[M-IS10] 南大洋・南極氷床が駆動する全球気候変動

[MIS10-P01] Massive Antarctic snowfall forced by iceberg discharge into North Atlantic during the last glacial period

*大藪 幾美^1,2、川村 賢二^1,2、藤田 秀二^1,2、東 久美子^1,2、Buizert Christo³、平林 幹啓^1,2、本山 秀明^1,2 (1.情報・システム研究機構　国立極地研究所、2.総合研究大学院大学、3.オレゴン州立大学)

キーワード：南極、最終氷期、ハインリッヒイベント、涵養量、氷床

Massive collapses of the North American ice sheet during the last glacial period, called Heinrich events, brought broad impacts on the global climate. Reorganization of atmospheric and oceanic circulation drove changes to Earth’s latitudinal heat distribution, low-latitude hydrological cycles and global carbon cycle. In Antarctica, the Heinrich events posed relatively small but abrupt warming as identified from ice-core isotopic records, but its impact on precipitation has remained unknown. Here, we show novel accumulation-rate reconstructions for the last glacial period at centennial-scale resolution for four sites in East Antarctica. Surprisingly, large and rapid accumulation increases on a millennial timescale occurred during the Heinrich events beyond what is expected from the minor warming amplitudes alone. The increased Antarctic snowfall may be attributed to atmospheric moisture content or meridional transport, which in turn may be driven by a cascade of a southward shift of the Intertropical Convergence Zone, a southward shift and strengthening of Southern Hemisphere westerly winds, and enhanced wind-driven upwelling of Southern Ocean deep water. An increased frequency or intensity of direct moisture transport (so-called atmospheric rivers) may also play a crucial role. The results provide a consistent picture of hydrological changes in the southern high-latitudes associated with warming due to the past Northern
Hemisphere forcing and possibly current anthropogenic forcing.