Extremely warm European summers preceded by sub-decadal North Atlantic ocean heat accumulation

• Published in: Earth System Dynamics
• Main Authors: L. Wallberg, L. Suarez-Gutierrez, D. Matei, W. A. Müller
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2024
• Subjects: Science; Q; Geology; QE1-996.5; Dynamic and structural geology; QE500-639.5; North Atlantic
• Online Access: https://doi.org/10.5194/esd-15-1-2024; https://doaj.org/article/0c4c53d9d9f043e4ae41300be363c145

The internal variability of European summer temperatures has been linked to various mechanisms on seasonal to sub- and multi-decadal timescales. We find that sub-decadal timescales dominate summer temperature variability over large parts of the continent and determine mechanisms controlling extremely warm summers on sub-decadal timescales. We show that the sub-decadal warm phases of bandpass-filtered European summer temperatures, hereinafter referred to as extremely warm European summers, are related to a strengthening of the North Atlantic Ocean subtropical gyre, an increase in meridional heat transport, and an accumulation of ocean heat content in the North Atlantic several years prior to the extreme summer. This ocean warming affects the ocean–atmosphere heat fluxes, leading to a weakening and northward displacement of the jet stream and increased probability of occurrence of high-pressure systems over Scandinavia. Thus, our findings link the occurrence of extremely warm European summers to the accumulation of heat in the North Atlantic Ocean and provide the potential to improve the predictability of extremely warm summers several years ahead, which is of great societal interest.