Rolling Stone - Jeff Goodell
Scientists aboard the Nathaniel B. Palmer watch a 25-mile-wide section of ice crumble into the sea
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View from the deck of an ice strengthened ship on an expedition cruise to Antarctica, 2013.
Global Warming Images/REX/Shutterstock |
The
Nathaniel B. Palmer has left Antarctica behind and
made the turn toward home. The last science experiments were completed,
and the ship headed north, toward Punta Arenas, Chile, where our
two-month journey will end. Scientists on board are packing up equipment
and writing rough drafts of papers based on discoveries they made
during our adventure into uncharted waters around Thwaites glacier. But
an almost existential question looms above it all: Did we just witness
what amounts to a climate catastrophe playing out in real time?
On
March 3rd, Bastien Queste, an oceanographer at the University of East
Anglia who is a key member of the science team aboard the ship, got a
WhatsApp message from a colleague back in the UK. She had sent him a
satellite image of Thwaites glacier and the surrounding region in West
Antarctica. At the time, we had just completed
our own close encounter with the awesome craggy blue glacier and were only a few miles away,
mapping the seabed in front of the glacier with the ship’s sonar device.
On this trip, satellite images have been indispensable in helping
scientists track the ever-changing ice in the regions we’ve been
exploring. But the map Queste received that morning was different. He
noticed dark cracks in parts of the ice shelf, which floats out over the
sea like a huge fingernail from the glacier itself. They had not been
there before. The ice shelf was clearly starting to break up. Queste’s
first thought: “Oh, shit.”
Queste knew as well as anyone, the whole point of this research trip
is to better understand the risk of collapse of Thwaites glacier, one of
the most consequential tipping points in the Earth’s climate system.
It’s not just that Thwaites is big, although it is (imagine a glacier
the size of Florida). But because of how the glacier terminates in deep
water, as well as the reverse slope of the ground beneath it, Thwaites
is
vulnerable to particularly rapid collapse.
Even more troubling, Thwaites is like the cork in the wine bottle for
the rest of the West Antarctica ice sheet. If Thwaites were to fall
apart, scientists fear the entire ice sheet could begin to collapse,
eventually raising sea levels more than 10 feet.
That’s what Queste’s “oh, shit” was about. It was
non-scientific-but-very-human-shorthand for, “Is Thwaites falling apart
in real time, right before our eyes?”
Queste showed the image to Rob Larter, the chief scientist on the
Palmer.
Larter was not entirely surprised by what he saw. A few days earlier,
as we cruised along the front of Thwaites, Larter had remarked on how
chaotic and jumbled the ice shelf looked. “I thought something like this
might happen because of how broken up the ice on the shelf appeared,”
he says.
Over the next few days, Queste and Larter — as well as nearly every
other scientist and student on the ship — watched the disintegration of
the Thwaites ice shelf. It was a spooky sensation, looking at the
satellite images then looking out the window as a parade of icebergs
floated right by us on their way out to sea. In a matter of 48 hours or
so, a mélange of ice about 25 miles wide and 15 miles deep cracked up
and scattered into the sea. As Queste says, “A part of the glacier that
is as big as the city I live in — it was just gone.”
Here are satellite images of Thwaites before and after the blowout. The red dot shows where the ship was located on those days.
For scientists both on and off the ship, the big question is, was the
blowout a sign that Thwaites is collapsing before our eyes, or was it a
more or less ordinary event in the lifecycle of a big glacier? These
are not easy questions to answer. Glaciers are practically alive, in
flux all the time, exquisitely sensitive to small changes in atmospheric
and ocean temperatures. Sometimes changes that look dramatic to
non-scientists, like the breakup of the Larsen B ice shelf in Antarctica
a few years ago, have an inconsequential impact on sea level rise
(unlike the Thwaites ice shelf, the Larsen B is not holding back a
massive city-drowning glacier).
And it’s important to point out that the Thwaites blowout is not the
same thing as what scientists typically call a “calving event,” which
you often see in movies and documentaries, where big slabs of ice fall
off glaciers into the sea. What we witnessed was the sudden
disintegration of an ice shelf, which is a very different thing. Unlike
the calving of land-based ice into the sea, the break-up of an ice shelf
does not itself contribute to sea level rise, because the ice is
already floating — just as when the ice in your whiskey melts, the level
of whiskey in your drink doesn’t rise.
