Offshore Forcing on the “Pressure Point” of the West Florida Shelf: Anomalous Upwelling and Its Influence on Harmful Algal Blooms

Authors

Yonggang Liu, University of South FloridaFollow
Robert H. Weisberg, University of South FloridaFollow
Jason M. Lenes, University of South FloridaFollow
Lianyuan Zheng, University of South Florida
Katherine Hubbard, Florida Fish and Wildlife Conservation Commission
John J. Walsh, University of South FloridaFollow

Document Type

Article

Publication Date

8-2016

Keywords

k. brevis harmful algal blooms, loop current, self-organizing map, upwelling, west florida shelf

Digital Object Identifier (DOI)

https://doi.org/10.1002/2016JC011938

Abstract

Gulf of Mexico Loop Current (LC) interactions with the West Florida Shelf (WFS) slope play an important role in shelf ecology through the upwelling of new inorganic nutrients across the shelf break. This is particularly the case when the LC impinges upon the shelf slope in the southwest portion of the WFS near the Dry Tortugas. By contacting shallow water isobaths at this “pressure point” the LC forcing sets the entire shelf into motion. Characteristic patterns of LC interactions with the WFS and their occurrences are identified using unsupervised neural network, self-organizing map, from 23 years (1993–2015) of altimetry data. The duration of the occurrences of such LC patterns is used as an indicator of offshore forcing of anomalous upwelling. Consistency is found between the altimetry-derived offshore forcing and the occurrence and severity of WFS coastal blooms of the toxic dinoflagellate, Karenia brevis: years without major blooms tend to have prolonged LC contact at the “pressure point,” whereas years with major blooms tend not to have prolonged offshore forcing. Resetting the nutrient state of the shelf by the coastal ocean circulation in response to deep-ocean forcing demonstrates the importance of physical oceanography in shelf ecology. A satellite altimetry-derived seasonal predictor for major K. brevis blooms is also proposed.

Rights Information

Terms of use for work posted in Scholar Commons.

Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

Journal of Geophysical Research: Oceans, v. 121, issue 8, p. 5501-5515

© 2016. American Geophysical Union. All Rights Reserved.

Scholar Commons Citation

Liu, Yonggang; Weisberg, Robert H.; Lenes, Jason M.; Zheng, Lianyuan; Hubbard, Katherine; and Walsh, John J., "Offshore Forcing on the “Pressure Point” of the West Florida Shelf: Anomalous Upwelling and Its Influence on Harmful Algal Blooms" (2016). Marine Science Faculty Publications. 270.
https://digitalcommons.usf.edu/msc_facpub/270