Abstract
The Tasman Sea off southeast Australia exhibited its longest and most intense marine heatwave ever recorded in 2015/16. Here we report on several inter-related aspects of this event: observed characteristics, physical drivers, ecological impacts and the role of climate change. This marine heatwave lasted for 251 days reaching a maximum intensity of 2.9 °C above climatology. The anomalous warming is dominated by anomalous convergence of heat linked to the southward flowing East Australian Current. Ecosystem impacts range from new disease outbreaks in farmed shellfish, mortality of wild molluscs and out-of-range species observations. Global climate models indicate it is very likely to be that the occurrence of an extreme warming event of this duration or intensity in this region is respectively ≥330 times and ≥6.8 times as likely to be due to the influence of anthropogenic climate change. Climate projections indicate that event likelihoods will increase in the future, due to increasing anthropogenic influences.
Highlights
The Tasman Sea off southeast Australia exhibited its longest and most intense marine heatwave ever recorded in 2015/16
marine heatwave (MHW) definition to daily, remotely sensed sea surface temperatures (SSTs), we found that the SEAus region was in a continuous MHW state from 9 September 2015 to 16 May 2016 (Fig. 1b,c, red shaded area)
We examined how Fraction of Attributable Risk (FAR) values of the intensity and duration of the 2015/2016 Tasman Sea MHW have changed over time, including the projected change into the future
Summary
The Tasman Sea off southeast Australia exhibited its longest and most intense marine heatwave ever recorded in 2015/16. The near-surface waters there are warming at nearly four times the global average rate[20,21] and these increasing temperatures are seen as deep as 750 m22 This warming has been linked to enhanced southward transport in the East Australian Current, driven by increased wind stress curl across the midlatitude South Pacific[21,23]. Future projections under anthropogenic climate change indicate continued strengthening of the southward transport in the East Australian Current Extension, linked with increased wind stress curl over the South Pacific, and a corresponding increase in the likelihood of extreme temperature events[25,26,27,28]
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