycle and Antarctic temperature during the deglaciation.

scholarly journals Ice core evidence for decoupling between mid-latitude atmospheric water cycle and Greenland temperature during the last deglaciation

2018 ◽  
Author(s):  
Amaëlle Landais ◽  
Emilie Capron ◽  
Valérie Masson-Delmotte ◽  
Samuel Toucanne ◽  
Rachael Rhodes ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Large Scale ◽  
Environmental Changes ◽  
Ice Core ◽  
Ice Cores ◽  
Last Deglaciation ◽  
Sequence Of Events ◽  
Decadal Scale ◽  
Abrupt Changes ◽  
The Last Deglaciation

Abstract. The last deglaciation represents the most recent example of natural global warming associated with large-scale climate changes. In addition to the long-term global temperature increase, the last deglaciation onset is punctuated by a sequence of abrupt changes in the Northern Hemisphere. Such interplay between orbital- and millennial-scale variability is widely documented in paleoclimatic records but the underlying mechanisms are not fully understood. Limitations arise from the difficulty in constraining the sequence of events between external forcing, high- and low- latitude climate and environmental changes. Greenland ice cores provide sub-decadal-scale records across the last deglaciation and contain fingerprints of climate variations occurring in different regions of the Northern Hemisphere. Here, we combine new ice d-excess and 17O-excess records, tracing changes in the mid-latitudes, with ice δ18O records of polar climate. Within Heinrich Stadial 1, we demonstrate a decoupling between climatic conditions in Greenland and those of the lower latitudes. While Greenland temperature remains mostly stable from 17.5 to 14.7 ka, significant change in the mid latitudes of northern Atlantic takes place at ~ 16.2 ka, associated with warmer and wetter conditions of Greenland moisture sources. We show that this climate modification is coincident with abrupt changes in atmospheric CO2 and CH4 concentrations recorded in an Antarctic ice core. Our coherent ice core chronological framework and comparison with other paleoclimate records suggests a mechanism involving two-step freshwater fluxes in the North Atlantic associated with a southward shift of the intertropical convergence zone.

Centennial-scale evolution of methane during the penultimate deglaciation

2020 ◽  
Author(s):  
Loïc Schmidely ◽  
Lucas Silva ◽  
Christoph Nehrbass-Ahles ◽  
Juhyeong Han ◽  
Jinhwa Shin ◽  
...  
Keyword(s):  
Temporal Resolution ◽  
Ice Core ◽  
Ice Cores ◽  
Before Present ◽  
Last Deglaciation ◽  
Rates Of Change ◽  
Maximum Resolution ◽  
The Last Deglaciation ◽  
First Time ◽  
Temporal Coverage

&lt;p&gt; Small air inclusions in ice cores represent a direct archive of past atmospheric compositions, allowing us to measure the concentration of the three most potent non-condensable Greenhouse Gases (GHG) CO&lt;sub&gt;2&lt;/sub&gt;, CH&lt;sub&gt;4&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O as far back as 800,000 years before present (kyr BP). These records demonstrate that transitions from glacial to interglacial conditions are accompanied by a substantial net increase of CO&lt;sub&gt;2&lt;/sub&gt;, CH&lt;sub&gt;4&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O in the atmosphere (L&amp;#252;thi et al. 2008, Loulergue et al. 2008, Schilt et al. 2010). A sound understanding of the interplay between the reorganization of the climate system and the perturbation of GHG inventories during glacial terminations is partly limited by the temporal resolution of the records derived from ice cores. In fact, with the exception of the last deglaciation (23-9 kyr BP) centennial-scale GHG variability remained uncaptured for precedings glacial terminations.&lt;/p&gt;&lt;p&gt;In this work, we exploit the exceptionally long temporal coverage of the EPICA Dome C (EDC) ice core to reconstruct, for the first time, centennial-scale fluctuations of CH&lt;sub&gt;4&lt;/sub&gt; mole fractions from 145 to 125 kyr BP, encompassing the entire penultimate deglaciation (138-128 kyr BP). With a temporal resolution of ~100 years, our new record is now unveiling all climate-driven signals enclosed into the EDC ice core, exploiting the maximum resolution possible at Dome C (). This offers us the opportunity to study the timing and rates of change of CH&lt;sub&gt;4&lt;/sub&gt; in unprecedented details.&lt;/p&gt;&lt;p&gt;Preliminary analysis reveals that the deglacial CH&lt;sub&gt;4 &lt;/sub&gt;rise is a superimposition of gradual millennial-scale increases (~0.01-0.02 ppb/year) and abrupt and partly intermittent centennial-scale events (~80-200 ppb in less than a millennium). We will investigate processes modulating the observed changes in the CH&lt;sub&gt;4&lt;/sub&gt; cycle, compare the structure of our record with the CH&lt;sub&gt;4&lt;/sub&gt; profile of the last deglaciation (Marcott, 2014) and contrast it with the EDC CO&lt;sub&gt;2&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O records over the penultimate glacial termination now available in similar resolution.&lt;/p&gt;

