Ocean Circulation and Ice Shelf Melting on the Amundsen Sea Continental Shelf

阿蒙森海大陆架上的海洋环流和冰架融化

• 批准号: NE/G001367/1
• 负责人: Adrian Jenkins
• 金额: $ 51.65万
• 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: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FG001367%2F1
• 关键词: Ocean; Circulation; Ice; Shelf; Melting

Sea levels around the world are currently rising by about 2 mm every year. That may not sound very much, but people living in areas such as Holland or East Anglia are already threatened by coastal erosion. If we are to say how that threat might change in the future we must learn how to forecast changes in sea level. To do this we must understand what is happening to the Earth's great reservoirs of freshwater, and whether or not they are slowly draining into the ocean. The largest of these reservoirs by far is the Antarctic Ice Sheet, which contains 70% of all the freshwater on the planet. At present we do not know whether the ice sheet is growing or shrinking overall, but we do know that some parts of it are getting smaller. The fastest changes are happening at the edge of the ice sheet, where it flows into the sea, in a place called Pine Island Bay. Nobody yet knows what is causing these changes, and their speed has taken scientists by surprise. Pine Island Bay is geographically the far south of the Pacific Ocean, and the image of warmth that this conjures up is not entirely misplaced. The air temperatures never rise above freezing and the coast is battered by storms, but beneath the cold surface of the sea, water temperatures rise as high as 1 degree Celcius. This may seem cold by our standards (sea temperatures around Britain rarely drop into single figures, even in winter), but it is warm enough to melt the ice. Pine Island Glacier is a vast river of ice that flows out into Pine Island Bay. It carries as much water as the River Rhine, but in frozen form. The last 75 km of the Glacier floats on the waters of Pine Island Bay, and the bottom melts so intensely that half of the ice carried in the glacier is lost within the space of 30 years. The other half breaks off the end of the glacier as icebergs, which drift away to melt elsewhere. It is not hard to understand that warm water causes rapid melting, but what do 'warm' and 'rapid' really mean? If we change the water temperature by a small amount, by how much will the melt rate change? To find the answers to those questions we must make measurements of the water temperature beneath the glacier, but to do so is enormously challenging. The glacier is between 300 m and 1 km thick, so we cannot get instruments through from above, while the drifting Antarctic pack ice bars access to the front of the glacier to all but the most powerful ships. Engineers working at the Southampton Oceanography Centre have, over many years, designed and built a solution to this problem in the form of a robotic submarine that they can programme to dive beneath the ice, make measurements along a pre-defined track, then return to the surface with the vital data. By teaming up with American scientists, who can make use of a powerful icebreaker, we hope to take the submarine right up to Pine Island Glacier and launch it on its mission beneath the ice.The underwater cavern beneath the glacier is completely unknown and the submarine must find its own way in and out, avoiding any obstacles that it finds along its path. The Antarctic pack ice is notoriously unpredictable and could prove a huge challenge to the ship. But the potential return makes the risks worthwhile. Armed with our new knowledge we will build a computer model that describes the flow of water within the remote cavern beneath the glacier and in the sea to the north of it. Using this model we will determine if there have been any changes in the water temperature in Pine Island Bay over the past 20 years and how such changes would have affected melting of the glacier base. Other scientists can then use our results to establish if changes in the glacier's melt rate could have caused the ice sheet to thin in the way that has been observed, and together we will be able to say with greater certainty what impact the glaciers of Pine Island Bay will have on the future coastlines of Holland and East Anglia.

