Testing the extent and timing of past glaciations on the largest sub-Antarctic island, South Georgia

亚南极洲岛屿是研究过去冰和气候变化的理想地点，其古代冰川作用的记录对于了解地球系统的各个方面非常重要。由于这些岛屿在温暖的海洋气候和寒冷的极地气候之间的独特位置，亚南极冰盖的大小为校准冰盖模型的灵敏度提供了一种潜在的有价值的手段，确保用于迫使它们的气候参数是现实的，并且输出对未来“好”。冰川事件的规模和时间的变化也可以提供关于区域和半球之间气候变化的机制和阶段的重要信息。同样的数据限制了冰川避难所的位置和持久性，并为生物学家提供了关于南大洋生物进化和多样性的地质条件的信息。 为了改进冰盖模型，解释气候变化的模式，并解释世界海洋的生物多样性，需要有关南极洲以南冰川历史的信息。然而，关于过去冰川的年龄、规模和数量的基本问题仍然没有答案。对于最大的亚南极洲岛屿南格鲁吉亚来说，从今天围绕岛屿的浅大陆架海底发现的冰刻槽和沉积脊（冰碛）中，已经知道至少有一次重大的冰川前进。其年龄不详。与南极洲的其他地区一样，最近的一次冰川作用--末次冰盛期--可能留下了冰盖前进和融化的最佳记录。然而，即使在这里，也没有达成共识，有两个相互矛盾的假设占主导地位：一个认为冰的范围有限，仅限于近岸峡湾;另一个认为冰帽是广泛的，达到了大部分岛屿周围的大陆架的外部。哪一种假设是正确的，答案在于对海底地形和沉积物的研究，这还有待于进行任何详细的调查。 该项目提出了一项开创性的研究，首次从海洋角度审查南格鲁吉亚过去冰川的范围和时间。我将提供一个强有力的测试的假设，要么：（一）末次冰期最大的冰帽是有限的范围，因此，一个或多个主要的冰帽冰川，达到外大陆架界限早于末次冰期;或（二）末次冰期最大的冰帽是广泛的，和撤退的年表记录在大陆架的景观和沉积物。 现有的和新收集的声纳测深数据将用于绘制前所未有的详细的南格鲁吉亚大陆架的冰川特征。将对从大陆架上首先采集的六个沉积物岩心进行分析和测定年代。该项目的目标将是标志着前冰盖界限的冰碛，从大陆架边缘到沿海峡湾。我将确定最广泛的冰川作用的年龄，以及中间退缩或终端极限的年龄。对沉积物的物理分析将重建末次冰盛期期间和自末次冰盛期以来到今天的环境条件，也许还有更古老的寒冷或温暖时期。该项目的一项主要成果是解决保存在亚南极记录中的前大陆架冰川的数量和范围，以及关于末次冰期冰盖的行为和范围的重要新信息。 将在地球气候和进化史的背景下创造新的记录，并形成对亚南极冰川作用的第一个海洋古限制，使建模人员，气候科学家和生物学家受益。该项目还将提供基线地质数据，供生境测绘项目和渔业使用。这项研究将为南大洋冰和气候历史提供新的线索，并为未来研究近极地地区过去冰川变化制定新的议程。

The sub-Antarctic islands are ideally placed to investigate past ice and climate changes, with records of their ancient glaciation important for understanding various aspects of the Earth system. Due to the islands' unique location between warm-maritime and cold-polar climates, the size of sub-Antarctic ice-cap advances provide a potentially valuable means of calibrating the sensitivity of ice-sheet models, ensuring the climate parameters used to force them are realistic and the outputs 'good' for the future. Variations in the scale and timing of glacial events can also provide critical information on the mechanisms and phasing of climate changes between regions and hemispheres. The same data constrain the whereabouts and persistence of glacial refugia, and inform biologists on the geological conditions governing the evolution and diversity of life in the Southern Ocean. To improve ice-sheet models, explain patterns of climate change, and interpret the biodiversity of the world's oceans, information on sub-Antarctica's glacial past is required. However, fundamental questions relating to the age, magnitude, and number of past glaciations remain unanswered. For the largest sub-Antarctic island, South Georgia, at least one major glacial advance is already known from ice-carved troughs and sediment ridges (moraines) found on the sea-floor of the shallow shelf surrounding the island today. Yet its age is unknown. As in other parts of Antarctica, the most recent episode of glaciation - The Last Glacial Maximum - is likely to have left behind the best record of ice-cap advance and melting. However, even here, there is no consensus, with two conflicting hypotheses prevailing: one suggesting a limited ice extent, restricted to the near-shore fjords; the other proposing that the ice cap was extensive, reaching the outer parts of the shelf around most of the island. Answers to which hypothesis is correct lie in the study of the submarine topography and sediments, which have yet to be investigated in any detail. This project proposes a pioneering study to examine the extent and timing of past glaciations on South Georgia, from a marine perspective, for the first time. I will provide a robust test of the hypotheses that, either: (i) the Last Glacial Maximum ice cap was of restricted extent and thus that one or more major ice cap glaciations that reached outer shelf limits pre-date the last glacial period; or that (ii) the Last Glacial Maximum ice cap was extensive, and a chronology of retreat is recorded in the shelf's landscape and sediments. Existing and newly-collected sonar bathymetry data will be utilised to map out the glacial features on the South Georgia shelf in unprecedented detail. Six sediment cores, among the first recovered from the shelf, will be analysed and dated. The project will target moraines marking the limits of former ice-caps, from the shelf edge to the coastal fjords. I will determine the age of the most extensive glaciation, and the age of intermediate retreat or terminal limits. Physical analyses of sediments will reconstruct environmental conditions during and since the Last Glacial Maximum, to the present day, and perhaps through older cold or warm periods. Resolving the number and extent of former shelf glaciations preserved in sub-Antarctic records will be a major outcome of the project, as will vital new information on the behaviour and reach of the Last Glacial ice cap. New records will be set in the context of Earth's climate and evolutionary histories, and form the first marine palaeo-constraints on sub-Antarctic glaciation, benefiting modellers, climate scientists and biologists. The project will also provide baseline geological data for use by habitat mapping projects and fisheries. This research will shed new light on Southern Ocean ice and climate history, and set a new agenda for future study of past glacial change in the near-polar regions.