scholarly journals Rapid changes in ice core gas records – Part 2: Understanding the rapid rise in atmospheric CO<sub>2</sub> at the onset of the Bølling/Allerød

2010 ◽  
Vol 6 (4) ◽  
pp. 1473-1501 ◽  
Author(s):  
P. Köhler ◽  
G. Knorr ◽  
D. Buiron ◽  
A. Lourantou ◽  
J. Chappellaz
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Ice Core ◽  
Age Distribution ◽  
Ice Cores ◽  
Atmospheric Co2 ◽  
Current Debate ◽  
Last Deglaciation ◽  
Rapid Changes

Abstract. During the last glacial/interglacial transition the Earth's climate underwent rapid changes around 14.6 kyr ago. Temperature proxies from ice cores revealed the onset of the Bølling/Allerød (B/A) warm period in the north and the start of the Antarctic Cold Reversal in the south. Furthermore, the B/A is accompanied by a rapid sea level rise of about 20 m during meltwater pulse (MWP) 1A, whose exact timing is matter of current debate. In situ measured CO2 in the EPICA Dome C (EDC) ice core also revealed a remarkable jump of 10±1 ppmv in 230 yr at the same time. Allowing for the age distribution of CO2 in firn we here show, that atmospheric CO2 rose by 20–35 ppmv in less than 200 yr, which is a factor of 2–3.5 larger than the CO2 signal recorded in situ in EDC. Based on the estimated airborne fraction of 0.17 of CO2 we infer that 125 Pg of carbon need to be released to the atmosphere to produce such a peak. Most of the carbon might have been activated as consequence of continental shelf flooding during MWP-1A. This impact of rapid sea level rise on atmospheric CO2 distinguishes the B/A from other Dansgaard/Oeschger events of the last 60 kyr, potentially defining the point of no return during the last deglaciation.

scholarly journals Abrupt rise in atmospheric CO<sub>2</sub> at the onset of the Bølling/Allerød: in-situ ice core data versus true atmospheric signals

2011 ◽  
Vol 7 (2) ◽  
pp. 473-486 ◽  
Author(s):  
P. Köhler ◽  
G. Knorr ◽  
D. Buiron ◽  
A. Lourantou ◽  
J. Chappellaz
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Radiative Forcing ◽  
Ice Core ◽  
Age Distribution ◽  
Ice Cores ◽  
Rate Of Change ◽  
Atmospheric Co2 ◽  
Abrupt Rise

Abstract. During the last glacial/interglacial transition the Earth's climate underwent abrupt changes around 14.6 kyr ago. Temperature proxies from ice cores revealed the onset of the Bølling/Allerød (B/A) warm period in the north and the start of the Antarctic Cold Reversal in the south. Furthermore, the B/A was accompanied by a rapid sea level rise of about 20 m during meltwater pulse (MWP) 1A, whose exact timing is a matter of current debate. In-situ measured CO2 in the EPICA Dome C (EDC) ice core also revealed a remarkable jump of 10 ± 1 ppmv in 230 yr at the same time. Allowing for the modelled age distribution of CO2 in firn, we show that atmospheric CO2 could have jumped by 20–35 ppmv in less than 200 yr, which is a factor of 2–3.5 greater than the CO2 signal recorded in-situ in EDC. This rate of change in atmospheric CO2 corresponds to 29–50% of the anthropogenic signal during the last 50 yr and is connected with a radiative forcing of 0.59–0.75 W m−2. Using a model-based airborne fraction of 0.17 of atmospheric CO2, we infer that 125 Pg of carbon need to be released into the atmosphere to produce such a peak. If the abrupt rise in CO2 at the onset of the B/A is unique with respect to other Dansgaard/Oeschger (D/O) events of the last 60 kyr (which seems plausible if not unequivocal based on current observations), then the mechanism responsible for it may also have been unique. Available δ13CO2 data are neutral, whether the source of the carbon is of marine or terrestrial origin. We therefore hypothesise that most of the carbon might have been activated as a consequence of continental shelf flooding during MWP-1A. This potential impact of rapid sea level rise on atmospheric CO2 might define the point of no return during the last deglaciation.

scholarly journals Rapid changes in ice core gas records – Part 1: On the accuracy of methane synchronisation of ice cores

