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南极冰盖流失将影响未来的气候变化 快报文章
资源环境快报,2020年第19期
作者:  薛明媚,王金平
Microsoft Word(14Kb)  |  收藏  |  浏览/下载:438/0  |  提交时间:2020/10/15
Antarctic Ice Sheet  Future Climate Change  Loss  
ISMIP6分析南极和格陵兰冰盖对未来海平面的贡献 快报文章
气候变化快报,2020年第19期
作者:  刘燕飞
Microsoft Word(15Kb)  |  收藏  |  浏览/下载:444/0  |  提交时间:2020/09/29
Greenland  Antarctica  Ice Sheet  Sea-level Rise  Mass Loss  Ensemble  Representative Concentration Pathway  
南北极冰盖损失正在沿最严重的气候预估情景发展 快报文章
气候变化快报,2020年第18期
作者:  刘燕飞
Microsoft Word(16Kb)  |  收藏  |  浏览/下载:403/0  |  提交时间:2020/09/20
Ice-sheet loss  Sea-level rise  IPCC  Antarctica  Greenland  
Ice retreat in Wilkes Basin of East Antarctica during a warm interglacial 期刊论文
NATURE, 2020, 583 (7817) : 554-+
作者:  T. Blackburn;  G. H. Edwards;  S. Tulaczyk;  M. Scudder;  G. Piccione;  B. Hallet;  N. McLean;  J. C. Zachos;  B. Cheney;  J. T. Babbe
收藏  |  浏览/下载:61/0  |  提交时间:2020/08/09

Uranium isotopes in subglacial precipitates from the Wilkes Basin of the East Antarctic Ice Sheet reveal ice retreat during a warm Pleistocene interglacial period about 400,000 years ago.


Efforts to improve sea level forecasting on a warming planet have focused on determining the temperature, sea level and extent of polar ice sheets during Earth'  s past interglacial warm periods(1-3). About 400,000 years ago, during the interglacial period known as Marine Isotopic Stage 11 (MIS11), the global temperature was 1 to 2 degrees Celsius greater(2)and sea level was 6 to 13 metres higher(1,3). Sea level estimates in excess of about 10 metres, however, have been discounted because these require a contribution from the East Antarctic Ice Sheet(3), which has been argued to have remained stable for millions of years before and includes MIS11(4,5). Here we show how the evolution of(234)U enrichment within the subglacial waters of East Antarctica recorded the ice sheet'  s response to MIS11 warming. Within the Wilkes Basin, subglacial chemical precipitates of opal and calcite record accumulation of(234)U (the product of rock-water contact within an isolated subglacial reservoir) up to 20 times higher than that found in marine waters. The timescales of(234)U enrichment place the inception of this reservoir at MIS11. Informed by the(234)U cycling observed in the Laurentide Ice Sheet, where(234)U accumulated during periods of ice stability(6)and was flushed to global oceans in response to deglaciation(7), we interpret our East Antarctic dataset to represent ice loss within the Wilkes Basin at MIS11. The(234)U accumulation within the Wilkes Basin is also observed in the McMurdo Dry Valleys brines(8-10), indicating(11)that the brine originated beneath the adjacent East Antarctic Ice Sheet. The marine origin of brine salts(10)and bacteria(12)implies that MIS11 ice loss was coupled with marine flooding. Collectively, these data indicate that during one of the warmest Pleistocene interglacials, the ice sheet margin at the Wilkes Basin retreated to near the precipitate location, about 700 kilometres inland from the current position of the ice margin, which-assuming current ice volumes-would have contributed about 3 to 4 metres(13)to global sea levels.


  
基于卫星数据的2003—2019年冰盖质量变化 快报文章
资源环境快报,2020年第10期
作者:  吴秀平
Microsoft Word(21Kb)  |  收藏  |  浏览/下载:128/0  |  提交时间:2020/05/28
ice sheet  mass loss  ocean and atmosphere processes  
Ice front blocking of ocean heat transport to an Antarctic ice shelf 期刊论文
NATURE, 2020, 578 (7796) : 568-+
作者:  Alexandrov, Ludmil B.;  Kim, Jaegil;  Haradhvala, Nicholas J.;  Huang, Mi Ni;  Ng, Alvin Wei Tian;  Wu, Yang;  Boot, Arnoud;  Covington, Kyle R.;  Gordenin, Dmitry A.;  Bergstrom, Erik N.;  Islam, S. M. Ashiqul;  Lopez-Bigas, Nuria;  Klimczak, Leszek J.;  McPherson, John R.;  Morganella, Sandro;  Sabarinathan, Radhakrishnan;  Wheeler, David A.;  Mustonen, Ville;  Getz, Gad;  Rozen, Steven G.;  Stratton, Michael R.
收藏  |  浏览/下载:44/0  |  提交时间:2020/05/13

The front of the Getz Ice Shelf in West Antarctica creates an abrupt topographic step that deflects ocean currents, suppressing 70% of the heat delivery to the ice sheet.