Nevertheless, ice shelves are important. They buttress the glacier
itself, providing stability and in effect holding it back from slipping
faster into the sea. The ice shelf that blew out at Thwaites was
particularly messy and chaotic — it’s a bunch of bergs glued together
with seasonal sea ice rather than a solid shelf. So maybe it wasn’t
doing much to stabilize Thwaites, and the blowout wasn’t a big deal.
But given the larger fragility of Thwaites, and the consequences of a
sudden collapse, any dramatic change in the structure of the glacier is
hardly an encouraging sign.
When it comes to melting glaciers and sea level rise, climate
scientists have traditionally been far more concerned about Greenland
than Antarctica. In our warming world, Antarctica was viewed as a stable
place: very big, very cold, very distant.
Then, in the early 1990s, improved satellite observations proved
those assumptions were wrong. Of special concern was West Antarctica,
which is particularly vulnerable to warm Circumpolar Deep Water
attacking the glaciers from below. A recent paper co-authored by
scientists from NASA’s Jet Propulsion Laboratory in California noted
that the main trunk of Thwaites accelerated 33 percent between 2006 and
2013 — it’s now sliding into the sea at a rate of about two miles per
year. In addition, parts of the glacier are thinning by as much as 13
feet each year.
Here’s a GIF that captures how much Thwaites has changed in just the
past five years. The orange and red sections are the fastest flowing
parts of the glacier.
And here’s a graph that shows how quickly the ice flow on Thwaites has accelerated — it’s almost doubled in the last five years.
So what does all this mean? Nobody can say for sure. “I’m holding my
breath to see what happens next,” says Larter. “The blowout could be the
start of a new phase of the evolution of Thwaites glacier. But I’m
wary, because sometimes you see things that you think are going to be
the start of something big, and then things settle down. I think it’s
too early to say which way this is going to go.”
In an email, Eric Rignot, a senior scientist at NASA’s Jet Propulsion
Laboratory who has co-authored recent papers suggesting the collapse of
Thwaites is already past the point of no return, told me that he
wouldn’t view the blowout as particularly alarming unless he saw retreat
of the front of the glacier itself during the process (which, in the
most recent satellite images, he hasn’t). But Rignot ended his email to
me with an important note: “This sort of event is a good reminder that
changes can happen fast in these environments, even though it may seem
that nothing much is happening when you are staring at the glacier from a
ship deck, right?”
Richard Alley, a highly respected glaciologist at Penn State, had a
more nuanced view of it all. Alley (who, like Rignot, is not on the
ship) pointed out that because the ice shelf that blew out was already
pretty chaotic, it was likely not providing much stability to the
glacier. “So its loss is not a huge issue for the still-grounded ice,”
Alley emailed. “But the chaotic ice was still doing something.” He
compared Thwaites to glaciers in Greenland, where the blowout of similar
mélanges are often followed by calving of ice from the glacier itself,
which is far more troubling. Alley also pointed out that the loss of ice
shelves leaves glaciers vulnerable to stress from what he called
“remote forcing” — storms across the Pacific, or tsunamis from an
earthquake. “To stretch the analogy a little bit,” Alley said, “if
Thwaites were a car, you could say that it has lost part of its bumper.
And, while that’s not hugely important, it is part of a pattern that is
pointing toward larger changes to come.”
This is, in short, what makes
climate change
so alarming, and so unlike other threats that humans have faced. By
loading the atmosphere with carbon, we are messing with a system that
even the best scientists in the world don’t fully understand. Individual
events are hard to interpret in real time. “In the history of human
civilization, we’ve never seen the rapid collapse of a glacier like
Thwaites,” Larter points out. “So we don’t know how exactly it starts,
or what it looks like while it’s happening.”
But in the long run, the arc of uncertainty bends toward catastrophe.
It may be that this blowout at Thwaites was driven by wind or a shift
in ocean temperature that, in the big picture, means little. Or it may
be further evidence that the collapse of Thwaites is already underway,
and it’s only a matter of time — perhaps even during the lifetimes of
kids alive today — before virtually every coastal city from Miami to
Jakarta is under six, seven, eight or more feet of water.
If that’s the case, then big parts of the world we live in today may already be doomed. We just don’t know yet.
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