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/E013503/1
• 负责人: Karen J. Heywood
• 金额: $ 21.74万
• 依托单位: Scottish Association For Marine Science
• 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%2FE013503%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.

海洋中含有盐分，这会使水更稠密。淡水不含盐，通常位于密度较高的咸水之上。我们现在知道，南极洲边缘的淡水数量会影响全球气候，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，我们认为模型的大规模行为可能与现实世界中的行为相似。当我们在模型中添加南极洲周围的额外淡水时，欧洲的气候在短至5年的时间范围内发生变化。这意味着，即使是我们认为遥远的地方，实际上也和那些离我们很近的地方一样重要。我们还认为南极洲是一个重要的研究地点，因为它是稠密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。如果这种温盐循环放缓，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，到达南极既困难又昂贵，我们对南极洲的海洋学特征知之甚少，比如温度或流速，以及水中的盐分含量，我们称之为盐度。冬季在南极洲附近进行测量尤其困难，因为大部分海洋被一层厚厚的冰冻海水覆盖，称为海冰。观察表明，全球气候的变化正在影响南极洲大陆架上的淡水数量。似乎(南极大陆上的)冰盖和冰架(冰盖的漂浮部分，在那里与海洋相遇)融化的速度可能比以前更快，至少在某些地方是这样。在正常的气候条件下，水从海洋中蒸发，以雪的形式落在南极洲上，然后被压实成冰。然后，这些冰慢慢流向大海，在那里崩解成冰山，然后冰山融化回到海洋中。这种水通过海洋、大气和冰层的循环被称为水循环。随着气候变化，现在可能发生的情况是，这个周期的某些部分比过去走得更快，打破了正常的平衡。这个项目将研究南极大陆架和陆坡上的淡水正在发生什么。我们将在陆架和斜坡上部署一些系泊仪器一年，测量海洋温度、盐度、海流速度和方向以及海平面。其中两台仪器非常新颖--其中一台每周采集水样，储存在一个袋子里，以备一年后我们回来时收集。另一个将坐在海床上，每天用一段钢丝把一个小豆荚送到海面上，然后再往下走，测量它前进时的温度和盐度。因为它位于深水中，所以不应该在冰山经过时被它们割掉！这些仪器将放置在最大的南极冰架的上游。我们将测试上游海水会影响流入深海的非常冷、稠密的水的数量。尽管研究南极洲周围的条件是一件雄心勃勃的事情，但我们并不是一个人在做这件事。世界各国齐聚一堂，迎接2007-2009年的国际极地年。我们已经同意在南极洲周围的不同地方同时测量海流速度。这将是第一次这样做，应该会告诉我们更多关于南极洲周围的海洋、冰和大气正在发生的事情以及为什么会发生这样的事情。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。