Arctic river channels changing due to climate change
Migration pace of large rivers in permafrost regions

Date:
March 9, 2023
Source:
University of British Columbia Okanagan campus
Summary:
A team of international researchers have found that the rivers in
Arctic Canada and Alaska are not behaving as expected in response
to the warming climate. The study focused on large rivers in
the region and their movement through permafrost terrain. Their
findings highlight the impact of atmospheric warming on these
vital waterways.


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FULL STORY ==========================================================================
A team of international researchers monitoring the impact of climate
change on large rivers in Arctic Canada and Alaska determined that, as
the region is sharply warming up, its rivers are not moving as scientists
have expected.


==========================================================================
Dr. Alessandro Ielpi, an Assistant Professor with UBC Okanagan's Irving K.

Barber Faculty of Science, is a landscape scientist and lead author
of a paper published this week in Nature Climate Change. The research, conducted with Dr.

Mathieu Lapo^tre at Stanford University, along with Dr. Alvise Finotello
at the University of Padua in Italy, and Universite' Laval's Dr. Pascale
Roy- Le'veille'e, examines how atmospheric warming is affecting Arctic
rivers flowing through permafrost terrain.

Their findings, says Dr. Ielpi, 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 owing to climate change has dominated the scientific community for decades.

"But the assumption had never been verified against field observations,"
he adds.

To test this assumption, Dr. Ielpi and his team analyzed a collection of
time- lapsed satellite images -- stretching back more than 50 years. They compared more than a thousand kilometres of riverbanks from 10 Arctic
rivers in Alaska, the Yukon and Northwest Territories, including major watercourses like the Mackenzie, Porcupine, Slave, Stewart and Yukon.

"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 says. "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." This growing and robust vegetation
along the riverbanks means the banks have become more stable.

"The dynamics of these rivers reflect the extent and impact of global
climate change on sediment erosion and deposition in Arctic watersheds,"
Dr. Ielpi and his colleagues write in the paper. "Understanding the
behaviour of these rivers in response to environmental changes is
paramount to understanding and working with the impact of climate warming
on Arctic regions." Dr. Ielpi points out that monitoring riverbank
erosion and channel migration around the globe is an important tool
that should be widely used to understand climate change. As part of
this research, a dataset of rivers found in non- permafrost regions and representative of warmer climates in the Americas, Africa and Oceania
was also analyzed. Those rivers migrated at rates consistent with what
was reported in previous studies, unlike those in the Arctic.

"We found that large sinuous rivers with various degrees of permafrost distribution in their floodplains and catchments, display instead a
peculiar range in migration rates," says Dr. Ielpi. "Surprisingly,
these rivers migrate at slower rates under warming temperatures."
The time-lapse analysis shows that the sideways migration of large
Arctic sinuous rivers has decreased by about 20 per cent over the last half-century.

"The migration deceleration of about 20 per cent of the documented Arctic watercourses in the last half century is an important continent-scale
signal.

And our methodology tells us that 20 per cent may very well be a
conservative measure," he says. "We're confident it can be linked to
processes such as shrubification and permafrost thaw, which are in turn
related to atmospheric warming.

"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," states 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."
* RELATED_TOPICS
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# Climate # Global_Warming # Environmental_Issues #
Environmental_Awareness # Tundra # Geography # Water #
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o Estuary

========================================================================== Story Source: Materials provided by University_of_British_Columbia_Okanagan_campus. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Alessandro Ielpi, Mathieu G. A. Lapo^tre, Alvise Finotello,
Pascale Roy-
Le'veille'e. Large sinuous rivers are slowing down in a warming
Arctic.

Nature Climate Change, 2023; DOI: 10.1038/s41558-023-01620-9 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/03/230309125031.htm

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