Increase in Arctic amplification and high-latitude marine extremes in the 21st century as obtained from high-resolution modelling

The Arctic is warming at a rate faster than any other oceans, a phenomenon known as Arctic amplification that has widespread impact on the global climate. In contrast, the Southern Ocean (SO) and Antarctica have been cooling over the past decades. The projection of these regions under global warming has a non-negligible model spread. Here we show that under a strong warming scenario from 1950 to 2100, comparing a cutting-edge high-resolution climate model to a low-resolution model version, the increase of Arctic amplification is 3 °C more and the SO and Antarctica warming is 2°C less. Previously ice-covered Arctic Ocean will exhibit greater SST variability under future global warming. This is due to an increased SST increase in summer due to sea ice retreat. Extreme warming events in the Arctic and SO, known as marine heat waves (MHW) that influence the ecology, are largely unknown. We find that the MHWs in the Arctic and SO are twice as strong in the high-resolution model version, where the increasing intensity of MHWs in the Arctic corresponds to strong decline (<-6% per decade) of sea ice. In both the high-resolution and low-resolution models, the duration of MHWs in the Arctic and SO shows a declining trend under global warming. The much stronger MHWs in the high-resolution model could be caused by two orders of magnitude more ocean turbulent energy. For example, the spatial patterns of SO MHW intensity correspond to the pattern of SO EKE. We conclude that the Arctic amplification and MHWs at high latitudes might be underestimated by the current generation of climate models with low resolution, and the SO and Antarctica warming might be overestimated. Our eddy- and storm-resolving model is expected to open new frontiers on how the system responds to human activities in a high CO₂ world by evaluating the impact on past and future climate and environmental extremes.