Record Ocean warming in 2021

Ocean warming in 2021: Relevance

• GS 3: Conservation, environmental pollution and degradation, environmental impact assessment.

Ocean warming in 2021: Context

• According to the recently published analysis in the Advances in Atmospheric Sciences journal, world’s oceans underwent record warming in 2021.

Record Ocean warming in 2021: Key points

• The report has stated that, the upper 2,000 metres of the ocean absorbed 235 zettajoules (ZJ) of heat in 2021 relative to the 1981-2010 average.
• The sum of the energy used by humans across the world in a single year is about half a ZJ (one ZJ is equal to 10^21 joules).
• The warming rates in 1986-2021 represents a maximum eight-fold increase compared to 1958–85.

Ocean warming in 2021: How oceans heat up?

• Oceans stabilise Earth’s climate by absorbing large amounts of heat from sunlight, water vapour and other greenhouse gases.
• The heat absorbed by the oceans find its way back into the atmosphere through melting ice shelves, evaporating water or directly reheating the atmosphere.
• If the ocean absorbs more heat than it releases, its heat content rises.
• Oceans are absorbing most of the heating from human carbon emissions like carbon dioxide and other greenhouse gases, due to which there is an energy imbalance.
• The experts have stated that the heating of ocean will continue until we reach net-zero carbon emissions.

Ocean warming in 2021: Impact of El Niño and La Niña

• During El Niño, the oceans release some amount of heat, contributing to a mini global warming. So, the warmest years in terms of surface temperature are El Niño years.
• During La Niña, oceans take up heat and bury it at depths away from the surface.
• Expert is of the opinion that this amount of energy is huge for the atmosphere, but the cumulative effect on ocean warming is much less.

Record Ocean warming in 2021: Effect on coastal communities

• Melting ice accelerates sea-level rise. Also, as oceans heat up, water expands (thermal expansion of water). This leads to an increase in the volume of water.
• Warmer oceans also supercharge weather systems, creating more powerful storms and hurricanes, as well as increasing precipitation and flood risk.
• The experts recommended that the coastal communities need to modify engineering designs, building codes and coastal development plans to tackle increased sea-level rise, as they are the first to bear the brunt of sea-level change.

Record Ocean warming in 2021: Effect on marine life

• Warming oceans could result in increased ocean stratification or separation, causing less mixing of the ocean layers.
• It means that heat, oxygen and carbon dioxide are not transported from the surface to the oceanic depths. It affects the marine life in the aphotic zones and the benthic zone.

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