The Aurora Basin North Ice Core record of temperature variability over the last 2000 years in East Antarctica

Abstract:

The climate variability of the past 2000 years over large areas of the Antarctic continent remains mostly understudied. The Aurora Basin North ice core covers the last two millennia, and was drilled on the lower edge of East Antarctic Plateau (71°S, 111°E). Here we compare the water isotopes with the temperature inferred from δ⁴⁰Ar and δ¹⁵N in trapped air. While δ¹⁸O remains relatively stable over the last 2000 years at -40.7 ± 1.3 ‰ (1σ), the gas-based temperature reconstruction reveals that surface temperatures were colder than average by about 1°C during the 1000 – 1400 CE period. This apparent discrepancy could be due to: (1) a change in precipitation seasonality with less snowfall in winter, and/or (2) fewer but more intense precipitation events, associated with a warming restricted in time. The results presented here are consistent with paleo-reconstructions of the Southern Annular Mode (SAM) that show an extended positive phase prior to 1400 CE, which is usually associated with lower temperatures and lower precipitation rates on the East Antarctic Plateau.