Arctic sea ice melting linked to strong El Niño phenomena

Climate events such as The boya pattern in which warm waters of the eastern Pacific feed a warmer climate, could become even stronger due to melting Arctic sea ice.

Using a combination of climate model simulations and observational data, researchers from Nanjing and Albany Universities found that the current interaction of Arctic sea ice with the atmosphere reduces the strength of El Niño events by up to 17%, in compared to when the interaction is removed.

The amount of sea ice that survives the Arctic summer has declined by 12.2% per decade since the late 1970s and projections show the region could experience its first ice-free summer by 2040.

“Climate models are already projecting a strengthened El Niño in the coming decades due to global warming. “Arctic sea ice is also expected to decline rapidly in the coming decades.”Aiguo Dai, professor of Atmospheric and Environmental Sciences at the University at Albany, said in a statement. co-author of the study published in Science Advances,

“Our new study suggests that interactions between sea ice and Arctic air in the current climate significantly reduce the amplitude of the El Niño-Southern Oscillation, compared to the case without such interactions. “This represents a new example of the diverse impacts of Arctic sea ice on our planet’s climate.”.

To arrive at their findings, the researchers conducted and analyzed two global climate model simulations over 500 years using the National Center for Atmospheric Research (NCAR) Community Earth System Model. The simulations, run on a computer housed at the University at Albany Data Center, had fixed levels of atmospheric CO2, one with sea ice-air interactions in the Arctic and one without.

Examining the difference between the two simulations, the researchers found that Arctic sea ice-air interactions weaken El Niño-related variations in the tropical Pacific Ocean by 12 to 17%, compared to when the interaction was removed.

“The difference between the two model simulations represents the impact of Arctic sea ice-air coupling, which led to significant changes in the mean climate states of the tropical Pacific Ocean and in the strength of the El Niño-Southern Oscillation. This was mainly due to the asymmetric impacts of positive and negative sea ice anomalies on surface fluxes, the cross-surface heat exchange between the ocean and the atmosphere.said Jiechun Deng, associate professor at Nanjing University of Information Science and Technology and lead author of the study.

“Our findings highlight the crucial role of sea ice-air interactions in regulating El Niño activity in the tropical Pacific. “It requires a more realistic representation of such interactions in current climate models, to better project El Niño and its various impacts into a future warming climate.”

The observed historical changes in El Niño events from 1921-1960 (with strong sea ice-air interactions) to 1971-2000 (with weak interactions) were qualitatively consistent with the model results.