A paleoclimate perspective on recent European summer heatwaves and droughts

The intensity and frequency of heatwaves and droughts are projected to increase in response to global warming.

However, extreme European heatwaves like 2003, 2010, 2015 or 2018 exceed by far the intensity and duration expected to emerge from the warming trend so far.

Scientific explanations for these events invoke more stationary high-pressure systems caused by a weaker Jetstream in response to rapid warming in the Arctic known as Arctic Amplification.

However, climate models do not support this explanation and hence fail to predict observed heatwaves.In this project, we investigate another explanation for persistent high-pressure systems and related heatwaves/droughts which is the observed cooling of the North Atlantic Ocean in response to a slowdown of the Gulfstream system, the Atlantic Meridional Overturning Circulation (AMOC).

Observations show a correlation of major European heatwaves with very cold ocean temperatures in recent decades.

As the AMOC is projected to slow down with future warming, we study past extreme events with partially collapsed AMOC: during a rapid warming period 12,000-years ago and during a 1-2 degrees warmer climate ~127,000-years ago.

To study the paleo-meteorology of atmospheric blocking and related extremes behind these periods, we perform and analyse very high-resolution full-complexity Earth System Model simulations and compare results with different climate proxies from central and northern Europe downwind of the North Atlantic Ocean.