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Global ocean heat content

Updated on 15 Feb. 2018
Global Environment and Marine Department

An increase in the globally integrated upper ocean heat content was observed from 1950 to 2017 with a linear trend of 2.28 × 1022 J per decade.

ocean heat content change

Time series representation of the globally integrated upper (0 – 700 m) ocean heat content anomaly
The 1981 – 2010 average is used as the normal.

The solid line with dots shows the annual mean for the global integrals of upper (0 – 700 m) ocean heat content anomalies. The shaded area indicates a 95% confidence level. These data are updated from Ishii and Kimoto (2009).

Heat content anomaly time series (txt file:2KB)

Analyzed global fields (ASCII files)

The values here may be replaced as new data is obtained.

Commentary

Oceans have a significant impact on the global climate because they cover about 70% of the earth's surface and have high heat capacity. According to the Intergovernmental Panel on Climate Change Fifth Assessment report (IPCC, 2013), more than 60% of the net energy increase in the climate system from 1971 to 2010 is stored in the upper ocean (0 – 700 m), and about 30% is stored below 700 m. Oceanic warming results in sea level rises due to thermal expansion, and impacts marine ecosystems.

It is virtually certain that globally integrated upper ocean (0 – 700 m) heat content (OHC) rose between 1950 and 2017 at a rate of 2.28 ± 0.30 × 1022J per decade as a long-term trend with interannual variations (the range indicated by '±' represents a 95% confidence level). Oceans exhibited marked warming from the mid-1990s to the early 2000s. Although the slope has become more moderate, OHC has continued to increase significantly since then. A rise of 0.024 ± 0.003°C per decade in the globally averaged upper ocean (0 – 700 m) temperature accompanied the OHC increase.

These long-term trends can be attributed to global warming caused by increased concentrations of anthropogenic greenhouse gases such as CO2 as well as natural variability.

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