The Antarctic ice core chronology (AICC2012): an optimized multi-parameter and multi-site dating approach for the last 120 thousand years

Abstract. The deep polar ice cores provide reference records commonly employed in global correlation of past climate events. However, temporal divergences reaching up to several thousand years (ka) exist between ice cores over the last climatic cycle. In this context, we are hereby introducing the Antarctic Ice Core Chronology 2012 (AICC2012), a new and coherent timescale developed for four Antarctic ice cores, namely Vostok, EPICA Dome C (EDC), EPICA Dronning Maud Land (EDML) and Talos Dome (TALDICE), alongside the Greenlandic NGRIP record. The AICC2012 timescale has been constructed using the Bayesian tool Datice (Lemieux-Dudon et al., 2010) that combines glaciological inputs and data constraints, including a wide range of relative and absolute gas and ice stratigraphic markers. We focus here on the last 120 ka, whereas the companion paper by Bazin et al. (2013) focuses on the interval 120–800 ka. Compared to previous timescales, AICC2012 presents an improved timing for the last glacial inception, respecting the glaciological constraints of all analyzed records. Moreover, with the addition of numerous new stratigraphic markers and improved calculation of the lock-in depth (LID) based on δ15N data employed as the Datice background scenario, the AICC2012 presents a slightly improved timing for the bipolar sequence of events over Marine Isotope Stage 3 associated with the seesaw mechanism, with maximum differences of about 600 yr with respect to the previous Datice-derived chronology of Lemieux-Dudon et al. (2010), hereafter denoted LD2010. Our improved scenario confirms the regional differences for the millennial scale variability over the last glacial period: while the EDC isotopic record (events of triangular shape) displays peaks roughly at the same time as the NGRIP abrupt isotopic increases, the EDML isotopic record (events characterized by broader peaks or even extended periods of high isotope values) reached the isotopic maximum several centuries before. It is expected that the future contribution of both other long ice core records and other types of chronological constraints to the Datice tool will lead to further refinements in the ice core chronologies beyond the AICC2012 chronology. For the time being however, we recommend that AICC2012 be used as the preferred chronology for the Vostok, EDC, EDML and TALDICE ice core records, both over the last glacial cycle (this study), and beyond (following Bazin et al., 2013). The ages for NGRIP in AICC2012 are virtually identical to those of GICC05 for the last 60.2 ka, whereas the ages beyond are independent of those in GICC05modelext (as in the construction of AICC2012, the GICC05modelext was included only via the background scenarios and not as age markers). As such, where issues of phasing between Antarctic records included in AICC2012 and NGRIP are involved, the NGRIP ages in AICC2012 should therefore be taken to avoid introducing false offsets. However for issues involving only Greenland ice cores, there is not yet a strong basis to recommend superseding GICC05modelext as the recommended age scale for Greenland ice cores.

Download Full-text

Bipolar volcanic synchronization of abrupt climate change in Greenland and Antarctic ice cores during the last glacial period

Climate of the Past ◽

10.5194/cp-16-1565-2020 ◽

2020 ◽

Vol 16 (4) ◽

pp. 1565-1580

Author(s):

Anders Svensson ◽

Dorthe Dahl-Jensen ◽

Jørgen Peder Steffensen ◽

Thomas Blunier ◽

Sune O. Rasmussen ◽

...

Keyword(s):

