Warming shapes Arctic river systems

2023-09-12 17:45:31

MADRID, 12 Sep. (EUROPA PRESS) –

Amplified global warming in the Canadian High Arctic has driven a profound change in the structure of an excavated river network in a permafrost landscape in just 60 years.

By documenting a powerful interaction between climate change, polygonal soil freeze-thaw dynamics, and surface water supply through flooding, as well as melting snow and ice, a team of researchers has developed a new view of the physical controls that govern the speed and development of river channel patterns in these fragile landscapes.

“One of the key processes we identified in the evolution of stream networks is that their development is influenced by the way water flows through fields of polygons approximately 10 meters wide, created through freezing and thawing of the soil in the Arctic regions,” says it’s a statement Shawn Chartrand, assistant professor in the School of Environmental Sciences at Simon Fraser University and lead author of the research published in Nature Communications.

“This influence is also affected by the timing, magnitude and duration of floods.as well as whether the underlying sediment particle substrates are frozen or partially frozen.”

Chartrand is part of an international research team that arrived on the uninhabited island of Axel Heiberg at the beginning of one of the most intense summer warming events ever recorded. Her field research focused on the island’s Muskox Valley, east of the Muller Ice Sheet. The researchers combined aerial photographs from 1959 with field observations and state-of-the-art light detection and ranging (LiDAR) data they collected in 2019. to understand how the landscape of Axel Heiberg Island has evolved over a period of 60 years.

“Interconnected physical processes can deepen river channels and expand river networks, creating more surface area for heat exchange, which can increase local rates of permafrost thaw,” says study co-author Mark Jellinek, professor of Earth, Ocean and Atmospheric Sciences at the University of British Columbia. “These cascading effects can enhance the release of greenhouse gases in the Arctic as soil organic carbon melts and permafrost recedes.”

Using the LiDAR data, the team produced a digital elevation model (DEM) of a 400-meter section of the valley. “Through modeling how water moves through the landscape, we found that flood waters channeled through interconnected polygonal channels increase the likelihood of erosion and channel development,” says Chartrand.

Valley lake flooding and seasonal melting of snowpack and land ice provide water that merges down the valley, setting the conditions for the transport of coarse sediments and the development of channel networks along the valley floor. . However, the timing of flooding during peak snowmelt can influence the amount of erosion that occurs.

“This is where the increase in air temperature influences,” he explains. “We predict that erosion and sediment transport are sensitive to whether flooding occurs before or after a period of elevated air temperatures, because this influences the depth at which sediment particle substrates thaw and therefore so much, “affects whether particles are transported by flood waters.”

The researchers say the future challenge will be to apply this data to produce predictive physical models that help understand how Arctic river networks will evolve in the coming decades marked by warming and intensifying climate variability. They point to greater urgency, as the expansion of river networks will transport greater loads of sediment, as well as nutrients and metals, to fragile watersheds and fisheries, with potentially significant consequences for wildlife, waters and coastal populations.