Ocean Circulation

Recall from last lecture that differential heating of the earth, along with the effects of the rotation of the globe cause generally predictable wind patterns...

These wind patterns are amajor force in creating oceanic surface currents

Ocean CirculationThe general pattern of oceanic circulation is clockwise in the northern hemisphere, and counterclockwise in the southern.

__

Ocean Circulation

Winds tend to result in oceanic surface currents at an approximately 45 degree angle relative to the wind direction.

This is primarily a function of the Coriolos effect, and can beexplained by the Ekman transport.

Ocean Circulation

Ocean Circulation

Ocean Circulation

Ocean Circulation

Flow of water along western boundary currents tend to meander... Sometimeslooping meanders connect to form distinct eddies, trapping cold or warm water in their centers.

Water masses of distinct temperature(and/or salinity) do not mix well withsurrounding water and tend to retainform... This may have important Implications for fishing vessels...

Ocean Circulation

In coastal areas, winds can result in local upwelling or downwelling.

In upwelling areas, deeper oceanic watercomes to the surface.

This deep water is typically colder, has more oxygen, and a lot more nutrients.

What are the implications of this?

Ocean CirculationLangmuir circulation

Wind blowing across an area of the ocean generate counter-rotating cells on the surfacewaters... Typically, we see these as either smooth lines, or lines with lots of foam ordebris on their surface… What is happening?

When these convergent and divergent zones are created, onecan often find birds hanging outaround the lines of convergence.Why do you think this is?

Ocean CirculationEl Niño!!!!

Simply put, El Niño, or the El Niño Southern Oscillation (ENSO), is a reversal of the current patterns typically associated with equatorial regions.

In the tropical regions of the Pacific, surface water is typically pushed from east to west, resulting an increase in the ocean elevation in the west, and upwelling of coolerdeep ocean water in the east.

During ENSO events (which regularly occur every few Years), the build up of waterin the west induces a reversal of the general flow pattern.

El Niño years are typically associated with major storms in the eastern side of the Pacific (e.g. Southern California), but drought conditions in Indonesia, Australia,and even India… major El Niño events of the last century included 1982-83 and 1997-98.There is significantly less upwelling in the eastern Pacific, resulting in major lossesfor the fishing industries… although the warmer waters do bring with them some“interesting” fish…

Reversal of El Niño conditions sometimes occur very fast, pushing the patterns beyondThe original ocean flow patterns… These events are referred to as La Niña.

Ocean CirculationEl Niño!!!!