Metadata record for data from ASAC Project 2534 See the link below for public details on this project. The Holocene sea-ice project brings together for the first time, records from the Antarctic continent and deep sea sediments that will allow us to calibrate three sea-ice extent surrogates, validate their use in contrast to satellite observations and explore climatic influence on the physio-ecological environment over the last 10,000 years. Taken from the 2004-2005 Progress Report: Progress Objectives: Our objective is to instigate synthesis between deep sea and continental ice core records of Antarctic sea ice variability over the Holocene (last 10,000 yrs BP). The relevance of this novel evaluation is three-fold: - To appraise for the first time the relationships between proxy sea ice predictions beyond the instrumental record from the land and sea. - To assess variability differences and similarities from the various records that can then be used to probe the dynamics of the climate/environmental system in the East Antarctic sector. - To provide insights on the ecological response sea ice plays through the Holocene. Public summary of the season progress: Basic analysis of samples from Core E27-23 have been complete except for seven new samples from near the top of the core. This includes counts of diatoms, foraminifera, ice-rafted debris, volcanic glass. A greater variety of parameters is available than expected. Dramatic downhole changes represent oceanographic changes over last 25 000 years at the site including in evidence for carbonate dissolution and water temperature. Now needs statistical analysis of diatom data, extra radiocarbon dates and integration with data from Law Dome ice-core.

Reconstructed sea spray and minerogenic data for a 12,000 year lake sediment record from Emerald Lake, Macquarie Island. Proxies are based on biological (diatoms) and geochemical (micro x-ray fluorescence and hyperspectral imaging) indicators. Data correspond to the figures in: Saunders et al. 2018 Holocene dynamics of the Southern Hemisphere westerly winds and possible links to CO2 outgassing. Nature Geoscience 11:650-655. doi.org/10.1038/s41561-018-0186-5. Detailed supplementary information: https://static-content.springer.com/esm/art%3A10.1038%2Fs41561-018-0186-5/MediaObjects/41561_2018_186_MOESM1_ESM.pdf Abstract: The Southern Hemisphere westerly winds (SHW) play an important role in regulating the capacity of the Southern Ocean carbon sink. They modulate upwelling of carbon-rich deep water and, with sea ice, determine the ocean surface area available for air–sea gas exchange. Some models indicate that the current strengthening and poleward shift of these winds will weaken the carbon sink. If correct, centennial- to millennial-scale reconstructions of the SHW intensity should be linked with past changes in atmospheric CO2, temperature and sea ice. Here we present a 12,300-year reconstruction of wind strength based on three independent proxies that track inputs of sea-salt aerosols and minerogenic particles accumulating in lake sediments on sub-Antarctic Macquarie Island. Between about 12.1 thousand years ago (ka) and 11.2 ka, and since about 7 ka, the wind intensities were above their long-term mean and corresponded with increasing atmospheric CO2. Conversely, from about 11.2 to 7.2 ka, the wind intensities were below their long-term mean and corresponded with decreasing atmospheric CO2. These observations are consistent with model inferences of enhanced SHW contributing to the long-term outgassing of CO2 from the Southern Ocean.

Ice-rafted debris is characterised by coarse material with typically angular grains, transported within icebergs and deposted in the ocean as the icebergs melt. This iceberg rafted debris (IBRD) flux data submitted here, was calculated by quantifying the coarse sand fraction (CSF) as a percentage of the bulk sample (weight of grains in the 250 micron to 2 mm size fraction), the dry bulk density (DBD) and the linear sedimentation rate (LSR) (following Krissek et al., 1995, Patterson et al., 2014). A method for quantifying the IBRD flux uses the coarse sand fraction (CSF) as a percentage of the bulk sample, dry bulk density (DBD) and the linear sedimentation rate (LSR) (Krissek et al., 1995, Patterson et al., 2014): The CSF (250μm-2mm) was acquired from samples at 10cm intervals along KC14 by wet-sieving approximately 20g of sediment per sample. Authigenic grains and microfossils were removed from the samples under a microscope. The remaining material was weighed on a microbalance and calculated as a percentage of the bulk sample. The DBD was calculated by subsampling approximately 8cm3 of sediment from the same depth intervals and dividing the dry weight of the sediment by the volume of the subsampler. The LSR was approximated by dividing the distance (cm) between the calibrated bulk carbon ages by the difference in time (kyr). The IBRD flux was then quantified using the above equation for each depth interval.

