Remote radar measurement of shelf currents off key largo, Florida, U.S.A.

B. K. Haus, J. D. Wang, J. Rivera, J. Martinez-Pedraja, Ned Smith

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

The coastal shelf of the Florida Keys is characterized by shallow and highly variable topography, where currents are influenced by tides, wind, and the very energetic offshore Florida Current system. The transient dynamics of variable scale are not easily captured with traditional fixed-mooring observation platforms. Consequently, an experiment combining moorings, Acoustic Doppler Current Profiler (ADCP) transects and a shore-based High-Frequency (HF) radar system (OSCR) was conducted to monitor the spatial and temporal variability of the flow field over the shelf and off-shore deeper waters. Both the wind- and tide-driven flows in the middle to inner shelf, called Hawk Channel, and two offshore eddy events of the Florida Current were sampled during the experiment. Qualitative agreement between OSCR, current meter moorings and ADCP transects was good in the shelf, however, at the inshore edge of the Florida Current there were significant differences. The ADCP captured the strong horizontal shear at the shelf edge, whereas OSCR smoothed the front over two kilometres due to its measurement cell size. These differences in the spatial sampling resolution in the high shear region prevented direct quantitative comparisons. Although there were significant local variations linked to topography, a major portion of the subtidal flow in the shelf was related to wind. Within the shelf both cross-shelf and along-shelf flows were highly spatially correlated, with r=0.82 and r=0.86, respectively. Two sub-mesoscale eddies that had characteristics consistent with the spin-off eddies described by Lee (1975), were observed to advect at velocities ranging from 0.53 ms-1 to 0.80 ms-1 along the inshore edge of the Florida Current. The two eddies had along-shelf length scales from 19 km to 47 km and cross-shelf scales of 15 km and 25 km. Each eddy consisted of a single cyclonic vortex rotating with tangential velocities of 0.30 ms-1 and 0.50 ms-1 respectively. The eddies had a strong signature at the shelf break, however they did not have any observable influence on flows over the inner-shelf. (C) 2000 Academic Press.

Original languageEnglish (US)
Pages (from-to)553-569
Number of pages17
JournalEstuarine, Coastal and Shelf Science
Volume51
Issue number5
DOIs
StatePublished - Jan 1 2000

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Keywords

  • Boundary currents
  • Coastal currents
  • Continental shelf break
  • Current data
  • Eddies
  • Florida Current
  • Remote sensing
  • Tidal variations

ASJC Scopus subject areas

  • Oceanography
  • Aquatic Science

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