14 July 2010

Ice Core at NEEM Approaching Greenland Bedrock

Posted by Dan Satterfield

Dome at NEEM on the Greenland Icecap- courtesy NEEM

While the lower 48 bakes this summer, a group of 30 researchers are drilling a big hole in the ice at the top of the world. It’s all in the name of science. The North Greenland Eemian ice core project is not the first ice core to be drilled through the Greenland icecap. It may be the most important though.

Rewriting Earth’s Climate History

Earlier cores have rewritten the climate text books. This core will likely do the same. Especially, if the group at NEEM are lucky enough to get a good core of ice from the Eemian.

The Eemian is the name for the warm period BEFORE the last ice age. Knowing how the climate behaved then, and in the transition to the ice last ice age, will tell us a lot about what we are facing in the future.

VOSTOK Ice Core showing the temperature over the last 500,000 years. The temperature data was derived using oxygen isotopes.

Playing With Fire and Ice

We are without doubt fiddling with the Earth’s thermostat. In spite of what you may think, the ice cores and sediment cores we have already tell us that our climate is not nearly as stable as written human history would indicate.

The last ten thousand years have been very unusual. The climate has been very benign and stable. Brian Fagan wrote a book about this period called “The Long Summer”.

Look at the data from previous ice cores. The Vostok ice core from Antarctica shows very well how stable the last 10,000 years have been and how unstable the previous 500,000 years before it were! The red line in the graphic shows a very stable climate for the past 10,000 years. Before that the climate is a roller coaster.

The Lines Go Up and Down Together For A Reason

You can also see how closely related to temperature the amount of carbon dioxide and methane (CH4) are. Both of these gases are called greenhouse gases and they act to magnify greatly any minor warming from changes in Earth’s orbit around the sun.

There is a growing acceptance among evolutionary biologists that the reason our African ancestors evolved much larger brains is climate related. The changing climate that kicked in about 3 million years ago forced it. NOVA did an especially interesting program on this in 2009.

Oxygen isotope record from two Greenland Ice Cores called GRIP and North GRIP. The stable climate called the Long summer is clearly visible from the left of the graph until about 10,000 ybp. The NEEM drill site is hoping to get higher resolution data back in the Eemian (115-130K ybp)

You might be wondering (and you should be) just how it is possible to tell what the temperature and levels of CO2 were in the atmosphere from an ice core? The answers lie in bubbles and isotopes.

The Technical Bit

The ice in these cores contain bubbles of gas that are filled with the air at around the time the snow fell. These bubbles actually disappear in the deeper core as the gas bubbles get merged into the ice. The gases are still detectable and readable though.

Oxygen comes in two main forms O18 has two extra neutrons but it's still Oxygen. Image from NASA. NASA has a detailed explanation of how this fact is used to measure temperatures thousands of years ago.

The temperature can be obtained by looking at the ratio of two types of Oxygen. Oxygen has 8 protons in each atom. That is why it’s called Oxygen. The oxygen we breath is actually O2 which is two atoms of Oxygen bonded together. O2 has 16 protons and 16 Neutrons. However, a very tiny percentage of oxygen that you breath has 2 extra neutrons.

This is not a big deal as your body thinks it is oxygen and it really is. It still has 16 protons and that’s all that counts. Atoms of the same element that have differing numbers of neutrons are called ISOTOPES. Oxygen has O16 and O18 isotopes.

O18 is 12.5% heavier than the usual O16 molecule. The heavier molecule falls out in rain or snow more quickly. How quickly is dependent on temperature and this means you can measure the ratio of O16 to O18 in the ice core and deduce the temperature of the ocean the snow evaporated from! Click the rotating molecules for a more detailed explanation.

Cocktail Party Advice From Dan

So, next time you hear someone say something like “How could they possibly know what the temperature was like 50,000 years ago”, you can tell them. If my experience is any guide, you will just get a mean look. ;)

CFA lab at NEEM- image ctsy. NEEM

Continuous Flow Analyzer

At NEEM this year, they are using a device called a continuous flow analyzer to measure the properties of the ice core. This is very helpful. It lets them know in near real time about what the age of the ice they are pulling up from the drill is. Only a part of the ice core is used for this. Much of the core will be kept intact and used for research for many years.

Dave Jones, the President of Storm Center Communications, has asked me to go up to the ice sheet and help tell the story. Dave is a Meteorologist. Those of you in the Washington DC area may remember him from WRC – TV a few years back.  His company is heavily involved in showing real science to a wider world.

The folks at NEEM will reach bedrock in a week or so. There is rock beneath all that ice. Those rocks have not seen the light of day for well over 100,000 years and probably much longer.

I may get to see some of those rocks come into the sunshine of the 21st century in person. I will leave for NEEM Monday.

It should be quite an adventure, and I will take plenty of pictures.