Ice Core ◽

Ice Cores ◽

Volcanic Eruptions ◽

Abrupt Climate Change ◽

Glacial Period ◽

Deuterium Excess ◽

Last Glacial Period ◽

Last Glacial ◽

The Antarctic ◽

The Last Glacial

Abstract. The last glacial period is characterized by a number of millennial climate events that have been identified in both Greenland and Antarctic ice cores and that are abrupt in Greenland climate records. The mechanisms governing this climate variability remain a puzzle that requires a precise synchronization of ice cores from the two hemispheres to be resolved. Previously, Greenland and Antarctic ice cores have been synchronized primarily via their common records of gas concentrations or isotopes from the trapped air and via cosmogenic isotopes measured on the ice. In this work, we apply ice core volcanic proxies and annual layer counting to identify large volcanic eruptions that have left a signature in both Greenland and Antarctica. Generally, no tephra is associated with those eruptions in the ice cores, so the source of the eruptions cannot be identified. Instead, we identify and match sequences of volcanic eruptions with bipolar distribution of sulfate, i.e. unique patterns of volcanic events separated by the same number of years at the two poles. Using this approach, we pinpoint 82 large bipolar volcanic eruptions throughout the second half of the last glacial period (12–60 ka). This improved ice core synchronization is applied to determine the bipolar phasing of abrupt climate change events at decadal-scale precision. In response to Greenland abrupt climatic transitions, we find a response in the Antarctic water isotope signals (δ18O and deuterium excess) that is both more immediate and more abrupt than that found with previous gas-based interpolar synchronizations, providing additional support for our volcanic framework. On average, the Antarctic bipolar seesaw climate response lags the midpoint of Greenland abrupt δ18O transitions by 122±24 years. The time difference between Antarctic signals in deuterium excess and δ18O, which likewise informs the time needed to propagate the signal as described by the theory of the bipolar seesaw but is less sensitive to synchronization errors, suggests an Antarctic δ18O lag behind Greenland of 152±37 years. These estimates are shorter than the 200 years suggested by earlier gas-based synchronizations. As before, we find variations in the timing and duration between the response at different sites and for different events suggesting an interaction of oceanic and atmospheric teleconnection patterns as well as internal climate variability.

Download Full-text

Aluminium and iron record for the last 28 kyr derived from the Antarctic EDC96 ice core using new CFA methods

Annals of Glaciology ◽

10.3189/172756404781814438 ◽

2004 ◽

Vol 39 ◽

pp. 300-306 ◽

Cited By ~ 11

Author(s):

Rita Traversi ◽

Carlo Barbante ◽

Vania Gaspari ◽

Ilaria Fattori ◽

Ombretta Largiuni ◽

...

Keyword(s):

Inductively Coupled Plasma ◽

Fine Particles ◽

Ice Core ◽

Flow Analysis ◽

High Sensitivity ◽

Glacial Period ◽

Last Glacial ◽

Al Content ◽

The Antarctic ◽

The Last Glacial

AbstractSpectrofluorimetric and spectrophotometric continuous flow analysis (CFA) methods were developed and applied to the determination of aluminium and iron in EPICA Dome C (East Antarctica) ice-core samples (6–585m depth). The methods are able to measure the fraction of Al and Fe which can be detected once the sample is filtered on a 5.0 μm membrane and acidified to pH 2. Both the methods present high sensitivity (detection limit of 10 ng L–1 for Al and 50 ng L–1 for Fe) and reproducibility (5% at sub-ppb level). The Fe and Al profiles show sharp decreases in concentrations in the last glacial/interglacial transition, reflecting the decreasing dust aerosol load. The two elements show a different pattern during the Antarctic Cold Reversal (ACR) climatic change, with high iron concentrations (similar to the glacial period) and low but increasing Al content during the ACR minimum. In order to interpret the Al and Fe data obtained by CFA, a comparison with Al and Fe composition, as measured by inductively coupled plasma sector field mass spectrometry (ICP-SFMS), was performed for Holocene, ACR and glacial periods. The percentage of CFA-Al with respect to ICP-SFMS-Al in the three periods shows a lower variability than CFA-Fe (3% in the glacial period and 64% in the ACR). This pattern may be explained by the different dominant iron sources in the different climatic periods. During the Last Glacial Maximum, Fe is proposed to arise mainly from insoluble continental dust, while a variety of ocean-recycled Fe, mainly distributed in fine particles and as more soluble species, shows a higher contribution in the ACR and, to a lesser extent, in the Holocene.

