Marine heatwaves, periods of unusually high temperature in the oceans, are becoming more common with rapidly increasing global warming. Now, a new study warns that they will frequently occur in the Arctic Ocean with higher human-induced greenhouse gas emissions.
The study, conducted by researchers from the University of Hamburg, found a concerning rise in marine heatwaves in the Arctic. From 2007 to 2021, the marginal zones of the Arctic Ocean experienced 11 marine heat waves, leading to an average temperature rise of 2.2 degrees Celsius above the seasonal norm and lasting an average of 37 days. Since 2015, there have been Arctic marine heat waves every year, the university’s press statement revealed.
The most powerful heatwave that the region experienced was in 2020, and it continued for 103 days. The highest temperatures were four degrees Celsius over the long-term average. The research team said without human-induced greenhouse gases, the probability of such a heatwave occurring in the Arctic is less than 1%. The findings indicate that marine heatwaves will be the norm in the near future.
In 2007, a new phase began in the Arctic, study author Armineh Barkhordarian said in the statement. "There is less and less of the thicker, several-year-old ice, while the percentage of thin, seasonal ice is consistently increasing,” Barkhordarian added. However, the thin ice melts more quickly, allowing solar radiation to heat the water's surface.
The study, published in the journal Communications Earth & Environment, also proved for the first time that heat waves are produced when sea ice melts early and rapidly after the winter. When this happens, a significant amount of heat energy can accumulate in the water by the time maximum solar radiation is reached in July.
According to the study, a marine heat wave occurs when temperatures at the water's surface are higher than 95% of the values from the past 30 years for at least five consecutive days.
The warming temperatures are a massively concerning issue today. "Not just the constant loss of sea ice but also warmer waters can have dramatic negative effects on the Arctic ecosystem,” Barkhordarian explained in the statement. Marine heatwaves have an impact on food chains and overall biodiversity.
Moreover, a previous study, published in the journal Nature Climate Change in September 2023, found that marine heatwaves last longer and can be more intense in deeper water, which could threaten the survival of certain marine species.