Preliminary10Be chronology for the last deglaciation of the western margin of the Greenland Ice Sheet

2009 ◽  
Vol 24 (3) ◽  
pp. 270-278 ◽  
Author(s):  
Vincent Rinterknecht ◽  
Yuri Gorokhovich ◽  
Joerg Schaefer ◽  
Marc Caffee
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Last Deglaciation ◽  
Western Margin ◽  
The Last Deglaciation

scholarly journals Leads and lags between Antarctic temperature and carbon dioxide during the last deglaciation

2017 ◽  
Author(s):  
Léa Gest ◽  
Frédéric Parrenin ◽  
Jai Chowdhry Beeman ◽  
Dominique Raynaud ◽  
Tyler J. Fudge ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Cores ◽  
Atmospheric Co2 ◽  
Last Deglaciation ◽  
High Accumulation ◽  
Volcanic Event ◽  
Sequence Of Events ◽  
The Last Deglaciation ◽  
Paleoclimate Records ◽  
The Antarctic

Abstract. To understand causal relationships in past climate variations, it is essential to have accurate chronologies of paleoclimate records. The last deglaciation, which occurred from 18 000 to 11 000 years ago, is especially interesting, since it is the most recent large climatic variation of global extent. Ice cores in Antarctica provide important paleoclimate proxies, such as regional temperature and global atmospheric CO2. However, temperature is recorded in the ice while CO2 is recorded in the enclosed air bubbles. The ages of the former and of the latter are different since air is trapped at 50–120 m below the surface. It is therefore necessary to correct for this air-ice shift to accurately infer the sequence of events. Here we accurately determine the phasing between East Antarctic temperature and atmospheric CO2 variations during the last deglacial warming based on Antarctic ice core records. We build a stack of East Antarctic temperature variations by averaging the records from 4 ice cores (EPICA Dome C, Dome Fuji, EPICA Dronning Maud Land and Talos Dome), all accurately synchronized by volcanic event matching. We place this stack onto the WAIS Divide WD2014 age scale by synchronizing EPICA Dome C and WAIS Divide using volcanic event matching, which allows comparison with the high resolution CO2 record from WAIS Divide. Since WAIS Divide is a high accumulation site, its air age scale, which has previously been determined by firn modeling, is more robust. Finally, we assess the CO2/Antarctic temperature phasing by determining four periods when their trends change abruptly. We find that at the onset of the last deglaciation and at the onset of the Antarctic Cold Reversal (ACR) period CO2 and Antarctic temperature are synchronous within a range of 210 years. Then CO2 slightly leads by 165 ± 116 years at the end of the Antarctic Cold Reversal (ACR) period. Finally, Antarctic temperature significantly leads by 406 ± 200 years at the onset of the Holocene period. Our results further support the hypothesis of no convective zone at EPICA Dome C during the last deglaciation and the use of nitrogen-15 to infer the height of the diffusive zone. Future climate and carbon cycle modeling works should take into account this robust phasing constraint.

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