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Up and Running in Greenland: Two Cores in the Bag

144087main_GREENLAND

Two graduate students from the University of Utah geography department, Clement Miege and Evan Burgess, have traversed over 400 km (250 miles) on snowmobiles, so far, on the Greenland Ice Sheet and acquired two ice cores. They will continue their traverse another 300 km (186 miles) acquiring a two more ice cores while profiling the ice sheet using an ice penetrating radar. They were delayed by weather for a time, but are now making up for lost time.

The ice cores are four-inch diameter tubes of ice that are drilled in one meter long segments. The upper 50 meters of the ice sheet is made of snow from the previous several decades that is denser than the snow we have in Utah—even at the bottom of our spring snow pack. But it is not compressed all the way into glacial ice; that typically occurs at 80 to 100 meter depths. The material in this transition between snow that fell this year and the glacier ice at depth is called “firn” and is defined as snow that has lasted through at least one summer melt season. Therefore, technically our cores are not ice cores, but firn cores. Our group is drilling cores about 50 meters deep, therefore it takes 50 individual core segments to make up one core.

Clement Miege preparing one of the core segments for storage on the ice sheet.

Once the hollow drill barrel is on the surface, the core is carefully pushed out of the drill onto a clean metal tray. (Recall that each segment is about one meter long.) The core is measured and slid into a long narrow plastic bag custom made for these cores. A note card is attached to the core indicating the latitude, longitude and elevation of the core site, along with its depth below the surface. The bagged core segment is then slid into a hard cardboard tube similar to a map tube and labeled again. Each of these core tubes are put into an insulated core box which holds six cores. These boxes are then left at the core site to be picked up by a small twin engine airplane equipped with skis.

The core boxes are flown back to the village in Greenland (Kangerlussuaq) where the U.S. National Science Foundation bases its operations for Greenland research. They are stored in a freezer until the end of summer when the U.S. Air National Guard flies them back to Schenectady, New York on an unheated C-130 cargo plane. From there the cores are put on a freezer truck and driven to the Desert Research Institute in Reno, Nevada where chemical analysis is used to date the annual snow layers. Once we have the relationship between age of the firn and depth, we can calculate the exact amount of snow that accumulated for each year represented in the core (typically back to the 1970’s for a 50 meter core).

This data will allow us better measure the amount of snow that has been accumulating on the south-east portion of the ice sheet. This area receives more snow than any other on the entire ice sheet. It is estimated that up to four meters (13 feet) of snow is added to the ice sheet each year. This information is required to measure the net amount of ice that is being lost from the Greenland Ice Sheet and contributing to current sea level rise as well as predict future sea level rise.

With all this snow typical for the area it is not surprising that the team has been delayed for nearly two weeks total due to a sequence of storms with blizzard conditions. To top it off, last month southern Greenland was about 20 degrees C (36 degrees F) colder than normal with temperatures around -45 C (-48 F) on most days. The team is now setting up camp to drill the third core and should have it done by the end of the week (May 6, 2011).

Ed. note:  A reminder to readers that you can track the team’s progress in real time by clicking here