Biophysical Submesoscale Processes in the Wake of Hurricane Ivan: Simulations and Satellite Observations

Smith Smith,Anderson Anderson,Walker Walker,Jolliff Jolliff

doi:10.3390/jmse7110378

Smith Smith, Anderson Anderson + Show 2 more

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https://doi.org/10.3390/jmse7110378

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Abstract

Tropical cyclone induced phytoplankton productivity is examined using a tropical cyclone version of the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®). A four-component Nutrient–Phytoplankton–Detritus biological model is integrated into COAMPS to create a fully integrated air-ocean-wave-biology model. This study investigates the upper ocean physical and biological states before and after Hurricane Ivan traversed the central Gulf of Mexico, in mid-September 2004. Elevated concentrations of surface chlorophyll-a appear in the simulation two days after the passage of the tropical cyclone, and these results are spatially and temporally coherent with Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data for this time period. Model results reveal enhancement of chlorophyll-a in submesoscale filaments on the periphery of a warm-core eddy that are dominated by large values of lateral strain and relative vorticity at the surface. The vertical circulation of the filament, with its associated upward vertical motion, permits surface ventilation of cold, nitrogen-rich water and subsequent stimulation of primary biological production. Here, we show for the first time that coupled biological-physical submesoscale processes may be simulated via a fully integrated air-sea-wave-biology tropical cyclone model that provides a mechanistic explanation of the conspicuous features revealed in satellite ocean color imagery following Ivan.

Highlights

This study utilizes the Naval Research Laboratory’s (NRL) Coupled Ocean Atmospheric Mesoscale Prediction System-Tropical Cyclone (COAMPS-tropical cyclone (TC)) model to analyze the ocean’s coupled biological-physical response that occurred after the passage of Hurricane Ivan through the central Gulf of Mexico (GOM) in September 2004
Whereas this offshore advection process may certainly occur following storm events [1,2] and at other times [3,4], the COAMPS-TC modeling results and satellite analysis presented demonstrate that the presumed horizontal advection that often appears in synoptic satellite images of the GOM may instead be due to submesoscale instabilities along the peripheries of larger circulation centers
It has been demonstrated that in the Gulf of Mexico, the cold core circulation centers’ upper ocean current velocity response to the TC near-inertial wave wake is nearly twice as large as in anticyclones [54,55], the spatial distribution of the TC wake cooling may be strongly influenced by the pre-existing distribution of the warm-core eddy (WCE) and cold-core eddy (CCE) circulation centers

Summary

Introduction

This study utilizes the Naval Research Laboratory’s (NRL) Coupled Ocean Atmospheric Mesoscale Prediction System-Tropical Cyclone (COAMPS-TC) model to analyze the ocean’s coupled biological-physical response that occurred after the passage of Hurricane Ivan through the central Gulf of Mexico (GOM) in September 2004. COAMPS-TC, with an ocean biological sub-model, is able to provide post-TC biological constituent forecasts resulting from the track and intensity of a TC These TC features, in turn, impact the coupled biophysical processes that result from TC-forced vertical mixing, entrainment, and upwelling. It is suggested that the intense wind stresses of Hurricane Ivan, and the resulting inertial current oscillations, intensified the surface current deformation on the southern periphery of the WCE background flow, and the development of a submesoscale cold filament ensued after 16 September 2004. The SWAN model configuration consisted of one 8 km resolution grid that encompassed the same geographic area as the NCOM grid

Biological Module in COAMPS-TC

Satellite Observations

Results

Discussion