2010 ◽  
Vol 6 (4) ◽  
pp. 1453-1471 ◽  
Author(s):  
P. Köhler
Keyword(s):  
Accumulation Rate ◽  
Ice Core ◽  
Age Distribution ◽  
Ice Cores ◽  
Atmospheric Gases ◽  
Climate Conditions ◽  
Rapid Changes ◽  
Transition Points ◽  
Drilling Site ◽  
Log Normal

Abstract. Methane synchronisation is a concept to align ice core records during rapid climate changes of the Dansgaard/Oeschger (D/O) events onto a common age scale. However, atmospheric gases are recorded in ice cores with a log-normal-shaped age distribution probability density function, whose exact shape depends mainly on the accumulation rate on the drilling site. This age distribution effectively shifts the mid-transition points of rapid changes in CH4 measured in situ in ice by about 58% of the width of the age distribution with respect to the atmospheric signal. A minimum dating uncertainty, or artefact, in the CH4 synchronisation is therefore embedded in the concept itself, which was not accounted for in previous error estimates. This synchronisation artefact between Greenland and Antarctic ice cores is for GRIP and Byrd less than 40 years, well within the dating uncertainty of CH4, and therefore does not calls the overall concept of the bipolar seesaw into question. However, if the EPICA Dome C ice core is aligned via CH4 to NGRIP this synchronisation artefact is in the most recent unified ice core age scale (Lemieux-Dudon et al., 2010) for LGM climate conditions of the order of three centuries and might need consideration in future gas chronologies.

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.

Determining the post-glacial evolution of a northeast Pacific coastal fjord using a multiproxy geochemical approachThis article is one of a series of papers published in this Special Issue on the theme Polar Climate Stability Network.

2008 ◽  
Vol 45 (11) ◽  
pp. 1331-1344 ◽  
Author(s):  
Tara S. Ivanochko ◽  
Stephen E. Calvert ◽  
John R. Southon ◽  
Randolph J. Enkin ◽  
Judith Baker ◽  
...  
Keyword(s):  
High Resolution ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ocean Circulation ◽  
Ice Core ◽  
Coarse Grained ◽  
Last Deglaciation ◽  
Northeast Pacific ◽  
Ice Core Record ◽  
Effingham Inlet

A 40.32 m piston core recovered from Effingham Inlet, on the west coast of Vancouver Island, provides the basis for a high-resolution geochemical study of the last deglaciation and the Holocene. Glacial retreat, basin isolation, sea-level rise, and productivity variations are determined using proxies for sediment composition (K/Al, Fe/Al, Mg/Al), grain size (Ti/Al, Zr/Al), sedimentary redox conditions (Mo/Al, U/Al), and productivity (wt.% organic carbon, wt.% opal). As local ice retreated and marine waters inundated the basin, coarse-grained glacimarine sediments were replaced by finer grained, laminated, opal-rich sediments. During meltwater pulse-1a, the dominance of local crustal rise over eustatic sea-level rise resulted in the progressive restriction of ocean circulation in Effingham Inlet and the formation of a temporary freshwater lake. The transition into stable Holocene conditions was initiated at ∼12 700 BP, which corresponds to the onset of the Younger Dryas, as identified by the Greenland Ice core Project (GRIP) ice core δ18O record and was completed by 10 700 BP, ∼800 years after the GRIP ice core record stabilized. Holocene Mo/Al and U/Al ratios range between 12–35 (×104) and 1–3.4 (×104), respectively, indicating that although large-amplitude, high-frequency fluctuations occur, the sediments of Effingham Inlet inner basin have remained organic rich and oxygen depleted for the entire Holocene period. The combination of anoxic bottom waters and a Holocene sedimentation rate of 217 cm/ka have preserved a high-resolution record of environmental change in the northeast Pacific over the last 11 000 years.

scholarly journals Greenland ice sheet contribution to sea level rise during the last interglacial period: a modelling study driven and constrained by ice core data

2013 ◽  
Vol 9 (1) ◽  
pp. 353-366 ◽  
Author(s):  
A. Quiquet ◽  
C. Ritz ◽  
H. J. Punge ◽  
D. Salas y Mélia
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Interglacial Period ◽  
Last Interglacial ◽  
Intergovernmental Panel ◽  
Orbital Configuration ◽  
Global Sea Level

