El Niño is coming and Ocean Temperature are already at record highs

Subject :Geography

Section: Physical geography

Context: El Niño tends to trigger intense and widespread periods of extreme ocean warming known as marine heat waves.

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By July, most forecast models agree that the climate system’s biggest player – El Niño – will return for the first time in nearly four years.
El Niño can also wreak havoc on the many marine ecosystems that support the world’s fishing industries, including coral reefs and seagrass meadows.
El Niño tends to trigger intense and widespread periods of extreme ocean warming known as marine heat waves.
Marine heat waves also unfold along the seafloor of coastal regions.
In the Bay of Bengal east of India, interactions between El Niño and a tropical air flow pattern known as the Walker Circulation elevate the risk for marine heat waves.

Marine Heatwaves:

Heatwaves are periods of extreme warmth when temperatures rise beyond the normal range for at least two consecutive days or nights.

Formation of Marine Heatwaves:

Marine heat waves form much like land-based ones: weather systems intensify over time, leading to extremely high temperatures over large ocean surface areas.
But there are key differences between them that drive their formation processes:
- Land-based heat waves depend on atmospheric conditions like high-pressure systems (anticyclones) over land masses such as continents or oceans that block cold air from reaching those areas.
- Marine heatwaves are periods when sea surface temperature reaches extreme levels for an extended period, sometimes lasting weeks or months. These events occur in various ocean regions and can be caused by natural variability or human-induced climate change.

Causes of Marine Heatwaves:

The main cause of marine heat waves is the increase in ocean temperature due to the absorption of greenhouse gases from the atmosphere, which leads to global warming.
Natural climate variability can also contribute to marine heat waves, including changes in ocean currents, weather patterns, and atmospheric circulation.
El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) can contribute to the occurrence of marine heat waves.

Impacts of Marine Heatwaves

Coral bleaching: Marine heatwaves can lead to coral bleaching, which is the loss of photosynthetic algae, called zooxanthellae, from the coral. This can ultimately lead to the death of coral.
Ocean acidification: Marine heatwaves can exacerbate ocean acidification, which is the increase in acidity of seawater due to the absorption of carbon dioxide from the atmosphere. This can have negative impacts on marine organisms that build shells or skeletons out of calcium carbonate, such as corals and some types of plankton.
Harmful algal blooms: Marine heatwaves can cause harmful algal blooms, which can produce toxins that are harmful to humans and marine life.
Ocean circulation: Marine heatwaves can also affect ocean circulationby altering the temperature and density of ocean water, which can have implications for ocean currents and the transport of nutrients and heat around the globe.
Marine biodiversity: Marine heatwaves can affect the composition and abundance of marine species, leading to changes in marine biodiversity.