2. Ocean Currents

Currents flow in complex patterns affected by wind, the water's salinity and heat content, bottom topography, and the earth's rotation. Ocean waters are constantly on the move. How they move influences climate and living conditions for plants and animals, even on land.

Types of Ocean Currents Surface currents –Anti-cyclonic current gyres are driven by the westward flow of equatorial surface wind. –Gravity driven roll-back from the resulting rise of western sea surface runs equatorial counter current. –Circum-Antarctic circulation, or “West Wind Drift” is driven by Earth’s rotation. Deep-water current –This is thermohaline circulation or the “Global Conveyor Belt”.

The North Atlantic Gyre System

The factors that govern the oceanic gyres Gulf stream N. Equatorial Current Canary Current

Atlantic Ocean meridional section at 25°W (a)Potential Temperatures (°C)

Atlantic Ocean meridional section at 25°W (b)Salinity (‰)

Atlantic Ocean meridional section at 25°W (c)Density at 0 dbar (  0F )

Atlantic Ocean meridional section at 25°W (d)Density at 4 dbar (  4F )

Atlantic Ocean meridional section at 25°W (e)Dissolved Oxygen (DO 2 in ml/l)

South Atlantic meridional section at 25°W (e)Silicate content (umol/Kg)

Surface currents in the Paficific

1.shoe spill, May 27, recovered, March 26, recovered, May 18, recovered, January-February recovered, November-December recovered, February-March recovered, April 4, recovered, May 9-10, several recovered, January-March 1993 Nike shoes and the Pacific gyre The North Pacific gyre has been dropping off shoes around the Pacific since The shoes washed ashore one at a time but were wearable after a scrub-down to remove barnacles, algae, and tar. Beachcombers held swap meets to find matched pairs

Pacific ocean meridional section at 150°W (a)Potential Temperatures (°C)

Pacific Ocean meridional section at 150°W (b)Salinity (‰)

Pacific Ocean meridional section at 150°W (c)Density at 0 dbar (  0F )

Pacific Ocean meridional section at 150°W (c)Density at 4 dbar (  4F )

Surface currents in the Indian Ocean

Circum-Antarctic Circulation

Pacific at normal times

During the El Niño Times

Equatorial surface wind High air pressure West East Cold deep waters Equatorial counter current The normal or La Niña conditions Warm surface waters Low air pressure

Animation of Monthly-averaged Sea Surface Temperatures

El Niño Continues to Grow: Pacific Ocean Shows Higher Than Normal Sea Surface Heights December 02, 2002 The latest image from NASA's Jason oceanography satellite, taken during a 10-day collection cycle ending December 2, 2002, shows the Pacific dominated by two significant areas of higher- than-normal sea level (warmer ocean temperatures). In the central equatorial Pacific, the large area of higher than normal sea surface heights (warmer than normal sea surface temperatures) associated with growing El Niño conditions has recently migrated eastward toward the coast of South America. Meanwhile, the influence of the 20- to 30-year larger than El Niño/La Niña pattern called the Pacific Decadal Oscillation continues to create warm, higher-than-normal sea-surface heights in the north Pacific that are connected in a warm horseshoe pattern with the western and southern Pacific.

Geostrophic Currents Upwelling and downwelling

The Ekman Spiral

Mapping the Gulf Stream

The Gulf Stream wobbles, much like the streams on land, so creating rings and eddies.

The Oceanic Conveyor Belt