South-East Greenland Trough Experiment

GrIS的稳定性及其未来可能对海平面上升的影响是科学界、媒体、公众和决策者广泛讨论的问题。引起这种关注是因为最近的结果显示冰盖发生了意想不到的变化；这意味着它导致海平面上升的速度比科学家预期的要快。格陵兰岛的冰川最近经历了一次同步退缩，伴随而来的是冰川变薄和冰川流动加速。雅各布港冰川就是一个例子，它是西海岸的一个主要冰川。在20世纪90年代末，它加速了，这一反应与进入冰川峡湾的温暖海水的增加有关。海洋变暖引发的冰川加速的进一步例子出现在格陵兰岛的东南部，特别是赫尔海姆冰川和康格尔德格斯瓦克冰川。然而，最新的结果表明，这些冰川现在已经减缓了速度。这种加速和减缓的反应与峡湾外海水的变化（变暖然后变冷）是一致的。越来越多的证据表明，海洋温度和冰川动态之间存在着关键联系，而冰川动态又是格陵兰冰盖和海平面上升的主要控制因素。潮水冰川流入深峡湾，这些深峡湾本身通过横穿浅大陆架的深沟槽（或峡谷）与海洋相连。很明显，峡湾和海沟是理解海水如何流向冰川的重要组成部分。虽然在峡湾有越来越多的观测工作，但还没有对跨大陆架槽的水文学进行研究。然而，正是通过这些海沟，温暖的海水被输送到峡湾口。从本质上讲，海槽目前是海洋学的“黑匣子”。要发展我们对海洋-冰川相互作用的理解，一个重要的要求是能够准确地模拟相邻的冰架。这需要观察波谷，以便理解和量化“黑箱”内的过程。在这个项目中，我们将重点关注主要的跨大陆架槽，它将温暖的海水输送到Kangerdlugssuaq冰川峡湾。以前一些稀疏的观测已经注意到通过这个槽携带的温水的存在，但还没有进行系统的观测。我们将收集海底测深、水质量分布、流速和通过槽的热输送等数据。这些是验证大陆架数值模型所必需的参数。我们还将测量湍流，并估计沿槽长散失热量的速率。这一点很重要，因为它最终决定了有多少热量将被输送到峡湾。对低槽内的海洋学过程进行分析和量化，将为解释该地区的海表温度（SST）卫星图像提供基础，从而能够分析1992年以来的情况，这与我们掌握的冰川速度大致相同。这样，我们就能够更清楚地了解潜在的水文过程，并评估对冰川速度的影响，从而解释存档的海温数据。科学界的最终目标是能够对海平面等关键参数提供更好的预测。了解冰川动态变化背后的海洋驱动因素是更好地预测格陵兰岛对海平面上升的贡献的关键。该项目的数据将是未来开发冰盖-海洋耦合模型的理想数据。

The stability of the GrIS, and its likely future contribution to sea level rise, is widely discussed by the scientific community, media, general public and policy makers. This attention has arisen because recent results have shown unexpected changes to the ice sheet; meaning that it is contributing to sea level rise at faster rates than scientists have expected. Glaciers in Greenland have recently undergone a synchronous retreat with associated thinning and acceleration of their flow. An example is Jakobshavn Isbrae, which is a major glacier on the west coast. In the late 1990s it accelerated, a response that has been linked to an increase in the warm ocean water that entered the glacier's fjord. Further examples of glacial acceleration triggered by ocean warming are identified in the south-east of Greenland, notably the Helheim and Kangerdlugssuaq Glaciers. However, the very latest results show that these glaciers have now slowed down. This acceleration and slowing response is coincident with changes in the oceanic waters outside of the fjords (warming and then cooling). There is mounting evidence that there is a critical link between ocean temperatures and glacier dynamics which in turn are the primary control of the Greenland Ice Sheet to sea-level rise. Tidewater glaciers discharge into deep fjords which are themselves connected to the ocean by deep troughs (or canyons) that cut across the shallow continental shelf. Clearly the fjords and troughs are an important component in understanding how ocean waters are delivered to the glacier. Whilst there is increasing observational effort in the fjords, there have been no studies of the hydrography of the cross-shelf troughs. Yet it is through these troughs that the warm ocean water is delivered to the mouth of the fjords. In essence, the troughs are currently an oceanographic 'black box'. An important requirement to be able to develop our understanding of ocean-glacier interactions is to be able to accurately model the adjacent shelves. This requires observations of the troughs in a bid to understand and quantify the process within the 'black box'. In this project we will focus on the major cross-shelf trough that transports warm oceanic waters to the fjord of Kangerdlugssuaq Glacier. Some previous, sparse observations have noted the presence of warm water carried through this trough yet there have been no systematic observations made. We will collect data on bathymetry, distribution of the water masses, flow rates and heat transport through the trough. These are the parameters essential for validating numerical models of the shelf. We will also make measurement of the turbulence and estimate the rate at which heat is lost along the length of the trough. This is important as it ultimately determines how much heat will be delivered into the fjord. Analysing and quantifying the oceanographic processes within troughs will provide a basis for interpreting satellite imagery of the Sea Surface Temperature (SST) of the region which then enables analysis of conditions back to 1992, which is approximately the same timescale as we have glacier velocities for. We would then be able to interpret archived SST data with a clearer appreciation of the underlying hydrographic processes and assess the effect on glacier velocities. Ultimately the goal of the scientific community is to be able to offer better predictions of key parameters like sea level. Understanding the oceanic drivers behind changes in glacier dynamics is key to better future prediction of Greenland's contribution to sea-level rise. The data from this project will be ideal for the development of future coupled of ice sheet-ocean models.