Now I’m no scientist, but …
When the people who do know what they’re talking about look deeply worried it unsettles me. When they can’t sleep, I start to feel a bit panicky. So this story about the Wilkins ice shelf, which scientists have been concerned (masters of understatement, scientists…) about for while now, is a bit, um, concerning.
I’ve taken the liberty of highlighting the passages that sounded a little, well, worriesome, to me:
An ice bridge, up to 40 kilometres long but at its narrowest just 500 metres wide, was thought to be holding the giant shelf to the Antarctic continent but it recently snapped.
From above, parts of the Wilkins Ice Shelf now look like giant panes of shattered glass.
British Antarctic Survey glaciologist Professor David Vaughan has been monitoring the Wilkins Ice Shelf for some time with the help of satellite imagery.
“The ice shelf has almost exploded into a large number, hundreds of small icebergs,” he said.
“The images on the European Space Agency website show that the ice bridge was relatively stable for the past month or two.
“In fact we visited the ice bridge – we landed on it with an aircraft and put a GPS, a satellite positioning system, onto the ice shelf. And that’s another way we’ve been monitoring its movements over the last few weeks.”
Researchers believe the ice bridge was an important barrier, keeping the rest of the ice shelf in place.
Dr Ted Scambos, the lead scientist at the National Snow and Ice Data Centre at the University of Colorado, told ABC Radio National he was concerned.
“The follow on is that large chunks of ice break away from the area that’s become unstable because it’s no longer braced,” he said.
“And we see a retreat to a smaller ice shelf, or perhaps no ice shelf at all. It’s in the last stages. Right now I think about half the Wilkins will remain after this is done.”
The size of the impact on sea levels is still being debated but scientists believe climate change is affecting the Antarctic to a greater extent than previously expected.
Scientific consensus is a little like an iceberg. The 2% that scientists can actually agree upon sits above the surface, while the most interesting discoveries, that they’re almost 95% sure on but just can’t say for sure, sits below the water line, with the rest of us blithely unaware.
So the next time you happen to bump into a prematurely grey climate scientist, walk on by quickly — and don’t ask, you don’t want to know…
9 Comments
No, it’s not bad it’s just normal.
Things change you know, haven’t you noticed that you got taller when you were young?
Every day I see it get light then dark! And now in Autumn it’s getting more dark!!
See, don’t panic, it’ll all be OK… A little knowledge can be a scary thing..
Let’s get this straight. If it is an ice SHELF we’re talking about – and Wilkins is indeed one – then it is already floating (that’s the definition of an ice shelf) and so it’s detachment and melting will not make any difference to sea level. It does however probably indicate that warming is procedding more rapidly than previously thought; and the danger of ice shelves like this breaking off is that the continental ice CAP that is not floating but flowing gradually down from the high centre of Antarctica to the coast, will flow more rapidly without the restraining force of a large ice shelf. If landlocked ice of the ice CAP becomes floating ice of an ice SHELF, then this will increase sea level.
Similarly, melting of the Arctic sea ice – already floating – will not affect sea level, though the reduction in albedo will accelerate the rate of melting and overall Arctic temperature rise; and again, the reduction in the restraining foce of sea ice and ice shelves will accelerate the flow (and melting) of the land-based Greenland ice cap.
Incidentally, while the overall impact of global warming on Arctic sea ice is undeniable, it too demonstrates anomalies…in the northern summer of 2006 I was stuck for a week in sea ice off Alaska in a 25,000HP ice breaker!
Normal? The Wilkins ice shelf has been there for about 10,000 years, so normal would
be it NOT breaking up. We aren’t talking about a calving glacier here (that’s normal), nor
are we talking about defrosting a freezer, we are talking about enough heat over enough
years to destabilise a 16,000 square kilometer area of 300 metre thick ice. And the
other shelves which have broken up (Wordie, Mueller, Jones, Larsen-A and Larsen-B,
just for starters)? Also normal?
Yes, a little knowledge can be scary, but it sure as hell beats total ignorance.
Geoff,
Ice shelves are dynamic in that they are fed by glacial flows, and discharge mass when the shelf becomes for a variety of reasons too tenuous or weak or extended. The extent of an ice shelf may remain similar very long periods of time but just like glaciers on the land, or a river, its contents are constantly renewed.
Structural failure in ice shelves has very little to do in some locations with environmental temperatures. In fact the Amery Ice Shelf in some recent studies was found to be thickening in places where the ice discharge was so cold that sea water froze to the underside, an additional structural burden that did not diminish until that point in the flow went further seawards.
