Arctic sea ice loss drives drier weather over California and wetter over Spain and Portugal
A new modelling study isolates the effect of Arctic sea ice melting from other factors
· ScienceDaily| Source: | Barcelona Institute for Global Health (ISGlobal) |
| Summary: | On decadal timescales, the loss of Arctic ice favors the climate of the south-west of the United States — and California in particular — becoming drier on average, especially in winter. This phenomenon would also affect the climate of Spain and Portugal, favoring conditions of higher humidity in winter, although in this case the observed effect is weaker. |
A study led by researchers from the Barcelona Institute for Global Health (ISGlobal), a centre supported by the "la Caixa" Foundation, has used a novel approach to unravel the influence of the loss of Arctic sea ice on the planet's climate, isolating it from other factors related to climate change.
The study, published in the journal Communications Earth and Environment, shows that on decadal timescales, the loss of Arctic ice favours the climate of the south-west of the United States — and California in particular — becoming drier on average, especially in winter. This phenomenon would also affect the climate of Spain and Portugal, favouring conditions of higher humidity in winter, although in this case the observed effect is weaker.
'There is much scientific disagreement about the remote effects of Arctic sea ice loss. So far, many studies have focused on the long-term effects, on a scale of centuries. Others have investigated the response to sea ice loss with modelling setups that artificially impose heat to melt the sea ice, potentially affecting the simulated response. Some studies have been changing Antarctic and Arctic sea ice cover at the same time, making it difficult to discern their individual contributions. In our study, we have developed a methodology to assess the impact of Arctic ice loss without adding any heat fluxes, and we focused on the impacts developing within a few decades,' explains Ivana Cvijanovic, ISGlobal researcher and lead author of the study.
To reach these conclusions, the team used three models of varying complexity. In each of them, they ran two sets of simulations, one with the historical amount of sea ice in the Arctic and one with substantially decreased sea ice cover.
The disappearance of sea ice changes the surface albedo, i.e. the reflectivity of the Arctic Ocean, but also removes the insulation between the atmosphere and the ocean surface and affects salinity profiles. These local changes in turn drive a variety of atmospheric and oceanic teleconnections that can propagate far from the Arctic.
'It should be made clear that the conclusion is not necessarily that it will rain less in California and more in the Western Mediterranean in the coming years. In addition to the ice cover loss in the Arctic, there are many other factors responding to greenhouse gas emissions and affecting the climate (atmospheric and oceanic feedbacks and circulation changes, Antarctic sea ice loss, vegetation feedbacks, etc.). In any case, understanding the influence of this phenomenon separately will help us to refine global predictions,' says Desislava Petrova, ISGlobal researcher and last author of the study.
Despite all the different influences in our planet's climate system, it is interesting to note that the anomalies in the atmospheric circulation patterns of the last few decades show some striking similarities to the patterns simulated in our study — especially events such as the Californian drought of 2012-2016,' observes Ivana Cvijanovic.