Anthropogenic and natural influences on record 2016 marine heat waves

In 2016 a quarter of the ocean surface experienced either the longest or most intense marine heatwave (Hobday et al. 2016) since satellite records began in 1982. Here we investigate two regions — Northern Australia (NA) and the Bering Sea/Gulf of Alaska (BSGA) — which, in 2016, experienced their most intense marine heat waves (MHWs) in the 35-year record. The NA event triggered mass bleaching of corals in the Great Barrier Reef (Hughes et al. 2017) while the BSGA event likely fed back on the atmosphere leading to modified rainfall and temperature patterns over North America, and it is feared it may lead to widespread species range shifts as was observed during the "Blob" marine heat wave which occurred immediately to the south over 2013–15 (Belles 2016; Cavole et al. 2016). Moreover, from a climate perspective it is interesting to take examples from climate zones with very different oceanographic characteristics (high-latitude and tropics). We demonstrate that these events were several times more likely due to human influences on the climate.