Diurnal along and cross-shelf transports variability in the Gulf of Mexico.
Juan Nieblas, Institute of Atmospheric Sciences and Climate Change, National Autonomous University of Mexico, Air-sea Interaction Group, Mexico City, DF, Mexico, Jorge Zavala-Hidalgo, National Autonomous University of Mexico, Atmospheric Science Center, Coyoacan, DF, Mexico, Oscar Calderon-Bustamante, Institute of Atmospheric Sciences and Climate Change, National Autonomous University of Mexico, Mexico City, DF, Mexico and Raúl González-Santamaría, National Autonomous University of Mexico, Center of Atmospheric Sciences, Mexico City, DF, Mexico
Abstract:
The Gulf of Mexico's (GoM) inner shelf circulation varies over a wide range of spatial and temporal scales where diurnal sea breeze may drive cross-shelf transport in a short time scale. In this study, the hourly along shelf (AS) and cross-shelf (CS) transport calculated using a 14-year free-run experiment configured for the GoM with the Hybrid Coordinate Ocean Model (HYCOM) is analyzed and compared with a Weather Research and Forecasting (WRF) reanalysis (1980-2016). The results of the hourly CS transport indicates a diurnal cycle in the entire GoM inner shelf circulation. Opposite surface and subsurface CS directions (inshore/offshore) were found most of the year, but with higher intensity from April to August, corresponding with clockwise AS circulation in the western GoM. The diurnal sign decreases throughout the fall due to the presence of strong northerly winds and remains weak until April, when the diurnal sign gets wider.
There's also a dephase in the diurnal cycle where perpendicular cross-shelf transport (to 20, 30, 50 and 200m isobaths) changes throughout the different regions in the GoM according to the sea breeze time scale. The inner shelf presents a complementary hour case of upwelling/downwelling alternation, in which upwelling intensity conditions occurred with greater presence at the north and northeastern GoM, while downwelling conditions are more evident at the northwestern and western GoM. At the Campeche Bank (CB) there is no important complementary hour alternation, as the upwelling condition predominates during the diurnal cycle. This upwelling/downwelling alternating condition is similar but with lower intensity on the outer-shelf, where the diurnal signal appears also at late-spring and summer in the West Florida Shelf (WFS), Tamaulipas-Veracruz Shelf (TAVE) and the CB but with predominant inshore/offshore transport direction over the 50m surface column.
