METHODS FOR DETECTING HOLOCENE SEA LEVEL SIGNALS IN ANTARCTICA

Mid to Late Holocene sea-level change can be used for evaluating long-term stability of the Antarctic ice sheet since the end of the last major, approximately 8,000 years ago. Ongoing global warming may trigger disintegration of this ice sheet, with collapse of the West Antarctic Ice Sheet alone potentially producing a more than 3 to 4 m global sea-level rise. Relative sea level records from sites far away from former ice sheet regions (far-field) provide information on total volume of the ocean mass change, which can be interpreted as global ice volume change. However, understanding mechanisms for the ongoing ice sheet fluctuations requires information on the source of meltwaters, provided by records near the Antarctic ice sheet. To address the paucity of information from this region, we have employed two new methods to understand melting history of Antarctic ice sheets, namely cosmogenic radionuclides (CRN) and compound specific isotopes (CSI) measurements, both of which will provide a more complete history of ice sheet behavior. Cosmic rays began bombarding the surface of rocks in Antarctica after deglaciation. Hence, the amount of CRN is proportional to minimum exposure age after ice sheet ablation. CSI is useful for analysis of sediments proximal to ice sheets due to the differing isotopic signals between ice and seawater, up to ca. 300 per mil for hydrogen isotopes. Therefore, meltwater signals can be recorded in CSI produced from surface dwelling algae. Another major obstacle for Antarctic marine geological study is the difficulty in applying radiocarbon dating for to two basic reasons; lack of foraminifers and anomalously old TOC ages because of old carbon contamination from the Antarctic continent. We are using compound specific radiocarbon dating to solve this problem. In this presentation, we introduce these two measures to reconstruct the melting history of Antarctic ice sheet during the Holocene using two particular examples from Lutzow Holm bay in East Antarctica and Ross Sea of West Antarctica.