Tracking passive drifters in a high resolution ocean model: implications for interannual variability of larval krill transport to South Georgia

A particle tracking scheme that uses velocity output from an interannually varying forced run of a global ocean circulation model (Parallel Ocean Climate Model; POCM_4C) allows variability in the transport pathways across the Scotia Sea to South Georgia to be examined for the first time. The time-variant surface fluxes introduce realistic variability into the model velocity fields. This causes large variations in near-surface, mixed-layer transport from the Antarctic Peninsula region to South Georgia, an island in the southwest Atlantic sector of the Southern Ocean. The variability occurs on a variety of timescales with seasonal and longer periods of variability apparent in the 18 year time series of results. A quasi-four year period of variability is evident across the region in the sea surface temperature fields of POCM_4C and appears in the particle tracking results. This period, noted in other Southern Ocean data sets and ascribed to the Antarctic Circumpolar Wave, has been observed in the reproductive success of higher marine predators breeding on the island. The predicted oceanographic variability is likely to be significant for the South Georgia ecosystem by affecting the influx into the region of Antarctic krill (Euphausia superba), the main prey of the higher predators.