Download Full-text

Vostok, Antarctica, Ice Core: The Dust Record Over The Last Climatic Cycle (∼160 ka) (Abstract)

Annals of Glaciology ◽

10.3189/s0260305500006625 ◽

1988 ◽

Vol 11 ◽

pp. 204-204

Author(s):

L. Mounier ◽

J. R. Petit ◽

J. Jouzel ◽

C. Lorius ◽

Ye. S. Korotkevich ◽

...

Keyword(s):

Total Concentration ◽

Ice Core ◽

Ice Cores ◽

Optical Microscope ◽

Ice Age ◽

Maximum Temperature ◽

Temperature Changes ◽

Last Glacial ◽

Chemical Measurements ◽

The Last Glacial

The 2083 m Vostok Antarctic ice core provides a unique opportunity for access to many paleoclimatic and paleo-environmental proxy data. This core, which has been dated by using a glaciological model, fully covers the last glacial-interglacial cycle, and goes back to the ice age which preceded the last interglaciai (−160 ka B P ).A continuous deuterium record is now available and we have interpreted it in terms of local temperature changes. This record is dominated by the large 100 ka glacial-inter-glacial oscillation, with a maximum temperature amplitude of about 11°C; the long Last Glacial period is very well documented and it is confirmed that the warmest part of the Last Interglaciai period was about 2°C warmer than the Holocene. Comparison with the ice-volume marine record shows that the Vostok climate record is of relatively large geographical significance, which makes it possible to establish, over the last 160 ka, the link between worldwide climatic changes and the Vostok dust record that we present here.This dust content corresponds to the non-soluble microparticles. It was obtained on a discontinuous basis (1 sample = about ∼10 m). Due to the very low concentration of some samples (down to 20 x 10−9gg−1) and cracks in the ice from the first 1000 m depth, we used stringent decontamination procedures. Size distribution and total concentration were measured, using a Coulter counter and an optical microscope; the results were tested against chemical measurements (aluminium concentration). In previous studies, it has been shown that the main proportion of insoluble microparticles is of terrigenous origin and represents the small-sized (radius <2 μm) dust produced on the continents.The Vostok record displays an increase in dust concentration of up to 20 times during the coldest climatic periods, coupled with the presence of larger particles. It confirms, on a much longer time-scale, a characteristic previously noted in Antarctic and Greenland ice cores over the Last Glacial Maximum. This large increase is attributed to a greater areal extent of global tropical aridity during the cold periods, coupled with higher efficiency of atmospheric circulation in respect of dust production and transport. Beyond this, the relationship between the dust input and the successive stages during the Last Glacial is now very well documented and will be discussed with a view to correlating the Vostok climatic record with other marine and terrestrial paleodata.

Download Full-text

Millennial and sub-millennial scale climatic variations recorded in polar ice cores over the last glacial period

Climate of the Past Discussions ◽

10.5194/cpd-6-135-2010 ◽

2010 ◽

Vol 6 (1) ◽

pp. 135-183 ◽

Cited By ~ 6

Author(s):

E. Capron ◽

A. Landais ◽

J. Chappellaz ◽

A. Schilt ◽

D. Buiron ◽

...

Keyword(s):

