Changes in the meridional overturning circulation at 32ºS in the Pacific Ocean in 2017

Abstract

The meridional circulation and transports at 32oS in the Pacific Ocean in 2017 are compared with analogous data from 2003 and 2009. The hydrographic data come from the GO-SHIP database and an inverse box model has been applied with several constraints. The Pacific Ocean overturning circulation pattern is similar for the three years, but the intensity of the overturning in 2009 (43.6 ± 2.3 Sv) is higher than in 2003 (32.1 ± 2.2 Sv) and in 2017 (34.9 ± 2.4 Sv). The horizontal distribution of mass transports at all depths in 2017 changes notably from the “bowed gyre” found in 2009 and resembles that regular shape of 2003. Furthermore, the East Australian Current transport decreases slightly from 2003 (51.1 ± 2.0 Sv) and 2009 (-49.9 ± 2.1 Sv) to 2017

(-39.2 ± 1.6 Sv). The Peru-Chile Current transport estimated in 2017 (4.4 ± 0.8 Sv) is

slightly higher than in 2003 (3.3 ± 0.9 Sv) and in 2009 (3.8 ± 1.2 Sv). The Peru-Chile

Undercurrent transport estimated in 2017 (-1.5 ± 0.8 Sv) is lower than in 2003 (2.8 ± 1.2

Sv) and 2009 (3.8 ± 1.2 Sv). Nevertheless, the heat transport in 2017 (0.4 ± 0.1 PW) has

the same value as in 2003 (0.4 ± 0.1 PW) and differs from 2009 (0.2 ± 0.1 PW). The freshwater transport results show an increase in net evaporation from 2003 (0.25 ± 0.02 Sv) to 2009 (0.50 ± 0.03 Sv), and a decrease in 2017 (0.34 ± 0.08 Sv).