Australia: The Land Where Time Began

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South Pacific Gyre “Spin-Up” Extending Understanding by Modelling the East Australian Current in a Future Climate

According to Oliver & Holbrook a global marine warming “hot spot” has been found to be waters of the western Tasman Sea where warming is taking place at almost 4 times the global average rate, and in the literature it has been argued that this is due to a “spin up” of the South Pacific subtropical gyre and extension of the East Australian Current (EAC). In this paper Oliver & Holbrook present the results of their investigation to test this paradigm further by analysing climate change simulations of the circulation and metrics of the Tasman Sea on output from the Ocean Forecasting Australia Model for the 20th and 21st centuries, forced by a global climate model simulation under the A1B carbon emissions scenario. Oliver & Holbrook have first shown that estimates of mean dynamic topography of the 1990s simulation, the location of the separation of the EAC at present, and the volume transport of the EAC, EAC extension, and flow along the Tasman Front, are consistent with observations that have been made recently. They also demonstrate that the volume transport of the EAC extension is projected to increase by 4.3 Sv at the expense of the flow along the Tasman Front, which is projected to decrease by 2.7 Sv. There is projected to be very little change in the flow, an increase of 0.2 Sv, in the core flow of the EAC transport, equatorwards of the separation point. A Tasman Sea-wide warming is projected by the model, with mean increases of up to 3oC. Oliver & Holbrook interpreted these results using a simple linear, barotropic model which captures the sign as well as the meridional distribution of the changes that are projected in mean transport, including negligible change in the core EAC transport but enhanced EAC extension. According to Oliver & Holbrook the meridional asymmetry in the transports is consistent with the ocean response to changes, which are wind forced, in the basin-wide wind stress curl.

Sources & Further reading

  1. Oliver, E. C. J. and N. J. Holbrook (2014). "Extending our understanding of South Pacific gyre “spin-up”: Modeling the East Australian Current in a future climate." Journal of Geophysical Research: Oceans 119(5): 2788-2805.


Author: M. H. Monroe
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