Climatic Variability ◽

Ice Sheets ◽

Ice Cores ◽

Glacial Period ◽

Last Glacial Period ◽

Last Glacial ◽

Dronning Maud Land ◽

Mis 5 ◽

The Last Glacial ◽

Millennial Scale

Abstract. Since its discovery in Greenland ice cores, the millennial scale climatic variability of the last glacial period has been increasingly documented at all latitudes with studies focusing mainly on Marine Isotopic Stage 3 (MIS 3; 28–60 thousand of years before present, hereafter ka) and characterized by short Dansgaard-Oeschger (DO) events. Recent and new results obtained on the EPICA and NorthGRIP ice cores now precisely describe the rapid variations of Antarctic and Greenland temperature during MIS 5 (73.5–123 ka), a time period corresponding to relatively high sea level. The results display a succession of long DO events enabling us to highlight a sub-millennial scale climatic variability depicted by i) short-lived and abrupt warming events preceding some Greenland InterStadial (GIS) (precursor-type events) and ii) abrupt warming events at the end of some GIS (rebound-type events). The occurrence of these secondary events is suggested to be driven by the Northern Hemisphere summertime insolation at 65° N together with the internal forcing of ice sheets. Thanks to a recent NorthGRIP-EPICA Dronning Maud Land (EDML) common timescale over MIS 5, the bipolar sequence of climatic events can be established at millennial to sub-millennial timescale. This provides evidence that a linear relationship is not satisfactory in explaining the link between Antarctic warming amplitudes and the duration of their concurrent Greenland Stadial (GS) for the entire glacial period. The conceptual model for a thermal bipolar seesaw permits a reconstruction of the Antarctic response to the northern millennial and sub-millennial scale variability over MIS 5. However, we show that when ice sheets are extensive, Antarctica does not necessarily warm during the whole GS as the thermal bipolar seesaw model would predict.

Download Full-text

NALPS19: Sub-orbital scale climate variability recorded in Northern Alpine speleothems during the last glacial period

10.5194/cp-2019-44 ◽

2019 ◽

Cited By ~ 1

Author(s):

Gina E. Moseley ◽

Christoph Spötl ◽

Susanne Brandstätter ◽

Tobias Erhardt ◽

Marc Luetscher ◽

...

Keyword(s):

Climate Variability ◽

Asian Monsoon ◽

Ice Core ◽

Ice Cores ◽

High Elevation ◽

Glacial Period ◽

Last Glacial Period ◽

Last Glacial ◽

Change State ◽

The Last Glacial

Abstract. Sub-orbital-scale climate variability of the last glacial period provides important insights into the rates that the climate can change state, the mechanisms that drive that change, and the leads, lags and synchronicity occurring across different climate zones. Such short-term climate variability has previously been investigated using speleothems from the northern rim of the Alps (NALPS), enabling direct chronological comparisons with highly similar shifts in Greenland ice cores. In this study, we present NALPS19, which includes a revision of the last glacial NALPS δ18O chronology over the interval 118.3 to 63.7 ka using eleven,newly-available, clean, precisely-dated stalagmites from five caves. Using only the most reliable and precisely dated records, this period is now 90 % complete and is comprised of 15 stalagmites from seven caves. Where speleothems grew synchronously, major transitional events between stadials and interstadials (and vice versa) are all in agreement within uncertainty. Ramp-fitting analysis further reveals good agreement between the NALPS19 speleothem δ18O record, the GICC05modelext NGRIP ice-core δ18O record, and the Asian Monsoon composite speleothem δ18O record. In contrast, NGRIP ice-core δ18O on AICC2012 appears to be considerably too young. We also propose a longer duration for the interval covering Greenland Stadial (GS) 22 to GS-21.2 in line with the Asian monsoon and NGRIP-EDML. Given the near-complete record of δ18O variability during the last glacial period in the northern Alps, we offer preliminary considerations regarding the controls on mean δ18O. We find that as expected, δ18O values became increasingly more depleted with distance from the oceanic source regions, and increasingly depleted with increasing altitude. Exceptions were found for some high-elevation sites that locally display δ18O values that are too high in comparison to lower-elevation sites, thus indicating a summer bias in the recorded signal. Finally, we propose a new mechanism for the centennial-scale stadial-level depletions in δ18O such as "pre-cursor" events GS-16.2, GS-17.2, GS-21.2, and GS-23.2, as well as the "within-interstadial" GS-24.2 event. Our new high-precision chronology shows that each of these δ18O depletions occurred shortly following rapid rises in sea level associated with increased ice-rafted debris and southward shifts in the Intertropical Convergence Zone, suggesting that influxes of meltwater from moderately-sized ice sheets may have been responsible for the cold reversals causing the AMOC to slow down similar to the Preboreal Oscillation and Older Dryas deglacial events.

