Interannual changes in thermocline properties in the subtropical Indian Ocean

B.A.King and E McDonagh
NOC
Empress Dock
Southampton
SO14 3ZH

UK

In March 2002, a transoceanic hydrographic cruise at 32S in the Indian Ocean
revealed changes in Mode Water properties since the previous occupation of the
section in 1987. Salinity had increased on isotherms warmer than 10C, with a
maximum salinity change exceeding 0.04 at the 13C isotherm in the western
part of the basin. Argo floats deployed during the cruise confirmed that the
change was consistent over a large region in the SW Indian Ocean. Data
reported by the floats during the subsequent 3 years show that floats are
capable of monitoring the changes with interannual resolution. There was
further increase in salinity during 2002 and 2003, but a levelling off during 2004.