Seasonal Variability of Upwelling off Central-Southern Chile

The central and northern Chilean coasts are part of the Humboldt Current System, which sustains one of the largest fisheries in the world due to upwelling. There are several upwelling focal points along the Chilean coast; however, from a physical standpoint, the region between 39◦ and 41◦ S has not been studied in detail despite being one of the most productive zones for pelagic extraction in Chile. Here, we evaluated the seasonal variability of coastal upwelling off central-southern Chile using principally daily sea surface temperature (SST) and sea surface wind (SSW), and 8-day composite chlorophyll-a concentration between 2003 and 2017. Through the seasonal evaluation of the net surface heat flux and its relationship with the SST as well as daily SST variability, we determined the “maximum upwelling” on our area. The direction of surface winds is controlled throughout the year by the Southeast Pacific Subtropical Anticyclone, which produces a cold tongue and an upwelling shadow north of Punta Galera (40◦ S) in austral spring and summer. A cross-correlation analysis showed a decrease of SST follow the alongshore SSW with a lag of 2 days in the months favorable to the upwelling. However, the correlations were not as high as what would be expected, indicating that there is a large advection of waters from the south that could be related to the greater volume of subantarctic water present in the zone.

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