Marine heatwaves (MHWs) and total heat exposures (THEs), extreme warming events occurring across the global oceans, seriously threaten marine ecosystems and coastal communities as the climate warms. However, future changes in MHWs and THEs in the Arctic Ocean, where unique marine ecosystems are present, are still unclear. Here, based on the latest CMIP6 climate simulations, we find that both MHWs and THEs in the Arctic Ocean are anticipated to intensify in a warming climate, mainly due to Arctic sea ice decline and long-term warming trend, respectively. Particularly striking is the projected rise in MHW mean intensity during the 21st century in the Arctic Ocean, surpassing the global average by more than sevenfold under the CMIP6 SSP585 scenario. This phenomenon, coined the ‘Arctic MHW Amplification’, underscores an impending and disproportionately elevated threat to the Arctic marine life, necessitating targeted conservation and adaptive strategies.