Subinertial flow patterns in a tropical coral reef system of the southwestern gulf of Mexico.

One-year subinertial flow profiles and near-bottom temperatures were recorded in a tropical coral reef of the southwestern Gulf of Mexico to determine whether baroclinicity affects flow distributions. The subinertial flow at four sites was predominantly influenced by three empirical modes of variability. The first mode (explaining 78% of the variance) was mostly associated to wind stress (r = 0.62). Its temporal variability had greatest energy during the northerly wind season (October–May), related to atmospheric cold fronts, at periods of 2–10 days and at 20–30 days. Mode 2 (with 6% of the variance) was related to sea-level slopes, linked also to northerly wind events; this mode induced an anticyclonic circulation around the reefs, although a less intense cyclonic circulation was also observed. Mode 3 (with 5% of the variance) was associated to a baroclinic pressure gradient that drove bidirectional flow profiles: Near-surface flows moving in opposite direction to near-bottom flows. Mode 3 dominated in the vertically stratified summer (June–September), the rainy season, but it was also occasionally observed during northerly winds. Near-bottom summer intrusions of relative cold water were baroclinically driven, linked to Mode 3, and unrelated to Ekman dynamics. Modes 2 and 3 of variability described additional flow distributions relative to the behavior already proposed for the reefs on the southwestern continental shelf of the Gulf of Mexico. • The first three EOF modes of velocity explained ∼90% of the variability around the Veracruz Reef System. • Currents driven by northerly winds were associated with semigeostrophic dynamics (∼80% of the variance). • Anticyclonic circulation around the reef area was related to northerly winds. • Bidirectional flow related with the baroclinic pressure gradient was a common structure during summer season. • Relatively colder water intrusion from the northwest near the bottom was observed in summer. [ABSTRACT FROM AUTHOR]