Nancy A. N. Bertler

GNS Science

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Paul A. Mayewski

University of Maine

Peter D. Neff

University of Minnesota System

Paul Vallelonga

University of Copenhagen

Rebecca L. Pyne

Victoria University of Wellington

Robert M. McKay

Victoria University of Wellington

Elizabeth D. Keller

GNS Science

T. Naish

Victoria University of Wellington

Nicholas R. Golledge

Victoria University of Wellington

B. Daniel Emanuelsson

British Antarctic Survey

Thomas Blunier

University of Copenhagen

Cooperative Institutions

British Antarctic Survey

Centre National de la Recherche Scientifique

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

Victoria University of Wellington

University of Copenhagen

Natural Environment Research Council

GNS Science

University of Tasmania

University of Maine

University of Bern

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Nature Comment Six priorities for Antarctic science & Supplementary information

Mahlon C. Kennicutt Steven L. Chown John J. Cassano Daniela Liggett RA Massom

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Comment on essd-2022-368

Elizabeth R. Thomas Diana Vladimirova Dieter Tetzner B. Daniel Emanuelsson Nathan Chellman

Abstract. Changes in sea ice conditions and atmospheric circulation over the Southern Ocean play an important role in modulating Antarctic climate. However, observations of both sea ice and wind conditions are limited in Antarctica and the Southern Ocean, both temporally and spatially. Ice core chemistry data can be used to reconstruct changes over annual, decadal, and millennial timescales. To facilitate sea ice and wind reconstructions, the CLIVASH2k working group has compiled a database of two species, sodium [Na⁺] and sulphate [SO₄^2-], commonly measured ionic species. The database contains records from 105 Antarctic ice cores, containing records with a maximum age duration of 2000 years. An initial filter has been applied, based on evaluation against climate observations, to identify sites suitable for reconstructing past sea ice conditions, wind strength, or atmospheric circulation.

Ice core

10.5194/essd-2022-368-rc2

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The new Kr-86 excess ice core proxy for synoptic activity: West Antarctic storminess possibly linked to ITCZ movement through the last deglaciation

Christo Buizert Sarah Shackleton Jeffrey P. Severinghaus William H. G. Roberts Alan Seltzer

Abstract. Here we present a newly developed ice core gas-phase proxy that directly samples a component of the large-scale atmospheric circulation: synoptic-scale pressure variability. Surface pressure variability weakly disrupts gravitational isotopic settling in the firn layer, which is recorded in krypton-86 excess (86Krxs). We validate 86Krxs using late Holocene ice samples from eleven Antarctic and one Greenland ice core that collectively represent a wide range of surface pressure variability in the modern climate. We find a strong correlation (r = -0.94, p < 0.01) between site-average 86Krxs and site synoptic variability from reanalysis data. The main uncertainties in the method are the corrections for gas loss and thermal fractionation, and the relatively large scatter in the data. We show 86Krxs is linked to the position of the eddy-driven subpolar jet (SPJ), with a southern position enhancing pressure variability. We present a 86Krxs record covering the last 24 ka from the WAIS Divide ice core. West Antarctic synoptic activity is slightly below modern levels during the last glacial maximum (LGM); increases during the Heinrich Stadial 1 and Younger Dryas North Atlantic cold periods; weakens abruptly at the Holocene onset; remains low during the early and mid-Holocene, and gradually increases to its modern value. The WAIS Divide 86Krxs record resembles records of monsoon intensity thought to reflect changes in the meridional position of the intertropical convergence zone (ITCZ) on orbital and millennial timescales, such that West Antarctic storminess is weaker when the ITCZ is displaced northward, and stronger when it is displaced southward. We interpret variations in synoptic activity as reflecting movement of the South Pacific SPJ in parallel to the ITCZ migrations, which is the expected zonal-mean response of the eddy-driven jet in models and proxy data. Past changes to Pacific climate and the El Niño Southern Oscillation (ENSO) may amplify the signal of the SPJ migration. Our interpretation is broadly consistent with opal flux records from the Pacific Antarctic zone thought to reflect wind-driven upwelling. We emphasize that 86Krxs is a new proxy, and more work is called for to confirm, replicate and better understand these results; until such time, our conclusions regarding past atmospheric dynamics remain tentative. Current scientific understanding of firn air transport and trapping is insufficient to explain all the observed variations in 86Krxs.