The sedimentological, chemical and isotopic characteristics of sediment cores from three slightly saline to hypersaline lakes (Highway, Ace and Organic Lakes) and two marine inlets (Ellis Fjord and Taynaya Bay) in the Vestfold Hills, Antarctica have been examined. Sections of the cores deposited in marine environments are characterised by uniform, regularly laminated, fine grained, organic-rich sediments, with uniform organic delta 13C values (-18.0 to 19.4 ppt vs. PDB) and sulfur contents. In contrast, sediments deposited in lacustrine environments are extremely heterogeneous, varying from finely laminated mat-like sequences to poorly sorted clastic-rich sediments. Authigenic monohydrocalcite and aragonite occur in some lake sediments. The delta 13C values of organic matter in the lacustrine sediments exhibit an extremely wide range (-10.5 to -25.3 ppt) that can be related to variations in physico-chemical conditions in the lake waters. Strongly negative organic-delta 13C values coupledwith high sulfur contents are indicative of an anoxic zone in the overlying lake waters, whereas less negative organic-delta 13C values coupled with low sulfur contents are indicative of well-mixed oxic conditions. Particularly high organic-delta 13C values result during high levels of microbial activity in the lakes, due to high rates of photosynthetic CO2 fixation. The large shifts in organic-delta 13C are not necessarily accompanied by any change in macroscopic sedimentological characteristics, illustrating the utility if isotopic investigations in these environments. The delta 13C composition of authigenic carbonate in hypersaline Organic Lake sediments provides a record of changes in palaeoproductivity, while the delta 18O of the carbonate provides information on rates of meltwater input and evaporation in the lake. 14C-dating suggests that Highway Lake was isolated from the sea by isostatic uplift at least 4600 years before present (BP) whereas Organic Lake was isolated at approximately 2700 years BP. Apparent emergence rates calculated from the 14C ages range from 1.0 to 2.1 mm per year. The 'reservoir effect' in the lacustrine and marine environments is variable, but probably does not exceed ~ 1000 years in any of the lakes examined.

The Holocene sea-ice project brings together for the first time, records from the Antarctic continent and deep sea sediments that will allow us to calibrate three sea-ice extent surrogates, validate their use in contrast to satellite observations and explore climatic influence on the physio-ecological environment over the last 10,000 years. Spreadsheet 1 (appendix A): Complete list of Accelerator Mass Spectrometry (AMS) dating completed on E27-23 from various identified sources with original 14CAge and reported error. Three dates identified as Burckle pers comm. here were provided by Dr Lloyd Burckle (LDEO) to Dr L. Armand for this work. Outlier attributions are identified; the term Averaged identifies the two samples where final calibrated dates were averaged in this work. All remaining AMS dates were converted to calendar ages using the linear-based CALIB07 (Stuiver and Reimer, 1993) with calibration to the Marine13 dataset (Reimer et al., 2013) at 95% confidence (sigma 2) and included a correction for the surface water reservoir age of ~752 years at the site of core E27-23 resolved from the marine radiocarbon reservoir correction database and software available from http://radiocarbon.LDEO.columbia.edu/ (Butzin et al., 2005). The percent Marine Carbon relative attribution is provided. The Median age (Cal Yr BP) used as the final age at each respective (mid) depth is provided. In Appendix A the dates are all ages in years, however some are uncalibrated ages and others are Cal yr BP (= calendar years before present). So in terms of headings in Table A: Raw 14C age yr BP - is the raw age provided by radiocarbon dating without any corrections applied. It is in years before present. Corrected raw age (RA=752) - is the raw age with a local RA (Reservoir Age) correction applied and is still in years before present. The remaining ages are calendar years before present having been calibrated. All formats follow recommendations for reporting raw 14C dates and their calibration ages. Spreadsheet 2 (appendix B): Comparison of calibration output from the input of accepted 14C dates using OXCAL 4.2 (Bronk Ramsey 2009; Blaauw 2010), and CALIB07 (Stuiver and Reimer, 1993), both using the Marine13 calibration curve (Reimer et al., 2013) at 95.4% confidence (sigma 2) and including a correction for the surface water reservoir age of ~752 years at the site of core E27-23. The calibration output difference between the median Cal Yr BP, regardless of calibration method employed, was greater than or equal to 40 Cal Yr BP. Calibration data from the output of CALIB07 has been used in this paper to determine chronostratigraphy. Spreadsheet 3 (appendix C): The foraminiferal stable isotope data from E27-23. Ratios of oxygen (delta 18O) measured from the planktonic foraminifer Neogloboquadrina pachyderma sinistral (greater than 150 microns). Isotope values are reported as per mil (%) deviations relative to the Vienna Peedee Belemnite (VPDB). Spreadsheet 4 (appendix D): The paleo winter sea-ice concentration (wSIC) estimates for marine sediment core SO136-111. The calendar ages, in thousands of years before present (kyr BP), are provided for each sample from core SO136-111. For each of the samples in core SO136-111, we have provided the estimates winter sea-ice concentration (%), along with the associated lower and upper bounds for the 95% confidence interval around the estimated winter sea-ice concentration (%), for both GAM/WSI/13 and GAM/WSI/ETS. The final two columns provide the estimated average annual monthly sea-ice cover for each sample within core SO136-111, originally estimated using the Modern Analogue Technique, by Crosta et al. (2004). Finally, we provide the estimated summer sea surface temperature, again using the Modern Analogue Technique, from Crosta et al. 2004. Spreadsheet 5 (appendix E): The paleo wSIC estimates for marine sediment core E27-23. The calendar ages, in thousands of years before present are provided for each sample from core E27-23. For each of the samples in core E27-23, we have provided the estimated winter sea-ice concentration (%), along with the associated lower and upper bounds for the 95% confidence interval around the estimates for winter sea-ice concentration (%).