Collaborative Research: Improving estimates of Greenland’s freshwater flux: Where do icebergs form and where do they melt?

格陵兰岛是一个巨大的水库，储存着新鲜的、冰冻的水，这些水向下流动，直到流入海洋。一些冰冻的水库在表面融化，直接进入海洋。一些冰会断裂，形成冰山，在海洋中漂浮时融化，就像一杯水中的冰块一样。这些淡水进入海洋的地点和时间会影响携带热量、盐和海洋生物重要营养物质的洋流。然而，我们无法判断最近格陵兰岛融化并混合到海洋中的冰量的变化是否重要，因为我们还没有准确的地图来确定这些淡水究竟是从哪里进入海洋的。在这个项目中，我们将结合1)从卫星上拍摄的格陵兰岛海岸线照片，以及2)从海洋中的船只和仪器上拍摄的温暖、咸水和快速沿海水域的测量结果。根据这些观测结果，我们将绘制出2010年至2023年格陵兰冰山融化量的新地图。我们的科学团队将开展以冰山融化为重点的外展活动，并将与一位艺术家合作，向公众宣传冰山融化的重要性，并激发他们更多地思考地球迷人的冰川特征。格陵兰冰盖淡水通量的增加影响着海洋特性，可能在地方到全球尺度上对环流、海洋生态系统和气候产生重大影响。下游影响的严重程度取决于：从冰盖表面流出的融水的指纹，在冰盖流入相对温暖和咸的海洋的地方产生的融水，以及冰山逐渐腐烂注入海洋的融水。冰山融化产生的淡水变化的地图绘制得很差，但可能非常重要，因为冰山可以将寒冷、新鲜的融水从冰盖边缘输送到遥远的海洋盆地。在这个项目中，我们将结合使用卫星和海洋观测的独立冰山融化速率估算方法。我们将调查冰山融化的驱动因素，并量化每种方法的潜在误差和不确定性。我们将冰山融化速率估算值与格陵兰冰盖的冰山生成观测值配对，构建2010 - 2023年冰山淡水通量的时间序列。该项目将产生冰山融水通量图的时间序列，并确定冰山融水与其他淡水来源（如冰盖表面和冰下融水径流）的比较。我们还将产生一些新的数据集（例如，冰山尺寸的空间分布、融化速率和淡水通量时间序列），这些数据集将对专注于冰盖-海洋相互作用的研究有价值。我们将把项目产生的数据产品整合到开源的QGreenland地理信息系统包中，作为增加数据可访问性和使用的努力的一部分。该项目还为两名女性早期职业科学家提供了一个机会，以加强她们的研究项目，我们将强调为初级人员招募代表性不足的群体。最后，项目团队将开展K-12外展活动，展示冰山在一个鱼缸峡湾融化，并将与一位在创造性地向广大受众传播极地研究方面有经验的艺术家合作；这将使我们能够更有效地向公众传达我们的项目发现。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Greenland is a large reservoir of fresh, frozen water that flows downhill until it reaches the ocean. Some of this frozen reservoir melts at the surface and directly enters the ocean. Some of the ice instead breaks off, making icebergs that melt as they float around the ocean like ice cubes in a glass of water. Where and when this freshwater enters the ocean can influence the ocean currents that carry heat, salt, and vital nutrients for marine life. However, we cannot tell if recent changes to the amount of Greenland ice that is melted and mixed into the ocean are important because we don’t yet have accurate maps of where exactly this freshwater enters the ocean. In this project, we will combine 1) photos of Greenland’s coastline taken from satellites and 2) measurements of the warm, salty, and fast coastal waters taken from ships and instruments in the ocean. From these observations we will create new maps of how much Greenland icebergs melted from 2010 to 2023. Our science team will develop outreach activities that focus on iceberg melting and will work with an artist to educate the public about the importance of iceberg melt and inspire them to think more about the Earth’s fascinating icy features. Increasing freshwater flux from the Greenland Ice Sheet influences ocean properties, with potentially large consequences for circulation, marine ecosystems, and climate at local-to-global scales. The severity of the downstream effects depends on: the fingerprint of meltwater runoff from the ice-sheet surface, meltwater produced where the ice sheet flows into the relatively warm and salty ocean, and meltwater injected into the ocean by the gradual decay of icebergs. Variations in freshwater produced by iceberg melt are poorly mapped and yet may be incredibly important since icebergs can transport cold, fresh meltwater far from the ice-sheet margins to remote ocean basins. In this project, we will combine independent iceberg melt rate estimation methods using satellite and ocean observations. We will investigate the drivers of iceberg melt and also quantify potential errors and the uncertainty in each of our methods. We will pair the iceberg melt rate estimates with observations of iceberg production from the Greenland Ice Sheet to construct time series of iceberg freshwater flux from 2010 to 2023. The project will yield time series of iceberg meltwater flux maps and determine how iceberg meltwater compares to other freshwater sources, such as surface and subglacial meltwater runoff from the ice sheet. We will also produce several novel datasets (e.g., spatially distributed iceberg size distributions, melt rates, and freshwater flux time series) that will be valuable for studies focused on ice sheet-ocean interactions. We will incorporate data products produced by the project into the open-source QGreenland geographic information system package as part of efforts to increase data accessibility and use. The project also provides an opportunity for two female early career scientists to strengthen their research programs, and we will emphasize recruitment of underrepresented groups for junior personnel. Finally, the project team will develop K–12 outreach activities that demonstrate iceberg melting in a fish-tank fjord and will work with an artist who has experience in creatively disseminating polar research to a broad range of audiences; this will enable us to communicate our project findings more effectively to the public.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.