Upper ocean response of the Mesoamerican Barrier Reef System to Hurricane Mitch and coastal freshwater inputs: A study using Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color data and a nested-grid ocean circulation model

Abstract

The passage of category-5 Hurricane Mitch through the Mesoamerican Barrier Reef System (MBRS) in October 1998 was an extreme event with the potential to create unusual patterns of reef connectivity. The impact of this hurricane on the upper ocean of the MBRS is investigated using a triply nested grid ocean circulation modeling system. The model results are validated with contemporaneous ocean color data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite and oceanographic measurements in the MBRS. The nested grid system is forced by 6-hourly National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) winds for the first 294 days prior to the arrival of the hurricane in the MBRS, and then by the combination of the NCEP/NCAR wind-forcing and an idealized vortex representative of Mitch for the following 20 days. The system is also forced by the monthly mean sea surface heat and freshwater fluxes and buoyancy forcing associated with major river discharges and storm-induced precipitation in the western Caribbean Sea. The simulated upper ocean circulation during Mitch is characterized by strong and divergent currents under the storm and intense near-inertial currents and sea surface temperature cooling behind the storm. The nested grid system also reproduces the buoyant estuarine plumes extending from the coast off Honduras as inferred from SeaWiFS satellite data and detected in field measurements at Gladden Spit in Belize shortly after the passage of Hurricane Mitch. The present model results suggest that populations of site-attached organisms associated with nearshore and offshore reef features that are dynamically isolated in normal conditions experienced greater potential for ecological connection under Mitch's extreme conditions.