Large diurnal temperature fluctuations in the nearshore water column

Large daily temperature fluctuations in the nearshore water column have been observed at several sites along the coast of central and northern Chile, particularly during summertime. These fluctuations are often on the order of the seasonal fluctuation in seasurface temperature for the area and are capable, in certain locations, of penetrating deep (10–15 m) into the water column during the course of a single day. We explain this phenomenon by a combination of solar heating of the sea surface and wind-driven transport and accumulation of these warm, surface waters near shore. Measurements of surface heat flux agree roughly with observed daytime changes in the heat content of the nearshore water column. The strength of these diurnal fluctuations is shown to vary with the strength of coastal upwelling in the area. The potential consequences of this process for nearshore larval transport are unknown, but we briefly speculate about its importance.