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Genesis of the Gulf Stream Subseasonal Variability in the Florida Straits
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  • Kandaga Pujiana,
  • Denis L. Volkov,
  • Shenfu Dong,
  • Gustavo J. Goni,
  • Molly O'Neill Baringer
Kandaga Pujiana
University of Miami-CIMAS/NOAA-AOML

Corresponding Author:kandaga.pujiana@noaa.gov

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Denis L. Volkov
University of Miami / AOML
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Shenfu Dong
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Gustavo J. Goni
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Molly O'Neill Baringer
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The properties and generation mechanisms of the Florida Current subseasonal variability (20 – 100 days) are evaluated from in-situ and satellite observations. The Florida Current volume transport estimates from submarine cable measurements reveal that subseasonal variability accounts for 37% of the total transport variance. It is most active through September - November and marked by quasi-monthly variation. Here we show that coastal-trapped waves generated by alongshore winds off the southern Mid-Atlantic Bight coast are the primary driver of the Florida Current transport subseasonal variability. In contrast, the role of local winds is insignificant. The subseasonal coastal-trapped waves cover a waveguide from Cape May to Port Isabel within 15 days with an average phase speed of 2.5 ± 0.4 m s-1. While transiting in the Florida Straits, the subseasonal waves modulate the Florida Current transport by up to 2.6 Sv, on average, close to the standard deviation of the total transport variability of 3.4 Sv. Under strong stratification in the Florida Straits, manifested in the Rossby deformation radius exceeding the cross-shelf length scale by a factor of 5, the waves exhibit Kelvin wave properties expected from theory. As the waves propagate into the Gulf of Mexico, their energy substantially dissipates. The wave amplitude at Cape May of up to 15 cm is more than five times higher than at Port Isabel.