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The North Atlantic significantly influences the weather in Europe. For instance, a cold spell in the subpolar North Atlantic can lead to a heat wave over Europe. A new study shows that climate models represent this relationship much more realistically when ocean dynamics are resolved in sufficient detail.
Joint press release by the Max Planck Institute for Meteorology and GEOMAR Helmholtz Centre for Ocean Research Kiel
Europe is struggling more and more with extreme heat in the summer. While climate change is the main reason for this increase, what specific physical mechanisms cause a heat wave? One important driver of weather conditions in Europe is the North Atlantic. For example, studies by the Max Planck Institute for Meteorology (MPI-M) have shown that heat build-up in the subtropical North Atlantic can lead to extremely hot summers in Europe several years later.
Another mechanism, which acts on a different timescale, originates in higher latitudes. Observations show that exceptionally low sea surface temperatures in the subpolar North Atlantic can trigger a heat wave in Europe. This may sound paradoxical at first, but it is the result of a chain reaction: An unusually cold sea surface, combined with a low-pressure system, increases the transport of energy from the ocean to the atmosphere. This further cools the sea surface and stabilizes the low-pressure system over the Atlantic, enabling the formation of a blocking high-pressure weather system downstream. This mechanism was responsible for heat waves on the European continent in the summers of 2015 and 2018, for example.
A study led by researchers from the MPI-M and the GEOMAR Helmholtz Centre for Ocean Research Kiel investigated how well current climate models reflect this mechanism. To accomplish this, the authors analysed climate simulations spanning 100 years. These simulations were created using seven models, six of which participate in the High-Resolution Model Intercomparison Project (HighResMIP). The team compared standard configurations with coarse grids to higher-resolution configurations, varying the resolution between 8 and 100 km in the ocean and between 18 and 200 km in the atmosphere. To determine the agreement with reality, the researchers compared the model results with reanalysis data from 1979 to 2019, which combine observations and weather models.
Better ocean dynamics, better representation of heat waves
“Our key finding is that high-resolution climate models more accurately represent heat waves linked to the North Atlantic mechanism than models with coarse resolution,“ says MPI-M scientist Julian Krüger, previously a doctoral researcher at GEOMAR and the study’s lead author. “This is mainly due to the higher resolution in the ocean.“ A more realistic representation of eddies and fronts in the North Atlantic improves the simulation of sea surface temperature and, consequently, the energy exchange between the ocean and the atmosphere. This makes both the low-pressure system over the Atlantic and the subsequent high-pressure system over Europe more persistent and pronounced. These results are consistent with observations.
The study makes it clear that improvements in simulating European heat waves largely depend on a realistic representation of the ocean. Eddy-permitting ocean models are proving to be the key to accurately capturing the large-scale interactions between the Atlantic Ocean and Europe. However, even the high-resolution models leave room for improvement. For instance, the intensity of heat waves is underestimated, and the geographical location of the high-pressure system deviates from reality. Since this study focused on a finer resolution of ocean dynamics, the authors now plan to examine whether a higher resolution in the atmosphere will yield further improvements.
Julian Krüger, Joakim Kjellsson, Katja Lohmann, Daniela Matei & Robin Pilch Kedzierski (2026): Improved European heat event simulation in eddy-resolving climate models. Commun Earth Environ 7, 123.
https://doi.org/10.1038/s43247-025-03145-9
https://www.geomar.de/n10180 – images for download
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Environment / ecology, Geosciences, Oceanology / climate, Physics / astronomy
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