More frequent atmospheric rivers hinder seasonal recovery of Arctic sea
ice

Date:
February 6, 2023
Source:
Penn State
Summary:
The Arctic is rapidly losing sea ice, even during winter months
when temperatures are below freezing and ice should be recovering
from the summer melt. A new study found powerful storms called
atmospheric rivers are increasingly reaching the Arctic in winter,
slowing sea ice recovery and accounting for a third of all winter
sea ice decline, according to a team led by Penn State scientists.


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FULL STORY ==========================================================================
The Arctic is rapidly losing sea ice, even during winter months when temperatures are below freezing and ice should be recovering from the
summer melt. A new study found powerful storms called atmospheric rivers
are increasingly reaching the Arctic in winter, slowing sea ice recovery
and accounting for a third of all winter sea ice decline, according to
a team led by Penn State scientists.


========================================================================== "Arctic sea ice decline is among the most obvious evidence of global
warming from the past several decades," said Pengfei Zhang, assistant
research professor of meteorology and atmospheric science at Penn
State and lead author of the study. "Despite temperatures in the
Arctic being well below freezing, sea ice decline in winter is still
very significant. And our research shows atmospheric rivers are one
factor in understanding why." Atmospheric rivers carry large amounts
of water vapor in narrow, ribbon-like storm systems that can stretch
for a thousand miles and produce extreme rainfall and flooding when they
make landfall. These storms regularly impact midlatitude coastal regions
like California, where atmospheric river events in January, for example, dropped 11 inches of rain.

Using satellite observations and climate model simulations, the scientists found these storms are increasingly reaching the Arctic -- particularly
the Barents and Kara seas off the northern coasts of Norway and Russia -- during the winter ice-growing season. They reported their findings Monday,
Feb. 6, in the journal Nature Climate Change.

"We often think that Arctic sea ice decline is a gradual process due to
gradual forcings like global warming," said L. Ruby Leung, Battelle Fellow
at Pacific Northwest National Laboratory, and a co-author. "This study
is important in that it finds sea ice decline is due to episodic extreme weather events - - atmospheric rivers, which have occurred more frequently
in recent decades partly due to global warming." Warm moisture carried
by these storms increases downward longwave radiation, or heat emitted
back to Earth from the atmosphere, and produces rain, both of which can
melt the thin, fragile ice cover regrowing during the winter months.

Using satellite remote sensing images, the scientists observed sea ice
retreat almost immediately following atmospheric river storms and saw
the retreat persisted for up to 10 days. Because of this melting and
because the storms are becoming more common, atmospheric rivers are
slowing down seasonal sea-ice recovery in the Arctic, the scientists said.

"When this kind of moisture transport happens in the Arctic, the
effect is not only the amount of rain or snow that falls from it,
but also the powerful melting effect on the ice," said Mingfang Ting,
a professor at Lamont-Doherty Earth Observatory, Columbia University
and a co-author. "This is important since we are losing Arctic sea ice
fast in the past few decades that brought many unwanted consequences
such as Arctic warming, erosion of Arctic coastlines, disturbance to
global weather patterns and disruption to the Arctic communities and ecosystems." The loss of Arctic sea ice has broad implications, the
scientists said. Open waters may enable new, more direct shipping routes
but also trigger geopolitical concerns between countries. Additionally, freshwater melting into the salty ocean may impact oceanic circulations patterns that stabilize global temperatures.

"Those factors make this study especially important from a science
perspective, but also from social and security perspectives, said Laifang
Li, assistant professor of meteorology and atmospheric science at Penn
State and a co-author.

"Sea ice melting has a big impact for the climate system and for society,
and our study finds the Arctic is an open system and that climate change
is way more complicated than temperature change alone can explain."
Using large-ensemble climate models, the scientists determined that human- induced warming has increased the rate of atmospheric river storms in
the Arctic. But they also found that one major mode of natural climate variabilities -- the so-called Interdecadal Pacific Oscillation --
also contribute to atmospheric river changes.

"This study, together with other work that noted the presence of
atmospheric rivers in the tropics, highlights that atmospheric rivers
represent a global phenomenon," said Bin Guan, Earth systems scientist at
the University of California, Los Angeles and Jet Propulsion Laboratory, California Institute of Technology. "Since they were discovered relatively recently -- in the 1990s, and even more recently in terms of recognizing
their societal impacts - - atmospheric rivers provide an opportunity for potentially coordinated research and applications globally, that is, with today's computational and technological capabilities." Also contributing
to this research was Gang Chen, professor at the University of California,
Los Angeles.

Researchers involved on this project received support from the National
Science Foundation, NASA and the Department of Energy.

* RELATED_TOPICS
o Earth_&_Climate
# Climate # Global_Warming # Atmosphere # Geography #
Snow_and_Avalanches # Weather # Ice_Ages # Severe_Weather
* RELATED_TERMS
o Ice_shelf o Greenland_ice_sheet o Ice_sheet o Sea_level o
Winter_storm o Antarctic_ice_sheet o Polar_Bear o Arctic_Circle

========================================================================== Story Source: Materials provided by Penn_State. Original written by
Matthew Carroll. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Pengfei Zhang, Gang Chen, Mingfang Ting, L. Ruby Leung, Bin Guan,
Laifang
Li. More frequent atmospheric rivers slow the seasonal
recovery of Arctic sea ice. Nature Climate Change, 2023; DOI:
10.1038/s41558-023-01599-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/02/230206130632.htm

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