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The surface salinity maximum of the South Atlantic
Progress in Oceanography ( IF 4.1 ) Pub Date : 2020-12-26 , DOI: 10.1016/j.pocean.2020.102499
N. Aubone , E.D. Palma , A.R. Piola

Like most other ocean basins, the maximum sea surface salinity region (MSR) in the South Atlantic shows a large displacement from the region of maximum difference between evaporation and precipitation (E-P), suggesting that ocean processes play a key role in determining the location of the MSR. We use outputs from a general circulation model (ECCO v4r3) to analyze the mixed layer salinity balance and disentangle the interaction of atmospheric forcing and oceanic processes in both regions. The MSR balance is dominated by evaporative surface fluxes and entrainment, while advection and diffusion play a secondary role. On the other hand, in the region of maximum E-P, the high surface freshwater loss is partially compensated by horizontal advection of low salinity waters, which is responsible for decreasing the salinity below that observed in the MSR. Using a particle tracking model, we find that MSR waters originate mostly from re-circulation in the Tropical South Atlantic and from the Tropical North Atlantic and Indian Oceans. After reaching the MSR, most of those waters flow southward in austral summer along the Brazil Current (1.6 Sv, 1 Sv = 106 m3 s−1), and northward in winter along the North Brazil Current (3.5 Sv). This seasonal variability in the fate of the salty water is modulated by the seasonal migration of the South Equatorial Current bifurcation region. Tracking of particles released at the base of the MSR mixed layer shows a subducted salt river with an estimated transport of 2.6 Sv on the 25.2 kg m−3 neutral density surface that flows northward along the North Brazil Current and retroflects just north of the equator as part of the Equatorial Undercurrent. These high-salinity waters are a significant contributor to the upper limb of the Atlantic meridional overturning circulation and the eastern Tropical Atlantic and their variability.



中文翻译:

南大西洋的表面盐度最大值

与大多数其他海盆一样,南大西洋的最大海面盐度区(MSR)与蒸发和降水之间最大差异(EP)的区域相比有很大的位移,这表明海洋过程在确定海床位置方面起着关键作用。 MSR。我们使用一般环流模型(ECCO v4r3)的输出来分析混合层盐度平衡,并弄清两个地区的大气强迫与海洋过程的相互作用。MSR平衡主要由蒸发的表面通量和夹带控制,而平流和扩散则起次要作用。另一方面,在最大EP区,低盐度水的水平对流可部分补偿高地表淡水损失,这导致盐度降低到MSR中所观察到的水平以下。使用粒子跟踪模型,我们发现MSR水主要来自热带南大西洋以及热带北大西洋和印度洋的再循环。到达MSR后,大部分水域在夏季南方沿巴西水流向南流动(1.6 Sv,1 Sv = 106 m 3 s -1),冬季沿北巴西洋流(3.5 Sv)向北。咸水命运的这种季节性变化受到南赤道洋流分叉区域的季节性迁移的影响。跟踪在MSR混合层底部释放的粒子,发现一条俯冲的盐河,在25.2 kg m -3中性密度表面上的运移速度估计为2.6 Sv,该表面沿北巴西洋流向北流动,并在赤道以北逆行。赤道暗流的一部分。这些高盐度水是大西洋经向翻转环流和东部热带大西洋及其变率的重要组成部分。

更新日期:2021-01-18
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