Shutdown of Thermohaline Circulation (Semper Idem)

The Shutdown of Thermohaline Circulation was a major effect of global warming on ocean currents and temperatures.

The Atlantic Meridional Overturning Circulation, or AMOC, as well as other ocean current systems, were severely affected by melting Arctic ice, which would decreased temperature and salinity levels within the North Atlantic by significant amounts. While the effect did slowdown thermohaline circulation to such an extent that notable changes were observed, the name is inaccurate as the entire system did not shutdown entirely.

History
A 2015 study suggested that the AMOC weakened by 15-20% in the past 200 years, and was one of the first major studies to suggest thermohaline circulation. Another study from NOAA in 2026 reinforced this claim, with predictions of a 40% slowdown between 2022-2050, based on the current rate of salinity.

However, most governments and organizations did not take the shutdown into account during climate change plans, as it was relatively minor compared to more severe changes, such as droughts and flooding.

Effects
See also: European Cool Period

The shutdown changed worldwide weather patterns throughout the 2040s, and did nullify some effects of climate change, while amplifying others. More frequent El Niño events were noted due to slowdowns in the East Australian and Kuroshio currents, as well as warming in the tropics and the Arctic.

The most pronounced effects, however, was the sudden drop in temperature in Europe, as it stopped receiving warm water from the Gulf Stream, leading to colder weather patterns. This is the direct cause of the 2053 European Famine, and is partly responsible for ending World War III.