The annual river ice cover will decline by about six days for every one-degree Celsius increase in global temperatures, a new study by researchers from the University of North Carolina’s Chapel Hill Department of Geological Sciences found. This decline will have economic and environmental consequences.
The study, titled “The Past and Future of Global River Ice,” was published on Wednesday in the journal Nature. It is the first study to look at the future of river ice on a global scale.
More than half of Earth’s rivers freeze over every year. Those rivers support important transportation networks for communities and industries located at high latitudes. Ice cover also regulates the amount of greenhouse gasses released from rivers into Earth’s atmosphere.
“We used more than 400,000 satellite images taken over 34 years to measure which rivers seasonally freeze over worldwide, which is about 56% of all large rivers,” said Xiao Yang, a geological sciences postdoctoral scholar at UNC-Chapel Hill and lead author of the paper. “We detected widespread declines in monthly river ice coverage. And the predicted trend of future ice loss is likely to lead to economic challenges for people and industries along these rivers, and shifting seasonal patterns in greenhouse gas emissions from the ice-affected rivers.”
The team also looked at changes to river ice cover in the past, and modelled predicted changes for the future. Comparing river ice cover from 2008-2018 and 1984-1994, the team found a monthly global decline ranging from3 to 4.3 percentage points. The greatest declines were found in the Tibetan Plateau, Eastern Europe, and Alaska.
“The observed decline in river ice is likely to continue with predicted global warming,” the study explains.
For the future, the team compared expected river ice cover through 2009-2029 and 2080-2100. Findings showed monthly declines in the Northern Hemisphere ranging from 9-15% in the winter months and 12-68% during the spring and fall. The Rocky Mountains, north-eastern United States, Eastern Europe, and the Tibetan Plateau are expected to take the heaviest impact.
“Ultimately, what this study shows is the power of combining massive amounts of satellite imagery with climate models to help better project how our planet will change,” said UNC-Chapel Hill Associate Professor of Global Hydrology Tamlin Pavelsky.