Intertropical Convergence Zone

Ice core

Deglaciation

10.5194/cp-2022-65

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Sea ice variability and primary productivity in the Ross Sea, Antarctica, from methylsulphonate snow record

Geophysical Research Letters (2009)

Rachael H. Rhodes Nancy A. N. Bertler Joel A. Baker Sharon B. Sneed Hans Oerter

The Ross Sea contains the most biologically productive continental shelf in Antarctica and is a region where the annual formation of sea ice drives substantial amounts of bottom water formation. We present snow pit chemistry data from Mt Erebus Saddle that provide a quantitative proxy to reconstruct summer sea ice conditions and rates of marine primary production. The methylsulphonate (MS) record is strongly correlated with changes in the area of open water (R 2 = 0.903, p < 0.05) caused by differences in atmospheric circulation and the sea‐ice‐damming effect of large icebergs, B‐15 and C‐19, which calved from the Ross Ice Shelf in 2000 and 2002 respectively. Furthermore, MS and phytoplankton net primary production correlate significantly (R 2 = 0.927, p < 0.01). Our results demonstrate the potential of the Mt Erebus Saddle ice core to reconstruct sea ice and primary productivity variability in the Ross Sea beyond the observational record.

Iceberg

Ice core

10.1029/2009gl037311

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Extreme snow metamorphism in the Allan Hills, Antarctica, as an analogue for glacial conditions with implications for stable isotope composition

Journal of Glaciology (2015)

Ruzica Dadić Martin Schneebeli Nancy A. N. Bertler Margit Schwikowski Margret Matzl

Abstract Understanding physical processes in near-zero accumulation areas can help us to better understand polar ice-core records, particularly during periods when accumulation rates were lower than today. We report measurements from a 5 m firn core from the Allan Hills, Antarctica, which include physical properties using computer tomography, stable isotope ratios δD and δ 18 O, and 210 Pb activity. The core shows a highly metamorphosed firn with homogeneous and stable structure, but with discrete layers near the surface. The observed firn structure is caused by a combination of unique depositional and post-depositional processes. The irregular δD and δ 18 O signal does not follow the stratigraphic sequence and implies post-depositional modification caused by microscopic pressure gradients in the firn that can result from either forced ventilation over rough surfaces in the presence of wind or alternating temperature-gradients between the firn and the atmosphere. Our results also indicate impact snow deposition under high winds and with a high initial density and air exchange between the atmosphere and the snowpack. 210 Pb activity below 0.3 m falls below the detection limit, implying that most of the core is more than 100 years old. We conclude that the Allan Hills record provides a unique opportunity to investigate important processes that would have affected ice-core records from glacial periods.

Firn

Ice core

Deposition

Dome (geology)

Accumulation zone

10.3189/2015jog15j027

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Citations (44)

Extreme metamorphism in a firn core from the Allan Hills, Antarctica, as an analogue for glacial conditions

EGU General Assembly Conference Abstracts (2015)

Ruzica Dadić Martin Schneebeli Nancy A. N. Bertler Margit Schwikowski Margret Matzl

Firn

Ice core

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Calculating uncertainty for the RICE ice core continuous flow analysis water isotope record

Atmospheric measurement techniques (2018)

Elizabeth D. Keller W. T. Baisden Nancy A. N. Bertler B. Daniel Emanuelsson Silvia Canessa

