Nesting the Gulf of Mexico in Atlantic HYCOM: Oceanographic processes generated by Hurricane Ivan

Abstract

The HYbrid Coordinate Ocean Model (HYCOM) has been configured for the Gulf of Mexico (GOM) at 1/25° horizontal grid resolution and has been nested inside a basin-scale 1/12° Atlantic version of HYCOM. The 1/25° nested GOM model is used to study temperature variations, current patterns, transport variations, and two coastal-trapped waves (CTWs) generated by Hurricane Ivan during mid September 2004. The model results indicate that the winds generated by Ivan: (1) induced a transport variation of approximately 2 Sv/day along the Yucatan Channel, (2) enhanced the oceanic mixing lowering the sea surface temperature more than 3 °C along Ivan’s path, (3) produced a thermocline vertical velocity of >100 m/day, and (4) generated a westward transport of ∼8 Sv along the northern coast of the GOM that was redirected by the Louisiana coastline inducing a southward transport of ∼6 Sv. Throughout its passage over the Caribbean Sea Ivan generated first a CTW along the south east coast of Cuba. After its generation this wave propagated along the coast and partially propagated along the western tip of the Cuban Island and continued its propagation along the northern coast of the Island. The model existence of CTWs along the coast of Cuba is reported for the first time. Later on, over the Florida–Alabama–Mississippi–Louisiana coast, Ivan’s westward winds drove a model oceanic onshore transport and generated a strong coastal convergence. The convergence raised the sea surface height ∼90 cm generating a second CTW, which is characterized by alongshore and cross-shore scales of ∼700 and ∼80 km, respectively. The CTW current pattern includes westward surface currents of more than 2.0 m/s. After its generation, the wave weakened rapidly due to Ivan’s eastward winds, however a fraction of the CTW propagated to the west and was measured by a tide gauge at Galveston, Texas. The descriptions, hypothesis, and discussions presented in this study are based on model results and those results are compared and validated with sea surface height coastal tide gauge observations and sea surface temperature buoy observations.