Sunday, November 23, 2014


Saturday morning was spent to the second and the last part of the field training around Utsteinen. Only Nicolas dropped out on this one because he had to revisit the cGPS station at Asuka. Frank dropped out as well ... because of not enough skidoos around. On the program: handling the skidoo ! Now, everyone is ready to get into the field in a secure way.


The remainder of the day was spent on verifying and testing different instruments: Frank and Brice took care of the pRES, GSSI, and several GPS systems (assembly of antennas, material checking, matlab code verifications, …). A novel part of the field trip is the use of a phase-sensitive radar (or pRES). As any other radar we commonly use in polar regions, the pRES enables to determine the thickness of the ice by sending out an electromagnetic signal that bounces off when it reaches the bottom of the ice and is received back at the instrument. The wave speed through ice is known, so that the ice thickness can be inferred. However, any radar is also capable of detecting internal structures in the ice. The pRES is capable of seeing changes in the position of these structures over time. So, if you send out at exact the same place an electromagnetic signal a year later, you may detect the change in position of these structures, from which the vertical flow of the ice can be inferred. This is quite unique, because we normally don't have any direct measurement of how ice moves at it interior. At the surface, horizontal flow speeds are easily detected through a GPS measurement, but not inside the ice mass. These parameters are essential in the IceCon project, because the ice dynamics need to be taken into account to interpret our geodetic GPS signals.

During this time, Morgane et Jean-Louis finished the assembly of the last parts of the drill. It is no easy task as some connections need to be welded, inside a very crucial section, called "the anti-torque". This fancy device aims at decoupling the movement of the drill motor, from the movement of the cable to which it is attached. Having done that, we assembled the winch that lifts up the drill from the horizontal to the vertical position. We are almost ready for the first test borehole. This one will be used to test another instrument, a borehole camera that produces a virtual image of the ice core. Another borehole will be drilled in blue ice, in order to test the efficiency of the new cutting head for drilling into stiff ice.


Once in the field, we will drill two 30 m deep ice cores on Derwael Ice Rise, 2 km on each side of the divide, to investigate the spatial variability of snow accumulation induced by this 300 m high topographic feature. We will then move the base camp on the "Roi Baudouin Ice Shelf", where we will drill all the way down the ice shelf to reach the ocean water (about 150 meters) and investigate the presence of marine ice. This ice is in fact refrozen meltwater that accumulates under the ice shelf, influencing its stability.






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