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/K003674/1
• 负责人: Michael Bentley
• 金额: $ 43.45万
• 依托单位: Durham University
• 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%2FK003674%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 altimetry (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.

该提案旨在提高南极对海平面贡献的估计。海平面目前的上升约为3mm/年。如果我们要了解为什么它正在上升，以及未来的海平面上升将如何继续 - 也许会加速 - 并带来广泛的社会影响，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的大冰块，但是从南极洲损失的冰块尤其难以建立。有三种主要方法可以测量从南极损失或获得的冰量 - 其“质量平衡”。这些是（i）卫星高度测定（准确地测量了冰盖表面如何随着时间的流逝而变化）； （ii）输入输出方法（计算南极降雪的估计数量之间的差异，以及沿海冰的多少或因熔化而损失）； （iii）卫星重量法（测量由于随着时间的推移而在南极冰上损失或增加地球引力场的微小变化）。理想情况下，这三种技术将提供类似的答案，但目前却没有。所有技术都有问题或缺点，所有这些都是正在进行的研究的主题。在此提案中，我们专注于卫星重量法。重量法的质量平衡特别棘手，因为对重力场的变化不仅受冰/增益的影响，而且还通过质量在地球外壳下方移动。在最后一个冰河时代结束时，南极融化的大量冰厚，地球深处的岩石仍在响应1000年后的这种变化。这种反应的后果 - 科学家称冰川相分化的调整或“ GIA” - 必须通过大量资金来纠正卫星测量值，以说明岩石材料的运动，从而为冰块质量损失/增益提供“真实的”数字。它的纠正措施是如此有问题，因为它要求我们知道超过10，000年的冰原历史（包括过去的雪堆积），并且还知道南极洲下方的地球结构。 NERC资助的最新项目在确定这一纠正方面做出了重大改进，但我们最近发表的工作非常清楚地表明，我们仍然缺乏数据来固定在南极洲东部地区的部分地区。换句话说，南极洲东部仍然存在不确定性的不确定性，这直接导致海平面贡献的不确定性。在此提案中，我们确定了一个在东南极东部的地区，该地区是GIA校正中剩余的不确定性，但我们设法确定了合适的地点，我们可以在其中获得必要的ICE历史信息，新的地震测量，对地壳结构进行新的地震测量，以及甲壳上的GPS测量值的GPS测量值（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进行一些世界领先的建模，并综合了现有的积雪数据，我们将为南极洲提供一种新的且改进的GIA校正。尽管我们的数据收集重点将放在大衣上，但随后的建模工作将涵盖整个南极的所有。数据将用于开发南极洲的GIA改进模型，以纠正宽限期数据集。我们保守地估计，通过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量表测量中的总不确定性减半，并且可能比这更好。该提议提高了对当今全球海平面上升的南极贡献的改进的前景。

项目成果

Exploring the Last Continent - An Introduction to Antarctica

探索最后的大陆——南极洲简介

• DOI: 10.1007/978-3-319-18947-5_25
• 发表时间: 2015
• 作者: Bentley M

Past and future dynamics of the Brunt Ice Shelf from seabed bathymetry and ice shelf geometry

• DOI: 10.5194/tc-13-545-2019
• 发表时间: 2019-02-14
• 期刊: CRYOSPHERE
• 影响因子: 5.2
• 作者: Hodgson, Dominic A.;Jordan, Tom A.;Vaughan, David G.
• 通讯作者: Vaughan, David G.

Low post-glacial rebound rates in the Weddell Sea due to Late Holocene ice-sheet readvance

• DOI: 10.1016/j.epsl.2014.12.039
• 发表时间: 2015-03-01
• 期刊: EARTH AND PLANETARY SCIENCE LETTERS
• 影响因子: 5.3
• 作者: Bradley, Sarah L.;Hindmarsh, Richard C. A.;King, Matt A.
• 通讯作者: King, Matt A.

Evaluation of Mumiyo Deposits From East Antarctica as Archives for the Late Quaternary Environmental and Climatic History

• DOI: 10.1029/2018gc008054
• 发表时间: 2019-01-01
• 期刊: GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
• 影响因子: 3.5
• 作者: Berg, S.;Melles, M.;Kuhn, G.
• 通讯作者: Kuhn, G.

Deglaciation and future stability of the Coats Land ice margin, Antarctica

• DOI: 10.5194/tc-12-2383-2018
• 发表时间: 2018-07
• 期刊: The Cryosphere
• 作者: D. Hodgson;K. Hogan;J. N. Smith;James R. Smith;C. Hillenbrand;A. Graham;P. Fretwell;C. Allen;V. Peck;J. Arndt;B. Dorschel;Christian Hübscher;A. Smith;R. Larter