Influence of the Amazon River runoff on the tropical atlantic

Physics and Chemistry of the Earth, Part B: Hydrology, Oceans and Atmosphere Pub Date : 2001-01-01 DOI:10.1016/S1464-1909(00)00230-6

S Masson, P Delecluse

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引用次数: 77

Abstract

The Amazon river has the biggest flow in the world, 0.2 Sv (1 Sv = 10⁶ m³/s), and is responsible for a large part of the low Sea Surface Salinity (SSS) in the west tropical Atlantic ocean. Very few Ocean General Circulation Model (OGCM) include runoff which brings a specific contribution to the Ocean physics. Comparison of simulations with constant or monthly runoffs shows that the spread of the Amazon fresh waters offshore of the north Brazilian coast is controlled by the ocean circulation and not by the Amazon flow. Therefore, in the model like in the observations, SSS minimum is observed in summer three months after the Amazon flood. In agreement with observations, a thick (more than 40 m) Barrier Layer (BL) is present every summer north of the Amazon mouth. Because of the strong and shallow salinity gradient associated with the Amazon freshwater, an important part of the solar radiation is trapped in the BL and creates an inversion of the vertical gradient of temperature. However with this forced model, BL does not seem to have a clear impact on SST and so on the air-sea interaction. Freshwater flux is also able to bend the sea surface. The geostrophic part of the North Brazilian Current (NBC) retroflection is then lightly weaker in presence of the Amazon runoff.

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亚马逊河径流对热带大西洋的影响

亚马逊河拥有世界上最大的流量，为0.2 Sv (1 Sv = 106 m3/s)，并负责西热带大西洋的大部分低海面盐度(SSS)。很少有海洋环流模式(OGCM)包括径流，径流对海洋物理有特殊的贡献。与恒定或每月径流的模拟比较表明，巴西北部海岸附近亚马逊淡水的扩散是由海洋环流控制的，而不是由亚马逊水流控制的。因此，与观测值一样，模型中观测到的SSS最小值出现在亚马逊洪水后3个月的夏季。与观测结果一致的是，每年夏季亚马逊河口北部都有一层厚(超过40米)的屏障层(BL)。由于亚马逊河淡水的盐度梯度强而浅，太阳辐射的重要部分被困在BL中，并造成垂直温度梯度的反转。然而，在这种强迫模式下，BL似乎对海温等海气相互作用没有明显的影响。淡水通量也能使海面弯曲。北巴西流(NBC)反射的地转部分在亚马逊河径流的存在下稍微减弱。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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Physics and Chemistry of the Earth, Part B: Hydrology, Oceans and Atmosphere

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