Fjord Dynamics and Modulation of Ice/Ocean Exchange

格陵兰冰盖是除南极洲外地球上最大的冰块，如果完全融化，其所含的冰足以使海平面上升7米。冰盖与周围的海洋在海洋终止（或tillage）出口冰川连接，对这两个系统都有重大影响。热量从相对温暖的海洋沃茨转移到冰上，融化了与海洋接触的部分冰川。近几十年来，由于海洋变暖，这种融化加速，引发冰川退缩，加速冰盖质量损失和海平面上升。作为回报，冰盖将淡水以液态融水和固态冰山的形式转移到海洋中，改变了格陵兰岛周围的海水性质和洋流。随着气候变暖，冰融化增加，这些影响预计将变得更加重要，可能会影响区域乃至全球范围的海洋环流和气候。因此，了解并预测冰盖与海洋之间的交换至关重要。实现这一目标的一个关键障碍在于连接格陵兰岛的潮汐出口冰川和开阔海洋的狭长而深的峡湾。这些峡湾受到一系列特定过程的影响，这些过程改变了冰盖和海洋之间的交换。例如，融化的水沿着冰盖的河床进入峡湾，在海面下很深的地方，它会剧烈上升，在这个过程中与峡湾的沃茨混合。这种融水的性质，因此它对海洋的影响，因此显着修改在其旅程峡湾。同样，峡湾的作用是阻碍和改变从海洋流向冰盖的温暖沃茨，这意味着到达格陵兰岛冰川的沃茨的温度可能与沿海环流的温度有很大差异，因此，如果要有效地理解和预测冰盖与海洋之间的相互作用，就必须考虑峡湾的过程。因此，在这个项目中，我们将使用一个新开发的数值峡湾模型，结合冰盖，峡湾和海洋特性的数据，系统地研究峡湾在格陵兰岛范围内的影响。我们将使用这个模型来确定峡湾的过程，对冰盖和海洋之间的热量和淡水交换有最大的影响，以及这些峡湾之间的差异，并随着时间的推移。利用这些知识，我们将研究这些过程对冰川退缩和区域海洋特性的影响。我们还将展望未来，考虑峡湾过程及其影响将如何在21世纪世纪演变，以及如何将其纳入用于预测气候变化对我们社会影响的大规模模型。

The Greenland Ice Sheet is the largest ice mass on Earth outside of Antarctica, containing enough ice to raise sea levels by 7 m if it were to melt completely. The ice sheet is connected to the surrounding ocean at marine-terminating (or tidewater) outlet glaciers, with significant implications for both systems. Heat is transferred to the ice from comparatively warm ocean waters, melting the part of the glaciers that is in contact with the ocean. In recent decades this melting has accelerated in response to ocean warming, triggering glacier retreat and accelerating ice sheet mass loss and sea level rise. In return, the ice sheet transfers fresh water to the ocean in the form of liquid meltwater and solid icebergs, modifying ocean water properties and currents around Greenland. As ice melting increases in a warming climate, these effects are predicted to become more significant, potentially impacting ocean circulation and climate on a regional to global scale. It is thus of critical importance that exchanges between the ice sheet and ocean are understood and can be predicted.A key barrier to achieving this aim lies in the long, narrow and deep fjords that connect Greenland's tidewater outlet glaciers to the open ocean. These fjords are subject to a specific set of processes that modify the exchange between the ice sheet and ocean. For example, meltwater draining along the bed of the ice sheet enters fjords at great depth below the sea surface, where it rises vigorously, mixing with fjord waters in the process. The properties of this meltwater, and consequently the impacts it has on the ocean, are thus significantly modified during its journey down-fjord. Similarly, fjords act to obstruct and modify warm waters flowing from the ocean towards the ice sheet, meaning that the temperature of waters reaching Greenland's tidewater glaciers may differ significantly from that circulating off the coast.It is therefore critical that fjord processes are taken into account if interaction between the ice sheet and ocean is to be effectively understood and predicted. In this project, we will therefore use a newly developed numerical fjord model, in conjunction with data on ice sheet, fjord and ocean properties, to systematically examine the impact of fjords on a Greenland-wide scale. We will use this model to identify the fjord processes which have greatest effect on the exchange of heat and freshwater between the ice sheet and ocean, and how these differ between fjords and over time. Using this knowledge, we will examine the impact of these processes on glacier retreat and regional ocean properties. We will also look into the future to consider how fjord processes and their impacts will evolve over the 21st century, and how this may be incorporated into the large-scale models that are used to predict the impacts of climate change on our society.