Clues to climate change trapped in Greenland ice sheet


JON GERTNER: It is difficult for us to imagine what the Greenland ice sheet looks like. This is thousands of miles from the United States as well as from Europe. It is a country that few people visit; it's an overpass – maybe when you're going to northern Europe you'll see this huge ice sheet. And the Greenland ice sheet, you can imagine a cupcake where the cover does not reach the edges. I mean, Greenland is not just the largest island in the world, but this ice sheet, which is about 1,500 miles long and 700 miles across, covers well over 80% of the island. So there is only that narrow strip of land around the banks that has been hospitable to the settlements. Because nothing really lives on the ice sheet. This is a place where frozen temperatures reach less than 80 degrees Fahrenheit. It is a place that was considered abandoned by the native Inuit, a place that was somewhere where you would be far away, where the evil spirits lived.

And it was also a place at its center – if you consider this type of cupcake cover, the center is 10,000 feet high. So it's that kind of giant ice dome, and it's two miles thick. A scientist with whom I spent a lot of time in Greenland called it the largest laboratory in the world. Which is a kind of weird phrase when you think of it as the biggest island in the world, and it's covered in ice. Well, why this? But if you look back on history, it offered this opportunity to study the only remaining ice sheet in the northern hemisphere; the other is in southern Antarctica. But it also offered some of these early scientists a way to look back in time. Because ice, in the words of many scientists, is depositional. Creates a record type of all deposits that have fallen on it through the snow. And we think, okay, well, there's old snow. But it's more than that. In fact, it contains old gases. Contains records of ancient volcanic eruptions. And the way we started to access that information, because it's really information, was to drill the ice.

And the first people to do it significantly were not really drilling the ice. There was this guy Ernst Sorge, who was positioned with Alfred Wegener's team at the center of the ice sheet in the 1930s. And he started, literally, he was camped under the ice with another guy – two other guys, actually – and he started dig with a shovel. He dug a ladder into the ice. He dug about 50 feet – 50 feet, excuse me, into the ice. And he began to carve blocks and bring them back to where they were sleeping, and measured them on a scale. And he wanted to measure its density. And what he discerned was that there was a kind of discernible variation between the snow and the summer of winter's density. And he could, by doing so, find out just how many years ago in time he was going. So that was the first big step. OK, you can actually measure this type of stripes on ice if you think that way by going down. And after that, he became much more ambitious.

In the 1950s and 1960s, scientists actually brought drilling rigs there. They have tried to figure out how you could deepen and extract a core, which may seem easier than you think, but actually it is quite difficult because you want to keep the pristine nature of the ice. Because what you really want to do is all sorts of experiments in chemical analysis to try to understand the ice isotopes. And these are the keys to understanding how old temperatures are. There are also these old bubbles trapped in the ice, and they are also keys to ancient atmospheres. So the further you are, the further back in time you will.

And we could say, well, okay. You may discover, perhaps, what the temperatures were like a thousand years ago. But this is not trivial information. Because it's not just telling us what the temperatures are like, you're telling us maybe what's changed. Explain bits of history we may not understand. Could you explain, for example, why the Nordic Greenland that came to Greenland a thousand years ago and then mysteriously disappeared, why did they go? Has there been a dramatic change in temperature? I could explain, for example, what happened to the Earth about 11,000 or 12,000 years ago when we see these dramatic changes in temperature that actually took place in the space of 10 or 15 years that make us wonder now, dammit. We always think that the climate is changing gradually and slowly but in fact the story, as we discovered from these ice cores, shows us that the climate can really change very rapidly, and Earth does not mind slowly changing. Sometimes it has different ways in which it can change quickly.

So there's all sorts of information we discovered in the center of the Greenland ice. It's a kind of key to the past. Sometimes it is not always comforting, but it always gives us new insights that help us think again about this place as a great laboratory, not just a big chunk of ice.


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