Water mass analysis and alongshore variation in upwelling intensity in the eastern Great Australian Bight

Abstract

A study of climatological and conductivity‐temperature‐depth (CTD) data for 2004 is made to provide a conceptual model of upwelling for the eastern region of the Great Australian Bight. In particular, the data and other studies provide strong evidence that shelf break upwelling is confined to the southwest Kangaroo Island region and does not occur farther to the west off the Eyre Peninsula. Rather, the upwelled water is likely to remain in a Kangaroo Island “pool” until subsequent upwelling events draw the water to the shallower and surface coastal regions of the eastern Bight. In this manner the surface upwelling apparent off the Bonney Coast, Kangaroo Island, and the eastern Great Australian Bight (GAB) can appear to be simultaneous. Moreover, it appears likely that the water within the Kangaroo Island pool remains nutrient rich. Support for this model comes from CTD sections collected in 2004 that show that the upwelled signal (cool, <17°C; fresher, <35.6; dense, σt > 26 kg m−3) diminishes in width and intensity with increasing distance from Kangaroo Island. The pattern of fluorescence is similar to that for temperature in the upwelled plume and indicates that the Kangaroo Island pool remains nutrient rich. Relatively low oxygen concentrations may indicate a previous bloom. The warmest water is found near the shelf break along with very low values of fluorescence and relatively higher levels of oxygen suggesting nutrient‐limited growth of phytoplankton. These data also support the notion that the upwelled nutrient‐rich water is supplied from the Kangaroo Island pool and not by shelf break upwelling in the eastern GAB. Anomalously salty and fresh water is identified as resulting from evaporation in coastal bays and groundwater aquifer discharge.

Process-oriented modeling studies of the 5500-km-long boundary flow off western and southern Australia

“…Between these pools of cooler water, the Spencer Gulf is warmer with $20 1C water in both the model results and satellite imagery. These results showing intermittent upwelling are also in agreement with recent CTD observations which show that the upwelling is intermittent (McClatchie et al, 2006b). …”

Importance of scale to the relationship between abundance of sardine larvae, stability, and food

“…1) (see water mass analyses in McClatchie et al [2006]). Survey timing is designed to coincide with peak spawning and egg abundance, and they are a snapshot across 20 to 28 days in February-March.…”

Is the East Australian Current causing a marine ecological hot-spot and an important fisheries near Fraser Island, Australia?

“…m -3 were reported, and events lasted about one week each. McClatchie et al (2006) proposed a GAB upwelling model that limits the original source of upwelled nutrient water to the most eastern of all GAB upwelling centres near Kangaroo Island, where an upwelled nutrient-rich sub-surface pool continues to supply the surface ocean along the eastern GAB shelf during subsequent upwelling events. Middleton et al (2007) investigated interannual variability of GAB events and Nieblas et al (2009) proposed a simple model to predict GAB Chl-a variability.…”