279 / 2024-09-13 11:45:48
Paleo-productivity reconstructions along the eastern coast of Australia: Implications for the variability of the East Australian Current over the last 1000 years
WBC,EAC,Productivity,eddy
Session 44 - Western Boundary Currents, Eddies and Their Impacts on Multi-disciplinary Aspects
Abstract Accepted
The East Australian Current (EAC) is a complex, fast and narrow western boundary current (WBC) that flows along the eastern coast of Australia. Like other WBCs, the EAC transports and redistributes water masses, heat and moisture from the tropics to the mid-latitudes. However, past EAC dynamics are still not well understood. Modern observations from the Coral Sea and the Tasman Sea have shown that eddy formation is an important component of the EAC flow with more eddies under a stronger EAC. In this context, cyclonic eddies can cause upwelling whereas anticyclonic eddies cause stronger stratification. Thus paleo-productivity records off eastern Australia can help to better understand eddy activity in this region and thus past EAC dynamics. For that reason, d13C and Cd/Ca (=proxies for productivity) in the tests of mixed-layer dwelling and thermocline planktic foraminifera from two multicores recovered off the eastern coast of Australia were measured to study changes in productivity over the past 1000 years. Our planktic foraminifera d13C record shows a decline in productivity while the sea surface temperature increased over the past 1000 years . We suggest that this could be the result of stronger anticyclonic eddies and thus enhanced water stratification of this region. We also measured benthic foraminifera d13C and Cd/Ca to evaluate the influence of the Antarctic Intermediate Water (AAIW) in the study area. The benthic foraminiferal d13C record reveal a decrease in d13C after ~1400 CE, which most likely indicate an increase in productivity, but which contradicts the d13C results of the planktonic foraminifera. It is assumed that the benthic d13C in this region are mainly controlled by the AAIW d13C signature and not productivity.