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Almost calibrated

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Editor’s note: Marine geophysicist Robin Bell is leading an expedition to Antarctica to explore a mysterious mountain range beneath the ice sheet. Following is the eleventh of her updates on the effort as part of ScientificAmerican.com‘s in-depth report on the "Future of the Poles."

McMURDO STATION, ANTARCTICA (December 10) — Flying over any town is an unusual request and McMurdo is not an exception.  When I asked if we could fly at 1,000 feet over town, I was greeted with skeptical looks.  McMurdo is nestled beneath a valley between Observation Hill and Hut Point.  The request sounded like a boondoggle.  I had to explain that to ensure the laser is correctly aligned with the aircraft frame, we have fly over pointed roofs.  Our Reigl laser is developed in Austria where there are ample pointed roofs for calibrating the instrument.  There are not many pointed roofs in Antarctica so flying over McMurdo seemed like the obvious answer. The large mess hall in McMurdo, and the central headquarters for the National Science Foundation each have pointed roofs. We would be aiming for the mess hall as it is a large and an easy target for the pilots. Eventually we were granted permission to overfly the town today.


Our laser  is mounted in the belly of the aircraft and  shoots  out the bottom.  A rotating mirror makes the laser beam point from one side to the other in rapid succession. Since the laser is pointing from side to side we can make an image several football fields wide as we fly. The first reduced images from our laser showed that we can image floating pieces of sea ice, icebergs and volcanic cones.   Lasers from space have been used to measure the vertical motion of the ice sheet.  In some places, the ice sheets are dropping at meters per year in response to changing climate. 

The same space laser, called IceSat, has captured parts of the ice sheet popping up by meters, while other sections collapse.  These surface motions are the result of lakes beneath the ice sheet filling up and draining. If we want to the use our laser data to understand whether things are changing we have to make sure the laser is properly aligned.  Hence we have to fly over one of those few pointed roofs.  We will use the information from the gravity meter on how the aircraft is tilting – correcting for the pitch roll and yaw. If the corrections are done properly the peaks of the roofs will be in the same position no matter which way we fly over McMurdo.

The flight is set for just after lunch.  We send people to the top of the ridges on either side of McMurdo.  Even our least outdoorsy team member climbs up to get a better view. Nick Frearson and I head to Observation Hill, locally called Ob Hill.  Atop Ob Hill is a cross erected by the surviving members of Scott’s 1913 expedition to the Pole commemorating their loss. 

The hike is a steep climb up the side of a volcanic cone.  We are soon sweating and listening to all the engines.  It is easy to mistake the large machinery around McMurdo for a Twin Otter.  We are only halfway up when the Twin Otter makes  its first pass, but we continue to scramble toward the top  it circles toward Castle Rock. 

Nick is beaming.  He has worked ridiculous hours for the last 20 months, away form his family in the U.K., while sharing time between New York and Kansas.  We usually only get to see the aircraft turn into a spec in the sky as it takes off from the snow.  We never get to admire her in the air.  On the final pass over McMurdo I am looking through my viewfinder when I yelp.  “Nick, they are going to buzz us.”  Nick is still shooting with his telephoto lens until the aircraft fills the view and he realizes the pilot Lexi is waving to him so he drops the camera and waves. 

After so many purchase orders, assembling boards and software it is marvelous to see the plane aloft collecting data. Nick’s enthusiastic wave to the aircraft – Sierra Julia Bravo – says everything.

Dispatches from the Bottom of the Earth: An Antarctic Expedition in Search of Lost Mountains Encased in Ice

CREDIT: Robin Bell



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