Deglaciation of Pope Glacier implies widespread early Holocene ice sheet thinning in the Amundsen Sea sector of Antarctica
Deglaciation of Pope Glacier implies widespread early Holocene ice sheet thinning in the Amundsen Sea sector of Antarctica
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DOI：
10.1016/j.epsl.2020.116501
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发表时间：
2020-10-15
影响因子：
5.3
通讯作者：
Smith, James A.
中科院分区：
文献类型：
--
作者：
Johnson, Joanne S.;Roberts, Stephen J.;Smith, James A.
南极冰盖的阿蒙森海部分目前在南极洲对海平面上升的贡献中占主导地位。在过去的几十年里，几个大的冰流，目前排水部门经历了快速流动加速，接地线撤退和变薄。然而，很少有人知道他们的长期千年尺度的退缩历史，尽管几个冰盖和冰川均衡调整模型依赖于这些数据，以改善海平面预测从这个关键地区。这项研究调查了这些冰流之一，教皇冰川，自末次冰期最大（LGM）以来，使用冰川地质证据前冰盖的表面降低的时间和程度。我们提出了一个新的冰川消退年表的冰川，来自表面暴露测年的冰川沉积的鹅卵石和冰冲刷基岩从墨菲山及其周围的山峰。宇宙成因Be-10暴露年龄从44个不稳定的鹅卵石和5个基岩样品，和原位C-14暴露年龄从一个不稳定的和8个基岩样品主要是在5.5-16 ka的范围内。虽然Be-10遗传从以前的曝光是普遍存在的一些erratics和可能所有的基岩样品，没有年龄早于末次冰期。根据这些结果，我们推断波普冰川表面在全新世早期至中期（9-6 ka）下降了560 m，平均速率为0.13 +/- 0.09/0.04 m yr（-1）。这一下降与该区域温暖的环极深水上涌到大陆架的时期相吻合。支撑作用的减少-由这种上涌促进-由一个冰架，被认为已经跨越海湾，直到10.6卡尔凯尔BP可能引发了同时在阿蒙森海湾教皇冰川和冰川的其他地方的全新世早期变薄。(C)2020作者（S）由爱思唯尔公司出版
The Amundsen Sea sector of the Antarctic ice sheet presently dominates the contribution from Antarctica to sea level rise. Several large ice streams that currently drain the sector have experienced rapid flow acceleration, grounding line retreat and thinning during the past few decades. However, little is known of their longer-term - millennial-scale - retreat history, despite the reliance of several ice sheet and glacial-isostatic adjustment models on such data for improving sea level prediction from this critical region. This study investigates the timing and extent of surface lowering of one of those ice streams, Pope Glacier, since the Last Glacial Maximum (LGM), using glacial-geological evidence for former ice cover. We present a new deglacial chronology for the glacier, derived from surface exposure dating of glacially-deposited cobbles and ice-scoured bedrock from Mount Murphy and its surrounding peaks. Cosmogenic Be-10 exposure ages from 44 erratic cobbles and 5 bedrock samples, and in situ C-14 exposure ages from one erratic and 8 bedrock samples are predominantly in the range 5.5-16 ka. Although Be-10 inheritance from prior exposure is prevalent in some erratics and probably all bedrock samples, none of the ages predate the LGM. From these results we infer that the surface of Pope Glacier lowered by 560 m during the early- to mid-Holocene (9-6 ka), at an average rate of 0.13 +/- 0.09/0.04 m yr(-1). The lowering coincided with a period of enhanced upwelling of warm Circumpolar Deep Water onto the continental shelf in the region. A reduction in buttressing - facilitated by such upwelling - by an ice shelf that is thought to have spanned the embayment until 10.6 cal kyr BP could have triggered simultaneous early Holocene thinning of Pope Glacier and glaciers elsewhere in the Amundsen Sea Embayment. (C) 2020 The Author(s). Published by Elsevier B.V.