Sea ice in the Weddell Sea plays important roles in the albedo, air-sea heat, freshwater, and gas exchanges and the formation of the Antarctic Bottom Water on the continental shelf that regulates global climate through deep thermohaline circulation. Sea ice extent (SIE) in the Weddell Sea does not show any significant trend in the four-decade satellite observation period but does experience large interannual-to-decadal variability. Physical processes underlying this variability are difficult to examine because of a paucity of prolonged observations. Using a coupled general circulation model, we corroborate the observational finding that decadal increases in SIE are preceded by weakening of the mean westerly winds linked to the Southern Annular Mode. Weakening of the westerly winds over the Weddell Sea reduces the northward Ekman current and suppresses upwelling of warm water from the subsurface ocean; this lowers the upper-ocean temperature, causing an increase in sea ice. In a sensitivity experiment where the interannual sea surface temperature variations are suppressed outside the South Atlantic and the Weddell Sea, decadal increase in the SIE over the Weddell Sea is induced by a decrease in the upper-ocean temperature owing to enhanced horizontal advection by the Weddell Gyre. The strengthening of the Weddell Gyre increases the upper-ocean salinity as a result of enhanced evaporation and brine rejection associated with the sea ice increase. These results demonstrate that both the remote atmospheric forcing and local ice-ocean interaction are crucial for generation of decadal sea ice variability in the Weddell Sea.

中文翻译：

---

控制威德尔海十年海冰变化的远程和本地过程

威德尔海的海冰在反照率、海气热、淡水和气体交换以及大陆架上南极底水的形成中起着重要作用，南极底水通过深层温盐环流调节全球气候。威德尔海的海冰范围 (SIE) 在 4 个十年的卫星观测期内没有表现出任何显着趋势，但确实经历了较大的年际至年代际变化。由于缺乏长时间的观察，很难检查这种可变性背后的物理过程。使用耦合环流模型，我们证实了观测结果，即 SIE 的十年增加之前是与南部环形模式相关的平均西风减弱。威德尔海的西风减弱减少了向北的埃克曼海流，并抑制了来自地下海洋的暖水上涌；这降低了上层海洋的温度，导致海冰增加。在南大西洋和威德尔海以外的年际海面温度变化受到抑制的敏感性实验中，威德尔海的 SIE 十年间增加是由于威德尔海平面水平平流增强导致上层海洋温度下降回旋。由于与海冰增加相关的蒸发和盐水排斥增强，威德尔环流的加强增加了上层海洋的盐度。