The contribution of the Weddell Gyre to the lower limb of the Global Overturning Circulation
The contribution of the Weddell Gyre to the lower limb of the Global Overturning Circulation
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DOI：
10.1002/2013jc009725
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发表时间：
2014-06-01
影响因子：
3.6
通讯作者：
Fahrbach, Eberhard
中科院分区：
文献类型：
--
作者：
Jullion, Loic;Garabato, Alberto C. Naveira;Fahrbach, Eberhard
利用包括流动海冰和涡旋输送在内的近期水文剖面构建的箱形逆模型，对威德尔环流的水平和垂直环流进行了诊断。该环流通过威德尔海中心输送42 +/- 8 Sv (1 Sv = 106 m3 s-1)，并在近海进一步增强至54 +/- 15 Sv。这种环流从南极绕极流向环流注入了36 +/- 13太瓦的热量，并向中纬度南大洋输出了51 +/- 23毫西弗的淡水，其中包括13 +/- 1毫西弗的海冰。环流的翻转环流具有不对称的双胞结构，其中13 +/- 4 Sv的环极深水（CDW）和相对较轻的南极底水（AABW）通过环流中上升流（速率为2 +/- 2 Sv）转化为上层海水团，而集中在西部边界的下行流（速率为8 +/- 2 Sv）转化为较密集的南极底水团。环流环流表现出相当大的通流成分，CDW和AABW从印度区进入环流，在环流内经历通风和致密化，并通过环流北缘出口到南大西洋。威德尔环流中相对温和的AABW净产量（6 +/- 2 Sv）表明，该环流在全球海洋翻转下肢闭合中的突出作用主要来自印度AABW的再循环和向赤道出口。
The horizontal and vertical circulation of the Weddell Gyre is diagnosed using a box inverse model constructed with recent hydrographic sections and including mobile sea ice and eddy transports. The gyre is found to convey 42 +/- 8 Sv (1 Sv = 106 m3 s-1) across the central Weddell Sea and to intensify to 54 +/- 15 Sv further offshore. This circulation injects 36 +/- 13 TW of heat from the Antarctic Circumpolar Current to the gyre, and exports 51 +/- 23 mSv of freshwater, including 13 +/- 1 mSv as sea ice to the midlatitude Southern Ocean. The gyre's overturning circulation has an asymmetric double-cell structure, in which 13 +/- 4 Sv of Circumpolar Deep Water (CDW) and relatively light Antarctic Bottom Water (AABW) are transformed into upper-ocean water masses by midgyre upwelling (at a rate of 2 +/- 2 Sv) and into denser AABW by downwelling focussed at the western boundary (8 +/- 2 Sv). The gyre circulation exhibits a substantial throughflow component, by which CDW and AABW enter the gyre from the Indian sector, undergo ventilation and densification within the gyre, and are exported to the South Atlantic across the gyre's northern rim. The relatively modest net production of AABW in the Weddell Gyre (6 +/- 2 Sv) suggests that the gyre's prominence in the closure of the lower limb of global oceanic overturning stems largely from the recycling and equatorward export of Indian-sourced AABW.