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Polar Radar for Ice Sheet Measurements

   
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  Thursday, July 21, 2005

Last night was the final chance to make ice cream with liquid nitrogen, as the liquid nitrogen generator was to be taken apart today. Robie, of the Georgia Tech team, took advantage of the available liquid nitrogen and made the last batch of ice cream. John and Torry returned to Summit around 11 p.m. last night after completing their first round-trip transects to GRIP. This round trip takes approximately 7 hours. They were tired from their first long day of driving the Tucker SnoCat, so they took it easy this morning, processing data and checking the equipment. Everything looks very good with the SAR radar survey so far.

Today was another beautiful day and a very productive day. We are still in the process of comparing the plane-wave radar echoes we measured from within the snow to the layering we see in the snow. Yesterday we (Tim and David) made measurements with the plane-wave radar at the shallow ice core drilling site six kilometers out of camp, and today four of us (David, Kirby, Pannir and Tim) examined a snow pit excavated by the U of Washington group near these measurements. David cut back the pit wall where samples had previously been collected, and shaped a flat wall to see the internal layers of the snow pack. After recording the types of internal layers and their depth and taking high-resolution digital images of the pit wall referenced with a ruler, Kirby made temperature measurements of the snow every 5 centimeters.

For lunch we returned to the Big House, where the water was off because of the construction, and we ate from paper plates and with plastic utensils. We were served burritos, rice, fruit salad, and honeydew melon. After lunch, Torry and John departed with the Tucker to make another roundtrip transect to GRIP, with hopes of doing two tomorrow.

The Georgia Tech team is digging a pit in the clean air zone, which should be about 3.5 meters deep by tomorrow. Gail and Robie are environmental engineering students, and Mike is their supervisor in the School of Earth and Atmospheric Sciences. Their research aims to understand the link between concentrations of carbon particles in the air and snow, and how these particles are modified once they are deposited in the snow. Their research will improve scientific understanding of the role of carbon particles in the atmosphere in past climate change by relating their findings to the concentrations of these particles in ice cores. Their work includes digging pits and collecting snow samples in jars, melting the snow, filtering the melt water, and then examining the filter with a Thermal Optical Transmitter. These measurements determine the amount of organic elemental carbon particles found in the snow. They take 10 samples per layer ; 8 are analyzed as described above and the last 2 are used to identify total organic carbon. While they are in the snow pit they wear clean suits to avoid contaminating the pits with carbon from their clothing. They will complete their sampling tomorrow, and will allow us to identify the internal layers and measure snow temperature in their 3.5-meter pit.

This afternoon, Tim, Pannir, and David began a 5-km traverse with the plane-wave radar sled along the “ATM” snow accumulation measurement line. After making measurements both out and back, they transferred the data from the sled to the computers in the WeatherPort. Tomorrow a snow pit will be excavated along this traverse path. For dinner we were served halibut, beef stew, lemon asparagus pasta, salad, broccoli, and German chocolate cake. John and Torry returned from their second traverse to GRIP at about 9 p.m. this evening. Everything went extremely well. They will be off again tomorrow morning.

NOTE: This was entire journal entry, not just page 1.

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