Abstract
The contribution of high-frequency wind to the Peruvian upwelling system during 2014–2016 was studied using the Regional Ocean Modeling System (ROMS), forced by four different temporal resolution (six-hourly, daily, weekly, and monthly) wind forcing. A major effect of the high-frequency wind is its warming of the water at all depths along the Peruvian coast. The mechanism for the temperature changes induced by high-frequency wind forcing was analyzed through heat budget analysis, which indicated a three-layer structure. Vertical advection plays a leading role in the warming of the mixed layer (0–25 m), and enhanced vertical mixing balances the warming effect. Analysis suggests that around the depths of 25–60 m, vertical mixing warms the water by bringing heat from the surface to deeper depths. In waters deeper than 60 m, the effect of vertical mixing is negligible. The differences among the oceanic responses in the sensitivity experiments suggest that wind forcing containing variabilities at higher than synoptic frequencies must be included in the atmospheric forcing in order to properly simulate the Peru upwelling system.
Highlights
The Peruvian coast is one of the most productive eastern boundary upwelling systems in the world, which supports important local fisheries [1]
Lee and Liu [9] showed that the effects of high-frequency wind on the ocean in the mid- to high-latitude regions are primarily derived from enhanced vertical mixing, whereas such effects in the tropical oceans are mainly derived from wind-induced advection
The results showed that heat correction could decrease the sensitivity of upwelling to high-frequency wind, but did not change the qualitative conclusions
Summary
The Peruvian coast is one of the most productive eastern boundary upwelling systems in the world, which supports important local fisheries [1]. High-frequency wind can enhance the turbulent diffusion in the ocean surface layer [3], deepen the mixed layer [4], increase downward heat flux [5], and cool the sea surface temperature (SST) [6,7]. The aim of this study was to document the impact of high-frequency (six-hourly) wind on the variability of ocean temperature and the upwelling system along the Peruvian coast by simulating the Peruvian upwelling system using a high-resolution regional model, and analyzing the causes of temperature changes through heat budget.
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