Daily polynya area and ice production in circumpolar polynya regions in the Arctic for 2002/2003 to 2014/2015

High-resolution MODIS thermal infrared satellite data are used to infer spatial and temporal characteristics of 17 prominent coastal polynya regions over the entire Arctic basin. Thin-ice thickness distributions (< 20 cm) are calculated from MODIS ice-surface temperatures, combined with ECMWF ERA-Interim atmospheric reanalysis data in an energy balance model for 13 winter-seasons (2002/2003 to 2014/2015; November to March). From all available MODIS swath-data, (quasi-) daily thin-ice thickness composites are computed in order to derive quantities such as polynya area and total thermodynamic (i.e., potential) ice production. A gap-filling approach is applied to account for cloud and data gaps in the MODIS composites. All polynya regions combined cover an average thin-ice area of 226.6 ± 36.1 x10³ km² in winter. This allows for an average total wintertime accumulated ice production of about 1811 ± 293 km³, whereby the Kara Sea region, the North Water polynya (both 15%), polynyas at the western side of Novaya Zemlya (20%) as well as scattered smaller polynyas in the Canadian Arctic Archipelago (all combined 12%) are the main contributors. Other well-known sites of polynya formation (Laptev Sea, Chukchi Sea) show smaller contributions and range between 2 and 5%. We notice distinct differences to earlier studies on pan-Arctic polynya characteristics, originating in some part from the use of high-resolution MODIS data, as the capability to resolve small-scale (> 2km) polynyas and also large leads is increased. Despite the short record of 13 winter seasons, positive trends in ice production are detected for several regions of the eastern Arctic (most significantly in the Laptev Sea region with an increase of 6.8 km³/yr) and the North Water polynya, while other polynyas in the western Arctic show a more pronounced variability with varying trends. We emphasize the role of the Laptev Sea polynyas as being a major influence on Transpolar Drift characteristics through a distinct relation between increasing ice production and ice area export. Overall, our study presents a spatially highly accurate characterization of circumpolar polynya dynamics and ice production, which should be valuable for future modeling efforts on atmosphere - sea ice - ocean interactions in the Arctic.

本研究采用高分辨率中分辨率成像光谱仪（MODIS）热红外卫星数据，反演了整个北极盆地内17处典型沿岸冰间湖区域的时空特征。基于MODIS冰面温度数据，结合欧洲中期天气预报中心（ECMWF）ERA-Interim大气再分析资料，通过能量平衡模型计算了2002/2003至2014/2015年共13个冬季（11月至次年3月）的薄冰厚度分布（<20cm）。从所有可用的MODIS条带数据中，我们生成了准每日薄冰厚度合成产品，以此推导冰间湖面积、总热力学（即潜在）冰产量等参数。针对MODIS合成产品中的云覆盖与数据缺失问题，我们采用了间隙填充方案进行处理。所有统计冰间湖区域的冬季平均薄冰总面积为226.6±36.1×10³ km²，对应冬季累计总冰产量约为1811±293 km³。其中，喀拉海区域、北冰间湖（均占总贡献的15%）、新地岛西侧的冰间湖（占20%）以及加拿大北极群岛内零散分布的小型冰间湖（总占比12%）为主要贡献者。其他知名冰间湖形成区域（拉普捷夫海、楚科奇海）的贡献占比相对较小，介于2%至5%之间。本研究结果与此前泛北极冰间湖特征相关研究存在显著差异，部分原因在于采用了高分辨率MODIS数据——其对尺度大于2km的小型冰间湖及大型冰缝的识别能力得到显著提升。尽管本次研究的冬季观测序列仅为13个，我们仍在北极东部多个区域以及北冰间湖检测到了冰产量的正增长趋势；其中拉普捷夫海区域的冰产量增长最为显著，达6.8 km³/yr。而北极西部的其他冰间湖则表现出更强的变异性，各区域趋势各不相同。我们着重指出，拉普捷夫海冰间湖的冰产量增长与海冰面积输出之间存在显著关联，这对跨极漂流特征具有重要影响。总体而言，本研究实现了环北极冰间湖动力学与冰产量的高精度空间特征刻画，可为未来北极大气-海冰-海洋相互作用的模拟研究提供重要参考价值。