Direct and seasonal legacy effects of the 2018 heat wave and drought on European ecosystem productivity
Ana Bastos, Philippe Ciais, Pierre Friedlingstein, Stephen Sitch, Julia Pongratz, Lei Fan, Jean‐Pierre Wigneron, Ulrich Weber, Markus Reichstein, Zheng Fu, Peter Anthoni, Almut Arneth, Vanessa Haverd, Atul K. Jain, Émilie Joetzjer, Jürgen Knauer, Sebastian Lienert, Tammas Loughran, Patrick McGuire, Hanqin Tian, Nicolas Viovy, Sönke Zaehle
Abstract
In summer 2018, central and northern Europe were stricken by extreme drought and heat (DH2018). The DH2018 differed from previous events in being preceded by extreme spring warming and brightening, but moderate rainfall deficits, yet registering the fastest transition between wet winter conditions and extreme summer drought. Using 11 vegetation models, we show that spring conditions promoted increased vegetation growth, which, in turn, contributed to fast soil moisture depletion, amplifying the summer drought. We find regional asymmetries in summer ecosystem carbon fluxes: increased (reduced) sink in the northern (southern) areas affected by drought. These asymmetries can be explained by distinct legacy effects of spring growth and of water-use efficiency dynamics mediated by vegetation composition, rather than by distinct ecosystem responses to summer heat/drought. The asymmetries in carbon and water exchanges during spring and summer 2018 suggest that future land-management strategies could influence patterns of summer heat waves and droughts under long-term warming.