Abstract. As pointed out by the forth assessment report of the Intergovernmental Panel on Climate Change, IPCC-AR4 (Meehl et al., 2007), the contribution of the two major ice sheets, Antarctica and Greenland, to global sea level rise, is a subject of key importance for the scientific community. By the end of the next century, a 3–5 °C warming is expected in Greenland. Similar temperatures in this region were reached during the last interglacial (LIG) period, 130–115 ka BP, due to a change in orbital configuration rather than to an anthropogenic forcing. Ice core evidence suggests that the Greenland ice sheet (GIS) survived this warm period, but great uncertainties remain about the total Greenland ice reduction during the LIG. Here we perform long-term simulations of the GIS using an improved ice sheet model. Both the methodologies chosen to reconstruct palaeoclimate and to calibrate the model are strongly based on proxy data. We suggest a relatively low contribution to LIG sea level rise from Greenland melting, ranging from 0.7 to 1.5 m of sea level equivalent, contrasting with previous studies. Our results suggest an important contribution of the Antarctic ice sheet to the LIG highstand.

scholarly journals Decadal-scale onset and termination of Antarctic ice-mass loss during the last deglaciation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Michael E. Weber ◽  
Nicholas R. Golledge ◽  
Chris J. Fogwill ◽  
Chris S. M. Turney ◽  
Zoë A. Thomas
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ross Sea ◽  
Ice Sheet ◽  
Rate Of Change ◽  
Last Deglaciation ◽  
Decadal Scale ◽  
Ice Sheet Modeling ◽  
Global Sea Level

AbstractEmerging ice-sheet modeling suggests once initiated, retreat of the Antarctic Ice Sheet (AIS) can continue for centuries. Unfortunately, the short observational record cannot resolve the tipping points, rate of change, and timescale of responses. Iceberg-rafted debris data from Iceberg Alley identify eight retreat phases after the Last Glacial Maximum that each destabilized the AIS within a decade, contributing to global sea-level rise for centuries to a millennium, which subsequently re-stabilized equally rapidly. This dynamic response of the AIS is supported by (i) a West Antarctic blue ice record of ice-elevation drawdown >600 m during three such retreat events related to globally recognized deglacial meltwater pulses, (ii) step-wise retreat up to 400 km across the Ross Sea shelf, (iii) independent ice sheet modeling, and (iv) tipping point analysis. Our findings are consistent with a growing body of evidence suggesting the recent acceleration of AIS mass loss may mark the beginning of a prolonged period of ice sheet retreat and substantial global sea level rise.

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.

Climate Change: What’s the Big Deal?

2019 ◽  
pp. 7-22
Author(s):  
Gilbert E. Metcalf
Keyword(s):  
Climate Change ◽  
Greenhouse Gases ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Core ◽  
Core Samples ◽  
History Of ◽  
The Cost ◽  
Climate Damages

Droughts, floods, soaring temperatures, sea-level rise, and melting ice are just some of the damages brought about by climate change. Chapter 1 details the cost of our failure to cut our emissions, from crop-destroying droughts to devastating floods. It also documents the inexorable build-up of greenhouse gases in the atmosphere as demonstrated by the Keeling curve and observations from Antarctic ice core samples. The chapter then provides a brief history of the science linking the build-up of atmospheric greenhouse gases and climate damages.

scholarly journals New constraints on the gas age-ice age difference along the EPICA ice cores, 0–50 kyr

2007 ◽  
Vol 3 (3) ◽  
pp. 527-540 ◽  
Author(s):  
L. Loulergue ◽  
F. Parrenin ◽  
T. Blunier ◽  
J.-M. Barnola ◽  
R. Spahni ◽  
...  
Keyword(s):  
Ice Core ◽  
Phase Relationship ◽  
Ice Cores ◽  
Climatic Conditions ◽  
Ice Age ◽  
Age Difference ◽  
Last Deglaciation ◽  
Last Glacial Period ◽  
Polar Ice Sheets ◽  
Dronning Maud Land

