At the end of the melting season, in September, sea ice coverage in the Arctic is normally at its lowest. After a record low maximum in March, the extent of sea ice is now in 10th place since the start of measurements. For about 20 years, Arctic sea ice has been declining much more slowly than before, especially in September. Climate models show that natural fluctuations in the climate can temporarily counteract the ongoing loss of sea ice in a warming climate.
Climate Models on the Pause
Recent research in Geophysical Research Letters shows that periods of reduced sea ice decline (as observed from 2007-2024, see figure 1) occur regularly in climate models. Namely, in about 20% of climate experiments that simulate the same period. This means that such a pause is not surprising; it is part of the normal natural variation in the climate.
According to climate simulations, it would not be unusual for the current pause in the decline of sea ice in the Arctic to last another 5 years (50% chance) to 10 years (25% chance). After that, melting will likely accelerate again and could increase sharply in a short time. It is quite possible that without the underlying climate warming, Arctic sea ice would have even grown.
Natural Variability
Natural fluctuations in the climate system can cause temporary changes, such as in the sea ice coverage of the Arctic, independent of climate warming due to human influence. These fluctuations are referred to as natural variability. Mechanisms that cause this include periods when certain ocean currents or wind patterns temporarily slow down the melting of sea ice. Since 2007, an Arctic dipole in air pressure seems to redistribute fresh water from Siberian rivers differently across the ocean. Because fresh water floats on top of salty seawater, it prevents the upper layer of the ocean from mixing and makes it easier for sea ice to form.