Did climate change cause Antarctica’s new Larsen C iceberg?

giant tabular iceberg cliff ocean shutterstock_549616561
tabular iceberg (not A-68) in the Weddell Sea near the Antarctic


  • Iceberg A-68, which recently calved from Antarctica’s
    Larsen C ice shelf, is the third-largest iceberg on
  • Some scientists have described the iceberg’s calving as
    a “natural” event that can’t yet be tied to human
  • Other scientists, however, have said an immediate lack
    of information on A-68 isn’t reason to dismiss the realities of
    climate change.

An iceberg about six times the mass of Mount Everest — the

ever recorded — is currently drifting away from

Blowing winds, ocean currents, and Earth’s rotation are all
slowly pushing the Delaware-size block,
dubbed A-68
by the US National Ice Center, into the Southern

antarctica larsen c iceberg a68 broken pieces adrian luckman twitter
Luckman/Twitter; NASA/Suomi

It’s already
beginning to fracture
into smaller pieces, and will
gradually melt
and vanish forever, perhaps within the next
two to three years.

Iceberg A-68 made up 12% of the area of Antarctica’s Larsen C ice
shelf’s area, and there’s a small yet significant chance that the
loss could destabilize the rest of the shelf. (A similar collapse
occurred with the nearby Larsen B ice shelf in 2002.)

Yet as researchers look into
the causes
of the rift that created the iceberg, a few have
reached something of an impasse about the degree to which human
activity contributed to this particular event — or if it did at

The ‘all-natural’ and ‘wait-and-see’ camps

One group that’s closely studied the Antarctic Peninsula, where
Larsen C is located, is Project Midas — a science program
co-led by Adrian
, a glaciologist at Swansea University.

Starting around 2014, Project Midas began tracking a growing rift
in the shelf’s ice. By 2016 that rift was increasing in speed,
and Luckman noted in
a blog post
that a calving was imminent and “will
fundamentally change the landscape of the Antarctic Peninsula.”

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larsen c ice shelf diagram antarctica
map of Antarctica’s biggest ice shelf systems. Larsen C was the
fourth-largest — now the fifth-largest — until iceberg A-68’s
calving between July 10 and July 12, 2017.

Torterat/Wikipedia (CC BY 2.0)

However, Luckman and his colleagues declined to pin any blame for
the calving event on global warming — at least not definitively.

“[D]espite the media and public fascination, the Larsen C rift
and iceberg ‘calving’ is not a warning of imminent sea level
rise,” Luckman wrote in
a July 12 opinion piece
for The Conversation. “This event has
also been widely but over-simplistically linked to climate

But Luckman acknowledged in the same essay that, as the planet
continues to warm due to greenhouse gas emissions, “ice shelves
are of particular scientific interest because they are
susceptible both to atmospheric warming from above and ocean
warming from below.”

He also said his team has highlighted
between the collapse of the nearby Larsen A ice
shelf in 1995 and Larsen B ice shelf in 2002 — both of which

tied to global

Luckman said he’s not surprised that people assume human activity
is responsible for the emergence of this particular iceberg.
After all, he added, “notable changes in the earth’s glaciers and
ice sheets are normally associated with rising environmental

But he thinks in this specific instance, it’s “probably too early
to blame this event directly on human-generated climate change.”

For one, he said, there’s not yet any direct evidence; second,
Larsen C has
thickened somewhat
in recent years; and third, warming air
and ocean water takes a long time to penetrate floating ice
sheets (which can be more than 1,000 feet thick).

Iceberg slideshow_02_thickness
The thickness of iceberg
A-68 is roughly double the height of the Statue of

Mike Nudelman/Business

Other scientists, such as Helen Amanda
, a glaciologist who studies Antarctic ice for the
Scripps Institution of Oceanography, have offered similar lines.

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“Large calving events such as this are normal processes of a
healthy ice sheet, ones that have occurred for decades,
centuries, millennia — on cycles that are much longer than a
human or satellite lifetime,” Fricker
wrote in The Guardian
prior to A-68’s calving. “What looks
like an enormous loss is just ordinary housekeeping for this part
of Antarctica.”

Martin O’Leary, a colleague of Luckman’s at Swansea and Project
Midas, took a similar position shortly after the iceberg broke

“Although this is a natural event, and we’re not aware of any
link to human-induced climate change, this puts the ice shelf in
a very vulnerable position,” he said in a statement.
“This is the furthest back that the ice front has been in
recorded history. We’re going to be watching very carefully for
signs that the rest of the shelf is becoming unstable.”

Missing the big picture?

However, other glaciologists and climate researchers have been
quick to push back against such statements.

Kevin Trenberth, a climatologist at
the US National Center for Atmospheric Research,
told CNN columnist John D. Sutter
that deeming an event like
this “natural” due to a lack of direct evidence is akin to
looking “through a microscope.”

Put another way, focusing too much on one iceberg misses the
bigger, inevitable, and more important picture: Earth today has
quickly warming oceans, warming air, and
a changing climate
(among other effects) due primarily to
human activity, and this begets melting, weakening ice and
sea-level rise

“To me, it’s an unequivocal signature of the impact of climate
change on Larsen C,” Eric Rignot, a glaciologist at NASA’s Jet
Propulsion Laboratory, told CNN. “This is not a natural cycle.
This is the response of the system to a warmer climate from the
top and from the bottom. Nothing else can cause this.”

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To this, Sutter adds, “Rignot said colleagues who say otherwise
are burying their heads ‘in the ice.'”

iceberg antarctica sunset illustration shutterstock_220203454
photo illustration of an Antarctic iceberg at


Indeed, as
Andrea Thompson wrote for Climate Central
, many ice shelves
have been shrinking at increasing rates. Most are being lapped
away from below by warmer ocean waters, since air temperatures
haven’t risen significantly enough to melt their surfaces.

“But on the Antarctic Peninsula — the arm that stretches
northward from the continent toward South America —
rising air temperatures
are impacting the ice,” she wrote.
“The region is a global hotspot for warming, with temperatures
that have risen by about 5°F in
the past 50 years
, while the globe as a whole has warmed by
about 1.3°F.”

Even Amanda Fricker warned in her Guardian column that people
shouldn’t be tempted into complacency about the effects of global

“Antarctic ice shelves overall are seeing accelerated thinning,
and the ice sheet is losing mass in key sectors of Antarctica,”
she wrote. “Continuing losses might soon lead to an irreversible