Ocean surface warming

Average Global Sea Surface Temperatures

Average Global Sea Surface Temperature: 1880 - 2015

Average Global Sea Surface Temperature, 1880–2015
(USA Environmental Protection Agency)

  • The thick orange line shows how “the average sea surface temperature of the world’s oceans” moved between 1880 and 2015.  
  • The temperatures have been rising since 1970.
  • The grey band shows the range of uncertainty in the data.

This rise of sea surface temperature is further evidence that the planet is warming.

The phytoplankton feedback loop


Unfortunately, when sea surface temperatures rise this can set up another cyclic sequence of cause and effect that tends to raise global temperatures further.  (See Self-amplifying feedback loops.)

This amplifying feedback loop involves phytoplankton. They are important as they produce up to half of the oxygen that we breathe and are the base of the ocean food chain. Since 1950 the phytoplankton numbers have dropped by about 40%.
Plankton: a small organism with a big role: (Ocean Conservancy: 9 Aug 2019)

In this feedback loop:

  • A warming atmosphere tends to warm the surface layers of the ocean.
  • This tends to make the surface layers more buoyant.
  • This tends to make winds less effective at driving upwelling, the mixing of the cold, nutrient-rich, deeper layers with the surface water.
  • This tends to decrease the fertility of the oceans.
  • This tends to reduce the population of phytoplankton.
  • This tends to decrease the amount of CO2 that the phytoplankton consume via photosynthesis. (Phytoplankton convert light energy from the sun into chemical energy by photosynthesis, consuming CO2 and releasing oxygen in very large quantities.)
  • This tends to increase the CO2 in the atmosphere.
  • This tends to warm our atmosphere, completing this cycle.

See Phytoplankton (NASA)

Heat-waves sweeping oceans like wildfires

The Guardian 5 March 2019
Damian Carrington

Extreme temperatures are destroying kelp, sea-grass, and corals – with alarming impacts for humanity. The number of heatwaves affecting the planet’s oceans has increased sharply, killing swathes of sea-life like wildfires on land that take out huge areas of forest. The damage caused in these hotspots is also harmful to humanity, which relies on the oceans for oxygen, food, storm protection and the removal of climate-warming carbon dioxide the atmosphere.

2018 was the hottest year ever measured for the earth’s oceans.

The current rate of ocean warming is equivalent to five Hiroshima-size atomic bombs exploding every second.
Our Oceans broke heat records in 2018 and the consequences are catastrophic
(The Guardian: 16 Jan 2019)

Updated 11 March 2019