The ocean is hotter than ever: what are the consequences?

The global ocean hit a new record temperature of 21.1 ºC in early April, 0.1 ºC higher than the last record in March 2016. According to the United States National Oceanic and Atmospheric Administration (NOAA) this is probably the highest ocean temperatire in more than 100,000 years. A few weeks ago the same NOAA reported that waters closest to the surface in the Gulf of Mexico have increased at a rate approximately twice that of the global ocean in the decades between 1970 and 2020.

According to Josh Willis, an oceanographer at NASA’s Jet Propulsion Laboratory from United States, “We are probably looking at a string of record highs over the next year or so ... This coming year is gonna be a wild ride if the El Niño really takes off.”

The El Niño Southern Oscillation (ENSO) is a natural, cyclical climate pattern. During the El Niño phase, winds over the Pacific are weakened or reversed, allowing warm waters to slosh eastwards in the Pacific. El Niño tends to coincide with warmer years both in the ocean and on land. The previous record of 21.0 ºC, for example, occurred during a very strong El Niño event. By the way, La Niña is the opposite phase to El Niño.

The ocean absorbs about 90% of the extra heat in the climate system resulting from global warming. But because it takes more energy to heat water than air, the surface water temperature is rising more slowly than the surface air temperature is.

Warm waters, physically means less capacity of hold dissolved oxygen, adding to the stress for marine life. More specifically, it can lead to:

• impacts to wildlife and fisheries

• harmful algal blooms

• corals bleach, and many of them die

• and about whales, they come closer to shore in search for food, getting entangled in fishing gear. And even colliding with ships.

Marine heatwaves can also trigger extreme weather, such as cyclones.

Click at the image below to read more at Nature. It also mentions that in the Southern Hemisphere, the sea ice extent hit a new all-time low in February 2023.

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