The 2023 North Atlantic marine heatwave could have evolved into a far more extreme event
Abstract
In 2023, the North Atlantic Ocean experienced a marine heatwave of unprecedented intensity and duration, raising the question of whether substantially more severe outcomes were physically plausible under comparable present-day preconditioning, and which processes could produce them. Here, we apply ensemble boosting to a coupled Earth system model to generate physically consistent alternative evolutions of a 2023-like event. The boosted ensemble produced marine heatwaves lasting up to 579 days, reaching maximum intensities of 4.5 °C above climatology and cumulative intensities of 717 °C·days, compared with 240 days, 2.9 °C and 224 °C·days in observations. Detailed analyses of the longest and most intense events highlight contrasting roles for persistent Euro-Atlantic high pressure, reduced turbulent heat loss, enhanced shortwave radiation and upper-ocean heat redistribution. Finally, we place these present-day storylines in the context of future warming, showing that events comparable to the observed 2023 event become increasingly common as global warming progresses.
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BibTeX
@article{gregory20262023,
title = {{The 2023 North Atlantic marine heatwave could have evolved into a far more extreme event}},
author = {Catherine H. Gregory and Urs Hofmann Elizondo and Thibault Guinaldo and Thomas L. Frölicher},
journal = {Nature Communications},
year = {2026},
month = oct,
doi = {10.1038/s41467-026-78863-5},
url = {https://www.nature.com/articles/s41467-026-78863-5},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - The 2023 North Atlantic marine heatwave could have evolved into a far more extreme event
AU - Catherine H. Gregory
AU - Urs Hofmann Elizondo
AU - Thibault Guinaldo
AU - Thomas L. Frölicher
PY - 2026
DA - 2026/10/19
JO - Nature Communications
DO - 10.1038/s41467-026-78863-5
UR - https://www.nature.com/articles/s41467-026-78863-5
AB - In 2023, the North Atlantic Ocean experienced a marine heatwave of unprecedented intensity and duration, raising the question of whether substantially more severe outcomes were physically plausible under comparable present-day preconditioning, and which processes could produce them. Here, we apply ensemble boosting to a coupled Earth system model to generate physically consistent alternative evolutions of a 2023-like event. The boosted ensemble produced marine heatwaves lasting up to 579 days, reaching maximum intensities of 4.5 °C above climatology and cumulative intensities of 717 °C·days, compared with 240 days, 2.9 °C and 224 °C·days in observations. Detailed analyses of the longest and most intense events highlight contrasting roles for persistent Euro-Atlantic high pressure, reduced turbulent heat loss, enhanced shortwave radiation and upper-ocean heat redistribution. Finally, we place these present-day storylines in the context of future warming, showing that events comparable to the observed 2023 event become increasingly common as global warming progresses.
SN - 2041-1723
ER -