Retreat of Southern Hemisphere Sea Ice, 130 000 to 116 000 years BP

海冰对全球气候、南极冰盖和南大洋的所有生命都至关重要。然而，预计南半球海冰覆盖的面积在下个世纪将急剧减少；2200年的降幅可能高达58%。这些预测海冰损失的模型从未在南半球海冰减少的记录下进行过测试。自1978年以来，北半球海冰的大规模退缩使气候和海冰模型能够对其复制退缩数据的能力进行评估。这有助于确保我们对北极海冰的预测有很高的信心。在南半球，自1978年以来就没有类似的海洋退缩，这意味着模型不能用退缩数据来检验。因此，海冰退缩数据的缺乏是目前南半球海冰预报缺乏信心的主要原因。在这里，我们建议解决这一缺乏数据的问题，这涉及到南半球海冰的退缩。我们发现，在距今13万年至11.6万年之间的末次间冰期（LIG），南半球海冰出现了实质性的退缩。在类似于今天的气候条件下，通过重建和模拟LIG时期的撤退，该提案旨在改变对南半球主要撤退事件的结构和原因的理解。该项目将是有史以来第一次对南半球大型海冰退缩进行定量调查，对海冰和古气候科学界都具有相当重要的意义。我们将使用一种强大的新统计方法生成一个新的LIG海冰数据集。这将利用并建立在我们科学团队成员的核心专业知识之上。我们新的南半球海冰数据数据将用于帮助确定LIG退缩的原因，并测试当前的气候和海冰模型。除了确定LIG期间海冰减少的最可能原因外，该项目还将首次建立海冰群落对我们基于英国模型的南半球海冰未来退缩预测的信心程度。

Sea ice is of huge importance to global climate, the Antarctic ice sheet, and to all life in the Southern Ocean. However the area covered by sea ice in the Southern Hemisphere is predicted to drastically decrease over the next century; the decrease by 2200 could be as much as 58%.The models, on which predictions of sea ice loss are based, have never been tested against a documented retreat of Southern Hemisphere sea ice. A major retreat in Northern Hemisphere sea ice since 1978 has enabled climate and sea ice models to be evaluated for their ability to replicate retreat data. This has helped ensure that we have high confidence in Arctic sea ice predictions. In the Southern Hemisphere, there has been no similar sea retreat since 1978, which has meant that models cannot be tested against retreat data. This lack of sea ice retreat data has thus been a major contributor to the current lack of confidence in Southern Hemisphere sea ice forecasts.Here we propose to address this lack of data which covers a retreat of the Southern Hemisphere sea ice. We have found a period during the Last Interglacial (LIG) between 130,000 and 116,000 years Before Present (BP), when there was a substantial retreat in Southern Hemisphere sea ice. By reconstructing and modelling a retreat during this LIG period, under a climate which was similar to that of today, this proposal aims to transform understanding of the structure and causes of a major Southern Hemisphere retreat event. The project will be the first ever quantitative investigation of a large Southern Hemisphere sea ice retreat, and will be be of considerable importance to both the sea ice and palaeoclimate science communities.We will generate a new LIG sea ice dataset, using a robust new statistical approach. This will draw from, and build upon, the core expertise of our science team members. Our new Southern Hemisphere sea ice data data will then be used to help establish the cause of the LIG retreat and to test current climate and sea ice models. In addition to identifying the most likely cause of the decrease in sea ice during the LIG, this project will establish for the first time the degree of confidence that the sea ice community can have in our UK model-based predictions of a future retreat in Southern Hemisphere sea ice.