[M-IS08] 南大洋・南極氷床が駆動する全球気候変動

[MIS08-04] 東南極シューマッハオアシスの湖沼堆積物を用いた完新世の氷床後退復元

鎌田 唯斗¹、*香月 興太²、菅沼 悠介³、金田 平太郎⁴、池原 実⁵ (1.島根大学　、2.島根大学　エスチュアリー研究センター、3.国立極地研究所、4.中央大学、5.高知大学)

キーワード：南極湖沼、堆積物、珪藻、元素組成

Recently, there has been concern over the rapid melting of the Antarctic ice sheet by global warming. While many instrumental and satellite ice sheet and ocean observations have been conducted in recent, there has been limited researches on the natural history of ice sheet retreating in the coastal regions of East Antarctica. Schirmacher Oasis is one of the small ice-free rocky areas near the shore and ice sheet of East Antarctica, and over 100 lakes cover the area. To reconstruct the migration history of East Antarctic Ice Sheet (EAIS), the sediment cores 19L0503 and 19L0602 were collected from lakes L5 and L6 located in western part of Schirmacher Oasis. Radiocarbon ages from the bottom of lacustrine sediments in these cores were both about 10,000 years ago. All major elements (Fe, Mn, K, Si, Ca, and etc.) in both cores showed more detailed ice retreat history. The major elements had showed the high contents in the bottom layers until about 7,000 years ago, and these had gradually decreased with high fluctuation until about 3,000 or 2,000 years ago. After that, major elements have indicated the low contents except for a few periods. These results suggested that the major elements were provided from EAIS with melt water. Lakes L5 and L6 were formed about 10,000 years ago due to EAIS retreating. At that time, the edge of EAIS was located adjacent to these lakes. EAIS had gradually retreated after 7,000 years ago. And then, the inflow of the melt water from EAIS stopped about 3,000 years ago in Lake L5, and 2,000 years ago in Lake L6, because the edge of EAIS retreated sufficiently away from these lakes. Fresh water diatom taxon, Stauroneis anceps had dominated in the majority of Holocene period in core 19L0503. On the other hand, oligotrophic fresh water diatom taxon, Humidophila cf. perpusilla had increased temporally after about 2,000 years ago. It means that Lake L5 became oligotrophic condition after the stop of the melt water input. Humidophila cf. perpusilla decreased again when the major elements showed relatively high contents about 1,800 years ago. The small readvance of EAIS probably occurred about 1,800 years ago.