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首页> 外文期刊>Journal of Physical Oceanography >Water Mass Conversion, Fluxes, and Mixing in the Scotia Sea Diagnosed by an Inverse Model
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Water Mass Conversion, Fluxes, and Mixing in the Scotia Sea Diagnosed by an Inverse Model

机译：通过逆模型诊断的斯科舍海中的水质转化，通量和混合

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An inverse box model of the Scotia Sea is constructed using hydrographic, tracer, and velocity data collected along the rim of the basin during the Antarctic Large-Scale Box Analysis and the Role of the Scotia Sea (ALBATROSS) cruise. The model provides an estimate of the time-mean three-dimensional circulation as the Antarctic Circumpolar Current (ACC) crosses the region. It concurrently solves for geostrophic and wind-driven Ekman transports across the boundaries of the basin, air-sea-driven diapycnal fluxes, and "interior" diapycnal fluxes below the ocean surface. An increase is diagnosed in the ACC volume transport from 143 +- 13 Sv (Sv ≡ 10~6 m~3 s~(-1)) at Drake Passage to 149 +- 16 Sv on leaving the Scotia Sea, supplied by the import of 5.9 +-1.7 Sv of Weddell Sea Deep Water (WSDW) over the South Scotia Ridge. There is a lateral redistribution of the transport, primarily in response to a topographically induced branching of the 70-80 Sv polar front (PF) jet and an increase in the transport associated with the subantarctic front (SAF) from 31 +- 7 to 48 +- 4 Sv. A vertical rearrangement of the transport also occurs, with differences O(2 Sv) in the transports of intermediate and deep water masses. These volume transport changes are accompanied by a net reduction (increase) in the heat (freshwater) flux associated with the ACC by 0.02 +- 0.020 PW (0.020 +- 0.017 Sv), the main cause of which is the cooling and freshening of the Circumpolar Deep Water (CDW) layer in the Scotia Sea. The model suggests that the Scotia Sea hosts intense diapycnal mixing in the ocean interior extending 1500-2000 m above the rough topography of the basin. Despite these model results, no evidence is found for a significant diapycnal link between the upper and lower classes of CDW (and hence between the "shallow" and "deep" cells of the Southern Ocean meridional overturning circulation). On the contrary, the boundary between Upper and Lower CDW separates two distinct regimes of diapycnal mixing involving volume fluxes of 1-3 Sv. Whereas in the denser waters topographic mixing is important, in lighter layers air-sea-driven diapycnal volume fluxes are dominant and diapycnal transfers of heat and freshwater are mainly effected by upper-ocean mixing processes. The model indicates that the ventilation of the deep ACC in the Scotia Sea is driven primarily by isopycnal exchanges with the northern Weddell Sea and to a lesser extent by diapycnal mixing with WSDW. The model reveals the existence of a mesoscale eddy-driven overturning circulation across the ACC core involving an isopycnal poleward transport of 8 +- 1 Sv of CDW and an equatorward transport of intermediate water of the same magnitude. This circulation induces a cross-ACC poleward heat flux of 0.022 +- 0.009 PW and an equatorward freshwater flux of 0.02 +- 0.01 Sv. Adequately scaled, the former compares favorably to measurements of the cross-stream eddy heat flux by moored current meters and floats in the ACC and to budget estimates of the circumpolar cross-ACC heat flux.
机译：利用南极大规模箱体分析和斯科海（ALBATROSS）航行的作用期间沿盆地边缘收集的水文，示踪和速度数据，构建了斯科海的逆箱模型。该模型提供了南极绕极洋流（ACC）穿越该区域时的时间平均三维环流的估计。它同时解决了穿越盆地边界的地转和风动埃克曼输运，海面驱动的通量通量以及海面以下的“内部”通量通量。经诊断，ACC体积传输量从德雷克海峡处的143 +-13 Sv（Sv〜10〜6 m〜3 s〜（-1））增加到离开斯科舍海时的149 +-16 Sv，由进口提供南斯科舍省脊上的韦德海深水（WSDW）的5.9 + -1.7 Sv。主要是响应地形诱导的70-80 Sv极地锋（PF）射流的分支以及与南极锋面（SAF）相关的传输力从31 +-7增加到48，横向迁移了传输的重新分布。 +-4 Sv。传输的垂直重排也会发生，中间和深水团块的传输具有O（2 Sv）差异。这些体积传输的变化伴随着与ACC相关的热（淡水）通量的净减少（增加）0.02 +-0.020 PW（0.020 +-0.017 Sv），其主要原因是冷却和新鲜的ACC。斯科舍海的极地深水（CDW）层。该模型表明，斯科舍海在该盆地的粗糙地形之上1500-2000 m的海洋内部具有强烈的辉石混合。尽管有这些模型结果，但没有发现证据表明CDW的上层和下层之间存在显着的diapycnal关联（因此，在南大洋子午翻转循环的“浅”和“深”单元之间）。相反，上CDW和下CDW之间的边界分隔了两种不同的二面体混合方案，涉及1-3 Sv的体积通量。在较稠密的水域中，地形混合很重要，而在较轻的层中，海气驱动的总双通量通量占主导地位，热量和淡水的总双向传递主要受上层海洋混合过程的影响。该模型表明，在斯科舍海深层ACC的通风主要是由与北部韦德海的等渗交换引起的，而在较小程度上是通过与WSDW的二叠氮混合来实现的。该模型揭示了横跨ACC核心的中尺度涡流驱动的倾覆环流，其中包括8±1 Sv CDW的等渗极向输送和相同幅度的中间水的赤道输送。这种循环引起的交叉ACC极向热通量为0.022 +-0.009 PW，赤道向淡水通量为0.02 +-0.01 Sv。适当地缩放，前者与通过系泊电流计和ACC中的浮子测量横流涡流热通量以及对绕极ACC横流通量的预算估算相比具有优势。

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