Ocean Temperature and Color Frontal Zones in the Gulf of Mexico: Where, When, and Why

The spatial and temporal patterns of ocean frontal zones in the Gulf of Mexico (GoM) are studied using ocean color and sea surface temperature (SST) imagery collected by the Moderate Resolution Imaging Spectroradiometer/Aqua (MODIS/A) over an 18-year (2002-2019) period. A gradient-based front detection algorithm is applied to each daily image to detect frontal features, from which a comprehensive data set of ocean frontal zones (both climatology and time series) is established. Prominent seasonality is found in both ocean color and SST frontal zones while their seasonal variations differ. Major persistent frontal zones are mainly distributed in coastal waters within the 130-m isobath, and they are often associated with wind forcing, wind-driven Ekman transport, upwelling/downwelling, river discharge, ocean currents, and topography. The seasonal and interannual variations in frontal distributions are also revealed in the dominant spatial and temporal modes derived from an empirical orthogonal function (EOF) decomposition analysis. These findings may have significant implications on fisheries and ocean ecology research. For example, both ocean color and SST frontal features in certain months are found to coincide with a well-known fishing ground in the eastern GoM, and surface macroalgae features are found to align well with the identified ocean frontal features.