Surface currents and upwelling in Kerguelen Plateau regions

TLDR

Physical transport processes on the Kerguelen Plateau can significantly affect biogeochemical element balances and recycling. 48 WOCE SVP drifters deployed during the 2011 KEOPS II cruise were analyzed using autocovariances, least‑squares streamfunctions, wind stress fields, Ekman pumping, and Taylor diffusivity to estimate mesoscale currents, wind‑driven upwelling, and horizontal dispersion. The analysis revealed a shelfbreak current on the southern and eastern Kerguelen shelf slopes, transport of surface waters from the shelf basin into the deep basin, and wind stress curl–driven upwelling, with estimated volume transports of 0.5 Sv (upper 50 m) and 1.7 Sv (below the mixed layer), vertical velocities up to 3.2 ± 7.4 m d⁻¹, and upwelling fluxes of ~0.7 and 1.1 Sv in the plateau and deep basin. Abstract.

Abstract

Abstract. Mean currents, horizontal diffusivity and upwelling on the Kerguelen Plateau and the deep basin east of the Kerguelen Islands were studied using 48 World Ocean Circulation Experiment (WOCE) Standard Surface Velocity Program (SVP) drifters deployed during the 2011 austral spring KEOPS II (KErguelen Ocean Plateau compared Study II) cruise. These drifter data were analyzed based on autocovariances for temporal scales, least-squares fitted streamfunctions for estimating mesoscale mean currents, wind stress fields and Ekman pumping, and Taylor's single particle diffusivity for estimating horizontal dispersion of surface waters. The results have revealed the shelfbreak current on the southern and eastern shelf slopes of the Kerguelen Islands, transport of surface waters from the Kerguelen–Heard shelf basin crossing the shelf slope into the deep basin off the plateau east of the Kerguelen Islands, and upwelling driven by wind stress curl in both the plateau and deep basin regions. The estimated volume transports off the Plateau in the upper 50 m based on surface drifters and below the mixed layer based on wind stress curl are 0.5 and 1.7 Sv, respectively, the mean and standard deviation of vertical velocities driven by wind stress curl averaged in the plateau and deep basin regions up to 3.2 ± 7.4 m d−1, and the upwelling fluxes in the surveyed plateau and deep basin regions are approximately 0.7 and 1.1 Sv, respectively. These physical transport processes can have significant effects on balances between biogeochemical elements and their recycling processes.