An international study published in the journal Nature Communications, co-authored by researchers at the Center of Excellence for Extreme Climates (CLEX) and the Institute of Marine and Antarctic Studies (IMAS), reveals that heat waves have increased over the last century in number, duration and intensity as a direct consequence of the warming of the oceans.
Researchers at the University of Dalhousie (Canada) have determined that the number of annual days in which marine heat waves are recorded globally has increased by 54% between 1925 and 2016, a trend that accelerated especially from 1982. Indeed, from 1925 to 2016, the study found that the frequency of marine heat waves increased by an average of 34% and the duration of each heat wave increased by 17%. Together, this resulted in a 54% increase in the number of days of marine heat wave each year. “Our research also showed that starting in 1982, there was a noticeable acceleration of the trend in marine heat waves,” says lead author Dr. Eric Oliver of Dalhousie University in Canada.
Oliver’s teams analyzed the temperature of the sea surface on a global scale from satellite images and direct measurements made between 1900 and 2016.
The scientists attribute the increased of marine heat waves to an increase in the average temperature of the oceans throughout the planet.
Although the internal temperature variability of the seas can play a role at the regional level, these local changes do not affect the long-term global trend, say Oliver and his group.
The authors of the paper suggest that given the probability that the warming of the ocean surface will continue to increase during this century, it is possible that the impact and implications for the biodiversity of marine heat waves will also continue to worsen.
Indeed, this extreme climatic phenomenon, in which there are long periods with abnormally high temperatures on the surface of the oceans, can have negative effects on marine ecosystems but also on the global economy, the scientists warn.
In 2011, for example, Western Australia saw a sea heat wave that pushed ecosystems from kelp dominance to seaweed dominance. This change persisted after the water temperatures returned to normal. In 2012, a sea heat wave in the Gulf of Maine led to an increase in lobsters, but a drop in prices severely affected industry profits.