Download Full-text

Ocean circulation, ice shelf, and sea ice interactions explain Dansgaard–Oeschger cycles

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1802573115 ◽

2018 ◽

Vol 115 (47) ◽

pp. E11005-E11014 ◽

Cited By ~ 14

Author(s):

Niklas Boers ◽

Michael Ghil ◽

Denis-Didier Rousseau

Keyword(s):

Sea Ice ◽

Ocean Circulation ◽

Waiting Times ◽

Ice Core ◽

Ice Cores ◽

Isotope Ratios ◽

Subsurface Water ◽

Unified Framework ◽

Last Glacial ◽

The Last Glacial

The last glacial interval experienced abrupt climatic changes called Dansgaard–Oeschger (DO) events. These events manifest themselves as rapid increases followed by slow decreases of oxygen isotope ratios in Greenland ice core records. Despite promising advances, a comprehensive theory of the DO cycles, with their repeated ups and downs of isotope ratios, is still lacking. Here, based on earlier hypotheses, we introduce a dynamical model that explains the DO variability by rapid retreat and slow regrowth of thick ice shelves and thin sea ice in conjunction with changing subsurface water temperatures due to insulation by the ice cover. Our model successfully reproduces observed features of the records, such as the sawtooth shape of the DO cycles, waiting times between DO events across the last glacial, and the shifted antiphase relationship between Greenland and Antarctic ice cores. Our results show that these features can be obtained via internal feedbacks alone. Warming subsurface waters could have also contributed to the triggering of Heinrich events. Our model thus offers a unified framework for explaining major features of multimillennial climate variability during glacial intervals.

Download Full-text

The Origin and Propagation of the Antarctic Centennial Oscillation

Climate ◽

10.3390/cli7090112 ◽

2019 ◽

Vol 7 (9) ◽

pp. 112 ◽

Cited By ~ 2

Author(s):

W. Jackson Davis ◽

Peter J. Taylor ◽

W. Barton Davis

Keyword(s):

Surface Wind ◽

Geographic Origin ◽

Ice Cores ◽

Temperature Cycle ◽

Cycle Period ◽

Last Glacial ◽

Time Periods ◽

Major Cycle ◽

The Antarctic ◽

The Last Glacial

The Antarctic Centennial Oscillation (ACO) is a paleoclimate temperature cycle that originates in the Southern Hemisphere, is the presumptive evolutionary precursor of the contemporary Antarctic Oscillation (AAO), and teleconnects to the Northern Hemisphere to influence global temperature. In this study we investigate the internal climate dynamics of the ACO over the last 21 millennia using stable water isotopes frozen in ice cores from 11 Antarctic drill sites as temperature proxies. Spectral and time series analyses reveal that ACOs occurred at all 11 sites over all time periods evaluated, suggesting that the ACO encompasses all of Antarctica. From the Last Glacial Maximum through the Last Glacial Termination (LGT), ACO cycles propagated on a multicentennial time scale from the East Antarctic coastline clockwise around Antarctica in the streamline of the Antarctic Circumpolar Current (ACC). The velocity of teleconnection (VT) is correlated with the geophysical characteristics of drill sites, including distance from the ocean and temperature. During the LGT, the VT to coastal sites doubled while the VT to inland sites decreased fourfold, correlated with increasing solar insolation at 65°N. These results implicate two interdependent mechanisms of teleconnection, oceanic and atmospheric, and suggest possible physical mechanisms for each. During the warmer Holocene, ACOs arrived synchronously at all drill sites examined, suggesting that the VT increased with temperature. Backward extrapolation of ACO propagation direction and velocity places its estimated geographic origin in the Southern Ocean east of Antarctica, in the region of the strongest sustained surface wind stress over any body of ocean water on Earth. ACO period is correlated with all major cycle parameters except cycle symmetry, consistent with a forced, undamped oscillation in which the driving energy affects all major cycle metrics. Cycle period and symmetry are not discernibly different for the ACO and AAO over the same time periods, suggesting that they are the same climate cycle. We postulate that the ACO/AAO is generated by relaxation oscillation of Westerly Wind velocity forced by the equator-to-pole temperature gradient and propagated regionally by identified air-sea-ice interactions.

