Ocean2ice

想象一下，海洋就像一大杯杜松子酒和奎宁水。当你在饮料中加冰时，杯子里的水就会上升。当冰块融化时，玻璃杯中的水平不会改变，因为冰是漂浮的。当目前停留在南极洲陆地上的冰以冰山或融水的形式流入大海时，世界各地的海平面都会上升。过去人们认为，南极的降雪量与冰山融化的水量相当，因此整个系统是平衡的。但南极(和格陵兰)的一些冰川似乎正在融化的速度比它们被取代的速度更快。因此，冰的总量正在变小，因为更多的水进入海洋，加剧了海平面的上升。这令人担忧，因为我们真的不知道为什么会发生这种情况，如果我们不能理解原因，就很难预测未来的海平面是否会以越来越快的速度继续上升，或者它是否会放缓或恢复平衡。各国政府计划在未来几十年在低洼地区进行海平面防御，需要对可能的海平面水平做出更确定的预测。这意味着他们用来预测未来气候的大型计算机模型需要比现在更好、更复杂的物理模型。那么，科学家们可以做些什么来找出冰层融化的原因呢？当冰川最终到达大海时，它们会像冰架一样漂浮在海水上。一种说法是，海洋提供了比过去更多的热量来融化冰层。尽管南极的海洋并不那么温暖，但它比冰点高出几度，如果它洗到冰架下面，它可以释放出大量的热量。我们在这个项目中计划做的是去南极阿蒙森海的松岛冰川，那里是融化最快的冰川之一。这是我们星球上最偏远的地方之一--想象一下去太平洋，然后向南行驶，直到你遇到南极洲。我们将在冰架附近的水中放置一些仪器，看看温暖的海水如何以及为什么会接近冰层。是风把水吹到那里的吗？它是在绕着南极大陆起伏吗？这些水会流向数千年前被冰川挖出的海底沟槽吗？我们计划在南极使用一些新的设备，比如将微型传感器粘在象海豹的皮毛上。海豹将在我们回家后很长一段时间里一直留在这个地区过冬。他们的传感器将传回有关海豹栖息地的信息--例如温度和盐度。这对我们很有用，因为我们无法在冬季以任何其他方式获得观测，因为该地区被海冰覆盖。这对海豹是有好处的，因为它将帮助我们的生物学家同事更好地了解象海豹可能对气候变化的脆弱性。我们还将在水中放置一种机械版本的密封件，称为海滑器。它在水中上下移动进行测量，就像海豹传感器一样，当它在水面上时，它会使用手机进行通信。当我们和船在一起时，我们将对水的温度和盐度进行大量测量，测量水的流动速度和混合程度。把所有这些数据集放在一起，应该会让我们更好地理解热量是如何到达冰川的。其中一个重要的工具将是各种计算机模型。这些模型的范围将从试图包括冰、海洋和大气所有相互作用的全能、全能的气候模型，到测试我们对正在发挥作用的物理学的理解的简单得多的模型。我们计划做的工作的最终结果应该是更好的气候模型来预测未来的海平面。

Imagine that the ocean is like a large gin and tonic. When you add ice to the drink, the level in the glass goes up. When the lump of ice melts, the level in the glass doesn't change, because the ice is floating. When ice that is currently resting on land in Antarctica goes into the sea, either as an iceberg or as meltwater, the sea level all over the world goes up. It used to be thought that the same amount of water went back to the Antarctic as snowfall, to compensate for the icebergs and meltwater, so the whole system was in balance. But some glaciers in the Antarctic (and Greenland) seem to be melting at a faster rate than they are being replaced. So the total amount of ice is getting smaller, because more of that water is in the ocean, adding to sea level rise. This is worrying, because we don't really know why this is happening, and if we can't understand why, it's difficult to predict whether future sea level will carry on increasing at a faster and faster rate, or whether it will slow down or go back to equilibrium. Governments planning sea level defences in low-lying areas for the next decades need to have a more certain prediction of likely levels. That means that the big computer models that they use to forecast future climates need to have even better and more complex physics than they do already.So, what can scientists do to find out why the ice is melting? When the glaciers finally reach the sea, they float on the seawater, as an ice shelf. One suggestion is that the ocean is providing more heat to melt the ice than it used to do. Even though the ocean isn't that warm in the Antarctic, it is a few degrees above freezing, and if it washes underneath the ice shelves it can give up a lot of heat. What we plan to do in this project is to go to one of the fastest melting glaciers, the Pine Island Glacier in the Amundsen Sea, Antarctica. This is one of the most remote parts of our planet - imagine going to the Pacific Ocean and then heading south until you meet Antarctica. We will put some instruments in the water near the ice shelf, to see how and why the warm ocean water gets close to the ice. Is it the wind that forces the water there? Is it waves going round the Antarctic continent? Does the water get channelled up troughs in the sea floor gouged by glaciers thousands of years ago?We plan to use some novel equipment in the Antarctic, such as gluing tiny sensors onto elephant seals' fur. The seals will remain in the area over winter, long after we've gone back home. Their sensors will send back information about the seals' habitat - for example the temperature and the saltiness. This is useful for us because we can't get observations in the wintertime any other way because the area is covered in sea ice. And it's good for the seals because it will help our biologist colleagues to better understand how vulnerable the elephant seals might be to climate change. We'll also put in the water a mechanical version of a seal, called a Seaglider. This goes up and down in the water making measurements as it goes, and much like the seal sensors, it will communicate when it's at the surface using mobile phone. While we're there with the ship, we'll make lots of measurements of the temperature and saltiness of the water, how fast it's going, and how mixed up it is. Looking at all these data sets together should give us a better understanding of how the heat is getting to the glacier.One of the important tools will be a variety of computer models. These will range from all-singing, all-dancing climate models, that try to include ice, ocean and atmosphere all interacting, to much simpler models that test our understanding of the physics at play. The final result of the work we plan to do should be better climate models to predict future sea levels.