Derivation of snow thickness information on sea ice using in-situ and satellite based multi-frequency polarimetric scatterometer and SAR data

最近北极海冰的迅速减少在过去十年中受到了科学和媒体的广泛关注。这种减少既发生在其季节性程度上，也发生在其厚度分布上。模拟研究表明，北极海冰范围和厚度的长期下降趋势将至少在未来几十年持续下去，这是由于人为产生的气体在大气中积聚造成的温室效应增强所致。参与最新的政府间气候变化专门委员会第四次评估报告（IPCC-AR4）的全球气候模型显示，北极向夏季无冰的过渡可能比先前预期的更突然和更早发生。然而，海冰覆盖在其范围和厚度分布方面，由于在整个北极的连续时间和空间尺度上起作用的大尺度大气环流型变化，其年复一年的变化仍然很大。一旦海冰形成，这些大气环流变化就会以积雪的形式在空间上沉积不同数量的降水，然而，由于云层覆盖和秋季和冬季大部分时间的24小时黑暗，我们使用基于光学的卫星遥感技术测量和量化这些量的能力受到严重限制。海冰上的积雪是雪/海冰系统的关键组成部分，因为它控制着冰的厚度和冰的融化行为。因此，它也在很大程度上控制着冰的机械性能，如冰的强度和破裂潜力。本研究将使用从冰面和卫星获取的全天候成像微波遥感数据，以及积雪覆盖的热力学海冰和微波散射模型，这些模型采用现场收集的雪和海冰性质数据。预期的结果将允许估计春季过渡期间不同时间的积雪特征（厚度分布、雪水当量、液态水含量），以便更好地了解雪对海冰的作用，从而确定其在北极海冰范围和厚度的年际变化中的作用。

The recent and rapid reduction in Arctic sea ice has received considerable scientific and media attention during the past decade. This decrease has occurred to both its seasonal extent and to its thickness distribution. Modelling studies suggest that the long-term declining trend for both the extent and thickness of Arctic sea ice will continue for at least the next several decades due to an enhanced greenhouse effect resulting from the atmospheric build-up of anthropogenic produced gases. Global climate models participating in the latest Intergovernmental Panel on Climate Change - Fourth Assessment Report (IPCC-AR4) show that a transition to a summertime ice-free Arctic could occur both abruptly and earlier than previously anticipated. However, the sea ice cover remains highly variable from year-to-year within respect to its extent and thickness distribution owing to large scale atmospheric circulation pattern changes which operate over a continuum of time and space scales throughout the Arctic. These atmospheric circulation changes manifest to deposit spatially varying amounts of precipitation in the form of snow accumulation once the sea ice has formed, however, our ability to measure and quantify these amounts using optically based satellite remote sensing techniques is severely limited owing to cloud cover and 24-hour darkness during much of the fall and winter. The snow cover on sea ice is a critical component of snow/sea ice system because it controls the ice thickness and melt behaviour of the ice. As a result, it also largely controls the mechanical properties of the ice such as ice strength and break-up potential. This research will use all-weather imaging microwave remote sensing data acquired from both the ice surface and satellites along with snow covered thermodynamic sea ice and microwave scattering models fed with in situ collected snow and sea ice property data. The expected results will permit an estimation the snow cover characteristics (thickness distribution, snow water equivalent, liquid water content) at various times during the spring transition such that an improved understanding of the role of snow on sea ice can be assessed towards determining its role in the interannual variability in Arctic sea ice extent and thickness.