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Northeast Greenland Begins Ominous Collapse — Giant Zachariae Isstrom Most Recent to Destabilize
12
November, 2015:
North,
south, east, and west. At all points of the compass, the entire outer
edge of the Greenland Ice Sheet is flooding into the oceans with
increasing velocity. For NASA it’s the absolute worst kind
of OMG realization.
For the world’s warming oceans and airs are clearly worsening an
already visible Greenland melt. And
a new report just out of the University of California (Irvine) today
shows that a massive glacier containing enough water to raise seas by
more than 1.6 feet (0.5 meters) is the most recent of a growing
number of these ice giants to initiate a swift rush into the ocean.
Called
Zachariæ Isstrøm, this enormous glacier dominates a large section
of the northeast-facing shores of Greenland. The glacier, hundreds of
feet tall and plunging hundreds more feet below the ocean surface,
like many in our world, now faces the combined threat of warming airs
and waters. A double insult that, according to researchers, over the
past 15 years has led to first destabilization and then a rapid
seaward acceleration.
(1975
to 2015 time lapse shows recent rapid retreat of the Zachariæ
Isstrøm glacier’s front. The dark green line marks the 2003 extent
of the glacial front. Note the rapid retreat through 2015 in lighter
shades blending toward white. Image source: Jeremie
Mouginot/UCI via Climate
Central.)
According
to the new study — Fast
retreat of Zachariæ Isstrøm, northeast Greenland —
published today in Science, the glacier’s rate of seaward movement
has tripled in velocity even as the pace of ice thinning along its
grounding line doubled:
Warmer air and ocean temperatures have caused the glacier to detach from a stabilizing sill and retreat rapidly along a downward-sloping, marine-based bed… After 8 years of decay of its ice shelf, Zachariæ Isstrøm, a major glacier of northeast Greenland that holds a 0.5-meter sea-level rise equivalent, entered a phase of accelerated retreat in fall 2012. The acceleration rate of its ice velocity tripled, melting of its residual ice shelf and thinning of its grounded portion doubled, and calving is now occurring at its grounding line.
In
total, more than 4.5 billion tons of ice is now estimated to be
flooding out from this glacier and into the ocean each year. That’s
a mountain of ice about 4.5 cubic kilometers in size hitting the
world’s waters from just this single glacier every time the Earth
completes one circuit around the sun. In other words, Greenland
just opened a new floodgate to the North Atlantic.
Researchers publishing the study estimate that it will take between
20 and 30 years for the glacier to melt back to an underwater ridge
line that should somewhat slow its melt. But the real news here is
that a human-forced warming of the globe has set a monstrous pile of
ice, once thought stable, into a motion that will result in yet more
global sea level rise.
To
the north of Zachariæ Isstrøm sits the also melting
Nioghalvfjerdsfjorden. A giant of ice in equal volume to that of
Zachariæ. Nioghalvfjerdsfjorden sits on an upward sloping bed and so
is not as subject to rapid destabilization as Zachariæ. However, the
study found
that the combined total ice mass of both glaciers in the range of 1
meter worth of sea level rise was now involved in a significant melt
that would “increase
sea-level rise from the Greenland Ice Sheet for decades to come.”
(Map
of Greenland topography showing large sections of the interior
resting near or below sea level. As a result, warming waters have
numerous avenues for invasion into the Greenland Ice Sheet. Numerous
ways to melt Greenland ice from below. Zachariæ Isstrøm covers the
upper right hand section of this image — sitting astride a low
elevation channel the plunges deep into the heart of the current ice
mass. Image source: Livescience.)
Greenland
is the last major remaining bastion of glacial ice in the Northern
Hemisphere. Surrounded on all sides by warming airs and waters, it is
the most vulnerable large ice mass to the forces set in play by a
human warming of the global environment. In total, Greenland
holds enough ice to raise seas by 23 feet.
And, in the geological past, just 1.5 to 2.5 degrees Celsius worth of
temperature increase above Holocene averages was enough to melt much
or all of it.
Currently,
human warming by Greenhouse gasses has pushed global average surface
temperatures into a range about 1 degree Celsius hotter than the
1880s. It’s a temperature running into ranges that are now
comparable with the
Eemian —
the interglacial period that occurred between 115,000 to 130,000
years ago. A period when oceans were about 13 to 20 feet higher than
they are today.
But
perhaps even more concerning is the fact that global greenhouse gas
concentrations in the range of 400 ppm CO2 and 485 ppm CO2e are
enough now to warm the Earth by 2 to 4 degrees Celsius long-term.
It’s a heat forcing that would likely spell the end for Greenland’s
ice if it remained in place for any significant period. A heat
forcing more comparable withPliocene and Miocene ranges
when the world’s glaciers were
even more greatly reduced and seas were 30 to 130+ feet higher than
they are presently.
Unfortunately,
what the building global heat and currently very high greenhouse gas
heat forcing means is that the Earth System will continue to
accumulate warmth for some time. And as this happens more and more
glaciers — both in Greenland and Antarctica — are going to
destabilize, speed up, and contribute increasing melt volumes to the
world ocean. Eliminating greenhouse gas emissions at this time and
pushing to return to atmospheric levels in ranges below 350 ppm CO2
is therefore absolutely necessary if we are to have much hope of
preventing ever-worsening rates of glacier destabilization and
related contributions to sea level rise.
Links:
Hat
tip to Todaysguestis
Hat
tip to Colorado Bob
Hat
tip to Ryan in New England
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