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Quitting Time for Greenland Crew: 430 Miles and Four Cores Later


The Arctic Circle Traverse 2011 (ACT-11) team finished drilling the fourth and final core.  This one was 61 meters (200 feet) deep into the Greenland Ice Sheet.  The total depth of all the cores is 156 meters (512 feet)–almost two football fields in lengths.  All of the ice from the cores has already been transported back to the village of Kangerlussuaq, Greenland (Kanger) where it is temporarily stored in a freezer.  Later this summer a U.S. Air National Guard cargo plane (Hercules C-130) will fly the cores back to Schenectady, New York.  There they will be met by a freezer truck and driven to the Desert Research Institute, in Reno, Nevada where they will be chemically analyzed to identify the annual layers.  We will use this information to calculate annual snow accumulation rates over the last several decades at these four core locations.   

The ACT11 team also profiled the entire length of their traverse in the return direction using an ice-penetrating radar.  The radar can map the subsurface annual layers between the core sites.  Therefore we can measure the snow accumulation rate not only at the four core locations but also along the entire 345 km of the traverse.  This allows us to observe how snow accumulation changes not just over the past decades but also how it changes over the distance from the center of the ice sheet to east coast.  This information is important to calculate the total amount of mass that is being added to the ice sheet each year.  The amount of ice mass lost from melting, ice berg calving, and sublimation of snow directly into the atmosphere is subtracted from the mass added by snow accumulation.  This difference is then used to determine the total amount of mass change on the Greenland Ice Sheet.  Greenland has been losing mass over the last 11 years.  The rate of this mass loss is increasing yearly, meaning there is an acceleration in the loss.  This lost mass eventually all ends up as water in the global oceans and is one of the contributors to present-day sea level rise. 

The ACT11 team is now back at their put-in/take-out site on the ice sheet, Raven.  Here a ski-equipped Air National Guard C-130 is scheduled to pick them up and take them back to Kanger on May 19th.  They will return to Salt Lake City via Schenectady a few days after that.  Our group will spend the summer and into next year analyzing the terabytes of data collected on the ground and with a NASA airborne radar system flown over the ACT11 traverse.

The photo above shows the snow mobile and radar sled used to profile the subsurface snow accumulation layers.  The 200 MHz radar antenna is in the square orange box on the sled.  The larger wooden box contains the radar controller, data storage, and marine battery for power.  The box is covered with solar panels used to recharge the battery.  The wooden box on the snow mobile contains the rover GPS and battery.  The GPS antenna is mounted on a pole attached to the GPS box.  When combined with a GPS base station deployed by the ACT11 team on the ice sheet, the GPS data will provide centimeter-scale topography of the traverse.