THE SOUTH EQUATORIAL CURRENT SYSTEM Sushmita Patwardhan,PhD Candidate,Graduate Program in Oceanography

 Southern Hemisphere.  In Indian, Pacific and Atlantic oceans.  THE SOUTH EQUATORIAL CURRENT  THE SOUTH EQUATORIAL UNDER CURRENT  THE 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: CSEC and NSEC:  Temperature: 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 m.  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.

REFERENCES  equatorial.html equatorial.html   Lothar Stramma Geostrophic transport of the South Equatorial Current in the Atlantic. Journal of Marine Research,49, 