Investigating the Dynamic Response of the Greenland Ice Sheet to Climate Forcing using a Geophysical, Remote-Sensing and Numerical Modelling Framework

使用地球物理、遥感和数值模拟框架研究格陵兰冰盖对气候强迫的动态响应

• 批准号: NE/G007195/1
• 负责人: Bernd Kulessa
• 金额: $ 14.69万
• 依托单位: Swansea University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FG007195%2F1
• 关键词: Investigating; Dynamic; Response; Greenland; Ice

Summary An increasing number of scientific studies show that human activities, e.g. burning of fossil fuels, have increased the concentration of heat-trapping gasses in the atmosphere. It is estimated that global temperatures will increase by 2-5 degrees C during this century if we continue to add carbon dioxide and other 'greenhouse' gasses to the atmosphere. In the Arctic, warming is expected to be even faster and mean annual temperature may increase by 4-7 degrees C. The implications of global warming are of immense proportions because glaciers and ice sheets will melt faster and become increasingly prone to collapse. In Greenland, discharge from outlet glaciers is responsible for about half the annual loss of ice. The other lost half is due to runoff of surface meltwater. The combined effect of iceberg discharge and surface melt are currently greater than the total amount of snowfall falling onto the Greenland Ice Sheet. This ice sheet is therefore shrinking while releasing freshwater into the Atlantic Ocean. The imbalance amounted to -90 cubic km per year for 1996 and increased to -140 cubic km per year by 2000. In 2005, this imbalance may have increased to as much as -220 cubic km per year. The size of the Greenland Ice Sheet is thus diminishing at what appears to be a growing rate. Worldwide concern is associated with this trend because ice-sheet decay results in global sea-level rise and possibly even an obstruction of oceanic circulation, which in key places - such as the North Atlantic - is sensitive to freshwater released from melting ice masses. The Greenland Ice Sheet rests on bedrock above or close to sea level. Glaciologists have for years assumed that such position would be stable and that demise of the ice sheet would require thousands of years even under extreme global warming scenarios. This assumption may need revision. It was shown recently that surface meltwater could penetrate through over 1km of ice to the base of the Greenland Ice Sheet and cause ice-flow speed-up due to faster basal sliding. This mechanism is potentially dangerous because accelerated ice flow leads to thinning, which in turn leads to an increase in surface melt since a larger part of the ice sheet moves into lower and warmer elevations. The Greenland Ice Sheet may therefore be far more prone to decay than it was assumed in earlier projections of global warming. However, up until now the mechanisms by which this dynamic response between surface melt and ice flow have only been generally understood and the present generation of climate-ice sheet models which are used to forecast future sea-level change do not include them in any rigorous manner. This is particularly true in respect of: 1) the extent to which the surface, interior and basal water-plumbing and ice flow systems can moderate, amplify and transmit the dynamic response away into the interior of the ice sheet thereby drawing the inland ice reservoir down and, 2) the extent to which future changes in Greenland temperatures may increase both the area and length of time of which the ice sheet directly experiences these effects. This project directly addresses both of these shortcomings in current models and will implement a set of fieldwork, satellite remote-sensing and comprehensive Greenland Ice Sheet modelling simulations that will fully assess and implement those 'dynamical processes related to ice flow not included in current models... (which) could increase the vulnerability of the ice sheets to warming, increasing future sea-level rise.' (IPCC, WG1 - 2007).

