Based on an ice concentration threshold of 90%, it has been identified that two polynya events occurred in the region north of Greenland during the 2017/2018 ice season. The winter event lasted from February 20 to March 3, 2018 and the summer event persisted from August 2 to September 5, 2018. The minimum ice concentration derived from Advanced Microwave Scanning Radiometer 2 (AMSR2) observations was 72% and 65% during the winter and summer events, respectively. The occurrence of both events can be related to strengthened southerly winds associated with an increased east-west zonal surface level air pressure gradient across the north Greenland due to perturbation of mid-troposphere polar vortex. The relatively warm air temperature during the 2017/2018 freezing season in comparison with previous years, together with the occurrence of the winter polynya, formed favourable pre-conditions for ice field fracturing in summer, which promoted the formation of the summer polynya. Diminished southerly winds and increased cover of new ice over the open water were the dominant factors for the disappearance of the winter polynya, whereas increased ice inflow from the north was the primary factor behind the closure of the summer polynya. Sentinel-1 Synthetic Aperture Radar (SAR) images were found better suited than AMSR2 observations for quantification of a new ice product during the polynya event because the SAR images have high potential for mapping of different sea ice regimes with finely spatial resolution. The unprecedented polynya events north of Greenland in 2017/2018 are important from the perspective of Arctic sea ice loss because they occurred in a region that could potentially be the last “Arctic sea ice refuge” in future summers.

基于90％的冰浓度阈值，已确定在2017/2018冰季期间，格陵兰以北地区发生了两次波尼雅事件。冬季事件从2018年2月20日持续到2018年3月3日，夏季事件从2018年8月2日持续到9月5日。从高级微波扫描辐射计2（AMSR2）观测得出的最低冰浓度在冬季分别为72％和65％和夏季活动。这两个事件的发生都可能与南风增强有关，这是由于对流层中层极涡的扰动导致整个格陵兰北部东西向地带水平气压梯度增加所致。与往年相比，2017/2018冷冻季节的气温相对较高，再加上冬季多面目的发生，为夏季冰原压裂创造了有利的前提条件，促进了夏季多面目的形成。南风减弱和开放水域上新冰的覆盖增加是冬季多面目消失的主要因素，而北方冰流入的增加是夏季多面目关闭的主要因素。发现在哨兵事件期间，Sentinel-1合成孔径雷达（SAR）图像比AMSR2观测更适合量化新冰产品，因为SAR图像具有以精细的空间分辨率绘制不同海冰区域的潜力。