Recent Antarctic Sea Ice Surface Melt from Satellite Remote Sensing(REASSESS)

2017年1月，日本南极昭和站附近发生大规模海冰表面融化事件。破冰船RV Shirase的实地考察队报告说，在陆地固定和自由浮冰的顶部有多个融化池。2016年1月，在麦克默多海峡观察到了大量的积水。融化的池塘，海冰顶部融化的水坑，在夏季的北极很常见，但在南极洲被认为是极其罕见的。在目前正在进行的REASSESS项目中，我们借助卫星数据显示，不仅在2017年1月，而且在2018年1月，2019年1月，2020年1月在昭和站附近观察到了融池，从而证明了一些融池之前由于缺乏现场观测而被忽视。我们第一次提出了全球南极融化池部分地图制作的每日平均从所有的卫星飞越的一天，并定位更多的潜在的融化积水事件也在其他地区的冰覆盖的南大洋。这些新数据正在被汇编成第一个一致的全球南极融化池/蓝冰数据集。我们能够提供多年卫星数据的南大洋融化池和蓝冰的卫星衍生面积分数，而不是定性估计“南极融化池是罕见的”。然而，需要验证我们的反演的特定条件的现场活动（阳光，无云条件）是罕见的，使验证和校准的开发检索来短。在拟议的更新项目，我们计划开展一项由AWI资助的专用飞机运动。其目标之一将是观察南极洲陆地上的融化池/蓝冰和自由漂浮的浮冰。这项活动的结果将是一个独特的原位数据集，将作为我们的遥感融化池检索的验证和校准。此外，我们计划采用非常高的空间分辨率的卫星图像作为验证数据的另一个来源。这些数据也将作为飞机活动的后续活动获得，并可能提供验证时间序列。校准融化池分数检索将用于新计划的跨学科比较融化池数据集与水母在南极海冰下的原位数据。因此，我们测试了一个假设，即冰下生态系统是通过增加海冰透光率的表面上的海冰条件的影响，基于上述研究将产生的改进的融化池分数的趋势将澄清有多少南极海冰变化，在最近20年的卫星观测。

In January 2017, a massive sea ice surface melt event occurred in the vicinity of the Japanese Syowa station in Antarctica. The field party of the icebreaker RV Shirase reported multiple melt ponds on top of landfast and free floating ice. Massive ponding has been observed in McMurdo Sound a year earlier, in January 2016.Melt ponds, puddles of melt water on top of the sea ice, are common in the Arctic during summer but are thought of as extremely rare in Antarctica. In the currently running project REASSESS we have shown with the aid of satellite data that the melt ponding observed in the vicinity of Syowa station not only in January 2017 but also in January 2018, 2019, 2020, and thus proved that some melt ponds have been simply overlooked before due to lack of in situ observations. We have for the first time presented global Antarctic melt pond fraction maps produced as daily average from all the satellite overflights of a given day, and located more potential melt ponding events also in other regions of the ice-covered Southern Ocean. These new data are being compiled into the first consistent, global Antarctic melt pond/blue ice dataset. Instead of qualitative estimates “Antarctic melt ponds are rare”, we are able to provide satellite-derived area fractions of the melt ponds and blue ice in the Southern Ocean for many years of satellite data.However, the in situ campaigns fitting to the specific conditions needed to validate our retrievals (sunlight, cloud free conditions) are rare, so that the validation and calibration of the developed retrievals comes short.In the proposed renewal project, we plan to carry out a dedicated aircraft campaign funded by AWI. One of its objectives will be to observe the melt ponds/blue ice on top of Antarctic landfast and freely floating pack ice. The outcome of this campaign will be a unique in situ dataset which will serve as validation and calibration for our remote sensing melt pond retrieval. In addition, we plan to employ satellite imagery of very high spatial resolution as one more source of validation data. These data will be acquired also as follow-up to the aircraft campaign and will potentially provide validation time series. The calibrated melt pond fraction retrieval will be used for a newly planned interdisciplinary comparison of melt pond dataset with the jellyfish in situ data under the Antarctic sea ice. Thus, we test a hypothesis that the under-ice ecosystem is affected by the sea ice conditions on the surface via the increased sea ice transmittance.The improved melt pond fraction trends which will be produced based on the above research will clarify how much did the Antarctic sea ice change in the recent 20 years of satellite observations.