Coupled Evolution of Ice Shelf and Ocean in the Amundsen Sea Sector of Antarctica

南极阿蒙森海区冰架与海洋的耦合演化

• 批准号: NE/Y000811/1
• 负责人: Pierre Dutrieux
• 金额: $ 54.73万
• 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: 2026
• 资助国家: 英国
• 起止时间: 2026 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FY000811%2F1
• 关键词: Coupled; Evolution; Ice; Shelf; Ocean

As our planet warms the ice cover shrinks, a process that transfers water from land to ocean and thereby raises sea level. The result, which could ultimately raise global sea level by 10s of metres, seems intuitively obvious. However, in the case of the Antarctic Ice Sheet, the processes at work are less than obvious. The atmosphere over the ice sheet is too cold to drive significant melting, so all the snow that falls in the interior is returned to the ocean as ice that only melts once it is afloat. The cold atmosphere creates cold surface waters, so most of the heat that melts the ice comes from deep within the ocean's interior. As it melts the floating ice from underneath, the thinning of the so-called ice shelves allows ice to flow off the land more rapidly, hence raising sea level.So, the underlying process is clear, but why should it drive a loss of ice from Antarctica as the climate warms? The waters that melt the ice are too deep in the ocean to feel atmospheric warming. However, as the atmosphere warms the circulation patterns change, influencing the winds that drive the ocean currents, and that delivers more of the deep warm water to the ice. Understanding how the processes work has been challenging. It is not immediately obvious why a change in the winds should deliver more, rather than less, warm water to the ice. Nevertheless, observation and modelling give us a consistent answer and our understanding of the processes grows as we focus our research on key unknowns.However, there is another puzzle that has received much less attention to date. More warm water leads to more rapid melting of the ice shelves, they thin and the flow of ice off the land accelerates. That acceleration of the flow delivers more ice to the ice shelves, and they should therefore start to grow, or at least thin less rapidly, unless the ocean heat delivery continues to grow. Until recently it was assumed that that is exactly what was happening, but as our record of ocean observations has lengthened, we have seen decadal cycles of warming and cooling. Why then should the ice shelves continue to thin?The answer must lie in the way in which the thinning of the ice shelves themselves affects the melt rate. Again, it is not immediately clear why the change in the ice should increase rather than decrease the melt. However, in this case observation of the key processes is exceptionally difficult because they take place beneath 100s or even 1000s of metres of ice.That is the challenge we will address with this project, by sending an autonomous submarine beneath the ice to make the critical measurements of the ocean, including the temperature of the water and the currents. Those direct observations of the ocean beneath the ice will allow us to verify that the ocean models we use to simulate the processes are correct, or to improve them if they are not.This will not be the first time such measurements have been made, but the new observations will differ in two important respects from the very few that have been made in the past. Some will be repeats of earlier measurements, so we will have observations from before and after a significant change in the extent of the ice shelf. Thus, we can directly answer the question of what change in the ocean circulation accompanied the change in shape of the ice cover. Other observations will target regions where the ice was grounded until recently. Because radar signals penetrate ice, but not seawater, we are able to map the topography only when the ice rests on the land and not when it is afloat. Thus, we paradoxically know the geometry of newly formed ocean cavities with much greater accuracy than we do the cavities that have been there since humans first explored the south polar regions. Our ability to understand the links between cavity geometry and ocean circulation is therefore enhanced in the newly opened cavities that are among the targets of our field campaign.

随着地球变暖，冰盖缩小，这一过程将水从陆地转移到海洋，从而导致海平面上升。其结果似乎直观地显而易见，最终可能使全球海平面上升数十米。然而，就南极冰盖而言，起作用的过程并不那么明显。冰盖上的大气太冷，无法导致明显的融化，因此所有落在内部的雪都会以冰的形式返回海洋，只有在漂浮时才会融化。寒冷的大气造成寒冷的表层海水，因此融化冰的大部分热量来自海洋内部深处。当它从下面融化浮冰时，所谓的冰架变薄使得冰更快地从陆地上流走，从而提高海平面。所以，潜在的过程很清楚，但为什么它会导致冰的损失随着气候变暖，来自南极洲？融化冰的海水太深，无法感受到大气变暖。然而，随着大气变暖，环流模式发生变化，影响驱动洋流的风，并将更多的深层温水输送到冰上。了解这些流程的工作原理一直具有挑战性。目前还不清楚为什么风向的变化会向冰层输送更多而不是更少的温水。尽管如此，观察和建模为我们提供了一致的答案，并且随着我们将研究重点放在关键的未知因素上，我们对过程的理解也会不断加深。然而，还有另一个难题迄今为止受到的关注要少得多。更多温暖的水导致冰架更快融化，冰架变薄，冰离开陆地的速度加快。水流的加速向冰架输送了更多的冰，因此它们应该开始增长，或者至少变薄得慢一些，除非海洋热量输送继续增长。直到最近，人们还认为这正是正在发生的事情，但随着我们对海洋观测记录的延长，我们已经看到了十年间的变暖和变冷循环。那么为什么冰架会继续变薄呢？答案一定在于冰架变薄本身影响融化速度的方式。同样，目前还不清楚为什么冰的变化会增加而不是减少融化。然而，在这种情况下，观察关键过程是异常困难的，因为它们发生在数百米甚至数千米的冰层之下。这就是我们在这个项目中要解决的挑战，通过在冰层下派遣一艘自主潜艇来进行关键的观测。海洋测量，包括水温和洋流。对冰下海洋的直接观察将使我们能够验证用于模拟过程的海洋模型是否正确，如果不正确，则可以对其进行改进。这不是第一次进行此类测量，但是新的观察结果将在两个重要方面与过去的少数观察结果有所不同。有些将是早期测量的重复，因此我们将获得冰架范围发生重大变化之前和之后的观测结果。这样，我们就可以直接回答海洋环流随着冰盖形状的变化而发生什么变化的问题。其他观测将针对直到最近冰才接地的区域。由于雷达信号可以穿透冰层，但不能穿透海水，因此我们只能在冰层位于陆地上而不是漂浮在水面上时才能绘制地形图。因此，矛盾的是，我们对新形成的海洋空洞的几何形状的了解，比我们对自人类首次探索南极地区以来就存在的空洞的几何形状的了解要高得多。因此，我们了解空腔几何形状与海洋环流之间联系的能力在新开放的空腔中得到了增强，这些空腔是我们实地活动的目标之一。