The Effects of Enhanced Sea Ice Export from the Ross Sea on Recent Cooling and Freshening of the Southeast Pacific
The Effects of Enhanced Sea Ice Export from the Ross Sea on Recent Cooling and Freshening of the Southeast Pacific
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DOI：
10.1175/jcli-d-18-0205.1
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发表时间：
2019-04-01
影响因子：
4.9
通讯作者：
Holland, Paul R.
中科院分区：
文献类型：
--
作者：
Cerovecki, Ivana;Meijers, Andrew J. S.;Holland, Paul R.
近几十年来，南大洋 2000 米的顶部已经变得清新并变暖。然而，与 2005-07 年相比，2008-10 年高纬度（南纬 50 度以南）东南太平洋的大深度范围（包括表层、模态和中间水域）的温度更低、更新鲜。使用海洋-海冰数据同化南大洋状态估计（SOSE）和基于观测的产品分析了该事件的原因和影响。 2008-10年，强烈的正南环模与负厄尔尼诺南方涛动和阿蒙森海深低压同时发生。增强的经向风推动了罗斯海东部强劲的海冰输出，将大量冰带到阿蒙森海冰缘。 2008年，随着降水量的增加，出现了强烈的淡水异常，并被南极绕极流（ACC）向东平流，并沿途混合。这种异常不仅以南极中层水的形式进入海洋内部，而且还以较轻的东南太平洋亚南极模式水（SEPSAMW）的形式进入海洋内部。在 SOSE 进行的数值颗粒释放实验表明，罗斯海区域是到达 SEPSAMW 形成区域的颗粒的主要来源。这表明大规模的气候波动会导致 SEPSAMW 的体积和性质发生强烈的年际变化。这些波动在不同的时间尺度上起作用：通过直接强迫而瞬时发生，并且还从上游区域滞后于数年的平流时间尺度。
The top 2000 m of the Southern Ocean has freshened and warmed over recent decades. However, the high-latitude (south of 50 degrees S) southeast Pacific was observed to be cooler and fresher in the years 2008-10 compared to 2005-07 over a wide depth range including surface, mode, and intermediate waters. The causes and impacts of this event are analyzed using the ocean-sea ice data-assimilating Southern Ocean State Estimate (SOSE) and observationally based products. In 2008-10, a strong positive southern annular mode coincided with a negative El Nino-Southern Oscillation and a deep Amundsen Sea low. Enhanced meridional winds drove strong sea ice export from the eastern Ross Sea, bringing large amounts of ice to the Amundsen Sea ice edge. In 2008, together with increased precipitation, this introduced a strong freshwater anomaly that was advected eastward by the Antarctic Circumpolar Current (ACC), mixing along the way. This anomaly entered the ocean interior not only as Antarctic Intermediate Water, but also as lighter Southeast Pacific Subantarctic Mode Water (SEPSAMW). A numerical particle release experiment carried out in SOSE showed that the Ross Sea sector was the dominant source of particles reaching the SEPSAMW formation region. This suggests that large-scale climate fluctuations can induce strong interannual variability of volume and properties of SEPSAMW. These fluctuations act at different time scales: instantaneously via direct forcing and also lagged over advective time scales of several years from upstream regions.