目前，全球海平面每年上升约2毫米。这听起来可能不多，但生活在荷兰或东英吉利亚等地区的人们已经受到海岸侵蚀的威胁。如果我们要说这种威胁在未来可能如何变化，我们必须学会如何预测海平面的变化。要做到这一点，我们必须了解地球上巨大的淡水水库正在发生什么，以及它们是否正在慢慢排入海洋。目前为止，这些水库中最大的是南极冰盖，它包含了地球上70%的淡水。目前，我们不知道冰盖总体上是在扩大还是缩小，但我们知道它的某些部分正在变小。最快的变化发生在冰盖的边缘，在那里它流入大海，在一个叫松岛湾的地方。目前还没有人知道是什么导致了这些变化，它们的速度让科学家们大吃一惊。松岛湾在地理位置上位于太平洋的最南端，这给人带来的温暖印象并不完全是错误的。空气温度从未超过冰点，海岸受到风暴的袭击，但在寒冷的海面下，水温上升高达1摄氏度。按照我们的标准，这似乎很冷（英国周围的海水温度很少下降到个位数，即使在冬天），但它足够温暖，可以融化冰。松岛冰川是一条巨大的冰河，流入松岛湾。它的水量和莱茵河一样多，但都是冰冻的。最后75公里长的冰川漂浮在松岛湾的沃茨上，底部融化得如此剧烈，以至于冰川中一半的冰在30年内消失了。另一半则从冰川的末端脱落，形成冰山，漂流到别处融化。不难理解，温暖的海水会导致快速融化，但“温暖”和“快速”到底是什么意思？如果我们稍微改变水温，融化速率会改变多少？为了找到这些问题的答案，我们必须测量冰川下的水温，但这样做是非常具有挑战性的。冰川的厚度在300米到1公里之间，所以我们无法从上面通过仪器，而漂移的南极浮冰阻碍了除了最强大的船只之外的所有船只进入冰川的前部。多年来，在南安普顿海洋学中心工作的工程师们设计并建造了一种机器人潜艇，他们可以编程潜入冰层下，沿着预定义的轨道进行测量，然后带着重要数据返回水面。通过与美国科学家合作，他们可以使用一艘强大的破冰船，我们希望将潜艇直接带到松岛冰川，并在冰下执行使命。冰川下的水下洞穴是完全未知的，潜艇必须找到自己的进出方式，避开沿着发现的任何障碍物。2南极浮冰是出了名的不可预测，这对这艘船来说是一个巨大的挑战。但潜在的回报让风险变得值得。有了我们的新知识，我们将建立一个计算机模型，描述冰川下遥远的洞穴和冰川以北的海洋中的水流。利用这个模型，我们将确定在过去的20年里，松岛湾的水温是否有任何变化，以及这些变化如何影响冰川底部的融化。然后，其他科学家可以利用我们的研究结果来确定冰川融化速度的变化是否会导致冰盖以观察到的方式变薄，我们将能够更确定地说松岛湾的冰川将对荷兰和东英吉利亚未来的海岸线产生什么影响。

项目成果

High-resolution sub-ice-shelf seafloor records of twentieth century ungrounding and retreat of Pine Island Glacier, West Antarctica

南极洲西部松岛冰川二十世纪脱底和退缩的高分辨率冰架下海底记录

• DOI: 10.1002/2017jf004311
• 发表时间: 2017
• 期刊: Earth Surface
• 作者: Davies D

Basal terraces on melting ice shelves

• DOI: 10.1002/2014gl060618
• 发表时间: 2014-08-16
• 期刊: GEOPHYSICAL RESEARCH LETTERS
• 影响因子: 5.2
• 作者: Dutrieux, Pierre;Stewart, Craig;Steffen, Konrad
• 通讯作者: Steffen, Konrad

Getz Ice Shelf melting response to changes in ocean forcing

• DOI: 10.1002/jgrc.20298
• 发表时间: 2013-09-01
• 期刊: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
• 影响因子: 3.6
• 作者: Jacobs, S.;Giulivi, C.;Mouginot, J.
• 通讯作者: Mouginot, J.

Geometric and oceanographic controls on melting beneath Pine Island Glacier

• DOI: 10.1002/2013jc009513
• 发表时间: 2014-04-01
• 期刊: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
• 影响因子: 3.6
• 作者: De Rydt, J.;Holland, P. R.;Jenkins, A.
• 通讯作者: Jenkins, A.

Seabed corrugations beneath an Antarctic ice shelf revealed by autonomous underwater vehicle survey: Origin and implications for the history of Pine Island Glacier

• DOI: 10.1002/jgrf.20087
• 发表时间: 2013-09-01
• 期刊: JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE
• 影响因子: 3.9
• 作者: Graham, Alastair G. C.;Dutrieux, Pierre;Jenkins, Adrian
• 通讯作者: Jenkins, Adrian