More than 90 percent of the extra energy that remains in the atmosphere due to greenhouse gases ends up in the sea. There, the warming has major consequences: the warmer water causes stronger storms and more expansion of the sea.
Since the 1990s, the heat content of the oceans has risen sharply, according to figures that two science teams, from China and the US, announced on Wednesday. The sea is also being disturbed in other ways: for example, the oceans are becoming more divided into separate layers, which means that the upper few kilometers of seawater can heat up extra hard.
Disruption of sea currents
In addition, saline areas are becoming saltier, and non-saline areas less salty, according to the Chinese research team. This can have consequences for the species that live there and thus have an impact on fisheries, among other things. Another problem is that large ocean currents can be disturbed. These now provide, for example, the supply of heat to Europe.
A ‘zetajoule’ is about a trillion joules, the measure of energy. The amount of energy that is added to heat in the sea every year is about 100 times the world’s electricity production – with these kinds of comparisons scientists try to make that enormous number somewhat comprehensible.
“The oceans absorb most of the warming from human carbon emissions,” said Michael Mann, the leader of the US research team, in a media statement. “Until we get to net-zero emissions, that warming will continue, and we will continue to break records in ocean heat content.”