A research team from the Northwest Institute of Eco-Environment and Resources (NIEER) of the Chinese Academy of Sciences (CAS), in collaboration with Beijing Normal University and the University of Chinese Academy of Sciences, found that summer rainfall in the Arctic would increase by about 17% under 2°C global warming, approximately 16% of which is attributed to sea ice retreat. The related paper was published in Geophysical Research Letters. 

As global warming continues to intensify, the Arctic, one of the most affected regions, is warming at a rate more than four times the global average. Arctic sea ice, one of the 16 global climate “tipping points”, is experiencing rapid retreat. 

The melting of sea ice not only weakens the “white cold cap” effect that reflects solar radiation, but also exposes a darker sea surface with a stronger heat absorption capacity, pushing the Arctic water cycle pattern to shift from “snow-dominated” to “rain-dominated”. 

This change has a significant impact on the retreat of Arctic glaciers, the melting of permafrost, runoff processes and ecosystem balance, and has a domino effect on global sea level rise and extreme climate events.

It is understood that the research team has successfully achieved precise attribution of the impact of sea ice melting on Arctic land precipitation by innovatively combining the large-sample ensemble simulations from the Polar Amplification Model Intercomparison Project (PAMIP) and the Coupled Model Intercomparison Project (CMIP), and by separating the climate responses to “total forcing” and “only sea ice forcing”.

“Liquid precipitation will further accelerate the sea ice retreat, not only forcing animals such as polar bears and reindeer that rely on sea ice and snow for food or shelter to face survival crises, but also altering the thermal conditions of the soil, intensifying permafrost thawing and subsequently releasing greenhouse gases, creating another feedback loop that drives global warming,” said Yang Jiao, an associate researcher at the NIEER.

The study further reveals that the contribution rate of sea ice retreat to increased rainfall even exceeds 30% in the Arctic coasts of Siberia and North America, forming two distinct rainfall enhancement belts.

The research also indicated that nearly 70% of the increased rainfall caused by the retreat of sea ice is attributed to the warming effect resulting from sea ice melting, which means that higher temperatures turn what should have been snowfall into rainfall. Another 30% is due to evaporation over open water areas, which increases water vapor in the air and increasing total precipitation.

“This study not only deepens our understanding of the warming and humidification processes in the Arctic, but also establishes a quantitative relationship model of ‘sea ice-precipitation’, providing a powerful tool for enhancing the prediction capability of extreme weather and climate events in the Arctic,” said YANG.