Shelf-oceanic dynamics of surface environmental parameters in the Kangaroo Island-Bonney Coast region

The shelf and oceanic waters of the Kangaroo Island-Bonney Coast region are important foraging habitats for top marine predators in the ecosystem; however, the dynamics between the two distinct water types have not been investigated. This study examined the spatial and temporal variability of oceanographic parameters in the southern waters of Australia (36-43 degrees S, 136-141 degrees E) associated with the Bonney Upwelling (shelf) and subtropical front (STF; oceanic). Using satellite data from 1997 to 2016, we found that productive oceanic waters were associated with the STF and eddy activity; they were generally furthest from the shelf break in spring-summer (upwelling season on the shelf) and closest to the shelf break in winter-autumn (downwelling season on the shelf). Inter-annual variabilities of chlorophyll-a concentration (Chl-a), sea-surface temperature and sea surface-height anomaly were generally higher in summer than in winter for both shelf and oceanic waters. El Nino-Southern Oscillation, Southern Annular Mode and Indian Ocean Dipole were cross-correlated with anomalous shelf and oceanic Chl-a at various lagged times (range = 15-0 months). This study provides a regional perspective of the spatial and temporal oceanographic variability in southern Australian waters, which may help with understanding apex-predator ecology in the ecosystem.

Automated summary

This study investigated the spatial and temporal variability of oceanographic parameters in the southern waters of Australia, focusing on the shelf and oceanic waters. Productive oceanic waters were found to be associated with the subtropical front and eddy activity, with varying distances from the shelf break depending on the season. Anomalous chlorophyll-a concentrations in both shelf and oceanic waters were cross-correlated with El Nino-Southern Oscillation, Southern Annular Mode, and Indian Ocean Dipole at various lagged times.