北极海冰输出区域海冰运动变化特征及其与北极航道适航性的关系

随着北极地区气候变暖的加剧，北极海冰正在急剧消融，海冰的减少增加了北极地区航道的适航性。本文利用遥感数据反演得到的海冰运动产品对北极海冰输出区域以及东北航道以北区域的海冰运动特征进行了量化。结果显示，从北极中央海域向弗拉姆海峡以及格陵兰海流出海冰的南向位移量呈现出显著增长趋势，海冰的平均南向位移量在2007-2014年间达到1511 km，是2007年之前（617 km）的两倍以上，反映了北极穿极流（TDS）强度在不断增强。通过长时间序列分析发现，春季东北航道以北区域的海冰北向漂移速度在喀拉海呈现+0.04 厘米/秒/年的显著增长趋势（P<0.05）。海冰北向漂移对于东北航道的开通具有显著的影响，在拉普捷夫海与喀拉海，海冰北向运动速度与航道适航期的决定系数分别达到0.33（P<0.001）和0.15（P<0.05）。东西伯利亚海、拉普捷夫海以及喀拉海存在冰间湖区域的春季海冰面积变化与航道的适航期密切相关，海冰的北向漂移对拉普捷夫海和喀拉海的海冰面积减少也有显著影响，这说明北向漂移促进了海冰的离岸输送，造成海冰面积减少的同时形成冰间水道或冰间湖促使航道开通。为探究大气环流指数对海冰运动以及东北航道适航期的影响，本文利用大气再分析数据计算了中央北极指数（CAI）和北极大气偶极子异常（DA）指数。相关性分析表明，CAI比DA更能解释东北航道的适航期，而且CAI能够解释北极海冰输出区域海冰南向位移量变化的45%。最近10年，夏季正相位的CAI进一步加强，通过加强海冰离岸输运和冰间湖活动加剧了东北航道区域海冰变薄及其强度变弱，从而促进了东北航道的开通。

Changes in sea ice kinematics in the Arctic outflow region and their associations with Arctic Northeast Passage accessibility

Amplification of climate warming in the Arctic is causing a dramatic retreat of sea ice, which means the Arctic sea routes are becoming increasingly accessible. This study used a satellite-derived sea ice motion product to quantify the kinematic features of sea ice in the Arctic outflow region which specially referred to the Fram Strait and to the north of the Northeast Passage (NEP). An observed trend of increased southward sea ice displacement from the central Arctic to the Fram Strait indicated enhancement of the Transpolar Drift Stream (TDS). In the regions to the north of the NEP, the long-term trend of northward sea ice speed in the Kara sector was +0.04 cm/s per year in spring. A significant statistical relationship was found between the NEP open period and the northward speed of the sea ice to the north of the NEP. The offshore advection of sea ice could account for the opening of sea routes by 33% and 15% in the Kara and Laptev sectors, respectively. The difference in sea level pressure across the TDS, i.e., the Central Arctic Index (CAI), presented more significant correlation than for the Arctic atmospheric Dipole Anomaly index with the open period of the NEP, and the CAI could explain the southward displacement of sea ice toward the Fram Strait by more than 45%. The impact from the summer positive CAI reinforces the thinning and mechanical weakening of the sea ice in the NEP region, which improves the navigability of the NEP.