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Heat waves over the world’s oceans (Part I)




IT is not just global air tempera­tures that are heating up. Heat waves over the world’s oceans are becoming longer and more frequent, damaging coral reefs and creating chaos for aquatic species, according to new research.

Marine heat waves (MHWs) are different than terrestrial heat waves in that they last longer, sometimes persisting for days to months, since oceans take in and give away heat at a much slower rate than air. They can also affect vast extensions of water, much greater in size than land heat waves, and can have a tremendous impact both on temperature and water vapor content of the air.

The researchers say that rising ocean temperatures, driven by human-caused climate change, are to blame. While natural cli­mate variations like El Nino do affect the frequency and severity of heat waves from one year to the next, the study suggests the increases are mainly linked to long-term changes in sea surface temperature. The rise in these marine heat waves has occurred while ever more heat is stored in the ocean because of accumu­lating greenhouse gases in the atmosphere.

Far less attention has been paid to heat waves over the ocean, which can have consequences of their own for both the marine environment and people. A study concludes that we can ex­pect further increases in marine heat wave days under continued global warming. The marine heat wave which stretches from Mexico to Alaska, is possibly the largest marine heat wave ever recorded. During 2014 and 2015, the so-called “warm blob”, the ocean became three degrees warmer than normal, causing widespread death and destruction to marine life. Many sea animals such as sea lions, whales and otters washed up dead or starving on beaches along the coast, and there was a mass death of seabirds.

(To be continued)