Quantifying Greenland Iceberg Melt Rates using Remotely-sensed Data

研究人员建议实施一种新的遥感技术来获得冰山体积变化#8232;，以估计格陵兰冰盖周边关键峡湾的海底融化率。&来自格陵兰冰盖的固体冰和液态淡水通量是海平面上升和海洋淡化的重要因素。固体通量以冰山的形式出现，这些冰山是从海洋冰川边缘崩解下来的。淡水通量包括表面融水径流和海底融化在产犊边缘。然而，当冰山漂离边缘时，它们会受到海底融化的影响，从而构成向海洋释放淡水的额外来源。冰川峡湾和邻近海洋盆地淡水通量的大小和空间分布的变化会影响海洋吗？&的分层，循环，生态结构以及冰-海洋的相互作用，影响冰流，因此，重要的是，融化的空间和时间的变化是量化的。融化率将获得约20个大型出口冰川的边缘附近的广泛收集的~0.5米分辨率的世界观立体卫星图像由极地地理空间中心汇编。数字高程模型（DEM）将使用在缅因州大学超级计算集群上实施的#8232; NASA艾姆斯立体管道软件从可用的立体对构建。&区分间隔约5 - 30天获得的共同登记的连续DEM，得出冰山干舷变化的估计值（即，海平面以上的表面高度），其可以转换为假定流体静力平衡的冰山吃水。& PI认为，在考虑了由于表面融化和潮汐引起的海拔变化后，DEM之间冰山干舷的剩余差异必须是由于海底融化。这项工作将为重点研究冰-海洋相互作用和淡水输入高纬度海洋提供新的见解。该项目为一名早期职业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咨询经验，学生将培养数据分析和解决问题的技能，这些技能是课堂教学无法获得的。

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.