Meltwater intensive glacial retreat in polar environments and investigation of associated sediments: example from Pine Island Bay, West Antarctica

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• 作者：Alex ; ra E. Witus ; Carolyn M. Branecky ; John B. Anderson ; Witold Szczuci艅ski ; Dustin M. Schroeder ; Donald D. Blankenship ; Martin Jakobsson
• 关键词：Subglacial meltwater ; Pine Island Bay ; Subglacial drainage ; Glacial sedimentology ; Plumite
• 刊名：Quaternary Science Reviews
• 出版年：1 February, 2014
• 年：2014
• 卷：85
• 期：Complete
• 页码：99-118
• 全文大小：4754 K

文摘

Modern Pine Island and Thwaites Glaciers, which both drain into Pine Island Bay, are among the fastest changing portions of the cryosphere and the least stable ice streams in Antarctica. Here we show that the uppermost sediment unit in Pine Island Bay was deposited from a meltwater plume, a plumite, during the late stages of ice sheet retreat 鈭?-8.6聽k聽cal聽yr聽BP and argue that this deposit records episodes of meltwater intensive sedimentation.

The plumite is a hydraulically sorted, glacially sourced, draping deposit that overlies proximal glacimarine sediments and thickens towards the modern grounding line. The uppermost sediment unit is interpreted as a product of non-steady-state processes in which low background sedimentation in large bedrock-carved basins alternates with episodic purging of sediment-laden water from these basins. The inner part of Pine Island Bay contains several basins that are linked by channels with a storage capacity on the order of 70聽km³ of stagnant water and significant sediment storage capacity. Purging of these basins is caused by changes in hydraulic potential and glacial reorganization. The sediment mobilized by these processes is found here to total 120聽km³.

This study demonstrates that episodes of meltwater-intensive sedimentation in Pine Island Bay occurred at least three times in the Holocene. The most recent episode coincides with rapid retreat of the grounding line in historical time and has an order of magnitude greater flux relative to the entire unit. We note that the final phase of ice stream retreat in Marguerite Bay was marked by a similar sedimentary event and suggest that the modern Thwaites Glacier is poised for an analogous meltwater-intensive phase of retreat.