Mass loss from the Antarctic Ice Sheet to the ocean has increased in recent decades, largely because the thinning of its floating ice shelves has allowed the outflow of grounded ice to accelerate(1,2). Enhanced basal melting of the ice shelves is thought to be the ultimate driver of change(2,3), motivating a recent focus on the processes that control ocean heat transport onto and across the seabed of the Antarctic continental shelf towards the ice(4-6). However, the shoreward heat flux typically far exceeds that required to match observed melt rates(2,7,8), suggesting that other critical controls exist. Here we show that the depth-independent (barotropic) component of the heat flow towards an ice shelf is blocked by the marked step shape of the ice front, and that only the depth-varying (baroclinic) component, which is typically much smaller, can enter the sub-ice cavity. Our results arise from direct observations of the Getz Ice Shelf system and laboratory experiments on a rotating platform. A similar blocking of the barotropic component may occur in other areas with comparable ice-bathymetry configurations, which may explain why changes in the density structure of the water column have been found to be a better indicator of basal melt rate variability than the heat transported onto the continental shelf(9). Representing the step topography of the ice front accurately in models is thus important for simulating ocean heat fluxes and induced melt rates.


  
Oceanic forcing of penultimate deglacial and last interglacial sea-level rise 期刊论文
NATURE, 2020, 577 (7792) : 660-+
作者:  Rizal, Yan;  Westaway, Kira E.;  Zaim, Yahdi;  van den Bergh, Gerrit D.;  Bettis, E. Arthur, III;  Morwood, Michael J.;  Huffman, O. Frank;  Grun, Rainer;  Joannes-Boyau, Renaud;  Bailey, Richard M.;  Sidarto;  Westaway, Michael C.;  Kurniawan, Iwan;  Moore, Mark W.;  Storey, Michael;  Aziz, Fachroel;  Suminto;  Zhao, Jian-xin;  Aswan;  Sipola, Maija E.;  Larick, Roy;  Zonneveld, John-Paul;  Scott, Robert;  Putt, Shelby;  Ciochon, Russell L.
收藏  |  浏览/下载:41/0  |  提交时间:2020/05/13

Sea-level histories during the two most recent deglacial-interglacial intervals show substantial differences(1-3) despite both periods undergoing similar changes in global mean temperature(4,5) and forcing from greenhouse gases(6). Although the last interglaciation (LIG) experienced stronger boreal summer insolation forcing than the present interglaciation(7), understanding why LIG global mean sea level may have been six to nine metres higher than today has proven particularly challenging(2). Extensive areas of polar ice sheets were grounded below sea level during both glacial and interglacial periods, with grounding lines and fringing ice shelves extending onto continental shelves(8). This suggests that oceanic forcing by subsurface warming may also have contributed to ice-sheet loss(9-12) analogous to ongoing changes in the Antarctic(13,14) and Greenland(15) ice sheets. Such forcing would have been especially effective during glacial periods, when the Atlantic Meridional Overturning Circulation (AMOC) experienced large variations on millennial timescales(16), with a reduction of the AMOC causing subsurface warming throughout much of the Atlantic basin(9,12,17). Here we show that greater subsurface warming induced by the longer period of reduced AMOC during the penultimate deglaciation can explain the more-rapid sea-level rise compared with the last deglaciation. This greater forcing also contributed to excess loss from the Greenland and Antarctic ice sheets during the LIG, causing global mean sea level to rise at least four metres above modern levels. When accounting for the combined influences of penultimate and LIG deglaciation on glacial isostatic adjustment, this excess loss of polar ice during the LIG can explain much of the relative sea level recorded by fossil coral reefs and speleothems at intermediate- and far-field sites.


  
Mass balance of the Greenland Ice Sheet from 1992 to 2018 期刊论文
NATURE, 2020, 579 (7798) : 233-+
作者:  Scudellari, Megan
收藏  |  浏览/下载:31/0  |  提交时间:2020/04/16

The Greenland Ice Sheet has been a major contributor to global sea-level rise in recent decades(1,2), and it is expected to continue to be so(3). Although increases in glacier flow(4-6) and surface melting(7-9) have been driven by oceanic(10-12) and atmospheric(13,14) warming, the magnitude and trajectory of the ice sheet'  s mass imbalance remain uncertain. Here we compare and combine 26 individual satellite measurements of changes in the ice sheet'  s volume, flow and gravitational potential to produce a reconciled estimate of its mass balance. The ice sheet was close to a state of balance in the 1990s, but annual losses have risen since then, peaking at 345 +/- 66 billion tonnes per year in 2011. In all, Greenland lost 3,902 +/- 342 billion tonnes of ice between 1992 and 2018, causing the mean sea level to rise by 10.8 +/- 0.9 millimetres. Using three regional climate models, we show that the reduced surface mass balance has driven 1,964 +/- 565 billion tonnes (50.3 per cent) of the ice loss owing to increased meltwater runoff. The remaining 1,938 +/- 541 billion tonnes (49.7 per cent) of ice loss was due to increased glacier dynamical imbalance, which rose from 46 +/- 37 billion tonnes per year in the 1990s to 87 +/- 25 billion tonnes per year since then. The total rate of ice loss slowed to 222 +/- 30 billion tonnes per year between 2013 and 2017, on average, as atmospheric circulation favoured cooler conditions(15) and ocean temperatures fell at the terminus of Jakobshavn Isbr AE(16). Cumulative ice losses from Greenland as a whole have been close to the rates predicted by the Intergovernmental Panel on Climate Change for their high-end climate warming scenario(17), which forecast an additional 70 to 130 millimetres of global sea-level rise by 2100 compared with their central estimate.