The Lake Hazen watershed as a sentinel of Arctic environmental change

目前的气候变化模型预测，到2100年，在加拿大高北极地区，大多数陆地地区的气温将上升3-5°C，但在加拿大北极群岛的最北部，气温将上升9°C。与此同时，预计北极的年平均降水量将增加~12%，而在变暖最严重的地区，年平均降水量将增加35%。预计这种变暖和变湿将极大地改变北极景观的能量平衡，导致冰川融化、永久冻土解冻、生长季节延长以及景观和淡水中植物产量增加。事实上，这些变化不仅在预料之中，而且大多数已经发生在Quttinirpaaq国家公园（QNP；北部埃尔斯米尔岛，努纳武特），加拿大最北端的国家公园。哈森湖位于QNP的中部，是世界上体积最大的湖泊，位于北极圈以北。它拥有最大的内陆北极木炭储量之一，历史上因纽特人、图勒人和古爱斯基摩人一直在收获这种木炭。黑森湖面积540平方公里，深265米，流域面积8400平方公里，一半被冰川覆盖。该流域的卫星观测显示，2006-2012年夏季冰川表面温度比2000-2005年升高了1.3°C，黑森湖的冰盖持续时间缩短。这导致最近流入哈森湖的冰川融水和沉积物增加了10倍。尽管流域最近发生了这些重大变化，但我们对它们如何影响黑森湖本身的水质和代谢知之甚少，黑森湖是加拿大高北极地区的淡水宝石。这些景观变化是否会导致一连串的影响，不仅会影响黑森湖的正常代谢功能（如藻类生产、沉积物微生物呼吸），还会降低具有社会经济意义的生态系统服务？我建议采用一种综合的全生态系统方法来量化气候变化对北极高纬度流域的影响，将黑森湖流域作为哨兵系统。我提出的研究有三个主要目标。我的第一个目标是量化黑森湖流域的净能量平衡是如何变化的，以及它是如何影响那里发生的物理（例如，永久冻土融化的程度）和生物（例如，植物生产）过程的。我的研究计划的第二个目标是量化从融雪、冰川融化和永久冻土融化中向哈森湖输入的有机碳、营养物质和其他化学参数，包括遗留污染物（例如，汞、全氟酸）。最后，我建议量化这些有机碳、营养物质和其他化学参数的输入如何影响黑森湖的代谢过程，如藻类生产和沉积物微生物呼吸，以及基本水质。从科学的角度来看，我的团队的研究将：1)为加拿大最未被充分研究但变化最大的生态区域提供急需的基线数据，所有未来的数据都可以以此为基准；2)协助建模者预测北极高纬度地区更广泛的变化；3)为遥感和卫星图像提供地面真实性。从更实用和社会经济的角度来看，提高我们预测北方生态系统变暖对流域生产力和水质影响的能力，对于确保北方人民的粮食、清洁饮用水和传统生活方式，以及可持续资源开发至关重要。所有资金将直接用于培训高素质人员，包括北方培训、咨询和外联。

Current climate change models predict that in the Canadian high Arctic, temperatures will rise 3-5°C over most land areas by 2100, but up to 9°C in the very northern Canadian Arctic Archipelago. At the same time, mean annual precipitation is predicted to increase ~12% for the Arctic, but up to 35% in regions with the highest warming. Such warming and wetting is anticipated to greatly alter the energy balance of Arctic landscapes, resulting in melting of glaciers, permafrost thaw, longer growing seasons and increased plant production on landscapes and in freshwaters. In fact, not only are these changes anticipated, but most are already occurring in Quttinirpaaq National Park (QNP; northern Ellesmere Island, Nunavut), Canada's most northerly National Park. Situated in the middle of QNP is Lake Hazen, the world's largest lake by volume north of the Arctic Circle. It supports one of the largest stocks of landlocked Arctic char, which has been historically harvested by Inuit, Thule and Paleo-Eskimo peoples. Lake Hazen is 540 km2 in surface area and 265 m deep, and has a 8400 km2 watershed that is half glaciated. Satellite observations of the watershed have revealed 2006-2012 summer glacier surface temperatures up to 1.3°C warmer than during 2000-2005, and a decline in ice cover duration on Lake Hazen. This has resulted in recent 10-fold increases in glacial meltwater and sediment inputs into Lake Hazen. Despite these recent and significant changes in the watershed, we know very little about how they are impacting water quality and metabolism in Lake Hazen itself, a freshwater jewel of Canada's high Arctic. Will these landscape changes lead to a cascade of effects that will not only impact the normal metabolic functioning of Lake Hazen (e.g., algal production, sediment microbial respiration), but also degrade ecosystem services of socio-economic significance? I am proposing an integrated whole-ecosystem approach to quantifying impacts of climate change on high Arctic watersheds, using the Lake Hazen watershed as a sentinel system. There are three overarching objectives to my proposed research. My first objective is to quantify how the net energy balance of the Lake Hazen watershed is changing and how that is impacting both physical (e.g., the extent of permafrost thaw) and biological (e.g., plant production) processes occurring there. The second objective of my research program is to quantify inputs of organic carbon, nutrients and other chemical parameters including legacy contaminants (e.g., mercury, perfluorinated acids) to Lake Hazen from snowmelt, glacial melt and permafrost thaw. Finally, I am proposing to quantify how these inputs of organic carbon, nutrients and other chemical parameters are impacting metabolic processes like algal production and sediment microbial respiration, as well as basic water quality, in Lake Hazen. From a scientific basis, my team's research will: 1) provide much-needed baseline data in Canada's most understudied yet most changing ecoregion, from which all future data can be benchmarked; 2) assist modelers in predicting broader changes across the high Arctic; and 3) provide ground-truthing for remote sensors and satellite imagery. From the more applied and socio-economic perspective, increasing our ability to predict impacts of warming northern ecosystems on watershed productivity and water quality is vital for securing food, clean drinking water and traditional lifestyles for Northern peoples, as well as for sustainable resource development. All funding will go directly towards the training of highly qualified personnel, including northern training, consultation and outreach.