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Huge ocean 'Frisbees' spin off Brazil's coast

Date:
March 21, 2011
Source:
University of Miami Rosenstiel School of Marine & Atmospheric Science
Summary:
Current rings have been known to exist off northeastern coast of Brazil for decades, but knowledge of their basic properties such as size, speed, depth, and rotation velocity has been limited. Researchers now describe the basic properties of 10 rings sampled between 1998 and 2000. Overall, this research has established that the North Brazil Current rings seem to be bigger, faster, and taller than previous observations suggested.
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Huge ocean "Frisbees™" spin off Brazil's coast. University of Miami researchers have found that the rings are bigger and faster than previously thought.
Credit: Image courtesy of University of Miami Rosenstiel School of Marine & Atmospheric Science

As the North Brazil Current (NBC) moves northward along the northeastern coast of Brazil, it draws water from the South Equatorial Current and the freshwater outflow from the Amazon River, providing a source for warm, nutrient-rich water. Just northwest of Brazil, part of the NBC banks a hard right and flows east along the equator. Occasionally, the turn is especially sharp and the current loops around, pinching off an independently- traveling parcel of warm water.

This portion travels northwest with a clockwise rotation, moving through the ocean like a Frisbee™ travels through air.

These current rings have been known to exist for decades, but knowledge of their basic properties such as size, speed, depth, and rotation velocity has been limited. Drawing on current profiles from both shipboard and stationary instruments, University of Miami researchers Guilherme Castelão and Bill Johns describe the basic properties of ten rings sampled between 1998 and 2000. The authors find that the rings are best described as solid, clockwise-rotating parcels of water enclosed within a band of lower-speed water that tends to protect them from the surrounding environment.

Overall, this research has established that the NBC rings seem to be bigger, faster, and taller than previous observations suggested.


Story Source:

The above story is based on materials provided by University of Miami Rosenstiel School of Marine & Atmospheric Science. Note: Materials may be edited for content and length.


Journal Reference:

  1. G. P. Castelão, W. E. Johns. Sea surface structure of North Brazil Current rings derived from shipboard and moored acoustic Doppler current profiler observations. Journal of Geophysical Research, 2011; 116 (C1) DOI: 10.1029/2010JC006575

Cite This Page:

University of Miami Rosenstiel School of Marine & Atmospheric Science. "Huge ocean 'Frisbees' spin off Brazil's coast." ScienceDaily. ScienceDaily, 21 March 2011. <www.sciencedaily.com/releases/2011/03/110321162003.htm>.
University of Miami Rosenstiel School of Marine & Atmospheric Science. (2011, March 21). Huge ocean 'Frisbees' spin off Brazil's coast. ScienceDaily. Retrieved May 25, 2015 from www.sciencedaily.com/releases/2011/03/110321162003.htm
University of Miami Rosenstiel School of Marine & Atmospheric Science. "Huge ocean 'Frisbees' spin off Brazil's coast." ScienceDaily. www.sciencedaily.com/releases/2011/03/110321162003.htm (accessed May 25, 2015).

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