A model study of the seasonality of sea surface temperature and circulation in the Atlantic North-eastern Tropical Upwelling System
A model study of the seasonality of sea surface temperature and circulation in the Atlantic North-eastern Tropical Upwelling System
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DOI：
10.3389/fphy.2015.00076
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发表时间：
2015-09-15
影响因子：
3.1
通讯作者：
Gaye, Amadou T.
中科院分区：
文献类型：
--
作者：
Faye, Saliou;Lazar, Alban;Gaye, Amadou T.
利用区域海洋环流模式的混合层热收支，研究了热带大西洋东北部（北纬7-25度，西经26-12度）海表温度的气候季节循环。该地区经历了热带地区较大的海温循环之一，形成了几内亚环流的主要部分。其特点是受热带辐合带（ITCZ）运动驱动的开放海洋和沿海上升流系统的季节性变化。模式年平均热收支有两种形式。在大约北纬12度以南，赤道水的平流，大部分是温暖的，由于垂直混合而变暖，被净海气通量平衡。在区域的其余部分，垂直混合冷却，海岸平流加强，由海气通量平衡。就季节周期而言，在一个狭窄的大陆带内，纬向平均海温早期下降（从9月开始，取决于纬度，直到12月）是由塞内加尔和毛里塔尼亚（北纬15-20度）附近的上升流动力驱动的，而不是由这些纬度的南北海气通量驱动的。矛盾的是，上升流强度的后期高峰（从3月到7月，随着纬度的增加）在海气通量的驱动下基本上抑制了变暖阶段。向西的开放海洋循环完全由季节性净海气通量驱动。但在-18°n以北的冬季，夏季和秋季的垂直混合倾向于使ITCZ北（南）面变冷（变暖），而平流冷却或变暖则是由地转几内亚环流和Ekman漂移引起的。这一分析支持了先前关于近海海气通量重要性的发现。它主要提供了海洋环流，特别是上升流动力对海温季节周期的调节的定量要素。
The climatological seasonal cycle of the sea surface temperature (SST) in the north-eastern tropical Atlantic (7-25 degrees N, 26-12 degrees W) is studied using a mixed layer heat budget in a regional ocean general circulation model. The region, which experiences one of the larger SST cycle in the tropics, forms the main part of the Guinea Gyre. It is characterized by a seasonally varying open ocean and coastal upwelling system, driven by the movements of the intertropical convergence zone (ITCZ). The model annual mean heat budget has two regimes schematically. South of roughly 12"N, advection of equatorial waters, mostly warm, and warming by vertical mixing, is balanced by net air-sea flux. In the rest of the domain, a cooling by vertical mixing, reinforced by advection at the coast, is balanced by the air-sea fluxes. Regarding the seasonal cycle, within a narrow continental band, in zonal mean, the SST early decrease (from September, depending on latitude, until December) is driven by upwelling dynamics off Senegal and Mauritania (15-20- degrees N), and instead by air-sea fluxes north and south of these latitudes. Paradoxically, the later peaks of upwelling intensity (from March to July, with increasing latitude) essentially damp the warming phase, driven by air-sea fluxes. The open ocean cycle to the west, is entirely driven by the seasonal net air-sea fluxes. The oceanic processes significantly oppose it, but for winter north of -18 degrees N. Vertical mixing in summer-autumn tends to cool (warm) the surface north (south) of the ITCZ, and advective cooling or warming by the geostrophic Guinea Gyre currents and the Ekman drift. This analysis supports previous findings on the importance of air-sea fluxes offshore. It mainly offers quantitative elements on the modulation of the SST seasonal cycle by the ocean circulation, and particularly by the upwelling dynamics.