Zonal circulation across 52°W in the North Atlantic
Zonal circulation across 52°W in the North Atlantic
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北大西洋西经 52° 的纬向环流
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
D. Torres
中科院分区：
文献类型：
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作者：
M. Hall;T. Joyce;R. Pickart;W. Smethie;D. Torres
[1]1997年7月至8月，作为世界海洋环流实验水文方案的一部分，在北大西洋的52°W沿线占用了一个水文/声学多普勒海流剖面仪/示踪器部分。根据航道数据计算出的地转速度；由一个反向模式提供的额外(小)速度调整，约束了17个中性密度层中的质量和硅酸盐输送，得到了52°W的绝对纬向速度场。在北部边界，在纽芬兰大浅滩的西侧，我们发现了向西流动的拉布拉多洋流(8.6 Sv)，其从我们断面以东的拉布拉多海的连续性一直存在争议。直接向南，我们发现了斜流(向东12.5Sv)和北部DWBC(向西12.5Sv)。在LADCP资料中发现了与内陆严格纬向气流的强烈偏离，这使得诊断那里的环流变得困难。南部孤立的深水性质极端，与东向和向西流动的交替带有关，这与我们剖面正东面的中大西洋海脊的粗糙地形导致南极底层水性质与具有明显不同性质的上覆水域的强化混合的想法是一致的。我们计算了跨越52°W的热量和淡水通量，比基于海-气交换的估计高出1.7倍。
[1] In July–August 1997, a hydrographic/Acoustic Doppler Current Profiler (ADCP)/tracer section was occupied along 52°W in the North Atlantic as part of the World Ocean Circulation Experiment Hydrographic Program. Underway and lowered ADCP (LADCP) data have been used to reference geostrophic velocities calculated from the hydrographic data; additional (small) velocity adjustments provided by an inverse model, constraining mass and silicate transports in 17 neutral density layers, yield the absolute zonal velocity field for 52°W. We find a vigorous circulation throughout the entire section, with an unusually strong Gulf Stream (169 Sv) and southern Deep Western Boundary Current (DWBC; 64 Sv) at the time of the cruise. At the northern boundary, on the west side of the Grand Banks of Newfoundland, we find the westward flowing Labrador Current (8.6 Sv), whose continuity from the Labrador Sea, east of our section, has been disputed. Directly to the south we identify the slopewater current (12.5 Sv eastward) and northern DWBC (12.5 Sv westward). Strong departures from strictly zonal flow in the interior, which are found in the LADCP data, make it difficult to diagnose the circulation there. Isolated deep property extrema in the southern portion, associated with alternating bands of eastward and westward flow, are consistent with the idea that the rough topography of the Mid-Atlantic Ridge, directly east of our section, causes enhanced mixing of Antarctic Bottom Water properties into overlying waters with distinctly different properties. We calculate heat and freshwater fluxes crossing 52°W that exceed estimates based on air-sea exchanges by a factor of 1.7.