A case study off the Tiwi Islands and the Coburg Peninsula: Baroclinic on one side and barotropic on the other

Observational data (ADCP and CTD) were collected from two areas on either side of the Tiwi Islands and Coburg Peninsula. Tides dominated the ocean dynamics in both areas, with contributions from solar radiation, nighttime convective cooling, surface wind mixing, and benthic frictional mixing. Despite the same dominating forcing factors, the dynamics and envrionments differed between the east and west sides of the Tiwi Islands and Coburg Peninsula. The east side was baroclinic with internal tides present along with tidal advection; however, the west side was barotropic and dominated by tidal advection of warmer, saltier water from shallower areas past the observation site with essentially no internal tides. The daily solar radiation cycle's influence reached the bottom on the western side, but was limited to above the thermocline on the eastern side. There, fluorescence was limited to the lower layer, whereas on the western side, it encompassed the entire water column in daytime and peaked below the upper layer, where warmer and higher oxygenated water were generated by solar radiation and surface mixing. Fluorescence vertically integrated over the water column was much higher on the eastern side than the western side. Fluorescence peaks also differed temporally between the east and west sides, with the eastern side dominated by semidiurnal tides and the western side by the daily solar cycle. These dynamics have distinct implications for biological activity and primary productivity.

Automated summary

Observational data from two areas near the Tiwi Islands and Coburg Peninsula in Australia show that tidal forces dominate the ocean dynamics in these regions. Factors such as solar radiation, convective cooling, wind mixing, and frictional mixing also contribute to the dynamics. However, the dynamics and environments differ between the east and west sides, with the east side being baroclinic and having internal tides, while the west side is barotropic and dominated by tidal advection. The variations in fluorescence and its temporal patterns have important implications for biological activity and primary productivity.