Global Ocean Heat Content

A recent study indicated that the amount of heat stored in upper 2,000 metres of the global ocean or Ocean Heat content reached 286 Zetajoules (ZJ) in 2023 relative to 1981–2010 average.

About Global Ocean Heat Content (OHC):

• OHC describes the amount of heat stored in the ocean in the upper levels, from the surface to 2,000 meters in depth.
• It is used to quantify the rate of global warming.
• Calculation: The ocean temperature is measured at many different locations and depths.
  • OHC = seawater density * Specific heat capacity * integrating the temperature over this depth
• High OHC can disrupt marine ecosystems, bleach coral, contribute to extreme weather events such as hurricanes, and affect sea-level rise.
• The oceans store 90% of the excess heat in the Earth’s system.
• As long as the level of greenhouse gases remains relatively high in the atmosphere, the oceans will keep absorbing energy, leading to the increase of the heat in the oceans.

Key Findings of the Study:

• The 2023 OHC value was 286 Zetajoules (ZJ), which increased by 15 ZJ from 2022.
• For comparison, the entire global energy consumption is around half a ZJ, emphasizing the magnitude of the ocean’s heat storage.
• The 2023 estimate is equivalent to approximately 4.6 billion Hiroshima nuclear bombs, underlining the immense heat accumulation in the oceans.
• Accelerated Warming: Warming rates in the Atlantic, North Pacific, Western Pacific, and Southern Oceans surpass the global average, indicating regional disparities in ocean temperature changes.
• Oceans, covering 70% of the planet, absorb about 90% of the heat from global warming, contributing to intensified storms, heavier rain, stronger winds, and increased flooding.
• Role of Ocean Heat Content: The Earth’s energy, water, and carbon cycles, significantly impact human society, by connection between ocean warming and extreme weather events.
• Data Analysis: Researchers from China, U.S., New Zealand, and Europe utilized the World Ocean Database to analyze OHC, sea surface temperature, salinity, and stratification.
• Variability: A long-term warming trend in the ocean due to global warming led to the 2023 ranking among the top five hottest years since 1955.
• The rate of increase in OHC has doubled or tripled since the late 1980s, indicating an acceleration in ocean heat accumulation.
• El Nino Influence: Trends in OHC tend to peak before an El Nino event and decline afterward, with the strong El Nino conditions in 2023 influencing the observed warming.
• Additional Climate Indicators: The research examined sea surface temperature, global mean surface temperature, and salinity levels, providing an overview of climate-related changes.
• Surface temperature: Anomalously high sea surface temperatures in 2023 were partly attributed to the three-year-long La Nina, contributing to the record-breaking warmth.

Ref: Source