A team of international researchers monitoring the impact of climate change on large rivers in Arctic Canada and Alaska have determined that, as the region is sharply warming up, its rivers are not moving as scientists have expected.
Their findings, says Dr. Alessandro Ielpi from UBC, were a bit surprising. “The western Arctic is one of the areas in the world experiencing the sharpest atmospheric warming due to climate change,” he says. “Many northern scientists predicted the rivers would be destabilized by atmospheric warming. The understanding was that as permafrost thaws, riverbanks are weakened, and therefore northern rivers are less stable and expected to shift their channel positions at a faster pace.”
This assumption of faster channel migration due to climate change has been prevalent in the scientific community for decades. “”But the assumption had never been verified against field observations,” he said.
To test this assumption, Dr. Ielpi and his team analyzed a collection of time-lapsed satellite images – going back more than 50 years. They compared more than one thousand kilometers of riverbanks from 10 Arctic rivers in Alaska, the Yukon and Northwest Territories.
“We tested the hypothesis that large sinuous rivers in permafrost terrain are moving faster under a warming climate and we found exactly the opposite,” he said. “Yes, permafrost is degrading, but the influence of other environmental changes, such as greening of the Arctic, counteracts its effects. Higher temperatures and more moisture in the Arctic mean the region is greening up. Shrubs are expanding, growing thicker and taller on areas that were previously only sparsely vegetated.”
The growing vegetation along the riverbanks means the banks have become more stable.
“Scientific thinking often evolves through incremental discoveries, although great value lies in disruptive ideas that force us to look at an old problem with new eyes,” said Dr. Ielpi. “We sincerely hope our study will encourage landscape and climate scientists elsewhere to re-evaluate other core assumptions that, upon testing, may reveal fascinating and exciting facets of our ever-changing planet.”
https://phys.org/news/2023-03-arctic-river-channels-due-climate.html