Synoptic Moisture Intrusion Provided Heavy Isotope Precipitations in
Inland Antarctica during the Last Glacial Maximum
Abstract
Stable water isotopes in inland Antarctic ice cores are powerful
paleoclimate proxies; however, their relationship with dynamical
atmospheric circulations remains controversial. Using a water isotope
climate model (MIROC5-iso), we assessed the influence of the Last
Glacial Maximum (LGM; ~21,000 years ago) sea surface
temperatures (SST) and sea ice (SIC) on Antarctic precipitation isotopes
(δ18Op) through atmospheric circulation. The results revealed that the
synoptic circulation mostly maintained southward moisture transport,
reaching inland Antarctica. The steepened meridional SST gradient in the
mid-latitudes increased δ18Op in inland Antarctica by enhancing the
baroclinic instability and synoptic moisture transport. In contrast,
enhanced SIC reduced the atmospheric humidity around Antarctica and
lowered δ18Op through extensive surface cooling and transport from the
ocean. These findings elucidate the isotopic proxies and enable us to
constrain the southern hemisphere atmospheric circulation, including the
westerlies, using ice cores during past climates, including the LGM.