Understanding the pace and drivers of marine-based ice-sheet retreat relies upon the integration of numerical ice-sheet models with observations from contemporary polar ice sheets and well-constrained palaeo-glaciological reconstructions. This paper provides a reconstruction of the retreat of the last British–Irish Ice Sheet (BIIS) from the Atlantic shelf west of Ireland during and following the Last Glacial Maximum (LGM). It uses marine-geophysical data and sediment cores dated by radiocarbon, combined with terrestrial cosmogenic nuclide and optically stimulated luminescence dating of onshore ice-marginal landforms, to reconstruct the timing and rate of ice-sheet retreat from the continental shelf and across the adjoining coastline of Ireland, thus including the switch from a marine- to a terrestrially-based ice-sheet margin. Seafloor bathymetric data in the form of moraines and grounding-zone wedges on the continental shelf record an extensive ice sheet west of Ireland during the LGM which advanced to the outer shelf. This interpretation is supported by the presence of dated subglacial tills and overridden glacimarine sediments from across the Porcupine Bank, a westwards extension of the Irish continental shelf. The ice sheet was grounded on the outer shelf at ~26.8 ka cal bp with initial retreat underway by 25.9 ka cal bp. Retreat was not a continuous process but was punctuated by marginal oscillations until ~24.3 ka cal bp. The ice sheet thereafter retreated to the mid-shelf where it formed a large grounding-zone complex at ~23.7 ka cal bp. This retreat occurred in a glacimarine environment. The Aran Islands on the inner continental shelf were ice-free by ~19.5 ka bp and the ice sheet had become largely terrestrially based by 17.3 ka bp. This suggests that the Aran Islands acted to stabilize and slow overall ice-sheet retreat once the BIIS margin had reached the inner shelf. Our results constrain the timing of initial retreat of the BIIS from the outer shelf west of Ireland to the period of minimum global eustatic sea level. Initial retreat was driven, at least in part, by glacio-isostatically induced, high relative sea level. Net rates of ice-sheet retreat across the shelf were slow (62–19 m a⁻¹) and reduced (8 m a⁻¹) as the ice sheet vacated the inner shelf and moved onshore. A picture therefore emerges of an extensive BIIS on the Atlantic shelf west of Ireland, in which early, oscillatory retreat was followed by slow episodic retreat which decelerated further as the ice margin became terrestrially based. More broadly, this demonstrates the importance of localized controls, in particular bed topography, on modulating the retreat of marine-based sectors of ice sheets.

中文翻译：

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末次冰期期间爱尔兰西部海陆过渡区冰盖撤退的时间和速度

了解海洋冰盖退缩的速度和驱动因素依赖于数值冰盖模型与当代极地冰盖观测和受良好约束的古冰川重建的整合。本文提供了最后一次盛冰期 (LGM) 期间和之后从爱尔兰西部大西洋大陆架退缩的最后一个英国 - 爱尔兰冰盖 (BIIS) 的重建。它使用放射性碳测年的海洋地球物理数据和沉积物核心，结合陆地宇宙成因核素和陆上冰缘地貌的光受激发光测年，重建冰盖从大陆架和穿过毗邻海岸线退缩的时间和速度。爱尔兰，因此包括从海洋冰盖边缘到陆地冰盖边缘的转变。大陆架上以冰碛和接地带楔形形式存在的海底测深数据记录了 LGM 期间爱尔兰西部的大面积冰盖，该冰盖推进到外大陆架。这种解释得到了来自爱尔兰大陆架向西延伸的豪猪银行（Porcupine Bank）的年代久远的冰下耕地和覆盖的冰川沉积物的支持。冰盖在约 26.8 ka cal 的外架上接地bp正在进行初始撤退 25.9 ka cal bp。撤退不是一个连续的过程，而是被边缘振荡打断，直到~24.3 ka cal bp。此后冰盖退回到中架，在那里形成了一个大的接地带复合体，大约为 23.7 ka cal bp。这次撤退发生在冰川环境中。内陆架上的阿兰群岛约 19.5 ka bp无冰，冰盖在 17.3 ka bp 时主要以陆地为基础。这表明一旦 BIIS 边缘到达内陆架，阿兰群岛就开始稳定和减缓整体冰盖后退。我们的结果将 BIIS 从爱尔兰西部外陆架的初始撤退时间限制在全球海平面最低的时期。最初的撤退至少部分是由冰川等静压引起的高相对海平面驱动的。冰盖穿过大陆架的净撤退速度缓慢 (62–19 ma ^-1 ) 并降低 (8 ma ^-1)，因为冰盖离开了内陆架并移动到了岸上。因此，爱尔兰西部大西洋大陆架上出现了一个广泛的 BIIS，其中早期的振荡后退之后是缓慢的间歇性后退，随着冰缘变得基于陆地而进一步减速。更广泛地说，这表明局部控制，特别是床地形，对调节冰盖海洋部分退缩的重要性。