The Arctic region is warming more than twice as fast as the global mean, and polar organisms and ecosystems are likely to be particularly vulnerable to heat waves due to their specific thermal niches and physiological thresholds and also the lack of poleward 'refugia' . The consequences of MHWs are exacerbated by concomitant sea ice melting and the freshening of surface waters, leading to secondary effects due to osmotic stress and failing pH homeostasis. Since sea ice-associated organisms are often critical components of polar food chains, cascading effects up to the top predators are expected. In 2015-2016, a MHW occurred in the Gulf of Alaska/Bering Sea  which was unprecedented in terms of surface temperatures and ocean heat content, geographical extent, depth range and persistence, impacting the entire marine food web. Persistent warming favoured some phytoplankton species and triggered one of the largest algal blooms recorded in this region, with concomitant oyster farm closures due to uncommon paralytic shellfish- poisoning events . There were also massive die-offs of common guillemots  and puffins , attributed to starvation resulting from warming-induced effects on food supply . A 2017 survey found a 71% decline in the abundance of Pacific cod  since 2015, likely due to an increase in metabolic demand and reduced prey supply during the MHWs .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report