The impact of future changes in weather patterns on extreme sea levels over southern Australia

This modeling study investigates the roll of anthropogenic climate change in inducing extreme sea level variability along southern Australia and Tasmania. ROMS is forced by two regionally downscaled CMIP3 climate models and one GCM for current and future climates, respectively. Model results show a reduction in extreme sea levels of about 1-10cm in response to a range of atmospheric forcing for future climates along southern Australia, Tasmania and Bass Strait. Results show a strong seasonality in the response. In austral autumn, a tendency of reduced extreme sea levels is observed in the study area. However, in austral winter, raised mean sea levels along Tasmania are simulated. Changes in maximum sea levels reflect changes in atmospheric conditions. Reduced maximum sea levels in austral spring and summer are associated with enhanced easterly winds near the southern coast and reduced westerlies over the Southern Ocean. In austral winter, enhanced westerlies lead to increased sea levels along Tasmania. Similarly, reduced maximum wind speeds over southern Australia further reduce sea levels there. The magnitudes of the projected changes in sea levels due to altered circulation patterns are within 10 cm of current climate extreme sea levels. This suggests that projected sea level rise will dominate future changes to extreme sea levels.