Polar meltdown sees us on an icy road to disaster

http://www.theguardian.com/environment/2015/may/04/polar-meltdown-icy-road-disaster-glaciers

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The Amundsen sea sector in west Antarctica is almost as big as France. Six glaciers drain into it and one of the largest of these is the Pine Island glacier, a 30-kilometre-wide estuary of ice that is more than 500km in length. Stand on it, on a clear day, and swaths of glittering ice stretch off to the horizon in every direction.

This is one of the world’s greatest bodies of fresh water, a vast frozen reservoir weighing more than 300tn tonnes. With that sort of resource, you could solve a great many of the planet’s freshwater problems.

But the Pine Island glacier is ailing. It is melting and losing, annually, an incredible 46bn tonnes of ice. Each year, more and more of the glacier slips down to the ocean where it forms a vast sheet of shelf ice that spreads over the sea and eventually disappears.

And the loss of this ice shelf is of crucial importance, for without it there is nothing to shore up the glacier on land, a problem that now affects many other glaciers on the continent. Think of the Antarctic as a large dollop of trifle set in a pastry case. Take away the case – its ice shelf – and there is nothing to stop the trifle from slowly spreading out all over the place. And that, unfortunately, is just what is happening in many other areas of the Antarctic. As their “pastry cases” of shelf ice dissipate, so glaciers are spilling, like trifle, into the sea – and at increasing speed. The Pine Island glacier just happens to be the most extreme example of this alarming phenomenon.

But why? What processes are driving the loss of shelf ice across the south pole? Given the fact that melting Antarctic ice would trigger sea-level rises round the globe, these questions are some of the most important affecting climate change policy today and are being tackled, directly, by scientists working for Britain’s iSTAR programme. Funded by the Natural Environment Research Council, the £7.4m project has involved scientists spending the past two Antarctic summers living on the Pine Island glacier, a region of stunning beauty – and hostility.

“It is certainly a very special place, though in one sense it is like every other spot on Earth,” says glacier expert Andy Smith, from the British Antarctic Survey. “It has its good days and it has its bad days. It is just that when it is a bad day it is usually absolutely awful.”

On occasion, winds can quickly whip up to speeds of 130kph or more and when that happens snow is thrown all over the place as high-velocity fine spray. “You cannot see a foot in front of you,” says Smith, the science programme manager of iSTAR. “You have to be incredibly careful where you go. As soon as we realise a gale is coming, we rig up rope lines so people follow them and move around safely.”

In general, though, there is no option for members of the expedition but to bunker down until these winds have passed. “We slept in two-man mountain tents at night but we also had one big function room, which we called the caboose but which was really a storage container that had been brought on to the glacier on skis,” recalls Smith. “That is where we had our kitchen where we could get hot food and get dry.”

And that, he says, is the real secret of living in the Antarctic. “You have to have some sanctuary where you can get some comfort. You cannot survive without it in the long run.” However, it should be noted that the caboose was not fitted with showers and bathrooms. “For that kind of trip – and yes it lasted three months – you just have to go grubby,” adds Smith.

Now the scientists of the iSTAR project are completing their work, a programme that had an initial two-year period when equipment was flown on to the glacier and assembled there. This was followed by a second period when Smith and his fellow researchers spent two three-month bouts of work during the Antarctic summer taking measurements of the ice below their feet. Two tracked vehicles carried the scientists along the tributaries of the Pine Island glacier so they could extract ice cores from various depths. In this way, they were able to obtain a continuous record of snowfall and its density on the glacier.

“We have gathered all our data over the past two years and now we have taken it off to our offices and will be analysing on our computers for the next few months,” says Smith. “The results should be ready for publication in about a year.”

The resulting papers should provide a new understanding of the shelf ice of the Pine Island glacier and of the general impact that melting ice shelves are likely to have on the planet. “What we have found is that the ocean is getting underneath the shelf ice at Pine Island and that the sea water is clearly getting warmer,” Smith says. “It is melting the ice from below and at a rate that is increasing over the years.”

In addition, other researchers have noted that winds are becoming more intense in the Antarctic. These are now churning up the warmer water round the coast of Antarctica and are driving it into the ice. Again, the effect is to melt the ice and break it up, destabilising the glaciers above.

These combined factors have produced dramatic changes: ice loss at the Pine Island glacier has increased by more than 50% in recent years, with the result that the glacier is beginning to roll down at a faster and faster rate into the ocean. “In the past, ice that melted in the sea is balanced by new ice that formed, from fallen snow, at the top of the glacier, high on the Antarctic plateau,” says Smith.

“But now it is becoming noticeable that the glacier is out of balance. More ice is being lost at the bottom than can be replaced at the top and this is causing the glacier to slide faster and faster into the sea. The Pine Island glacier is being eaten from the base, by warming waters.”

But what is really extraordinary is the global impact of this melting ice. As a result of the colossal influx of meltwater from the Pine Island glacier, about 1.5mm is being added to global sea levels every decade. “Of all the glaciers in the world, none of them are losing more ice than the Pine Island and none of them are contributing more to sea level rises,” adds Smith.

It is a sobering thought. The worrying example of Pine Island suggests there could be enough loss of shelf ice in the Antarctic to produce several metres of sea rise over the next few decades, while if all the ice on Antarctica and Greenland were to turn to water, Earth’s oceans would rise by a catastrophic 60 metres or more, drowning most of the world’s major cities. Fortunately, there is little prospect of such a continent-wide melting and consequent inundation occurring – at least not this century. But with coastal communities the world over already experiencing unprecedented flooding, that’s cold comfort indeed.