Rivers speeding up Arctic ice melt at alarming rate

Date:
January 18, 2022
Source:
University of Arizona
Summary:
Freshwater flowing into the Arctic Ocean from the continent is
thought to exacerbate Arctic amplification, but the extent of its
impact isn't fully understood. New research measures how the flow
of the Yenisei River - - the largest freshwater river that flows
into the Arctic Ocean -- has changed over the last few hundred
years, and describes the impact freshwater has had on the Arctic.



FULL STORY ========================================================================== Irina Panyushkina grew up in Siberia, near the Arctic Circle. She was
raised on stories of explorers trudging through seas of ice to reach
the North Pole.


==========================================================================
Now, she is a climate scientist and associate research professor of dendrochronology in the University of Arizona Laboratory of Tree-Ring
Research.

And she is trying to understand how a warming world is transforming the
place she once called home.

Someday, the Arctic Ocean may no longer host ice, since the northern
regions of the world are warming are faster than the rest -- a trend
scientists refer to as Arctic amplification. As Arctic ice melts, new opportunities and challenges for humans will arise, researchers say.

Freshwater flowing into the Arctic Ocean from the continent is thought
to exacerbate Arctic amplification, but the extent of its impact isn't
fully understood. New research led by Panyushkina measures how the
flow of the Yenisei River -- the largest freshwater river that flows
into the Arctic Ocean -- has changed over the last few hundred years,
and describes the impact freshwater has had on the Arctic.

Previous studies have attributed recent changes in wintertime freshwater
flow into the Arctic to warming air temperature, seasonal precipitation
changes or snowpack. But more recent research, including Panyushkina's
study, suggests that the primary driver is actually degradation
of permafrost -- or frozen ground -- as well as forest fires across
southern Siberia.

Panyushkina's research, funded by the National Science Foundation Polar
Office, is published in the journal Environmental Research Letters.



==========================================================================
What trees can tell us Data collected by instruments at the upper reaches
of the Yenisei River in Tuva, in southern Siberia, only goes back so
far. To overcome this, Panyushkina and her team used tree-ring data
to double the number of years' worth of the stream flow data they had,
allowing them to look back 300 years.

Stream flow, or the amount of water that moves through a certain area
of a river over time, can be inferred by measuring changing tree-ring
thickness over the years. Measurements of stream flow over specific
seasons can even be teased out of the data.

Annual stream flow information is commonly used by water managers to
reveal the average changes in stream flow trends. But Panyushkina and
her team did something novel when they decided to also investigate winter stream flow specifically.

"We found an unprecedented increase in the winter flow rate over the
last 25 years," Panyushkina said. This winter flow rate is nearly 80%
above the average seen over approximately 100 years.



==========================================================================
"In contrast, annual flow fluctuated normally during the 300-year period,
with only a 7% increase over the last 25 years," Panyushkina said.

The winter stream flow data revealed the role of permafrost melt on
Arctic ice.

Since ice covers rivers during winter in Siberia, the team's stream
flow measurements only captured information about river waterthat
originated underground rather thanfrom the sky. That includes water
from thawing permafrost, as well as water from sub-permafrost aquifers,
as permafrost loss leads to an increased exchange of water between the
river and aquifers. These two sources of groundwater are warm compared
to the frigid air above, and when they eventually flow into the Arctic
Ocean, they melt the ice.

An uncertain future Forest fires are also thought to be a driver of
Arctic ice melt.

"We know the frequency and intensity of forest fires in Siberia have
been increasing," Panyushkina said. "When fires happen in forests
with permafrost, there is deep thawing under the fire event, and the
affected area often doesn't recover for up to 60 years. When we have large-scale fires and long-burning fires and more frequent fires, we're
maybe hitting the critical point when permafrost degradation cannot
return to normal. Forest fires are also another process that increases connectivity between aquifers and stream flow." The combined effects of permafrost degradation and fires are very strong at the Yenisei River
basin, with more fresh water and heat flowing into the Arctic Ocean in
recent decades, according to the study. In turn, melting sea ice also exacerbates global warming.

"Research interest in the region is booming because the surface
temperature is warming much faster here than anywhere else in the world," Panyushkina said.

"It's a hot spot for climate research, and because I grew up there and understand how the system works, it's a natural topic of study for me. I'm
also very interested in knowing the impact of an ice-free Arctic on the surrounding landscape. Humans have never seen an ice-free Arctic before,
ever. My mind still cannot comprehend how the Arctic Ocean can be free
of ice." By the middle of the century, changing sea ice conditions are expected to lead to greater navigability for open water-vessels crossing
the Arctic. A future trans-Arctic shipping route called the Supra Polar
Route will link the Atlantic and Pacific Oceans through the Arctic,
potentially paving the way for more trans-Arctic commerce.

There is a need to quantify the Arctic amplification impacts to manage
and regulate Arctic seas of the future, Panyushkina said.

"This strong prospect of the global trade fleet entering the Arctic opens
the Pandora's box of near-future geopolitical and environmental issues and reinforces the urgency for a new regulatory framework by international organizations to ensure adequate environmental protections and vessel
safety standards," she said.

To understand more about Arctic amplification and its consequences,
Panyushkina and her team plan to study other rivers in Siberia.

"There are two more Siberian rivers similar in size to the Yenisei,"
she said.

"If we can quantify the stream flow from those rivers, we'll have
more precise and clear understanding of its impact on the Arctic." ========================================================================== Story Source: Materials provided by University_of_Arizona. Original
written by Mikayla Kelley. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Irina P Panyushkina, David M Meko, Alexander Shiklomanov, Richard D
Thaxton, Vladimir Myglan, Valentin V Barinov, Anna V Taynik.

Unprecedented acceleration of winter discharge of Upper Yenisei
River inferred from tree rings. Environmental Research Letters,
2021; 16 (12): 125014 DOI: 10.1088/1748-9326/ac3e20 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220118104146.htm

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