Ice and Medicine at the end of the earth

Why WAIS Divide? Part 1

Antarctica is one of the few spots in the world dedicated to research. Jessie has done a great job explaining many of the research projects happening on the continent.  I’m going to try to explain why I am out here at the West Antarctic Ice Sheet (WAIS) Divide drilling an ice core.

We’re near an ice divide, which means ice flows away in two (or more) directions.  WAIS Divide has ice flow to the Ross Sea on one side (towards McMurdo) and to the Amundsen Sea (towards the Antarctic Peninsula) on the other side.

We are here at WAIS Divide because it’s the best spot in the world to examine how temperature and carbon dioxide affect each other.  We are not here simply to look at Antarctica; we are here because only in Antarctica is this record preserved.  This is not the first ice core drilled, but it will help answer a fundamental question about our climate:

How do changes in temperature and carbon dioxide affect each other?

Ice cores can help answers this because they have two really important properties:

  1. They trap samples of the past atmosphere in bubbles
  2. They can be dated with great precision (each year can be counted for many thousands of years)

From ice cores drilled in Greenland, we know that temperature can change rapidly: 5 degrees C in a decade or so (go to the bottom if you’re interested in how we know what the temperature was in the past).  That’s much faster than what we’re experiencing today.  If the climate can change so rapidly without any human input, what will the current emission of carbon dioxide do? We are looking for information from the past to inform us about what the future holds.

When you hear “rapid climate change” this is what scientists are talking about.  But in Greenland, the carbon dioxide record is not preserved; too much dust is deposited in the snow which causes a chemical reaction altering the amount of carbon dioxide trapped in the bubbles.  Antarctica gets very little dust because there is much less land mass in the southern hemisphere than in the northern. And the carbon dioxide trapped in the bubbles does not get changed with time. 

Other ice cores in Antarctica give great records of carbon dioxide, but for much longer time periods.  The Dome Concordia Ice Core goes back ~750,000 years.  From this, we know temperature and carbon dioxide vary together. However, the relative timing of the changes is not known because the long length of time means that there is less precision. For instance, a data point may average conditions over a thousand years when we want to know what happened every hundred years. 

WAIS Divide is the best spot in the world to get a record of temperature and carbon dioxide changes for the past ~100,000 years. The age of the ice spans the many interesting rapid climate changes while also giving high precision dating to the changes in temperature and carbon dioxide.

I will keep posting additional blogs explaining more about the glaciology of this site (that’s what I do after all) and more about the climate questions we are trying to answer. Please post questions so I know what you are interested in.

 

*Temperature changes can be recorded in three ways:

1. The water isotopes in the ice. Oxygen typically has 8 protons and 8 neutrons (oxygen 16), but it can also have 18 protons and 10 netutrons (oxygen 18).  When the climate is colder, there is less oxygen 18 in the snow. This occurs because molecules move less when it’s colder (there’s less energy), so the heavier oxygen 18 falls out before it reaches the ice sheet. This is a complicated topic and 3 sentences do not do it justice. So don’t feel bad if it’s not making much sense – it’s because I can’t explain it well not being a chemist!

2. Borehole temperature profiles.  We can measure the temperature from the surface to the bed of the ice sheet by lowering a thermometer down a borehole (it’s fluid filled, but I’ll explain about that in a later post).  The temperature profile depends on three things: 1) the temperature at the surface; 2) the flow of the ice; and 3) the heat coming from the earth. With an ice flow model, you can reconstruct what the surface temperature must have been in the past.

3.  Mass and Temperature Dependent Fractionation of Stable Isotopes in Gases. Yeah, I’m frightened by the concept too, so I’m not even going to try to explain this one.

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