Schloesser, F., Thompson, P.R., and Piecuch, C.G. (2020)
Presented at: Ocean Sciences Meeting 2020
Recent sea surface height (SSH) trends in the South Pacific are substantially greater than trends in the Northern Hemisphere. Version 4 of the data-constrained ocean state estimate from the Estimating the Climate and Circulation of the Ocean consortium (ECCO-V4r4) and Ocean Reanalysis System 5 (ORAS5) reproduce the spatial structure in observed SSH trends, which allows for a diagnosis of the forcing and mechanisms that account for meridional asymmetry in the rate of change.
Thermosteric contributions dominate the spatial structure in Pacific SSH trends for years 2004-2015, however, contributions from surface heat fluxes are small. Wind stress trends drive a spin-up of the South Pacific Subtropical Gyre and a northward shift of the North Pacific Subtropical Gyre. A reduced gravity model forced with observed winds qualitatively reproduces the meridional seesaw in sea level, suggesting that asymmetric trends in subtropical wind stress drive a cross-equatorial heat transport. A reversal in forcing associated with this process could have important implications for near-term rates of coastal sea level change, particularly in Pacific Island communities.