Precision, Accuracy, and Aliasing of Sea Ice Thickness from Multiple Observing Platforms

人们对北冰洋海冰范围及其变化的关注主要集中在面积覆盖上。同样，如果不是更重要的话，需要考虑的是冰的厚度，它随着年龄的变化而变化，也是由于冰的移动。厚度在几何上很粗糙，有山脊、碎石场和开阔水域的引线。这些特征在一个水平方向上不对称地从厘米到米，在另一个方向上从米到公里。用于感知冰层厚度的仪器通常有很宽的足迹，将这些粗糙的特征混叠成更平滑、更平坦的特征。为了减少全球厚度数据档案中的不确定性，需要这些变形区域的准确厚度分布。这样的结果导致区域和全球海冰体积估计的准确性更高。单一仪器的高精度和一致性不能量化混叠的影响。海冰界目前正在寻求一种综合仪器方法，根据吃水、干舷和表面高程(包括积雪负荷)的组成部分来测量海冰厚度，目前正在开发厚度档案。这个项目将解决中心问题，“在测量海冰厚度、其分布和由此产生的体积时，空间混叠的影响是什么？”这种方法是使用数据集，其中包括由两台或更多仪器在同一位置使用不同足迹进行的测量，基于最近发现的5M和40M足迹粗糙度之间的关系，这些关系源于一次野外实验。使用该数据集，使用两次测量之间的粗糙度比找到了有效的校正(优于10厘米)。研究人员提出，这种类型的关系可以推广到所有类型的海冰厚度测量。调查员将整理和存档气候数据记录，其中包含来自不同足迹的仪器测量的一致海冰厚度，并将这些数据与现有的海冰厚度档案合并。主要的科学贡献将是改进元数据关系，以确定导致气候数据档案记录厚度不确定的属性。一篇博士论文将使用机载电磁(EM)测量来提出混叠假说，通过利用已经集成到EM技术中的随附的高分辨率激光高度计来设计校正。这项工作的更广泛影响包括改善厚度档案和培训博士生。

Much attention on the extent, and changes therein, of Arctic sea ice focuses on areal coverage. Equally if not more important to consider is the thickness of the ice, which varies with age and also due to movement of the ice. Thickness is geometrically rough with ridges, rubble fields, and open-water leads. These features are asymmetrically shaped from centimeters to meters in one horizontal direction and meters to kilometers along the other. Instruments used to sense ice thickness typically have wide footprints that alias these rough features into smoother flatter features. Accurate thickness distribution of these deformed areas is needed to reduce uncertainties in global thickness data archives. Such results lead to higher accuracy in regional and global sea ice volume estimates. High precision and consistency from a single instrument cannot quantify the impact of aliasing. The sea ice community currently seeks an integrated- instrument approach to measure sea ice thickness from its components of draft, freeboard, and surface elevation (including snow loads) and thickness archives are being developed. This project would address the central question, "What is the impact of spatial aliasing when measuring sea ice thickness, its distribution, and resulting volume?" The approach is to work with datasets that include measurements made by two or more instruments with different footprints in the same location, based on a recently discovered relationship between the roughness of 5m and 40m footprints stemming from one field experiment. Using this dataset a valid correction (to better than 10 cm) was found using the roughness ratio between the two measurements. The investigator proposes that this type of relationship can be generalized for all types of sea ice thickness measurements. The investigator will organize and archive climate data records containing coincident sea ice thickness measurements from instruments of different footprints and incorporate these data with existing sea ice thickness archives. The main scientific contribution will be an improved metadata relationship to characterize properties that contribute to thickness uncertainties in climate data archive records. A Ph.D. thesis will advance the aliasing hypothesis using airborne electromagnetic (EM) measurements to devise a correction by leveraging the accompanying high-resolution laser altimeter already integrated into the EM technology. The broader impacts of the work include the improved thickness archive and the training of a Ph.D. student.