Record low sea-ice concentration in the central Arctic during summer 2010

Abstract

The Arctic sea-ice extent has shown a declining trend over the past 30 years. Ice coverage reached historic minima in 2007 and again in 2012. This trend has recently been assessed to be unique over at least the last 1450 years. In the summer of 2010, a very low sea-ice concentration (SIC) appeared at high Arctic latitudes—even lower than that of surrounding pack ice at lower latitudes. This striking low ice concentration—referred to here as a record low ice concentration in the central Arctic (CARLIC)—is unique in our analysis period of 2003–15, and has not been previously reported in the literature. The CARLIC was not the result of ice melt, because sea ice was still quite thick based on in-situ ice thickness measurements. Instead, divergent ice drift appears to have been responsible for the CARLIC. A high correlation between SIC and wind stress curl suggests that the sea ice drift during the summer of 2010 responded strongly to the regional wind forcing. The drift trajectories of ice buoys exhibited a transpolar drift in the Atlantic sector and an eastward drift in the Pacific sector, which appeared to benefit the CARLIC in 2010. Under these conditions, more solar energy can penetrate into the open water, increasing melt through increased heat flux to the ocean. We speculate that this divergence of sea ice could occur more often in the coming decades, and impact on hemispheric SIC and feed back to the climate.

摘要

在过去30年, 北极海冰范围正在经历减退的趋势. 海冰覆盖范围在2007和2012年达到历史最低值. 这一变化是过去1450年以来唯一的减退事件. 在2010年夏季, 在北极高纬度海域出现非常低的海冰密集度, 甚至比较低纬度的海冰密集度还要低. 这个显著低的海冰密集度在我们研究的2003-2015年间只出现这唯一的一次, 我们将其称为北极中央区极低海冰密集度(CARLIC). 研究结果表明, CARLIC不是海冰融化导致的, 因为发生时海冰还很厚;是海冰的辐散运动导致了CARLIC. 海冰密集度与风应力旋度之间有很好的相关, 表明海冰漂移特性的改变很好地响应局地风强迫. 在大西洋扇区, 海冰的漂移轨迹呈现穿极流的特征, 而在太平洋扇区体现为一个向加拿大北极群岛方向的漂流, 这种漂流方向的不一致有利于形成2010年的CARLIC现象. 在这种海冰减少的条件下, 更多的太阳辐射能进入海洋, 加剧了海冰的融化. 我们推测, 由于海冰在不断减少, 海冰的辐散在未来可能更加频繁, 这种现象还会发生, 并对更大范围的海冰和北极气候产生显著影响.