Seabed corrugations beneath an Antarctic ice shelf revealed by autonomous underwater vehicle survey: Origin and implications for the history of Pine Island Glacier
Seabed corrugations beneath an Antarctic ice shelf revealed by autonomous underwater vehicle survey: Origin and implications for the history of Pine Island Glacier
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DOI：
10.1002/jgrf.20087
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发表时间：
2013-09-01
影响因子：
3.9
通讯作者：
Jenkins, Adrian
中科院分区：
文献类型：
--
作者：
Graham, Alastair G. C.;Dutrieux, Pierre;Jenkins, Adrian
冰架是关于西南极冰盖变化和海平面上升的争论中的关键特征，这既是因为它们限制了冰的排放，也是因为它们对周围海洋的变化很敏感。松岛冰川冰架至少自20世纪90年代初以来一直在迅速变薄，这导致它的树干加速后退。尽管冰架前缘在过去60年中一直保持稳定，但过去的冰架崩塌时期已从残留的海底波纹（波纹脊）中推断出来，这些波纹脊保存在距离松岛海槽冰川340公里的地方。在这里，我们提出了高分辨率的水深测量收集的自主水下航行器在南极冰架下运行，这提供了长期变化的证据松岛冰川。冰下架山脊上的波纹和犁痕（以前是接地线）与海上观察到的非常相似，之前被解释为冰山接地的结果。同样的解释表明，在过去的11kyr冰架的范围显着减少，这意味着全新世冰川退缩超过目前的限制，或过去的冰川制度与今天不同。另一种选择，即波纹不是在开放水域形成的，将质疑从地质记录中解释的冰架崩塌事件，揭示了发生在冰川边缘的另一个床形成过程的细节。我们评估的假设，并建议定期接地冰架龙骨在冰川unpinning作为一个可行的起源。这种解释既不需要冰架的损失，也不需要冰川退缩，并且与整个全新世的稳定接地线配置一致。
Ice shelves are critical features in the debate about West Antarctic ice sheet change and sea level rise, both because they limit ice discharge and because they are sensitive to change in the surrounding ocean. The Pine Island Glacier ice shelf has been thinning rapidly since at least the early 1990s, which has caused its trunk to accelerate and retreat. Although the ice shelf front has remained stable for the past six decades, past periods of ice shelf collapse have been inferred from relict seabed corrugations (corrugated ridges), preserved 340km from the glacier in Pine Island Trough. Here we present high-resolution bathymetry gathered by an autonomous underwater vehicle operating beneath an Antarctic ice shelf, which provides evidence of long-term change in Pine Island Glacier. Corrugations and ploughmarks on a sub-ice shelf ridge that was a former grounding line closely resemble those observed offshore, interpreted previously as the result of iceberg grounding. The same interpretation here would indicate a significantly reduced ice shelf extent within the last 11kyr, implying Holocene glacier retreat beyond present limits, or a past tidewater glacier regime different from today. The alternative, that corrugations were not formed in open water, would question ice shelf collapse events interpreted from the geological record, revealing detail of another bed-shaping process occurring at glacier margins. We assess hypotheses for corrugation formation and suggest periodic grounding of ice shelf keels during glacier unpinning as a viable origin. This interpretation requires neither loss of the ice shelf nor glacier retreat and is consistent with a stable grounding-line configuration throughout the Holocene.