Is the Ocean to Blame for Extreme Heat Waves?

During a severe heat wave, while you’re longing to be at the beach, the ocean itself might be causing the extreme hot spell! This is because the circulation within the planet’s largest masses of water is intimately linked to conditions in the atmosphere—and changes to either may drive extreme climate events, resulting in huge economic and human losses. However, assessing the potential feedbacks of the ocean on the atmosphere and on climate is a new topic of research. Dr. Aurélie Duchez’ research aims at understanding the links between altered ocean circulation and severe weather events, such as droughts, intense rainfall, severe winters and heat waves. This knowledge is the first step toward her ultimate goal: to improve weather predictions and prepare for these devastating weather events.
The oceans’ influence should not be underestimated: they store 1,000 times more heat than the atmosphere and large-scale circulation patterns transport it around the planet. Northwest Europe would become considerably colder if climate change caused these ocean currents, carrying heat northward from the equator, to slow. Using data from the RAPID array, a series of sensors spanning the Atlantic from Morocco to Florida, Aurélie Duchez and her team showed that a 30% slowdown of circulation in the North Atlantic did, in fact, precede the extremely cold European winters of 2009-10 and 2010-11. Then, in the first study of its kind, they have established the role of anomalously cold North Atlantic Ocean temperatures as a precursor to the highest temperatures ever recorded in Central Europe during the summer of 2015. Since the 1980s, the appearance of the same exceptional cold patch has preceded several extreme heat waves. This points to “a previously unknown role of the Atlantic Ocean as a driver for these devastating events,” she explains. Next, she will work on understanding how, specifically, this oceanic phenomenon might lead to such intense hot spells.
Understanding the mechanisms that link oceanic conditions to extreme climate events—which are expected to increase with climate change—would reveal if the latter can be predicted. This knowledge could yield improved forecasting of severe weather and sufficient lead-time for governments, health services, insurers and citizens to prepare.

Scientific title: Dynamics Of European Extreme Weather: A Climate Model Intercomparison