Ocean circulation and melting beneath the ice shelves of the south-eastern Amundsen Sea

阿蒙森海东南部冰架下的海洋环流和融化

基本信息

批准号：
NE/J005770/1
负责人：
Adrian Jenkins
金额：
$ 66.56万
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：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FJ005770%2F1
关键词：
Ocean circulation melting beneath ice

项目摘要

Sea levels around the world are currently rising, threatening coastal populations with flooding and increased erosion, and evaluating the future threat requires an ability 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, and we know that parts of the ice sheet are thinning. The fastest changes are happening near the edge of the ice sheet, where it flows into the sea in a place called Pine Island Bay, and the speed of the changes 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, but beneath the cold surface of the sea, water temperatures rise as high as 1 degree Celsius, well above the freezing point. Pine Island Glacier is a vast river of ice that flows out into Pine Island Bay, carrying as much water as the River Rhine in frozen form. The last 60 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. 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? And critically, what might cause the ocean temperature to change?To find the answers to those questions we must make measurements of the water temperature beneath the glacier, and simultaneous measurements of the rate at which the base of the glacier is melting into the ocean, but to do so is enormously challenging. The glacier is between 300 m and 1 km thick, so it is difficult to access its base. The key is cutting-edge technology, in the form a robotic submarine capable of diving beneath the ice, making measurements along a pre-defined track, then returning to the surface with the data, and a set of rugged, autonomous radar systems that can left on the glacier's surface throughout the Antarctic winter precisely measuring the rate at which the thickness of the ice changes.The robot submarine has been designed and built by NERC engineers and has already proved itself on preliminary missions beneath Pine Island Glacier in 2009. The radar systems will be developed as part of this project. They will combine a well-known radar technique, FMCW radar, with careful measurement of the phase of the return echoes to establish the position of unique features in the image, such as the bottom of the glacier, with very high precision of the order of 1 mm over a 1 km range. Four of these radar instruments will be left on the surface of Pine Island Glacier, engineered to allow year-round autonomous operation and monitoring of the gradual change of ice thickness with time. Armed with the data from these new instruments we will use 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 how heat that is transported into the cavern by ocean currents is used to melt the ice shelf and what impact changes in the climate of this part of Antarctic will have on the ocean currents and resulting melt rates. This information will allow others to assess with greater certainty how future climate change will impact the glaciers of Pine Island Bay and hence how this remote part of the world will influence the future coastlines of places such as Holland and East Anglia.

目前，世界各地的海平面正在上升，威胁着洪水和侵蚀增加的沿海人口，并评估未来威胁需要预测海平面变化的能力。为此，我们必须了解地球上淡水的巨大水库正在发生的事情，以及它们是否正在慢慢排入海洋。到目前为止，这些水库中最大的水库是南极冰盖，它含有地球上所有淡水的70％，我们知道部分冰盖正在变薄。最快的变化正在冰盖边缘附近发生，在冰盖边缘，它在一个名为Pine Island Bay的地方流入大海，而变化的速度使科学家惊讶。PineIsland Bay在地理位置上是太平洋南部的地理位置，而这种温暖的形象表明，这种结识并没有完全放错了位置。空气温度永远不会升高，但是在海面的寒冷表面下，水温升高高达1度摄氏摄氏度，远高于冰点。派恩岛冰川（Pine Island Glacier）是一条巨大的冰河，流入派恩岛湾（Pine Island Bay），含有与冷冻形式的莱茵河一样多的水。最后60公里的冰川漂浮在松岛湾的水域上，底部融化得如此强烈，以至于冰川中携带的一半冰在30年的时间内丢失了。不难理解温水会导致快速熔化，但是“温暖”和“快速”的意思是什么？如果我们将水温少量改变，熔体速率会改变多少？至关重要的是，什么可能导致海洋温度发生变化？要找到这些问题的答案，我们必须对冰川下的水温进行测量，并同时测量冰川底部融化到海洋的速率，但要这样做是巨大的挑战。冰川厚度为300 m至1 km，因此很难进入其底座。关键是最先进的技术，形式是一种能够在冰下潜水的机器人潜艇，沿着预定的轨道进行了测量，然后用数据返回表面，以及一组坚固的，坚固的，可以留在冰川的自主雷达系统上，这些系统可以在整个冬季构建的速度上构建冰的速度，并在冰上变化。在2009年松树岛冰川下方的初步任务上。雷达系统将作为该项目的一部分开发。他们将结合一种众所周知的雷达技术FMCW雷达，并仔细测量返回阶段回声，以在图像中建立独特特征的位置，例如冰川的底部，在1 km范围内的1毫米阶数非常高。这些雷达仪器中的四种将留在派恩岛冰川的表面上，设计为全年自主操作，并随着时间的推移监测冰厚度的逐渐变化。在这些新仪器的数据中，我们将使用计算机模型，该计算机模型描述了冰川下方和海洋北部的偏远洞穴中的水流。使用该模型，我们将确定如何使用洋流传输到洞穴的热量来融化冰架，以及南极这一部分气候的变化将对洋流和由此产生的熔体速率产生影响。这些信息将使其他人可以更确定地评估未来的气候变化将如何影响派恩岛湾的冰川，从而影响世界的这个偏远地区如何影响荷兰和东安格利亚等地方的未来海岸线。