One of the robust features of global warming under increasing greenhouse gas concentrations is that different places warm at different paces.
One of the robust features of global warming under increasing greenhouse gas concentrations is that different places warm at different paces.
Observations had already shown that the Earth’s surface warms fastest in the polar regions and slowest in the tropics. On the other hand, observations and model results had revealed that the ocean warms fastest over midlatitudes and the Arctic (Levitus et al. 2012, Wu et al. 2012, Armour et al. 2016).
Indeed, the pattern of ocean warming is not quite the same as the pattern of atmospheric warming. What is causing the ocean warming to follow a different pattern than the atmospheric warming, and how are the two linked?
We set out to answer these questions by exploring climate model simulations over the ongoing century. We started out by constructing a heat budget for the global ocean in the Norwegian Earth System model (NorESM), a fully coupled ocean-atmosphere model used in Norway. The model results clearly agreed with the observational data; the ocean was warming fastest in the midlatitudes and in the Arctic.
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Image: Temperature change per decade in the air (left) and the surface of the ocean (right) between 2005 and 2100, as projected by the Norwegian Earth System model under a strong emission scenario (RCP8.5). Notice the rapid ocean warming at around 40S, 40N, and in the Arctic, in contrast to the surface atmospheric warming mainly in the Arctic. (Credit: Aleksi Nummelin)
