Underestimated Arctic warming and potential ecosystem impact due to unresolved marine heatwaves

The Arctic is warming faster than any other regions, a phenomenon known as Arctic amplification, which has far-reaching effects for global climate. Modelled historical simulations show a significant underestimation of the amplification and the future projection exhibits non-negligible model spread. Here we show that in a future warming scenario, the warming in the Arctic is generally larger when comparing high-resolution climate models with low-resolution versions. We attribute the different extent of Arctic warming to Arctic marine heatwaves (MHWs), known as episodes of extreme ocean surface warming. The resolution of the MHWs, which are stronger and more realistic in the high-resolution model versions, increases the melting of sea ice and thus the absorption of solar radiation by the ocean in the short term, thereby reinforcing the long-term trend of Arctic warming. We point out that the amplification of Arctic warming is underestimated by the current generation of climate models, which generally have low resolution, thereby underestimating Arctic marine heat waves. In addition, Arctic heatwaves cause extreme temperature fluctuations associated with increased stratification. This poses major challenges to Arctic ecosystems and has a negative impact through direct physiological temperature effects and indirectly through nutrient supply and taxonomic shifts. We conclude that the eddy- and storm-resolving models provide a new perspective on how the Earth system responds to past and future climate and environmental extremes.