# Ocean dynamics shape marine heatwaves and their predictability

## TL;DR

Ocean dynamics play a key role in making marine heatwaves more intense and predictable, especially in the North Atlantic and eastern tropical Pacific.

## Contribution

The study reveals how ocean dynamics influence marine heatwave intensity, duration, and predictability, particularly in relation to Atlantic Meridional Overturning Circulation.

## Key findings

- Ocean dynamics enhance marine heatwave intensity and duration in mid-to-high latitude oceans and eastern tropical Pacific.
- North Atlantic marine heatwaves show multi-year potential predictability due to Atlantic Meridional Overturning Circulation.
- Vertical mixing and horizontal transport processes strongly influence heat accumulation during marine heatwaves.

## Abstract

Marine heatwaves have become more frequent and intense under anthropogenic warming, posing increasing threats to marine ecosystems and coastal societies, necessitating a better understanding of their mechanism and predictability. Here we show how ocean dynamics modulate marine heatwaves globally by comparing dynamic and slab ocean climate model simulations. We discover that ocean dynamics significantly promote marine heatwave intensity and duration in mid-to-high latitude oceans, as well as the eastern tropical Pacific where marine heatwaves are inherently linked to extreme El Niño events. Our mixed-layer heat budget analysis unravels that heat accumulation during marine heatwave episodes is strongly influenced by vertical mixing and horizontal transport processes, so that warm sea surface temperature extremes in dynamic ocean differ in magnitude and evolution rhythm from those in slab ocean. We further find robust multi-year potential predictability of marine heatwave in the North Atlantic with a dynamic ocean, owing primarily to the predictability of the Atlantic Meridional Overturning Circulation. Our findings emphasize the irreplaceable role of oceanic dynamics in marine heatwave evolution and predictability, with important implications for future climate extreme prediction and adaptation strategies.

Ocean dynamics extend and intensity marine heatwaves (MHWs) in mid-to-high latitude oceans and the eastern tropical Pacific. In particular, the Atlantic overturning’s predictability makes North Atlantic MHWs potentially predictable over several years.