The Variation of Transport Through the Straits of Florida: A Barotropic Model Study

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  • 1 Department of Physics, Memorial University of Newfoundland, St John's, Newfoundland, Canada
  • | 2 Pacific Marine Environmental Laboratory/NOAA, Seattle, Washington
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Abstract

A high-resolution, barotropic model of the North Atlantic is used to study the variation of transport through the Straits of Florida on timescales from a few days to seasonal. The model is driven by wind and atmospheric pressure forcing derived from ECMWF twice daily analyses for the years 1985, 1986, 1987, and 1988. The model-computed transports are compared with the cable-derived estimates of daily mean transport. Atmospheric pressure forcing is found to have an insignificant effect on the model results and can be ignored. A visual comparison between the model-computed transport and the cable data shows many similarities. Coherence squared between the two time series has peaks between 0.4 and 0.5 and is significant at the 95% confidence level in the period range from 6 to 100 days, with a drop in coherence near 10 days. The model overestimates the autospectral energy in the period range of 4 to 20 days but underestimates the energy at longer periods. The authors find that remote forcing to the north of the straits does not significantly affect coherence squared and phase between the model-computed transport and the cable data but is necessary to explain the autospectral energy in the model-computed transports at periods greater than 10 days. The most significant failing of the model is its inability to capture 8–10 mo timescale events in the cable data. Interestingly, the World Ocean Circulation Experiment Community Modeling Effort, driven by synoptic wind forcing, does exhibit roughly 8-month timescale events, as seen in the cable data but missed by the barotropic model.

Abstract

A high-resolution, barotropic model of the North Atlantic is used to study the variation of transport through the Straits of Florida on timescales from a few days to seasonal. The model is driven by wind and atmospheric pressure forcing derived from ECMWF twice daily analyses for the years 1985, 1986, 1987, and 1988. The model-computed transports are compared with the cable-derived estimates of daily mean transport. Atmospheric pressure forcing is found to have an insignificant effect on the model results and can be ignored. A visual comparison between the model-computed transport and the cable data shows many similarities. Coherence squared between the two time series has peaks between 0.4 and 0.5 and is significant at the 95% confidence level in the period range from 6 to 100 days, with a drop in coherence near 10 days. The model overestimates the autospectral energy in the period range of 4 to 20 days but underestimates the energy at longer periods. The authors find that remote forcing to the north of the straits does not significantly affect coherence squared and phase between the model-computed transport and the cable data but is necessary to explain the autospectral energy in the model-computed transports at periods greater than 10 days. The most significant failing of the model is its inability to capture 8–10 mo timescale events in the cable data. Interestingly, the World Ocean Circulation Experiment Community Modeling Effort, driven by synoptic wind forcing, does exhibit roughly 8-month timescale events, as seen in the cable data but missed by the barotropic model.

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