Global Ocean Heat Content in 2023: Alarming Trends, Implications, & Rising Pattern

Context:

According to a new study published in Advances in Atmospheric Sciences, the amount of heat stored in the upper 2,000 meters of the global ocean reached 286 Zetajoules (ZJ) in 2023 relative to the 1981–2010 average.

Ocean Heat Content in 2023: Insights from Comprehensive Data Analysis

  • Researchers analyzed data from the World Ocean Database, a collection of uniformly formatted, quality-controlled, publicly available ocean profile data.
  • They used parameters such as ocean heat content, sea surface temperature, salinity, and stratification to describe ocean changes in 2023.
  • The Atlantic, North Pacific, Western Pacific and Southern oceans are warming faster than the global average. 
Year Ocean heat content trend
1958-1985 3.1 ± 0.5 ZJ per year 
1986 -2007  9.2 ± 0.5 ZJ annually.
2007-2023 10.8 ± 1.2 ZJ per year 
  • Warming Oceans Globally: 

    • The upper 2,000 m of the world’s ocean has warmed on average by 6.6 ± 0.3 ZJ per year from 1958-2023 signifying a two- to three-fold increase in the rate of increase in ocean heat content since the late 1980s.
    • The 2023 ocean heat content is ranked as one of the five hottest years of the world’s ocean.
  • Climate Shifts in 2023: Record CO2 Levels, Ocean Heat Surge, and Unprecedented Sea Surface Warming

    • CO2 concentration: It is 50 per cent above the preindustrial level in 2023 in the atmosphere.
    • Global sea surface temperature:  The annual mean was roughly 0.23 degrees Celsius higher than in 2022 reaching record high.

Zeta Joules

  • Heat is measured  in a unit called a Joule.
  • The amount of heat in the oceans is  reported in zeta Joules which is  1021 Joules
  • The entire globe consumes around half a ZJ of energy to fuel economies
  • The 2023 ocean heat content value was 15 ZJ more from 2022  representing the heat of around 4.6 billion Hiroshima nuclear bombs.
    • Mean  sea surface temperature: It  was 0.54°C higher than the 1981–2020 average.
    • Surface  temperatures : Reached  1.48C above the preindustrial era making 2023 the warmest year on record.The Salinity Contrast index : It shows the  difference between the salinity averaged over high and low-salinity regions, reaching 7.2 mg per kg in 2023, showing a robust increase in salt levels in the last 50 years.
    • Ocean density Stratification: In 2023, The upper 2,000-meter stratification reached record-high levels mainly due to the development of a strong El Nino.

Ocean stratification:  A Dive into the Layers of Global Waters

  • Ocean stratification is the mixing between the less dense, warm, and fresh waters near the surface and the deeper layers. 

The Critical Impact of Warming Seas on Climate and Extreme Weather Events

  • The oceans absorb about 90 percent of the heat from global warming.
  • When the ocean warms, it releases extra heat and moisture into the atmosphere, making storms more severe with heavier rain, stronger winds and more significant flooding.
  • Ocean heat content also plays an essential role in Earth’s energy, water, and carbon cycles acting as a  robust indicator of climate change. 
  • El Nino, a recurring climate pattern in the Pacific at intervals of 2–7 years, is associated with releasing ocean heat into the atmosphere, mainly through increased evaporation.

News Source: Down to Earth

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