Modeling the seasonal and interannual variability of the northern Gulf of California salinity

Abstract

The 7 years (2003-2009) of output from a regional version of the Hybrid Coordinate Ocean Model (HYCOM) nested in global HYCOM are used to study the seasonal and interannual variability of the salinity in the northern Gulf of California (NGOC). Previous studies illustrate that the NGOC is characterized by an annual evaporation of ∼0.9 m/yr. This evaporation generates high-sea-surface-salinity (SSS) water, which reaches a maxima in the NGOC (>37) and decreases to ∼35 toward the entrance of the Gulf of California. The NGOC surface water is interannually modulated by fluctuations in evaporation and by fluctuations in the low-salinity water transported into the region by poleward eastern boundary currents. The fluctuations in the transport of low-salinity water are linked to the arrival of equatorially originated coastally trapped waves. The crucial role of the transport of low-salinity water for the interannual variability of SSS is illustrated by the 2006 and 2008 fall seasons, which include the lowest simulated salinity of the period 2003-2009. The lowest salinity in 2006 and 2008 cannot be explained solely by evaporation because 2006 was characterized by the largest evaporation of the period 2003-2009. However, the presence of the lowest-salinity environment can be attributed to the evaporation in conjunction with the largest upper ocean transport of low-salinity water carried to the NGOC by the 2006 and 2008 coastally trapped waves intensified poleward eastern boundary currents. Copyright 2011 by the American Geophysical Union.