Decadal Variability of South Pacific Subtropical Gyre from Satellite Altimetry and Argo

Abstract:

Decadal variability of the subtropical gyre in the South Pacific is investigated with satellite altimeter data from 1992 to 2013 and Argo data from 2004 to 2013. Sea surface height in most region of the South Pacific exhibits an increasing trend, and the significant signal is mainly located in the western part. Argo data shows that sea surface height increase north of 30ºS is primarily caused by thermohaline variation in the upper 500 m, while that south of 30ºS is determined by the variation of the whole water column from 0 to 1800 m, with signals below 1000 m accounting for about 50 % of the total variance. Correspondingly, the subtropical gyre in the South Pacific is strengthened. The South Equatorial Current transport increased by 20-30% from 2004 to 2013, and the transport of the deep gyre at 1000 m increased by 10-30%. Further analysis shows these variations are mainly caused by the wind stress curl variation at basin scale, which is closely related to climate modes in the South Pacific.