Reducing the uncertainty in estimates of the sea level contribution from the westernmost part of the East Antarctic Ice Sheet

减少东南极冰盖最西端海平面贡献估计的不确定性

• 批准号: NE/K003933/1
• 负责人: Robert Mulvaney
• 金额: $ 13.54万
• 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%2FK003933%2F1
• 关键词: Reducing; uncertainty; estimates; sea; level

This proposal aims to improve estimates of Antarctica's contribution to sea level. Sea level is currently rising at approximately 3mm/yr. If we are to understand why it is rising and how future sea-level rise will continue - perhaps accelerate - and lead to a wide range of societal impacts then we need to understand the different contributions to sea level. Some of the largest contributions come from the great ice sheets in Antarctica and Greenland but the amount of ice being lost from Antarctica is particularly difficult to establish. There are three main ways to measure the amount of ice being lost or gained from Antarctica - its 'mass balance'. These are (i) satellite altimetery (measuring very precisely how the ice sheet surface is going up or down through time); (ii) the input-output method (calculating the difference between estimates of how much snow falls on Antarctica, and how much ice breaks off at the coast or is lost by melting); (iii) satellite gravimetry (measuring minute changes in Earth's gravitational field caused by loss or gain of ice in Antarctica through time). Ideally, these three techniques would provide similar answers but they currently do not. All the techniques have problems or drawbacks and all are the subject of ongoing research. In this proposal we focus on the satellite gravimetry method. Mass balance from gravimetry is particularly tricky to calculate because the changes to the gravitational field are not only affected by ice loss/gain but also by mass moving around beneath the Earth's crust. At the end of the last ice age, a large thickness of ice in Antarctica melted and the rocks deep within the Earth are still responding to this change 1000s of years later. The consequence of this response - which scientists call glacial-isostatic adjustment or 'GIA' - is that the satellite measurements have to be corrected by a very large amount that accounts for movements of the rocky material and thus to provide the 'real' figure for ice mass loss/gain. It is getting this correction right that has been so problematic because it requires us to know the history of the ice sheet (including past snow accumulation) for over 10,000 years and also to know the structure of the Earth underneath Antarctica. Recent projects including a previous one by our group that was funded by NERC have made substantial improvements in determining this correction but our recently published work has shown very clearly that we still lack data to pin down the GIA correction tightly enough in parts of East Antarctica. In other words there is still an unacceptable level of uncertainty in East Antarctica, which leads directly to uncertainty in sea-level contribution. In this proposal we have identified a region called Coats Land, in East Antarctica, which accounts for the greatest remaining uncertainty in the GIA correction but where we have managed to identify suitable sites where we can obtain the necessary ice history information, new seismic measurements of crustal structure, and GPS measurements of crustal uplift (a key part of testing GIA models). By visiting these sites and undertaking some world-leading modelling using our field data and a synthesis of existing snow accumulation data we will provide a new and much improved GIA correction for Antarctica. Whilst our data collection focus will be on Coats Land our subsequent modelling effort will encompass all of Antarctica. The data will be used to develop an improved model of GIA in Antarctica in order to correct the GRACE dataset. We conservatively estimate that with the measurements and modelling that we propose to carry out then we can at least halve the total uncertainty in satellite gravimetry measurements of Antarctic mass balance, and probably do substantially better than this. This proposal raises the prospect of getting an improved estimate of the Antarctic contribution to present-day global sea level rise.

