Melting Arctic sea ice during the summer of 2018

Date:
July 29, 2020
Source:
Cell Press
Summary:
A study details the changes that occurred in the Arctic in September
of 2018, a year when nearly 10 million kilometers of sea ice were
lost throughout the summer. Its findings give an overview of how
sea ice has receded over the 40 years of the satellite era and show
how the summer's extensive decline is linked to global atmospheric
processes as far south as the tropics.



FULL STORY ==========================================================================
As sea ice in the Arctic retreats further and melts faster every decade, scientists are racing to understand the vulnerabilities of one of the
world's most remote and unforgiving places. A study appearing July 29 in
the journal Heliyon details the changes that occurred in the Arctic in September of 2018, a year when nearly 10 million kilometers of sea ice
were lost over the course of the summer. Their findings give an overview
at different timescales of how sea ice has receded over the 40 years of
the satellite era and show how the summer's extensive decline is linked
to global atmospheric processes as far south as the tropics.


==========================================================================
At the peak of its melting season, in July 2018, the Arctic was losing
sea ice at a rate of 105,500 square kilometers per day -- an area bigger
than Iceland or the state of Kentucky. "On the ground, I am sure it would
have looked like an excellent summer month in the Arctic, in general,
but over the past four decades, September sea-ice loss has accelerated
to a rate of 12.8% per decade and 82,300 square kilometers per year,"
says co-author Avinash Kumar, a senior scientist at the National Centre
for Polar and Ocean Research (NCPOR) in India.

The researchers followed the warm water currents of the Atlantic north
to the Arctic Ocean and tracked the ice as it subsequently retreated
through the Chukchi, East Siberian, Laptev, Kara, and Barents seas. Thanks
to higher temporal resolution and greater satellite coverage than had previously been available, they could also measure the ice's decline
through variables such as its thickness, concentration, and volume in
addition to its extent throughout the Arctic. This dramatic loss of
sea ice culminated at the end of the boreal summer, when in September,
the ice had been reduced to a mere third of its winter extent.

Then, the team compared the decline to the previous four decades of
data. "In the summer of 2018, the loss of sea ice was three times
higher than the reported loss at the beginning of the satellite era,"
says Kumar. "Our study shows that both the minimum sea-ice extent and
the warmest September records occurred in the last twelve years." "Every
year, news pops up of a new record of high temperature or fastest loss of
sea ice in the Arctic region, but in the global system, each portion of
the planet receiving climate feedback will lead to changes in the other
parts as well," Kumar says. "If the sea-ice decline continues at this
pace, it can have a catastrophic impact by raising air temperatures and
slowing down global ocean circulation." These global impacts are partly
why he became interested in trying to decipher the mysteries of the polar regions as a doctoral student studying the coastal zone in India. Now,
he works at NCPOR, whose scientific programs, he says, are "truly trans-hemispheric, cutting across from north to south." The researchers
also turned their attention to the atmosphere, where they were able to
gain insight into the processes that contribute to the loss of Arctic sea
ice. They found not only that September of 2018 was the third warmest on record, but that there was a temperature difference within the Arctic
itself: the temperature of the air above the Arctic Ocean (~3.5DEGC)
was slightly higher than that of the Arctic land (~2.8DEGC).

Their findings provide further evidence that ocean warming around the
globe has influenced the natural cycle of the wind and pressure patterns
in the Arctic.

El Nin~os, or warm phases in long-term temperature cycles stemming from tropical regions, have long been known to drive extreme weather events
around the world and are occurring with greater frequency as the world
warms. El Nin~o cycles in the equatorial Pacific Ocean can carry warm
air and water from tropical circulations to the Arctic, spurring the sea
ice to melt. As the ice retreats, it cascades the Arctic into a positive feedback loop known as Arctic amplification, whereby the reduced ice
extent gives way to darker ocean waters that absorb more of the sun's radiation. As it retains more heat, temperatures rise and more ice melts, causing the Arctic region to heat up faster -- about four times so --
than the rest of the world.

"If the decline of sea ice continues to accelerate at a rate of 13%
per decade in September, the Arctic is likely to be free of ice within
the next three decades," Kumar says. And just as sea-ice retreat is
largely the result of anthropogenic pressures from across the globe,
its impacts will be felt worldwide: this work adds to the mounting body
of evidence that changes in the Arctic sea ice could be detrimental to
weather patterns spanning the globe. He says, "The changes taking place in
the Arctic can lead to other changes in lower latitudes, such as extreme weather conditions. The world should be watching tropical countries like
India, with our research center saddled close to the beaches of Goa,
and trying to understand -- even in a small way -- more about climate
change and the polar regions." This work was supported by the National
Centre for Polar and Ocean Research, Goa, the Ministry of Earth Science,
New Delhi, and the University Grants Commission, New Delhi.


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


========================================================================== Journal Reference:
1. Kumar et al. Global warming leading to alarming recession of
the Arctic
sea-ice cover: Insights from remote sensing observations and model
reanalysis. Heliyon, 2020 DOI: 10.1016/j.heliyon.2020.e04355 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200729114844.htm

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