When I went to McMurdo Sound in 1979 divers wearing wet suits filled with warm water were exploring the underside of a section of the Ross Ice Shelf via a hole drilled through it. The water below was super chilled, at -8C. The Larsen ice shelves are in the relatively temperate Antarctic Peninsula. This is a region of high snowfall. An empirical test of their behaviour should be possible in a very short time frame when evidence is sought of any regeneration from the neve catchment zones that fed ice down into the embayments where the discharge merged into ice shelves. However this will not necessarily prove anything other than that if there is enough snowfall net of melting or ablation glacial ice will form. I wrote an item for Crikey today about the Wilkins event.
Ben, I’ve just read your Crikey piece (from yesterday). Strictly speaking, attributing any discrete event
. Wikipedia has a list of 43 ice shelves of which
to global warming demonstrates a lack of understanding of the way climate changes, but it doesn’t
follow that global warming causes no events
7 have “collapsed” … maybe not all in quite the same way. Wilkins, according to some
realclimate comments, isn’t glacier fed and its collapse looks to have more to do
with localised warming and anthropogenic SAM changes. I think of it like a pot of
water which is close to boiling with a few rising bubbles. Turn up the heat just a little and the
number of bubbles increases. Is any PARTICULAR bubble caused by the heat increment? Not really. But
when a particularly big bubble erupts from the bottom of the pot, then attributing that to
the excess heat seems reasonable. This is my take on the Wilkins collapse, and it seems consistent with
the discussion on realclimate which involves quite a few people who know rather more than
me and who aren’t given to exaggerated claims.
Geoff,
The filtering of all events through the prism of global warming is the issue I was drawing attention too. There is clear evidence of major ice berg breakouts from ice shelves in the 18th and 19th century from the shipping records. What will warming do to Antarctica? It will clearly produce melting in those areas where the temperature begins to exceed freezing point. It will also elevate snowfall over the continent where the air is so cold at present that precipitation is inhibited. Antarctica is the world’s largest desert, just icy rather than sandy, with most of the precipitation falling around its edges. And copiously, as it does in the Palmer Peninsula.
The response times for some of the ice flows from the interior of Antarctica is incredibly slow. Some of the ice that has been studied for clues as to past conditions is in excess of 800,000 years old, and so compressed that it exhibits granite like characteristics. So while in time and without even considering continental drift, Antarctica may completely deglaciate, the focus of attention is properly on those most vulnerable areas of the peninsula and those mainland ice repositories that actually extend below sea level. These areas will respond more rapidly to rising temperatures, and indeed rising snowfall, which will manifest itself eventually in higher rates of outflow as well as disintegration.
I’m not participating in this truly important discussion to argue against anthropogenic climate forcing, which I firmly believe is proven and serious. Rather I’m concerned that the real science is prostituted in some quarters by those who want to engineer the message to serve an agenda, which may not actually deliver the focus on the core issues of greenhouse gas reductions which deserves to dominate our attention.
The general debate about climate change in these times is too much like a circus and not enough about real action. The lunatic fringe of climate change denial isn’t worth pursuing. But the reasoned, closely argued and empirically validated pursuit of research and action is of critical importance to us all.
Ben, you contend global warming is real and caused by human activity and yet you try to argue that it has not played a part in causing this ice shelf to break off. What do you contend happens to ice when the globe warms? The cleaving of ice shelves is a natural occurrence and it is unquestionable that it will be facilitated by global warming. I tend to agree with you that not all weather events are the result of global warming with the current Australian drought being one example but ice melts when it is warmed and as a consequence natural events like the cleaving of ice shelves are facilitated.
Simply put the two events are related and to argue otherwise is unwise.
Some scientists are petrified of making a judgment without conclusive evidence.
Being wrong is more frightening to them than getting Ebola. The coal lobby just
love this. They don’t have doubts, qualifications, uncertainties. Keep it simple is
their motto and it’s a motto which works. Guy Pearse’s “Quarry Vision” makes
a convincing case that many of our politicians are skeptical of climate change because
they keep getting briefings from people who are sure about what they are saying,
who probably dress really well, and who are sure that AGW isn’t certain.
I’d say that the break up of so many ice shelves in such a short time
is more consistent with GW than no-GW. If these shelves were being “constantly
renewed” as you put it, then there would be little net loss. The Grace satellite work
shows that there is now a net loss of ice to go with the net loss of ice shelves. To
me this looks like a really big bubble in my boiling pot analogy given above. I’m
happy to say I was wrong if somebody finds a mistake in the Grace data, or finds
some new ice shelves, or some other unanticipated proof.
Geoff,
Those are good points to consider. I would add that while precipitation constantly adds to the ice mass that feeds glaciers and in the right locations, ice shelves, the discharge of glaciers tends to be a break and release process. The literature on the largest of them, the Ross Ice Shelf, has referred to it going back to perhaps less than a third of its current extent since the end of the last ice age, but also exceeding its current boundaries on occasions since then. I did not say, and would not agree with any inference that might have been taken, that global warming will not affect Antarctica. Unless there is some bizarre feedback or mechanism that has until now escaped discovery and resolution.