Satellite remote sensing of surface oceanic fronts in coastal waters off west–central Florida

• Published in: Remote sensing of environment Vol. 112; no. 6; pp. 2963 - 2976
• Main Authors: Wall, Carrie C., Muller-Karger, Frank E., Roffer, Mitchell A., Hu, Chuanmin, Yao, Wensheng, Luther, Mark E.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 16.06.2008; Elsevier
• Subjects: Animal, plant and microbial ecology; Applied geophysics; Biological and medical sciences; Earth sciences; Earth, ocean, space; Exact sciences and technology; Front detection; Fundamental and applied biological sciences. Psychology; General aspects. Techniques; Internal geophysics; Marine; Oceanic fronts; Remote sensing; Scomber; Scomberomorus cavalla; SST; Teledetection and vegetation maps; West Florida shelf; Central Florida; Tampa Bay; Florida; United States; ASW, USA, Florida, Tampa Bay; Front detection; SST; West Florida shelf; Oceanic fronts; Remote sensing; algorithms; detection; Gradient; histograms; Space remote sensing; Satellite observation; concentration; Deep water; Sea surface temperature; North America; Profile; Chlorophyll a; coastal zone; fluorescence; imagery; Coastal water; Height; Front detection;West Florida shelf;SST;Remote sensing;Oceanic fronts; Pixel; radiance
• ISSN: 0034-4257; 1879-0704
• DOI: 10.1016/j.rse.2008.02.007

Two algorithms designed to detect deepwater oceanic features and arbitrary edge profiles were tuned to automatically delineate fronts in coastal waters off west–central Florida using satellite-derived sea surface temperature (SST), chlorophyll- a concentration (Chl), normalized water-leaving radiance ( nL w ), and fluorescence line height (FLH) images during select periods in the spring and fall of 2004 and 2005. The dates correspond to recreational king mackerel, Scomberomorus cavalla, tournaments. A histogram-based algorithm was useful to detect coastal surface SST, nL w , and FLH fronts, specifically. A gradient-based algorithm, with a smaller kernel box of 3 × 3 pixels, best identified nearshore (< 10 m depth) features in Chl images at the mouth of Tampa Bay, but was less effective for fronts farther offshore where gradients were weaker. Local winds and tide levels estimated from a coastal observing buoy, and bathymetric gradients were examined to help understand the factors that influenced front formation and stability. Periods of strong and variable winds led to front movement of up to 10 km per day or dissipation within 2–3 days in over 80% of the fronts detected in SST, Chl, nL w , and FLH imagery. Short episodes of less variable wind velocities typically led to more stable and stationary fronts, within 3–5 km, for up to four days. The occurrence of fronts closely associated with the coastal bathymetry, namely at the 20 m and 30 m isobaths, was significantly higher in the fall SST imagery and in the spring Chl imagery. Fall SST fronts related to bathymetric gradients likely resulted from progressive cooling of the water with depth. Stronger Chl and nL w 443 gradients at the mouths of estuaries in the fall compared to the spring were attributed to increased precipitation and periods of stronger winds or tides. The FLH imagery was most useful in delineating coastal algal blooms. The automatic front detection techniques applied here can be an important tool for resource managers to track coastal oceanographic features daily, over synoptic spatial scales.