Abstract. Gas is trapped in polar ice sheets at ~50–120 m below the surface and is therefore younger than the surrounding ice. Firn densification models are used to evaluate this ice age-gas age difference (Δage) in the past. However, such models need to be validated by data, in particular for periods colder than present day on the East Antarctic plateau. Here we bring new constraints to test a firn densification model applied to the EPICA Dome C (EDC) site for the last 50 kyr, by linking the EDC ice core to the EPICA Dronning Maud Land (EDML) ice core, both in the ice phase (using volcanic horizons) and in the gas phase (using rapid methane variations). We also use the structured 10Be peak, occurring 41 kyr before present (BP) and due to the low geomagnetic field associated with the Laschamp event, to experimentally estimate the Δage during this event. Our results seem to reveal an overestimate of the Δage by the firn densification model during the last glacial period at EDC. Tests with different accumulation rates and temperature scenarios do not entirely resolve this discrepancy. Although the exact reasons for the Δage overestimate at the two EPICA sites remain unknown at this stage, we conclude that current densification model simulations have deficits under glacial climatic conditions. Whatever the cause of the Δage overestimate, our finding suggests that the phase relationship between CO2 and EDC temperature previously inferred for the start of the last deglaciation (lag of CO2 by 800±600 yr) seems to be overestimated.

Response of benthic species to post-glacial sea-level rise on the northern Adriatic shelf revealed by stratigraphic unmixing of fossil assemblages

2020 ◽  
Author(s):  
Rafał Nawrot ◽  
Daniele Scarponi ◽  
Adam Tomašových ◽  
Michał Kowalewski
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Age Distribution ◽  
Ecosystem Dynamics ◽  
Time Averaging ◽  
Burial Depth ◽  
Shelf Area ◽  
Benthic Species ◽  
Northern Adriatic ◽  
Fossil Assemblages

&lt;p&gt;Late Quaternary fossil record offers a window into ecosystem dynamics during episodes of abrupt climate warming and sea-level rise following the Last Glacial Maximum, but in marine settings ecological inferences might be hindered by high time-averaging affecting transgressive deposits. However, the signature of temporal shifts in local skeletal production rates may be preserved in the age-frequency distributions (AFDs) of death assemblages. We use carbonate-target radiocarbon ages of 191 shells to examined variation in AFDs among four bivalves species collected from a 2.3-meter-long core recording the post-glacial transgression on the northern Adriatic shelf over the last the last ~14,500 yr.&lt;/p&gt;&lt;p&gt;The scale of time-averaging within species (interquartile age range) varied from 200 to 7,400 yrs, while the between-species age offsets (differences between the median ages of species) ranged from ~2 to 6,400 yrs within 5-cm-thick core intervals. Although the median ages of &lt;em&gt;Varicorbula&lt;/em&gt;, &lt;em&gt;Timoclea&lt;/em&gt; and &lt;em&gt;Parvicardium&lt;/em&gt; increased with increasing burial depth, shells of &lt;em&gt;Lentidium&lt;/em&gt; appeared age-homogeneous throughout the core. Age unmixing revealed a single massive peaks in the abundance of this opportunistic, shoreface species around 14 cal ka BP, coincident with the initial marine flooding of this shelf area during the melt-water pulse 1A. Moreover, a prominent gap in the AFDs between 11 and 12.5 cal ka BP corresponds to a minor sea-level fall associated with the Younger Dryas cold spell. Importantly, the reconstructed onsets and durations of shell production pulses across the four species are consistent with independently-derived relative sea-level history at the site. The species gradually replaced each other through time as the dominant component of the assemblage in accordance with their bathymetric preferences estimated from surveys of the modern Adriatic benthic fauna.&lt;/p&gt;&lt;p&gt;The diachronous production histories of four bivalve species coupled with subsequent exhumation of old shells and burial of younger shells through bioturbation and sediment reworking resulted in the ecologically mixed fossil assemblages. These assemblages are thus characterized by multi-modal age distribution and millennial-scale age offsets between species co-occurring in the same stratigraphic increments. Although this stratigraphic homogenization and disorder greatly limits the resolution of the raw stratigraphic record, our results demonstrate the power of AFDs to capture shifts in abundance of benthic species during recent episodes of rapid sea-level rise. Fossil assemblages from transgressive deposits preserved on continental shelves represent a rich and underutilized source of data on long-term biotic responses to global climate change and associated shifts in sea level.&lt;/p&gt;

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