Equatorial Circulation • Subtle changes in winds give rise to complicated surface current patterns • Equatorial Undercurrent • Focus on Pacific circulation, Atlantic patterns are similar. Indian ocean ones are not... • Transient behavior - El Nino/Southern Oscillation
Equatorial Circulation. Subtle changes in winds give rise to complicated surface current patterns Equatorial Undercurrent Focus on Pacific circulation, Atlantic patterns are similar. Indian ocean ones are not... Transient behavior - El Nino/Southern Oscillation. Equatorial Currents. - PowerPoint PPT Presentation
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Equatorial Circulation
• Subtle changes in winds give rise to
complicated surface current patterns
• Equatorial Undercurrent
• Focus on Pacific circulation, Atlantic
patterns are similar. Indian ocean ones
are not...
• Transient behavior - El Nino/Southern
Oscillation
Equatorial Currents
Munk’s Solution
Wind-Driven Equatorial Circulation
Wind-Driven Equatorial Circulation
Equatorial Surface Currents
Wind-Driven Equatorial Circulation
Wind-Driven Equatorial Circulation
Equatorial Convergence
Photographs of the convergent front from R/V Thompson, taken by Edward Peltzer
.
Equatorial Convergence
Photograph from the Space Shuttle Atlantis, at an altitude of 230 km on 7 August, 1992. Distance scale is ~ 100 km.
Equatorial Surface Currents
• Subtle changes in wind stress give
rise to a complicated set of currents
– South Equatorial Current (SEC)
– North Equatorial Counter Current (NECC)
– North Equatorial Current (NEC)
• Vertical circulation cells are also
observed
Equatorial Divergence
• Westward trades drive a divergence
of Ekman transports from equator
• Results in upwelling of cool water
• Strongest in the eastern portion
of Pacific
• The cool tongue
Equatorial Divergence
Equatorial Divergence
Equatorial Divergence
Ocean Biogeochemistry in a Nutshell
• Light energy drives the net fixation of carbon
• Within the euphotic zone, nutrients & CO2 produce
CO2 & fixed carbon
• Below the euphotic zone, the rxn’s reverse
PelagicEcosystems
NUTS
CO2
Fixed Carbon
O2
h
Equatorial Divergence
Equatorial Divergence
Equatorial Divergence
The Equatorial Undercurrent
• West wind drift piles up water in
western equatorial Pacific
• Creates a return subsurface flow
that is locked to the equator
• Rises as a goes across the
Pacific
• Also found in Atlantic
Equatorial Undercurrents
• West wind drift piles up water in
western equatorial Pacific
• Creates a subsurface return flow
locked to the equator
• EUC flow rates are huge ~100 cm/s!!
• EUC rises due to equatorial divergence
• A transient feature
Equatorial Undercurrent
Equatorial Undercurrent
EUC @ 150W
EUC @ 155W
ADCP Observatio
ns
ADCP Observations
Frequency Range Resolution 38 kHz 800-1000m 24m 75 kHz 560-700m 16m 150 kHz 380-425m 8m