Bischof, Sabine , Pilch Kedzierski, Robin , Hänsch, Martje, Wahl, Sebastian and Matthes, Katja (2023) The Role of the North Atlantic for Heat Wave Characteristics in Europe, an ECHAM6 Study. Geophysical Research Letters, 50 (23). Art.Nr. e2023GL105280. DOI 10.1029/2023GL105280.

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Abstract

The recent severe European summer heat waves of 2015 and 2018 co-occurred with cold subpolar North Atlantic (NA) sea surface temperatures (SSTs). However, a significant connection between this oceanic state and European heat waves was not yet established. We performed two AMIP-like model experiments: (a) employing daily 2018 SSTs as observed and (b) applying a novel approach to remove the negative NA SST anomaly, while keeping SST daily and small-scale variability. Comparing these experiments, we find that cold subpolar NA SSTs significantly increase heat wave duration and magnitude downstream over the European continent. Surface temperature and circulation anomalies are connected by the upper-tropospheric summer wave pattern of meridional winds over the North Atlantic European sector, which is enhanced with cold NA SSTs. Our results highlight the relevance of the subpolar NA region for European summer conditions, a region that is marked by large biases in current coupled climate model simulations.

Key Points:
- Model study designed to investigate the ocean impact on European heat waves by prescribing observed and realistic ocean surface conditions
- Cold subpolar North Atlantic sea surface temperatures significantly enhance heat wave intensity and duration over the European continent
- North Atlantic ocean and European surface temperature and circulation anomalies are bridged by the upper-tropospheric summer mean wave

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