Antarctic sea ice is ‘astonishingly’ low this melt season

Right now, on the shores of Antarctica, there’s open water
crashing against the largest ice shelf in the world. The annual
ice-free season has begun at the Ross Ice Shelf — a month ahead
of schedule.

The frozen region
of freshwater ice
the size of France partially protects the
West Antarctic Ice Sheet from collapsing into the sea. In recent
years, the ice-free season in the Ross Sea has become a routine
event — but it happened this year on New Year’s Day, the
earliest time in history.

“Antarctic sea ice extent is astonishingly low this year, not
just near the Ross Ice Shelf, but around most of the continent,”
says Cecilia Bitz, a polar scientist at the University of
Washington.

In recent years, scientists have
set up seismic monitoring stations on the ice shelf
to track
the wave energy as it percolates inland, potentially causing stress
fractures on the Ross Ice Shelf along the way.

Bitz pointed to low ice concentration also happening right now
in the Amundsen Sea, more than 1,000 miles away from Ross, and
that’s potentially even more worrying. In a
worst-case scenario
, with continued business as usual
greenhouse gas emissions, ice shelves all across West Antarctica
could collapse within decades, melted from above and below and
shattered by wave action.

After that, it would probably be just a matter of time before
West Antarctica’s massive land-based glaciers, like
the “Doomsday glaciers” at Thwaites and Pine Island
,
collapse as well, sending sea levels upward by as much as 10 feet
and flooding every coastal city on Earth.

Sea ice concentration on
January 1, 2019. The Ross Sea is on the lower edge of West
Antarctica and Amundsen is north and near this map’s West
Antarctica labeling. National Snow & Ice Data Center

Across the entire continent, there are more than 750,000 square
miles of sea ice missing, a record
deficiet for this time of year
. Because it’s approaching
mid-summer in the Southern Hemisphere, Antarctica will keep
shedding sea ice
for about another six weeks or so, and is
currently on pace to drop far below the all-time record low set in
2016.

The North Pole and South Pole are both very cold, of course, but

they couldn’t be more different
in how climate change is
affecting them.

The Arctic is an ocean fringed by cold continents, and has
already passed a tipping point. Sea ice there has been declining
sharply for decades
— so much so that about a year ago,
scientist declared
the start of a “New Arctic,”
with conditions likely unseen
in at least 1,500 years, and
probably much, much longer
.

Owing to its unique geography (a cold continent fringed by a
relatively warmer ocean), sea ice in the Antarctic region has long
been considered something of a climate wildcard. A sharp decline in
the Antarctic began only two years ago, and scientists
aren’t sure yet if it will continue
. If 2019 and the rapidly
warming Southern Ocean is any indication, it will.

This story was originally published by Grist with the headline
Antarctic sea ice is ‘astonishingly’ low this melt season

on Jan 3, 2019.

Source: FS – All – Science – News
Antarctic sea ice is ‘astonishingly’ low this melt season