Sea ice type distribution in the Antarctic from microwave satellite observations (SITAnt)

海冰是地球气候的组成部分之一，在过去几十年中表现出最大的变化。例如，海冰控制着极地地区海洋和大气之间的能量和气体通量。由于它的高反射率，它可以有效地将短波辐射反射回太空，并影响生态系统。北极的海冰面积正以每十年约-4%的速度迅速减少，而南极的海冰面积则在缓慢增加（每十年约1.5%）。特别明显的是，北极地区厚厚的多年海冰以每十年约-13%的速度减少。北极多年海冰的面积可以通过微波卫星观测来确定。在南极，常年冰，即夏季融化后幸存的海冰面积小于北极，但仍有300万平方公里。目前还没有任何方法可以在整个季节或十年时间尺度上监测南极常年冰的分布和时间发展。本文提出了一种利用微波卫星观测南极海冰类型，特别是常年冰的方法，由于夏季海冰融化后盐度的降低，常年冰的介电性质和孔隙度发生了变化，这使得利用主动和被动微波传感器区分常年冰与其他冰型成为可能。在南极，高雪负荷可能导致冰泛滥、雪融化-再冻结循环和边缘冰区的海冰动态（导致脊状冰增加、浮冰变小、饼状冰），这使得海冰类型的区分，例如将常年冰与季节冰分开更具挑战性。最近开发的方法，以减轻这种影响，导致错误的冰型分类的北极。我们建议在这里适应和扩展的冰型检索算法，这已被应用在大学的不莱梅北极海冰，包括两个校正方案，以减轻错误的分类南极海冰的条件。所提出的方法依赖于结合微波辐射计和散射计观测的冰型判别和卫星派生的海冰漂移和大气再分析的冰型分类校正。其结果将是第一个南极海冰类型（常年冰和季节冰，以及可能的年轻冰）的环极长期时间序列。

Sea ice is one of the Earth's climate components exhibiting the greatest change during the last decades. For example, sea ice controls the energy and gas fluxes between ocean and atmosphere in polar regions. Due to its high albedo it efficiently reflects shortwave radiation back to space, and affects the ecosystem. While the sea ice area in the Arctic is rapidly decreasing with a rate of about -4%/decade the sea ice area in the Antarctic is slowly increasing (about 1.5%/decade). Especially pronounced is the decrease in thick, multiyear sea ice in the Arctic with a rate of about -13%/decade. The area of multiyear sea ice in the Arctic can be determined from microwave satellite observations. In the Antarctic the area of perennial ice, i.e. sea ice surviving the summer melt, is smaller than in the Arctic, however, with 3 million square kilometres still quite significant. No method exists today to monitor the distribution and temporal development of perennial ice in the Antarctic throughout the season or on decadal time scales. Here we propose to develop a method to observe Antarctic sea ice types, especially perennial ice, from microwave satellite observations.Due to a decrease in salinity after the summer melt the dielectric properties and porosity of the perennial sea ice change, which makes it possible to distinguish from other ice types by active and passive microwave sensors. In the Antarctic the high snow load, which can cause ice flooding, snow melt-refreeze cycles, and sea ice dynamics in the marginal ice zone (leading to increasing ridging, smaller floes, pancake ice) makes the discrimination of sea ice types, e.g. separation of perennial from seasonal ice more challenging. Recently methods were developed to mitigate such influences leading to false ice type classification for the Arctic. We propose here to adapt and extend an ice type retrieval algorithm, which has been applied at the University of Bremen to Arctic sea ice, including two correction schemes for mitigating false classifications to the conditions of Antarctic sea ice. The proposed method relies on combined microwave radiometer and scatterometer observations for the ice type discrimination and on satellite derived sea ice drift and atmospheric reanalysis for the ice type classification correction. The outcome will be the first circumpolar, long-term time series of Antarctic sea ice types (perennial and seasonal ice, and potentially also young ice).