THE SOUTH EQUATORIAL

CURRENT SYSTEMSushmita Patwardhan,PhD Candidate,Graduate Program in Oceanography

Southern Hemisphere. In Indian, Pacific and Atlantic oceans.THE SOUTH EQUATORIAL CURRENTTHE SOUTH EQUATORIAL UNDER CURRENTTHE SOUTH EQUATORIAL COUNTER CURRENT

THE SOUTH EQUATORIAL CURRENT

Westward flowing current with a depth of 100 m. Northern boundary is at 4°N and southern boundary is

between 15°S- 25°S depending on time of the year and longitude.

It’s a geostrophic flow. It can be divided into three branches:1.Southern South Equatorial Current (SSEC)2.Central South Equatorial Current (CSEC)3.Northern South Equatorial Current (NSEC)

CURRENTS OF THE WORLD

SOUTHERN SOUTH EQUATORIAL CURRENT

It flows westwards. It is fed by the Benguela Current. SSEC turns northwards at 30°W. Bulk of the flow joins the North Brazil Current. Northern branch also feeds SECC. A small part flows south pole wards and joins the Brazil

Current. Sluggish flow. Average transport is 20 Sv for upper 500m.

CENTRAL SOUTH EQUATORIAL CURRENT

Located between South Equatorial Undercurrent and South Equatorial Counter Current.

It bifurcates around 5-6°S. Northern flow merges with North Brazil Current. Part of the northern flow turns north-eastwards and supplies

to the SEUC. Southern part initially flows southwestwards and then makes

a turn towards the north around 9°S and joins the southernmost part of the SSEC.

Average transport is 17 Sv in upper 200m and maximum is 29Sv.

THE NORTHERN SOUTH EQUATORIAL CURRENT

Located between 1°N and SEUC (3-5°S).Speed is 30cm/s.Volume transport is 12 Sv in upper layer.

TEMPERATURE AND SALINITY

The Southern South Equatorial Current is more saline than the Central and Northern branches.

Salinity of: SSEC: 37-37.2 CSEC and NSEC: 36-36.2Temperature: 26-28°C at the surface and 22-24°C at

a depth of 100m.The annual temperature is pretty stable with a

season variability of 4°C.

THE SOUTH EQUATORIAL UNDERCURRENT

Eastward flowing subsurface current. Depth is between 100-1000m. Flow is maximum in boreal fall i.e. Sept-Oct and minimum

in boreal spring i.e. April-June. The SEUC has oxygen rich water. Flow in the surface above the SEUC is towards the east

during austral summer and towards the west during austral winter.

The transport is about 15 Sv. Salinity is less then 36

THE SOUTH EQUATORIAL COUNTER CURRENT

It flows eastwards. Flow is from surface to depth of 400m. Is formed around 30°W. Crosses the South Atlantic up to Prime Meridian. Around 5°S it is entrained by the CSEC. Surface water is warm and salty. High oxygen concentration. Salinity 36.2 at surface and 38 at depth of 400m.

IMPORTANCE OF THE SECS It transfers net heat from the Southern

Hemisphere to the Northern Hemisphere. It links the two important subtropical gyres of

the Atlantic Ocean.The Brazil current is an important western

boundary current in the South Atlantic gyre.Plays a role in formation of Gulf stream.Replenishes water in the North Indian Ocean.

REFERENCEShttp://oceancurrents.rsmas.miami.edu/atlantic/south-

equatorial.html

http://oceanmotion.org/html/introduction-general.htm

Lothar Stramma.1991. Geostrophic transport of the South Equatorial Current in the Atlantic. Journal of Marine Research,49,281-294.

http://www.gfdl.noaa.gov/bibliography/related_files/sgp0102.pdf