Synoptic Antarctic Shelf-Slope Interactions Study: SASSI UK

南极陆架-斜坡相互作用天气研究：SASSI UK

• 批准号: NE/E01335X/1
• 负责人: Karen J. Heywood
• 金额: $ 4.77万
• 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%2FE01335X%2F1
• 关键词: Synoptic; Antarctic; Shelf; Slope; Interactions

The oceans contain salt that makes the water denser. Fresh water does not contain salt, and usually lies on top of the denser salty water.We now know that the amount of fresh water on the margins of Antarctica affects global climate, at least in the latest climate models. These climate models are still very crude, because we have to simplify them to make them run on our fastest computers in a reasonable time. Nevertheless we think that the large-scale behaviour of the models is probably similar to that in the real world. When we add additional fresh water around Antarctica in the model, the climate of Europe changes over a time scale as short as 5 years. This means that even places we think of as remote are in fact just as important to study as those close to us. We also believe that Antarctica is an important place to study because it is one of the places where the dense cold water sinks to the sea bed and flows towards the equator in what oceanographers call the thermohaline circulation. If this thermohaline circulation slows down then global climate is affected, as was dramatised in the film 'The Day After Tomorrow'. Because Antarctica is remote, and difficult and expensive to get to, we have very little information about the oceanographic characteristics, such as temperature or current velocity, and the amount of salt in the water, which we term salinity. It is especially difficult to obtain measurements close to Antarctica in winter, because most of the ocean is covered in a thick layer of frozen sea water, called sea ice. Observations suggest that changes in global climate are affecting the amounts of fresh water on the continental shelf of Antarctica. It seems that the ice sheets (on the Antarctic continent) and ice shelves (the floating parts of the ice sheet, where it meets the sea) may be melting more quickly than before, at least in some locations. Under normal climate conditions, water evaporates from the ocean, falls as snow onto Antarctica and is compacted into ice. This ice then flows slowly towards the sea, where it calves into icebergs, which then melt back into the ocean. This circle of water through the ocean, atmosphere and ice is called the hydrological cycle. What may be happening now as climate changes is that some parts of this cycle are going faster than they used to, knocking the cycle out of its normal equilibrium. This project will study what is happening to the fresh water on the Antarctic continental shelf and slope. We will deploy for one year some moored instruments on the shelf and slope, measuring ocean temperature, salinity, current speed and direction, and sea level. Two of these instruments are very novel - one of them collects a sample of water every week and stores it in a bag ready for collection when we return a year later. The other will sit on the sea bed, and every day sends a little pod up to the surface on a length of wire and down again, measuring temperature and salinity as it goes. Because it sits in the deep water, it shouldn't get mown down by icebergs as they go by! These instruments are going to sit just upstream of the largest Antarctic Ice Shelf. We're going to test the idea that the ocean water upstream influences the amount of very cold, dense water that descends to the deep ocean there. Although studying the conditions around Antarctica is an ambitious thing to do, we are not doing it alone. Countries around the world are coming together for the International Polar Year in 2007-2009. We have agreed to all make measurements of the current velocity at the same time in different places around Antarctica. This will be the first time that this has been done and ought to tell us much more about what is happening to the oceans, ice and atmosphere around Antarctica, and why. This in turn should help us to make better climate models to predict the future of our planet.

海洋中含有盐，使水的密度更大。淡水不含盐，通常位于密度较大的咸水之上。我们现在知道，南极洲边缘的淡水量影响着全球气候，至少在最新的气候模型中是这样。这些气候模型仍然非常粗糙，因为我们必须简化它们，使它们在合理的时间内在我们最快的计算机上运行。尽管如此，我们认为模型的大尺度行为可能与真实的世界中的行为相似。当我们在模型中增加南极洲周围的淡水时，欧洲的气候在短至5年的时间内发生变化。这意味着即使我们认为遥远的地方实际上也和我们附近的地方一样重要。我们还认为，南极洲是一个重要的研究地点，因为它是密集的冷水下沉到海床并流向赤道的地方之一，海洋学家称之为温盐环流。如果这种温盐环流减缓，那么全球气候就会受到影响，正如电影《后天》中所戏剧化的那样。由于南极洲地处偏远，到达南极洲既困难又昂贵，因此我们对海洋学特征的信息很少，例如温度或流速，以及水中的盐量，我们称之为盐度。在冬季，在南极洲附近进行测量尤其困难，因为大部分海洋都覆盖着一层厚厚的冰冻海水，称为海冰。观测表明，全球气候的变化正在影响南极大陆架的淡水量。看起来，冰盖（在南极大陆）和冰架（冰盖的漂浮部分，在那里它与海洋相遇）可能比以前融化得更快，至少在某些地方。在正常的气候条件下，水从海洋中蒸发，福尔斯以雪的形式落到南极洲，然后被压缩成冰。这些冰然后慢慢地流向大海，在那里它变成冰山，然后融化回海洋。水在海洋、大气和冰中的循环称为水文循环。随着气候变化，现在可能发生的情况是，这个循环的某些部分比过去更快，使这个循环脱离了正常的平衡。该项目将研究南极大陆架和斜坡上的淡水正在发生什么。我们将在大陆架和斜坡上部署一些停泊的仪器，测量海洋温度、盐度、流速和方向以及海平面。其中两台仪器非常新颖--其中一台每周收集一次水样，并将其储存在袋子中，以便一年后我们回来时收集。另一个将坐在海床上，每天用一段电线把一个小豆荚送到海面上，然后再下来，测量温度和盐度。因为它坐落在深水中，所以当冰山经过时，它不应该被冰山击倒！这些仪器将位于最大的南极冰架上游。我们将测试这样一个观点，即上游的海水会影响到那里的深海中非常冷的、密度很大的水的数量。虽然研究南极洲周围的条件是一件雄心勃勃的事情，但我们并不是独自在做。2007-2009年是国际极地年，世界各国将齐聚一堂。我们已经同意在南极洲周围的不同地方同时测量流速。这将是第一次这样做，应该告诉我们更多关于南极洲周围的海洋，冰和大气正在发生什么，以及为什么。这反过来应该有助于我们建立更好的气候模型来预测我们星球的未来。