Download Full-text

Millennial and sub-millennial scale climatic variations recorded in polar ice cores over the last glacial period

Climate of the Past ◽

10.5194/cp-6-345-2010 ◽

2010 ◽

Vol 6 (3) ◽

pp. 345-365 ◽

Cited By ~ 113

Author(s):

E. Capron ◽

A. Landais ◽

J. Chappellaz ◽

A. Schilt ◽

D. Buiron ◽

...

Keyword(s):

Climatic Variability ◽

Ice Core ◽

Ice Sheets ◽

Ice Cores ◽

Glacial Period ◽

Last Glacial Period ◽

Last Glacial ◽

Mis 5 ◽

The Last Glacial ◽

Millennial Scale

Abstract. Since its discovery in Greenland ice cores, the millennial scale climatic variability of the last glacial period has been increasingly documented at all latitudes with studies focusing mainly on Marine Isotopic Stage 3 (MIS 3; 28–60 thousand of years before present, hereafter ka) and characterized by short Dansgaard-Oeschger (DO) events. Recent and new results obtained on the EPICA and NorthGRIP ice cores now precisely describe the rapid variations of Antarctic and Greenland temperature during MIS 5 (73.5–123 ka), a time period corresponding to relatively high sea level. The results display a succession of abrupt events associated with long Greenland InterStadial phases (GIS) enabling us to highlight a sub-millennial scale climatic variability depicted by (i) short-lived and abrupt warming events preceding some GIS (precursor-type events) and (ii) abrupt warming events at the end of some GIS (rebound-type events). The occurrence of these sub-millennial scale events is suggested to be driven by the insolation at high northern latitudes together with the internal forcing of ice sheets. Thanks to a recent NorthGRIP-EPICA Dronning Maud Land (EDML) common timescale over MIS 5, the bipolar sequence of climatic events can be established at millennial to sub-millennial timescale. This shows that for extraordinary long stadial durations the accompanying Antarctic warming amplitude cannot be described by a simple linear relationship between the two as expected from the bipolar seesaw concept. We also show that when ice sheets are extensive, Antarctica does not necessarily warm during the whole GS as the thermal bipolar seesaw model would predict, questioning the Greenland ice core temperature records as a proxy for AMOC changes throughout the glacial period.

Download Full-text

Potential analysis reveals changing number of climate states during the last 60 kyr

Climate of the Past Discussions ◽

10.5194/cpd-5-2223-2009 ◽

2009 ◽

Vol 5 (5) ◽

pp. 2223-2237 ◽

Cited By ~ 1

Author(s):

V. N. Livina ◽

F. Kwasniok ◽

T. M. Lenton

Keyword(s):

Time Series ◽

Ice Core ◽

Polynomial Potential ◽

Potential Wells ◽

Potential Analysis ◽

Last Glacial ◽

Proxy Records ◽

Time Series Estimation ◽

Wide Range ◽

The Last Glacial

Abstract. We develop and apply a new statistical method of potential analysis for detecting the number of states of a geophysical system, from its recorded time series. Estimation of the degree of a polynomial potential allows us to derive the number of potential wells in a system. The method correctly detects changes in the number of wells in artificial data. In ice-core proxy records of Greenland paleotemperature, a reduction in the number of climate states from two to one is detected sometime prior to the last glacial maximum (LGM), 23–19 kyr BP. This bifurcation can be interpreted as loss of stability of the warm interstadial state of the Dansgaard-Oeschger events. In data spanning the last glacial termination, up to four climate states are detected, plausibly representing the LGM, Bolling-Allerod, Younger Dryas, and the Holocene. The proposed method can be applied to a wide range of geophysical time series exhibiting bifurcations.

Download Full-text