这项建议旨在改进对南极洲对海平面影响的估计。海平面目前正以每年约3毫米的速度上升。如果我们要了解海平面上升的原因以及未来海平面上升将如何继续-也许会加速-并导致广泛的社会影响，那么我们需要了解对海平面的不同贡献。一些最大的贡献来自南极洲和格陵兰岛的大冰盖，但南极洲的冰量损失特别难以确定。有三种主要方法可以测量南极洲的冰量损失或增加-它的“质量平衡”。（一）卫星高度计（非常精确地测量冰盖表面如何随时间上升或下降）;（ii）投入产出法（计算南极洲上有多少福尔斯降雪量与有多少冰在海岸断裂或因融化而消失的估计值之间的差异）;（iii）卫星重力测量（测量南极洲冰随时间增减而引起的地球重力场的微小变化）。理想情况下，这三种技术将提供类似的答案，但它们目前没有。所有的技术都有问题或缺点，都是正在进行的研究的主题。在这个建议中，我们专注于卫星重力测量方法。重力测量的质量平衡计算起来特别棘手，因为重力场的变化不仅受到冰的损失/增加的影响，而且还受到地壳下质量移动的影响。在最后一个冰河时代结束时，南极洲的一大片冰层融化了，地球深处的岩石在1000年后仍然对这种变化做出反应。这种反应的结果-科学家称之为冰川均衡调整或“GIA”-是卫星测量必须进行非常大的修正，以解释岩石材料的运动，从而提供冰质量损失/增加的“真实的”数字。正确地进行这种校正是很有问题的，因为它要求我们知道冰盖的历史（包括过去的积雪）超过10,000年，也要知道南极洲下面的地球结构。最近的项目，包括我们小组之前由NERC资助的项目，在确定这种校正方面取得了实质性的改进，但我们最近发表的工作非常清楚地表明，我们仍然缺乏足够严格的数据来确定东南极洲部分地区的GIA校正。换句话说，东南极洲的不确定性仍然是不可接受的，这直接导致了海平面影响的不确定性。在本提案中，我们确定了位于南极洲东部的一个名为科茨地的地区，该地区是GIA校正中剩余不确定性最大的地区，但我们已设法确定了合适的地点，在那里我们可以获得必要的冰史信息，地壳结构的新地震测量结果以及地壳隆起的GPS测量结果（测试GIA模型的关键部分）。通过访问这些站点并使用我们的现场数据和现有积雪数据的综合进行一些世界领先的建模，我们将为南极洲提供一个新的和大大改进的GIA校正。虽然我们的数据收集重点将放在科茨地，但我们随后的建模工作将涵盖整个南极洲。这些数据将用于开发一个改进的南极GIA模型，以纠正GRACE数据集。我们保守地估计，通过我们提议进行的测量和建模，我们至少可以将南极质量平衡的卫星重力测量的总不确定性减半，并且可能做得比这更好。这一提议提出了一个前景，即对南极洲对当今全球海平面上升的贡献作出更好的估计。

项目成果

Changes in Holocene climate and the intensity of Southern Hemisphere Westerly Winds based on a high-resolution palynological record from sub-Antarctic South Georgia

• DOI: 10.1177/0959683614557576
• 发表时间: 2015-02
• 期刊: The Holocene
• 作者: Stephanie L. Strother;U. Salzmann;S. Roberts;D. Hodgson;J. Woodward;Wim Van Nieuwenhuyze;E. Verleyen;W. Vyverman;S. Moreton

A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum

• DOI: 10.1016/j.quascirev.2014.06.025
• 发表时间: 2014-09-15
• 期刊: QUATERNARY SCIENCE REVIEWS
• 影响因子: 4
• 作者: Bentley, Michael J.;Cofaigh, Colm O.;Zwartz, Dan
• 通讯作者: Zwartz, Dan

Sea ice led to poleward-shifted winds at the Last Glacial Maximum: the influence of state dependency on CMIP5 and PMIP3 models

• DOI: 10.5194/cp-12-2241-2016
• 发表时间: 2016-12
• 期刊: Climate of The Past
• 影响因子: 4.3
• 作者: L. Sime;D. Hodgson;T. Bracegirdle;C. Allen;Bianca B. Perren;S. Roberts;A. M. Boer

Antarctic ice rises and rumples: Their properties and significance for ice-sheet dynamics and evolution

• DOI: 10.1016/j.earscirev.2015.09.004
• 发表时间: 2015-11
• 期刊: Earth-Science Reviews
• 影响因子: 12.1
• 作者: K. Matsuoka;R. Hindmarsh;G. Moholdt;M. J. Bentley;H. Pritchard;Joel Brown;H. Conway;R. Drews;G. Durand;D. Goldberg;T. Hattermann;J. Kingslake;J. Lenaerts;C. Martín;R. Mulvaney;K. Nicholls;F. Pattyn;N. Ross;T. Scambos;P. Whitehouse