I'm down here working with scientists from the POLENET project. Our aim is to collect GPS and seismic data from both Greenland and Antarctica. There is some information, and podcasts from last year, here: http://www.polenet.org/
In my normal life I run computer models which attempt to reconstruct the extent of the Antarctic ice sheet over the last 20,000 years - the time since the last ice age. The Antarctic ice sheet was bigger 20,000 years ago, and since this time ~3.6 x 10^18 kg of ice has
melted; enough to raise sea level by ~10m. The removal of this mass of ice from Antarctica causes the land underneath the ice to rebound upwards, like a set of scales. However, the Earth actually behaves like a viscous fluid, therefore the rebound is not instantaneous, but continues to the present-day, even though most of the ice melting took place several thousand years ago. The GPS receivers that we are deploying will sit on rocky outcrops and measure this rate of rebound - the picture opposite is the GPS receiver here at McMurdo.
melted; enough to raise sea level by ~10m. The removal of this mass of ice from Antarctica causes the land underneath the ice to rebound upwards, like a set of scales. However, the Earth actually behaves like a viscous fluid, therefore the rebound is not instantaneous, but continues to the present-day, even though most of the ice melting took place several thousand years ago. The GPS receivers that we are deploying will sit on rocky outcrops and measure this rate of rebound - the picture opposite is the GPS receiver here at McMurdo.Meanwhile, the seismometers record the passing of seismic waves. These are released whenever there is an earthquake anywhere around the world; the waves travel through the interior of the Earth, and the time taken for the waves to reach our seismometers in Antarctica tells us about the structure of the Earth beneath; it's density, elasticity and viscosity. This information allows us to predict how the solid Earth will respond to changes in ice mass, i.e. the rate of postglacial rebound.
It gets a little tricky at this point. The rate of rebound measured by the GPS receivers is actually a combination of two processes: rebound due to past ice mass changes, and rebound due to present-day ice melting. Any mismatch between my model predictions (of rebound due to past ice melting) and the GPS observations may therefore be attributed to current melting.
The particular GPS receivers that I'll be installing will be around Pine Island Glacier (PIG) - this is thought to be the fastest-melting glacier in Antarctica so our measurements will provide an important insight into precisely how fast it is melting, and hence how much it is contributing to sea-level rise.Flights are still all over the place, with another two cancelled this morning, but we are still firmly on the departure board, so have our fingers crossed that we will escape today...
On a lighter note here is a link to the start of the Turkey Trot:
http://www.youtube.com/watch?v=5k-MNP-WraM&NR=1I am in my usual camouflage black.
No comments:
Post a Comment