越来越多的科学研究表明，人类活动，例如燃烧化石燃料，增加了大气中吸热气体的浓度。据估计，如果我们继续向大气中排放二氧化碳和其他“温室”气体，本世纪全球气温将上升2-5摄氏度。在北极，预计变暖的速度会更快，年平均气温可能会上升4-7摄氏度。全球变暖的影响是巨大的，因为冰川和冰盖将融化得更快，越来越容易崩溃。在格陵兰岛，出水口冰川的排放造成了每年冰损失的一半左右。另外一半的损失是由于地表融水的径流。目前，冰山排放和表面融化的综合影响大于落在格陵兰冰盖上的降雪量。因此，这片冰盖在向大西洋释放淡水的同时正在萎缩。这种不平衡在1996年达到每年-90立方公里，到2000年增加到每年-140立方公里。2005年，这种不平衡可能增加到每年-220立方千米。因此，格陵兰冰盖的大小正在以似乎正在增长的速度缩小。这一趋势引起了全世界的关注，因为冰盖的腐烂导致全球海平面上升，甚至可能阻碍海洋环流，而在关键地区，如北大西洋，海洋环流对融化冰块释放的淡水很敏感。格陵兰冰盖位于高于或接近海平面的基岩上。冰川学家多年来一直认为，这样的位置是稳定的，即使在极端的全球变暖情况下，冰盖的消失也需要数千年的时间。这种假设可能需要修正。最近的研究表明，表面融水可以穿透超过1公里的冰，到达格陵兰冰盖的底部，并由于基底滑动更快而导致冰流加速。这种机制具有潜在的危险性，因为冰流加速会导致冰层变薄，而冰层变薄反过来又会导致冰盖表面融化的增加，因为大部分冰盖移动到海拔更低、更温暖的地方。因此，格陵兰冰盖可能比先前对全球变暖的预测所假定的更容易腐烂。然而，到目前为止，地表融化和冰流之间这种动态响应的机制只是大致了解，而目前用于预测未来海平面变化的气候-冰盖模式没有以任何严格的方式包括它们。在以下方面尤其如此：1)地表、内部和基础水管道系统和冰流系统能够在多大程度上缓和、扩大和传递动态响应到冰盖内部，从而使内陆冰库下降；2)格陵兰岛未来温度的变化可能在多大程度上增加冰盖直接经历这些影响的面积和时间长度。该项目直接解决了当前模型中的这两个缺点，并将实施一套实地考察、卫星遥感和全面的格陵兰冰盖建模模拟，这些模拟将充分评估和实施“当前模型中未包括的与冰流相关的动态过程”……这可能会增加冰盖对变暖的脆弱性，增加未来海平面的上升。（ipcc, 1 - 2007）。

项目成果

Ice tectonics during the rapid tapping of a supraglacial lake on the Greenland Ice Sheet

格陵兰冰盖上冰上湖快速流淌过程中的冰构造

• DOI: 10.5194/tcd-6-3863-2012
• 发表时间: 2012
• 作者: Doyle S

Ice tectonic deformation during the rapid in situ drainage of a supraglacial lake on the Greenland Ice Sheet

• DOI: 10.5194/tc-7-129-2013
• 发表时间: 2013-01-01
• 期刊: CRYOSPHERE
• 影响因子: 5.2
• 作者: Doyle, S. H.;Hubbard, A. L.;Box, J. E.
• 通讯作者: Box, J. E.

Seismic evidence for complex sedimentary control of Greenland Ice Sheet flow.

• DOI: 10.1126/sciadv.1603071
• 发表时间: 2017-08
• 期刊: Science advances
• 影响因子: 13.6
• 作者: Kulessa B;Hubbard AL;Booth AD;Bougamont M;Dow CF;Doyle SH;Christoffersen P;Lindbäck K;Pettersson R;Fitzpatrick AAW;Jones GA
• 通讯作者: Jones GA

Theory and numerical modeling of electrical self-potential signatures of unsaturated flow in melting snow

融雪中非饱和流电自电位特征的理论和数值模拟

• DOI: 10.1029/2012wr012048
• 发表时间: 2012
• 期刊: Water Resources Research
• 影响因子: 5.4
• 作者: Kulessa B

Modeling of subglacial hydrological development following rapid supraglacial lake drainage.

• DOI: 10.1002/2014jf003333
• 发表时间: 2015-06
• 期刊: Journal of geophysical research. Earth surface
• 作者: Dow CF;Kulessa B;Rutt IC;Tsai VC;Pimentel S;Doyle SH;van As D;Lindbäck K;Pettersson R;Jones GA;Hubbard A
• 通讯作者: Hubbard A