Understanding controls on rapid ice-stream retreat during the last deglaciation of Marguerite Bay, Antarctica, using a numerical model
Understanding controls on rapid ice-stream retreat during the last deglaciation of Marguerite Bay, Antarctica, using a numerical model
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使用数值模型了解南极洲玛格丽特湾末次冰消期期间冰流快速退缩的控制
DOI：
10.1002/2013jf002934
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发表时间：
2014
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影响因子：
--
通讯作者：
Jamieson S
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文献类型：
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作者：
Jamieson S
利用具有强大接地线动力学的一维冰流数值模型，研究了末次冰消期南极玛格丽特湾古冰流退缩的控制因素。大陆架上的地形限制了数值模型，并表明退缩是迅速的，但被一系列减速所打断。我们研究了冰流退缩对冰下地形和侧地形变化的敏感性，以及对海平面上升、冰架下加速融化、大气变暖和冰架解冻等强迫过程的敏感性。我们的实验一致地再现了在内陆加深的河床上间断的后退，后退速度的减慢受地形变窄的控制。敏感性实验表明，单个强迫机制启动撤退所需的变化幅度高得不切实际，但当各个过程联合起作用时，阈值会降低。然而，冰流对海洋变暖和相关的冰架融化最为敏感，而退缩最有可能是对整个退缩期间持续的外部强迫的反应，而不是对单一触发“事件”的反应。后退的时间尺度进一步受到来自接地线上游的冰的输送的控制。由于地形的影响，模拟的退缩模式对强迫演化的时间模式不敏感。因此，我们认为，尽管区域强迫机制相似，但景观控制着相邻但地形不同的流域之间退缩行为的显著差异。因此，预计过去、现在和未来冰流退缩的模式将发生显著变化。
Using a one‐dimensional numerical model of ice‐stream flow with robust grounding‐line dynamics, we explore controls on paleo‐ice‐stream retreat in Marguerite Bay, Antarctica, during the last deglaciation. Landforms on the continental shelf constrain the numerical model and suggest that retreat was rapid but punctuated by a series of slowdowns. We investigate the sensitivity of ice‐stream retreat to changes in subglacial and lateral topography and to forcing processes including sea‐level rise, enhanced melting beneath an ice shelf, atmospheric warming, and ice‐shelf debuttressing. Our experiments consistently reproduce punctuated retreat on a bed that deepens inland, with retreat‐rate slowdowns controlled by narrowings in the topography. Sensitivity experiments indicate that the magnitudes of change required for individual forcing mechanisms to initiate retreat are unrealistically high but that thresholds are reduced when processes act in combination. The ice stream is, however, most sensitive to ocean warming and associated ice‐shelf melting, and retreat was most likely in response to external forcing that endured throughout the period of retreat rather than to a single triggering “event.” Timescales of retreat are further controlled by the delivery of ice from upstream of the grounding line. Due to the influence of topography, modeled retreat patterns are insensitive to the temporal pattern of forcing evolution. We therefore suggest that despite regionally similar forcing mechanisms, landscape controls significant contrasts in retreat behavior between adjacent but topographically distinct catchments. Patterns of ice‐stream retreat in the past, present, and future should therefore be expected to vary significantly.