The influence of ocean circulation on local biogeochemistry and melting tidewater glaciers in northern Baffin Bay

“气候变化对北极的影响不成比例，最近IPCC的第六次评估报告指出，北极极有可能继续以两倍于全球平均速度变暖。在格陵兰岛和南极洲之外，加拿大北极群岛冰川的融化是最近海平面上升的最大原因。这使得加拿大北极群岛成为一个需要了解的关键地区，但由于地处偏远，它仍未得到充分研究。在加拿大北极群岛有超过300个与海洋接触的潮汐冰川。为了了解这些冰川最近的融化和冰块的损失，了解海洋如何影响它们是非常重要的。这项工作将集中在加拿大北极群岛的一个名为巴芬湾北部的地区，由于该地区存在两个后退最快的潮汐冰川，这是一个重要的地区。巴芬湾北部也有北水波利亚，这是一大片没有海冰的开放水域。这个地区的初级生产力非常高，它维持着大量的海洋生物多样性，这使得它被加拿大渔业和海洋部列为生态和生物重要地区。这项工作的目的是提高对巴芬湾北部海洋环流的认识，以及海洋环流对该地区潮汐冰川融化和当地营养物质分布的影响。这项研究将使用来自海洋环流模型的数据，以及一个名为ARIANE的软件，在巴芬湾北部的潮汐冰川附近释放模拟颗粒。这些模拟的虚拟粒子将在时间上向后追溯，提供关于粒子起源和水进入该区域时所遵循的路径的信息。一旦我们确定了这些通道，我们就会考虑沿着这些通道流动的水的温度，以及温暖的水能够进入的地方。特别是，我们将评估来自大西洋的更温暖、更深的水是否能够到达该地区的潮汐冰川。了解这一点很重要，因为温暖的海水能够推动更多的冰川融化，所以了解温暖的大西洋水是否与潮汐冰川接触是至关重要的。我们还将考虑已确定的海洋环流途径向该地区提供的营养物质。浮游植物是一种光合生物，与植物类似，构成了许多海洋食物链的基础。它们生长在海洋表面，那里有充足的光线，它们也需要营养来生长。海洋环流途径可以向海洋表层提供这些营养物质，因此它是对初级生产力的重要控制。潮汐冰川可以影响向海洋表层提供的营养物质，因为在冰川与海洋接触的地方，从冰川输入的淡水浮力可以导致更深的富含营养物质的水上涌向海洋表层，这些营养物质可以刺激浮游植物的生长。总之，这项工作的主要目的是：1)确定水运至巴芬湾北部的途径，以提高对该地区海洋环流的了解；2)评估海洋环流和暖水通道对潮水冰川融化的影响；3)评估海洋环流对养分分布的影响，从而影响初级生产力。

"NERC : Emma Louise White : NE/S007512/1"Climate change has disproportionately affected the Arctic, and the recent Sixth Assessment Report from the IPCC states that the Arctic is highly likely to continue warming at twice the average global rate. Outside of Greenland and Antarctica, the melting of glacial ice in the Canadian Arctic Archipelago has made the largest contribution to recent sea-level rise. This makes the Canadian Arctic Archipelago a critical region to understand, yet it remains understudied due to its remoteness. There are over 300 tidewater glaciers in the Canadian Arctic Archipelago which are in contact with the ocean. To understand the recent melting and ice mass loss from these glaciers, it is highly important to understand how the ocean influences them. This work will focus on an area of the Canadian Arctic Archipelago called northern Baffin Bay, which is an important area to understand due to the presence of the two fastest retreating tidewater glaciers in the region. The North Water Polynya is also present in northern Baffin Bay, which is a large area of open water which remains free of sea ice. There is very high primary productivity in this area, and it sustains a large diversity of marine life which has led to it being classified as an Ecologically and Biologically Significant Area by Fisheries and Oceans Canada. The aim of this work is to improve understanding of ocean circulation in northern Baffin Bay, and the influence that ocean circulation has on melting tidewater glaciers in the region as well as local nutrient distributions.This study will use data from an ocean circulation model, along with a software called ARIANE, to release modelled particles in the vicinity of tidewater glaciers in northern Baffin Bay. These modelled virtual particles will be traced backwards in time, providing information on the origin of the particles and pathways that water follows as it enters the region. Once we have identified these pathways, we will then consider the temperature of water travelling along these pathways, and where warmer water is able to access. In particular, we will assess if warmer, deeper water originating from the Atlantic Ocean is able to reach the tidewater glaciers in the region. This is important to understand, as warmer water is able to drive more melting of glaciers, so it is crucial to understand if warmer Atlantic Water is in contact with tidewater glaciers. We will also consider the nutrients that are supplied to the region by the ocean circulation pathways identified. Phytoplankton are photosynthetic organisms that form the base of many marine food chains, similar to plants. They are found in the surface ocean where there is light availability, and they also require nutrients to grow. Ocean circulation pathways can provide these nutrients to the surface ocean, and it is therefore an important control on primary productivity. Tidewater glaciers can influence the supply of nutrients to the surface ocean because where the glaciers are in contact with the ocean, the freshwater buoyancy input from them can lead to upwelling of deeper, nutrient rich waters towards the surface, where these nutrients can stimulate phytoplankton growth. In summary, the main aims of this work will be to 1) identify pathways of water transport to northern Baffin Bay to improve understanding of ocean circulation in the region; 2) assess the influence of ocean circulation and pathways of warmer water on melting tidewater glaciers; and 3) assess the impact that ocean circulation has on nutrient distributions, and therefore primary productivity.