The Use of a New Paleoclimate Archive to Reconstruct Holocene Sea-Ice Variability in the eastern Weddell Sea, Antarctica
Authors: Penny Claire , Bentley Michael , Hodgson Dominic , McClymont Erin 
Published: March 2024

Proxies of paleoclimate are essential tools in reconstructing past Antarctic climates, understanding its natural climate variability, and providing context for change under future warming. Constraining past changes in Antarctic sea ice is particularly challenging, and current proxy records have significant temporal and spatial limitations1. Here, we report use of a new sea-ice proxy, namely the geochemical signature of prey remains preserved in snow petrel (Pagodroma nivea) stomach oil deposits. &#160;Antarctica&#8217;s relatively stable Holocene climate provided a backdrop for the establishment and development of modern ecosystems. Close to the margin of the East Antarctic Ice Sheet, the Theron Mountains provided one such ecological niche in the form of a snow petrel colony, estimated to have established approximately 6,000 years ago2. During each summer breeding season, snow petrel adults travelled towards the retreating sea-ice edge to hunt for food for their young, or towards areas of open water (polynyas). Prey species varied in proportion according to proximity to the continental shelf, whether proximal (fish), distal (krill) or within a polynya (increased proportion of fish)3. These dietary signatures are preserved in the form of lipid biomarkers within their fossilised stomach oil deposits, accumulated outside nest crevices during defensive regurgitation. The presence of this colony in the Holocene therefore offers a unique lens to examine the response of the Antarctic environment to fluctuating sea-ice conditions4. A multi-proxy methodology is employed here, comparing key elements and trace metals, fatty acid profiles and bulk isotopic (&#948;13C and &#948;15N) compositions. This study aims to address the uncertainties current paleoclimate proxies have, and our results show centennial-scale dietary fluctuations across the last 2,000 years in response to retreating sea-ice. We therefore offer a more comprehensive insight into reconstructing Holocene climate variability within the eastern Weddell Sea region of Antarctica.1Collins, M., Knutti, R., Arblaster, J., Dufresne, J.-L., Fichefet, T., Friedlingstein, P., Gao, X., Gutowski, W. J., Johns, T., Krinner, G., Shongwe, M., Tebaldi, C., Weaver, A. J., and Wehner, M.: Long-term Climate Change: Projections, Commitments, and Irreversibility, in: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to 735 the Fifth Assessment Report of the Intergovernmental Panel on Climate Change edited by: Stocker, T. F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S. K., Boschung, J., Nauels, A., Xia, Y., Bex, V., and Midgley, P. M., Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA., 2013.2Berg, S., Melles, M., Hermichen, W.-D., McClymont, E. L., Bentley, M. J., Hodgson, D. A., &amp; Kuhn, G. (2019). Evaluation of mumiyo deposits from East Antarctica as archives for the Late Quaternary environmental and climatic history. Geochemistry, Geophysics, Geosystems, 20(1), 260&#8211; 276.3Barbraud, C., &amp; Weimerskirch, H. (2001). Contrasting effects of the extent of sea-ice on the breeding performance of an Antarctic top predator, the snow petrel, Pagodroma nivea. Journal of Avian Biology, 32(4), 297&#8211; 302.4Delord, K., Pinet, P., Pinaud, D., Barbraud, C., De Grissac, S., Lewden, A., et al. (2016). Species-specific foraging strategies and segregation mechanisms of sympatric Antarctic fulmarine petrels throughout the annual cycle. Ibis, 158(3), 569&#8211; 586.