A Comparison of South Pacific Antarctic Sea Ice and Atmospheric Circulation Reconstructions Since 1900

Abstract. The recent changes and record minima in Antarctic sea ice extent implore the need for longer estimates beyond the short satellite observation period commencing near 1979. However, Antarctic sea ice extent reconstructions based on paleo records and those generated based on instrumental observations from the Southern Hemisphere midlatitudes are markedly different, especially prior to 1979. Here, these reconstructions are examined with the goal of understanding the relative strengths and limitations of each reconstruction better so that researchers using the various datasets can interpret them appropriately.

Overall, it is found that the different spatial and temporal resolutions of each dataset play a secondary role to the inherent connections each reconstruction has with its underlying atmospheric circulation. Several Southern Hemisphere pressure reconstructions spanning the 20^th century are thus examined further. There are different variability and trends poleward of 60° S between paleo-based and station-based 20^th century pressure reconstructions which are connected to the disagreement between the Antarctic sea ice extent reconstructions examined here. Importantly, sensitivity experiments based on only coral paleoclimatological records provide the best agreement between the early pressure reconstructions, suggesting a contributing role of tropical variability is present in the station-based pressure (and therefore sea ice) reconstructions, while high latitude ice core information strongly constrains paleo-based reconstructions (of both pressure and sea ice) near the Antarctic continent. Our results reveal the greatest consistencies and inconsistencies in available datasets and highlight the need to better understand the relative roles of the tropics versus high latitudes in historical sea ice variability around Antarctica.