Abstract. We describe a systematic approach to the calibration and uncertainty estimation of a high-resolution continuous flow analysis (CFA) water isotope (δ2H, δ18O) record from the Roosevelt Island Climate Evolution (RICE) Antarctic ice core. Our method establishes robust uncertainty estimates for CFA δ2H and δ18O measurements, comparable to those reported for discrete sample δ2H and δ18O analysis. Data were calibrated using a time-weighted two-point linear calibration with two standards measured both before and after continuously melting 3 or 4 m of ice core. The error at each data point was calculated as the quadrature sum of three factors: Allan variance error, scatter over our averaging interval (error of the variance) and calibration error (error of the mean). Final mean total uncertainty for the entire record is δ2H=0.74 ‰ and δ18O=0.21 ‰. Uncertainties vary through the data set and were exacerbated by a range of factors, which typically could not be isolated due to the requirements of the multi-instrument CFA campaign. These factors likely occurred in combination and included ice quality, ice breaks, upstream equipment failure, contamination with drill fluid and leaks or valve degradation. We demonstrate that our methodology for documenting uncertainty was effective across periods of uneven system performance and delivered a significant achievement in the precision of high-resolution CFA water isotope measurements.

Ice core

δ18O

10.5194/amt-11-4725-2018

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Citations (7)

Deuterium isotope ratios of Victoria Lower Glacier Ice Core

Nancy A. N. Bertler Paul A. Mayewski Lionel Carter

Ice core

10.1594/pangaea.866368

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Citations (1)

Retreat of the Antarctic Ice Sheet during the Last Interglaciation and implications for future change

Nicholas R. Golledge Peter U. Clark Feng He Andrea Dutton Chris Turney

Earth and Space Science Open Archive This work has been accepted for publication in Geophysical Research Letters. Version of RecordESSOAr is a venue for early communication or feedback before peer review. Data may be preliminary. Learn more about preprints. preprintOpen AccessYou are viewing the latest version by default [v2]Retreat of the Antarctic Ice Sheet during the Last Interglaciation and implications for future changeAuthorsNicholas R.GolledgeiDPeter UClarkFengHeiDAndreaDuttonChrisTurneyChrisFogwillTimNaishiDRichard H.LevyiDRobert MurrayMcKayiDDaniel PLowryiDNancy A.N.BertlerGavin BDunbarAnders E.CarlsonSee all authors Nicholas R. GolledgeiDCorresponding Author• Submitting AuthorVictoria University of WellingtoniDhttps://orcid.org/0000-0001-7676-8970view email addressThe email was not providedcopy email addressPeter U ClarkOregon State Universityview email addressThe email was not providedcopy email addressFeng HeiDUniversity of Wisconsin-MadisoniDhttps://orcid.org/0000-0002-3355-6406view email addressThe email was not providedcopy email addressAndrea DuttonUniversity of Floridaview email addressThe email was not providedcopy email addressChris TurneyUniversity of New South Walesview email addressThe email was not providedcopy email addressChris FogwillKeele Universityview email addressThe email was not providedcopy email addressTim NaishiDAntarctic Research Centre, Victoria Univ. of WellingtoniDhttps://orcid.org/0000-0002-1185-9932view email addressThe email was not providedcopy email addressRichard H. LevyiDGeological and Nuclear Sciences - Te Pu AoiDhttps://orcid.org/0000-0002-8783-0167view email addressThe email was not providedcopy email addressRobert Murray McKayiDVictoria University of WellingtoniDhttps://orcid.org/0000-0002-5602-6985view email addressThe email was not providedcopy email addressDaniel P LowryiDGNS ScienceiDhttps://orcid.org/0000-0002-9668-0850view email addressThe email was not providedcopy email addressNancy A.N. BertlerVictoria University of Wellingtonview email addressThe email was not providedcopy email addressGavin B DunbarVictoria University of Wellingtonview email addressThe email was not providedcopy email addressAnders E. CarlsonOregon Glaciers Instituteview email addressThe email was not providedcopy email address

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10.1002/essoar.10504661.2

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Antarctic evidence for an abrupt northward shift of the Southern Hemisphere westerlies at 32 ka BP-Dataset

Figshare (2023)

Abhijith U. Venugopal Nancy A. N. Bertler James E. Lee Rebecca L. Pyne

RICE glacial data

Westerlies

10.6084/m9.figshare.23435966

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Citations (1)