The warming of the Arctic has a major impact both locally and on the climate as a whole. The decline of Arctic sea ice is one of the most striking consequences of the ongoing global warming. The latest version of the global climate models in the major collaborative initiative for global climate modelling, CMIP6, shows that Arctic sea ice will on average disappear during summer in 2061. But there are large differences between models. Some climate models show that sea ice will remain in summer throughout the century, in other models it will melt much earlier.
“When we sort out the climate models that are not as good at reflecting the processes that we know are crucial for sea ice, we can show that sea ice disappears much faster than what the average of all climate models shows. As early as around 2035, the Arctic could be ice-free in summer if we have a fossil-fuelled societal development with high greenhouse gas emissions,” says David Docquier, former climate researcher at SMHI's Rossby Centre, now at the Royal Meteorological Institute of Belgium.
Based on the same method and if society instead moves towards a more sustainable development with less greenhouse gas emissions, sea ice could remain a little more. However, even in the low-emission scenario, sea ice area would be strongly reduced until 2050 with a risk for a complete disappearance in summer, but there is also about a chance for the sea ice cover to remain at a low level, 1-2 million km2, compared to about 4 million km2 today.
A sea ice cover of 1 million km2 in September, at the end of the melting season, is usually used as a criterion for ice-free Arctic, then there is no major contiguous area with ice left. Still, scattered areas of ice can mainly be found along the north coast of Canada and Greenland.
Both atmosphere and ocean heat affect sea ice
The Arctic sea ice cover is affected both by the atmosphere and ocean. Traditionally, studies of Arctic sea ice have been based on sea ice area or volume measured by satellites since 1979 and computed by climate models. In the new study, the researchers selected the climate models which best represent the observed development and, at the same time, best reflected the northward Atlantic and Pacific ocean heat transport and present Arctic sea ice, to study the future development for sea ice.
“The latter is a new approach and we can see that it shows a faster melting than the common approach to use all models available. It is important that we in our research constantly develop our methods when we build knowledge about future climates and this is a new way to use results from the global climate models to create new knowledge,” says Torben Königk, responsible for global climate modelling at SMHIs Rossby Centre.
The study is based on results from the global climate models included in the global collaborative initiative CMIP6, where SMHI has contributed with climate simulations with the EC-Earth model. The researchers have studied the development of Arctic sea ice in the climate scenarios SSP5-8.5, describing a continued fossil-fuelled society with high greenhouse gas emissions and a global average temperature in 2100 which is about 4 degrees higher relative to the years 1995-2014, and SSP1-2.6, which represents a sustainable societal development with low greenhouse gas emissions and with a global average temperature in 2100 which is about 1 degree higher relative to the years 1995-2014.
The research was peer-reviewed and published in the scientific journal Communications Earth & Environment in July 2021.