Greenland Ice Core Drilling Project Reaches Milestone
“It’s tough to make predictions, especially about the future.”
Yogi wasn’t talking about climate change when he said these immortal words (if he said them at all; Yogi has also asserted that “I didn't really say everything I said.”) Either way, it applies. We know for a fact that carbon dioxide is a heat-trapping greenhouse gas, and we know that humans have been adding carbon dioxide (CO2) to the atmosphere, mostly through the burning of fossil fuels. Virtually nobody, including so-called climate skeptics, disputes that global temperatures are rising as a result.
But there’s disagreement over exactly how fast greenhouse gases will make the world heat up over the next century, and exactly how hot it will actually get. In large part, that’s due to incomplete knowledge of feedback mechanisms — changes in ice, cloud cover, vegetation, dust in the atmosphere, ocean circulation and more. These could either speed up the warming or tamp it down, depending on how things play out, and nobody knows precisely how it will work out. Climate models help, but the real world is more complex than any model, which keeps things uncertain.
But we do know that climate has changed dramatically in the past, and one of the most effective ways scientists have of figuring out what happened, when, and under what conditions, is to drill into the ancient ice that has been sitting for hundreds of thousands of years atop the landmasses of Greenland and Antarctica.
That’s why an announcement out of northern Greenland last week could be so important. Last Tuesday, after three years of careful drilling through the island’s thick layer of ice, a team of scientists working on the North Greenland Eemian Ice Drilling project, or NEEM, hit bedrock, exactly 2537.36 meters (nearly 8,325 ft.) below the surface. The ice they dredged up from that depth dates to the Eemian period, about 130,000 years ago, a time when the planet had emerged from a long period of glaciation into an interglacial period like we’re in today — except that the temperature was two to three degrees Celsius, or up to five degrees Fahrenheit, warmer than it is at present, and sea levels were 13-20 feet higher.
The warming during the Eemian was triggered by a shift in the alignment of the Earth and Sun that brought more direct sunshine to the Arctic than we see now. But figuring out how the climate responded to warming, even if the trigger is different now, could prove crucial in projecting what will go on in the next century or so.
With this ancient ice in hand, that’s just what the NEEM researchers are planning to do. The ice was originally laid down as snowflakes, which were eventually compressed into solid ice by later snowfalls, accumulating over the years. Tiny air bubbles trapped inside preserve the atmosphere from the time of the original snowfall, so scientists can measure the amount of CO2 and other gases that were present. The ice itself, meanwhile, contains a mix of different oxygen isotopes that depend on the atmosphere’s temperature at the time. Beyond that, trapped plant material, such as pollen grains, can help the scientists figure out how green Greenland really was.
Dr. Jorgen Peder Steffensen explains the goals of the North Greenland Eemian Ice Drilling project and what the ice cores can tell us about our climate history. Filmed on location in Greenland in July, 2009.
Here’s how Richard Alley, a Penn State ice core expert, put it to me in an email (I love how he calls the Eemian “Eem”; it’s so familiar to him that he uses a nickname):
The Eem is a time when the orbits brought more summer sunshine to the far north than occurred a few thousand years ago, so the Eem gives us a view of what a warmer climate might be like (how did snowfall, and dust transport, and other things, change as the temperature changed, for example?), and what it might have meant to the Greenland ice sheet (how much melting from the warmth, how big was the ice sheet?). The experiment is not perfect — changing CO2 and changing the summer sunshine are not exactly the same thing — but the experiment is certainly instructive, so we can learn a lot from it.
This isn’t the first Greenland project that has tapped into the Eemian, but Alley says that ice cores from other sites haven’t gotten a clean record; for whatever geological reason, the ice has been disturbed and mixed in with other time periods. At the NEEM location, the ice is relatively pristine, making good information easier to extract.
Last year, Climate Central’s Heidi Cullen visited the NEEM project, and filed this report.
This isn’t the only ice-drilling project on the planet by any means: they’re going on in other parts of Greenland, in Antarctica (where the ice is much thicker, and thus gives a record going back much longer), and in mountain glaciers in temperate and even tropical regions (including Tanzania’s Mt. Kilimanjaro), most of which are receding. The US National Oceanic and Atmospheric Administration maintains a list of many of them.
Collectively, they reach back some 800,000 years, and show that periods of higher temperature and higher sea levels are generally accompanied by greater atmospheric concentrations of CO2.