That’s not exactly good news: Researchers have found that hurricanes not only stir up water on the surface, but also push heat deep into the ocean where it can persist for years, ultimately affecting regions far from the ocean storm away.
Mathilde Fontez, editor-in-chief of the science magazine Epsilon, talks to us today about hurricanes. Researchers discover that they store heat in the oceans.
franceinfo: Oceanologists have studied the effects of hurricanes: not their devastating effects on the earth, but on the oceans?
Mathilde Fontez: Yes, that’s another aspect of hurricanes that this University of California team is discovering: It’s not about how the climate, the heat of the ocean, shapes these storms – it’s now widely accepted that global warming is driving their intensity and Strength increased. But how, conversely, do hurricanes change the distribution of heat in the oceans – a sensitive variable for global warming? We are currently measuring a marine heatwave of unprecedented proportions in the North Atlantic.
And what the researchers found is that hurricanes do in fact have an impact on the heat stored by the oceans. They whirl up the water masses much more than one would expect. Until the heat is stored in the depths.
Hurricanes warm the ocean?
It is a multi-stage mechanism: these storms first cool the sea surface and extract heat from a layer about fifty meters thick – this energy gives them their power. At the same time, however, the cyclone’s winds create turbulence, waves that mix the water masses deep down and heat up the layers below.
The researchers draw a parallel to a vinaigrette: Normally, hot and cold water pile up without mixing, the cyclone mixes everything up. As a result, the colder sea surface warms up in the sun immediately after the cyclone impacts – the ocean’s absorption capacity at the surface increases. But underneath, the layer heated by the cyclone falls down several hundred meters and gets stuck there. The cyclone warms the ocean deep down.
This hot water then remains blocked at depth?
It all depends on the dynamics of the currents. The heat from hurricanes can remain trapped at depth for decades—so it would tend to smooth out the effects of air warming and somehow mitigate them. But it can also alter the circulation of currents over thousands of kilometers months after the cyclone’s passage.
The researchers’ observations in the Philippine Sea — they’ve measured three typhoons in particular with sensors that dive 300 meters deep — show that the deep warm layer can begin to circulate and continue to rise thousands of kilometers where it would amplify warming locally. It could be involved in reef stress, coral bleaching. A new twisted effect of global warming to consider in the future.