Is ice loss from West Antarctica driven by ocean forcing or ice and ocean feedbacks?

南极洲西部的冰损失是由海洋强迫还是冰和海洋反馈驱动的？

基本信息

批准号：
NE/M001660/1
负责人：
Paul Holland
金额：
$ 39.38万
依托单位：
British Antarctic Survey
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2014
资助国家：
英国
起止时间：
2014 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FM001660%2F1
关键词：
ice loss West Antarctica driven

项目摘要

The Antarctic Ice Sheet is a mass of ice larger than Europe, in some places several kilometres from top to bottom. Fed by snowfall over its interior, it spreads out under its own weight, going afloat at its edge in the form of enormous ice shelves with areas ranging from that of Greater London to that of France. The ice shelves are then melted from below by waters from the Southern Ocean. The inputs and outputs of the system are so massive that even very small imbalances can have catastrophic effects on global sea level: the portion of Antarctica known as the West Antarctic Ice Sheet (WAIS), suspected unstable due to the shape of its underlying bedrock, would contribute 3-5 m of sea level rise were it to collapse completely.Satellite observations have shown that some of the fast-flowing outlet glaciers that carry ice out of Antarctica have sped up dramatically. Pine Island Glacier, which drains a significant portion of WAIS, has nearly doubled its speed in the last several decades, creating a large negative imbalance for the ice sheet. The acceleration is thought to be connected to the high under-ice shelf melt rates observed in the region. This melting reduces the ability of the Pine Island Ice Shelf to hold back the glacier feeding it. Increased ice-shelf melt rates are possibly due to warming oceans; but recent studies suggest that melting could actually be strongly dependent on ice shelf and ice sheet behaviour as well. Additionally, a recent glaciological modelling study suggests a "tipping point" may have been crossed, and that ice retreat, though triggered by oceans, is now self-perpetuating regardless of melting. Determining whether the observed retreat is due to ongoing climate forcing, or to feedbacks of the coupled ice-ocean system, is of utmost importance to predicting (and if possible mitigating) future sea level contributions from WAIS.In the proposed work we will address this question through the development of a sophisticated computer model of interacting ice sheet and oceans, and by investigation of the processes involved in ice retreat through controlled modelling experiments. Idealized experiments of ice-ocean interactions will lead up to a realistic modelling study of Pine Island Glacier, designed to assess the relative importance of forcing and feedback in its observed retreat.This study will be unprecedented in terms of the tools developed, the experiments undertaken, and the knowledge gained. Presently no numerical model exists that can fully represent the close interaction between ice sheets, ice shelves, and the ocean circulating beneath them. Furthermore the ice and ocean codes, as well as being ideally suited for coupling together, share properties that will allow for in-depth investigation of model sensitivity and controls, and for the incorporation of ice-sheet observations in a physically consistent manner, vastly improving the reliability of results.

南极冰盖是一块比欧洲还大的冰块，有些地方从上到下有几公里。在其内部降雪的作用下，它在自身重量的作用下展开，以巨大的冰架形式漂浮在其边缘，其区域范围从大伦敦到法国。然后冰架被南大洋的海水从下面融化。该系统的输入和输出如此巨大，即使是非常小的不平衡也会对全球海平面产生灾难性影响：南极洲被称为西南极冰盖（WAIS）的部分由于其底层基岩的形状而被怀疑不稳定，如果完全塌陷，海平面将上升3-5米。卫星观测表明，一些将冰带出南极洲的快速流出冰川的流速急剧加快。派恩岛冰川消耗了 WAIS 的很大一部分水，在过去几十年里，它的速度几乎翻了一番，给冰盖造成了巨大的负不平衡。人们认为这种加速与该地区观察到的高冰架融化速率有关。这种融化降低了松岛冰架阻止冰川为其补给的能力。冰架融化速度加快可能是由于海洋变暖所致；但最近的研究表明，融化实际上也很大程度上取决于冰架和冰盖的行为。此外，最近的一项冰川学模型研究表明，可能已经跨越了一个“临界点”，尽管冰层消退是由海洋引发的，但无论是否融化，现在都会自我延续。确定观察到的退缩是由于持续的气候强迫，还是由于耦合的冰海系统的反馈，对于预测（如果可能的话减轻）WAIS 未来海平面的贡献至关重要。在拟议的工作中，我们将解决这个问题通过开发冰盖和海洋相互作用的复杂计算机模型，并通过受控建模实验研究冰退缩过程，来解决这个问题。冰-海相互作用的理想化实验将导致对松岛冰川的现实建模研究，旨在评估在其观察到的退缩中强迫和反馈的相对重要性。这项研究在开发的工具和进行的实验方面将是前所未有的，以及所获得的知识。目前还没有数值模型能够完全代表冰盖、冰架及其下方循环的海洋之间的密切相互作用。此外，冰和海洋代码以及非常适合耦合在一起的共享属性将允许深入研究模型灵敏度和控制，并以物理一致的方式合并冰盖观测，从而大大提高结果的可靠性。