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首页> 外文期刊>Journal of Physical Oceanography >Absolute Transports of Mass and Temperature for the North Atlantic Current- Subpolar Front System
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Absolute Transports of Mass and Temperature for the North Atlantic Current- Subpolar Front System

机译：北大西洋电流-亚极前锋系统的质量和温度绝对传输

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The flow of subtropical waters carried into the northern North Atlantic Ocean by the North Atlantic Current-subpolar front system (NAC-SPF) is an important component of the meridional overturning circulation. These waters become colder and denser as they flow through the subpolar region, both by mixing with the colder subpolar waters and by atmospheric cooling. The relative roles of these two processes remain to be quantified, and the mechanisms driving lateral mixing need to be better understood. To address those questions, a new methodology is developed to estimate the mean absolute transports of mass and heat for the top 1000 dbar in the region of the NAC-SPF for the time period 1993-2000. The transports are obtained by combining historical hydrography with isopycnal RAFOS float data from the area. The mean absolute transport potential field shows an NAC-SPF "pipe," defined by two bounding transport potential contours. This pipe transports 10.0 ± 3.5 Sv (Sv ≡ 10~6 m~3 s~(-1)) (top 1000 dbar) from the subtropics into the eastern subpolar North Atlantic. In contrast to earlier studies, the northward-flowing NAC follows a distinct meandering path, with no evidence of permanent branches peeling off the current before reaching the "Northwest Corner." As the current enters the Northwest Corner, it loses its tight structure and maybe splits into two or more branches, which together constitute the eastward flow along the SPF. The eastward flow between the Northwest Corner and the Mid-Atlantic Ridge is not as tightly defined because of the meandering and/or eddy shedding of the branches constituing the SPF. As the flow approaches the Mid-Atlantic Ridge, it converges to cross above the Charlie-Gibbs and Faraday Fracture Zones. The mean absolute temperature transport (top 1000 dbar) by the 10-Sv pipe was estimated across 10 transects crossing the NAC-SPF. Because the mean mass flux is constant in the pipe, variations in the mean temperature transports result from lateral exchange and mixing across the pipe's side walls and from air—sea fluxes across the surface of the pipe. The NAC-SPF current loses 0.18 ± 0.05 PW on its transit through the region, most of the loss occuring upstream of the Northwest Corner. The heat loss is 10 times the corresponding heat lost to the atmosphere. We conclude that cross-frontal exchange induced by the steep meanders of the northward-flowing NAC is the main mechanism by which heat is lost along the current in the region between the "Tail of the Grand Banks" and the Mid-Atlantic Ridge.
机译：北大西洋洋流－亚极锋面系统（NAC-SPF）带入北大西洋北部的亚热带水流是子午翻转环流的重要组成部分。这些水通过与较冷的亚极水混合并通过大气冷却而流过亚极区域时，变得越来越冷和稠密。这两个过程的相对作用仍有待量化，驱动横向混合的机理需要更好地理解。为了解决这些问题，开发了一种新的方法来估算1993-2000年期间NAC-SPF区域顶部1000 dbar的平均质量和热量的绝对传输。通过将历史水文资料与该地区的等渗RAFOS浮标数据结合起来获得运输。平均绝对传输电势场显示了一个NAC-SPF“管道”，由两个边界传输电势轮廓定义。该管道将​​10.0±3.5 Sv（Sv≡10〜6 m〜3 s〜（-1））（最高1000 dbar）从亚热带输送到东部亚极北大西洋。与早期的研究相反，向北流动的NAC遵循一条明显的曲折路径，没有证据表明永久的树枝在到达“西北角”之前就剥离了水流。当水流进入西北角时，它失去了紧密的结构，并可能分裂成两个或多个分支，这些分支共同构成了沿SPF向东流动。由于构成SPF的分支蜿蜒和/或涡流脱落，因此西北角与大西洋中脊之间的向东流动没有严格定义。当水流接近大西洋中脊时，它会汇合以越过Charlie-Gibbs和Faraday断裂带。通过10个横穿NAC-SPF的断面估计10-Sv管道的平均绝对温度传输（最高1000 dbar）。由于管道中的平均质量通量是恒定的，因此平均温度传输的变化是由于在管道侧壁上的横向交换和混合以及在管道表面上的空气-海洋通量引起的。 NAC-SPF电流在流经该区域时损失0.18±0.05 PW，大部分损失发生在西北角的上游。热量损失是相应的热量损失到大气的10倍。我们得出的结论是，由北向流动的NAC的蜿蜒曲折引起的跨额交换是在“大银行的尾巴”和大西洋中脊之间的区域沿流散失热量的主要机制。

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