NASA's Ice, Cloud, and Land Elevation Satellite‐2 (ICESat‐2) mission launched in September 2018 and is now providing high‐resolution surface elevation profiling across the entire globe, including the sea ice cover of the Arctic and Southern Oceans. For sea ice applications, successfully discriminating returns between sea ice and open water is key for accurately determining freeboard (the extension of sea ice above local sea level) and new information regarding the geometry of sea ice floes and leads. We take advantage of near‐coincident optical imagery obtained from the European Space Agency (ESA) Sentinel‐2 (S‐2) satellite over the Western Weddell Sea of the Southern Ocean in March 2019 and the Lincoln Sea of the Arctic Ocean in May 2019 to evaluate the surface classification scheme in the ICESat‐2 ATL07 and ATL10 sea ice products. We find a high level of agreement between the ATL07 (specular) lead classification and visible leads in the S‐2 imagery in these two coincident images across all six ICESat‐2 beams, increasing our confidence in the freeboard products and deriving new estimates of the sea ice state. The S‐2 overlays provide additional, albeit limited, evidence of the misclassification of dark leads due to clouds. Dark leads are no longer used to derive sea surface and thus freeboard as of the third release (r003) of the ICESat‐2 sea ice products. We show estimates of lead fraction and more preliminary estimates of chord length (a proxy for floe size) using two metrics for classifying sea surface (lead) segments across both the Arctic and Southern Ocean for the first winter season of data collection.

中文翻译：

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利用Sentinel-2图像评估ICESat-2海冰表面分类：对干舷的影响以及铅和浮冰几何的新估计

美国国家航空航天局（NASA）的``冰，云和陆地高程卫星2（ICESat-2）''任务于2018年9月发射，目前正在提供包括北极和南大洋海冰覆盖在内的整个地球的高分辨率地表高度剖面图。对于海冰应用而言，成功地区分海冰和开阔水域的收益对于准确确定干舷（海冰在当地海平面以上的延伸）以及有关海冰浮冰和铅的几何形状的新信息至关重要。我们利用了从欧洲航天局（ESA）的Sentinel-2（S-2）卫星获得的近乎一致的光学图像，这些图像于2019年3月在南大洋的西韦德尔海和2019年5月在北冰洋的林肯海评估ICESat-2 ATL07和ATL10海冰产品中的表面分类方案。我们发现，在所有六个ICESat-2光束中的这两个重合图像中，ATL07（镜面）导线分类与S-2图像中的可见导线之间存在高度一致性，从而增加了我们对干舷产品的信心，并得出了对干舷产品的新估计。海冰状态。S-2覆盖层提供了额外的证据，尽管有限，但可以证明由于云而导致的暗线错误分类。从ICESat-2海冰产品的第三个版本（r003）起，不再使用深色铅来导出海面，从而也不再使用干线。我们使用两个指标对北极和南洋的第一个冬季数据收集的海表（铅）段进行分类，显示铅含量的估算值和弦长的更初步估算（絮凝物大小的代表）。