Quantifying Greenland Iceberg Melt Rates using Remotely-sensed Data

研究人员建议采用一种新的遥感技术来获取冰山体积的变化。以估计格陵兰冰原周边主要峡湾的海底融化速度。来自格陵兰冰盖的固体冰和液体淡水的通量是海平面上升和海洋变新鲜的重要因素。固体通量以冰山的形式从海洋冰川边缘崩解而来。淡水通量由地表融水径流和崩解边缘的海底融水组成。然而，当冰山从边缘漂离时，它们会受到海底融化的影响，从而构成向海洋释放淡水的另一个来源。幅度和空间分布的变化&amp；#8232；冰川峡湾和邻近海洋盆地的淡水通量会影响海洋吗？因此，对冰川融化的时空变化进行量化研究是十分重要的。利用由极地地理空间中心汇编的约0.5 m分辨率的WorldView立体卫星图像的广泛收集，将获得大约20个大型出口冰川边缘附近的融化速率。数字高程模型（dem）将使用&amp；#8232；NASA Ames Stereo Pipeline软件在缅因大学的超级计算集群上实现。将相隔约5-30天获得的共登记连续dem进行差分，可得出冰山干舷（即海平面以上表面高度）变化的估计值。假定流体静力平衡，可转换为冰山吃水。ppi认为，在考虑了由于海面融化和潮汐引起的高程变化后，dem之间的冰山干舷剩余差一定是由于海底融化造成的。这项工作将为关注冰海相互作用和高纬度海洋淡水输入的研究提供新的见解。该项目为一名职业生涯早期的科学家和一名本科生提供支持。指导本科生研究助理将为早期职业科学家提供宝贵的建议经验，并且学生将发展数据分析和解决问题的技能，这些技能是课堂教学无法轻易获得的。

The investigators propose to implement a new remote sensing technique for deriving iceberg volume changes
in order to estimate submarine melt rates in key fjords around the Greenland Ice Sheet periphery. The fluxes of solid ice and liquid freshwater from the Greenland Ice Sheet are important contributors to sea level rise and ocean freshening. Solid fluxes come in the form of icebergs calved from marine-terminating glacier margins. Freshwater fluxes are comprised of surface meltwater runoff and submarine melting at calving margins. As icebergs drift away from the margin, however, they are subject to submarine melting and thus constitute an additional source of freshwater release to the ocean. Variations in the magnitude and spatial distribution
of freshwater fluxes in glacial fjords and adjacent ocean basins can impact the ocean?s stratification, circulation, and ecological structure as well as ice-ocean interactions that influence ice flow, so it is important that spatial and temporal variations in melting are quantified.Melt rates will be obtained near the margins of about 20 large outlet glaciers using an extensive collection of ~0.5 m-resolution WorldView stereo satellite images compiled by the Polar Geospatial Center. Digital elevation models (DEMs) will be constructed from available stereo pairs using
the NASA Ames Stereo Pipeline software implemented on the University of Maine supercomputing cluster. Differencing the co-registered sequential DEMs acquired ~5-30 days apart yields an estimate of the change in iceberg freeboard (i.e., surface elevation above sea level) which
can be converted to an iceberg draft assuming hydrostatic equilibrium. The PIs contend that after accounting for elevation change due to surface melting and tides, the residual difference in iceberg freeboard between the DEMs must be due to submarine melting. This work will provide new insights for studies focused on ice-ocean interactions and freshwater input to high latitude oceans. The project provides support for an early-career scientist and for an undergraduate student. Mentoring the undergraduate research assistant will give the early-career scientist valuable advising experience, and the student will develop data-analysis and problem solving skills that are not readily obtained by in-class instruction.