The world experienced record-breaking climate and weather disasters in 2021, from destructive flash floods to heat waves and wildfires. Also, under the surface, ocean temperatures set new heat records in 2021, which are a better indicator of how excess heat is accumulating on the planet.
As oceans warm, their heat turbocharges weather systems, creating more powerful storms and hurricanes, and more intense rainfall, which threatens human lives and livelihoods as well as marine life.
The oceans absorb about 93% of the extra energy trapped by the increasing gases from human activities, particularly burning fossil fuels. The warmer oceans also supply atmospheric rivers of moisture to land areas, increasing the risk of flooding.
Warmer oceans provide extra moisture to the atmosphere and the extra moisture fuels storms, especially hurricanes.
In the oceans, warm waters sit on top of cooler denser waters. However, the oceans warm from the top down, and consequently the ocean is becoming increasingly more stratified. This inhibits mixing between layers that would otherwise allow the ocean to warm to deeper levels and to take up carbon dioxide and oxygen. This impacts all marine life.
The study found that the top 500 meters of the ocean has clearly been warming since 1980; the 500-1000 meter depths have been warming since about 1990; the 1000-1500 meter depths since 1998; and below 1500 meters since about 2005.
This slow penetration of heat downward means that oceans will continue to warm, and sea level will continue to rise even after greenhouse gases are stabilized.
To monitor changes in the oceans, scientists are using the Argo array consisting of about 3900 floats that send back data on temperature and salinity from the surface to about 2000 meters in depth.