On April 19, Dan Blake, Daniel Hansen and Dr. Rhett Herman will be leaving on a one-week trip to perform a preliminary geophysical study of the North Pole ice cap. These three will be part of a research team from the NASA Goddard Space Flight Center, Michigan State University, Bay Mills Community College (Michigan), Yale University, and the U. S. Army's Cold Regions Research and Engineering Laboratories (CRREL). This team will establish a long-term study of the thickness of the polar ice cap in order to better understand the how the volume of this ice may be changing over time.
The Radford University participants will be bringing an EM-31 electromagnetic geophysical device around which this research will be built. This device transmits and receives low frequency (9.8 kilo-Hertz) radio waves from opposite ends of a 3.7-meter-long tube. As with all electromagnetic waves, these waves can be interfered with due to whatever materials are nearby. The electrical properties of these nearby materials determine the amount of interference, and thus the interference recorded by this instrument gives an indication of the type and amount of the materials near this device.
The EM-31 translates this interference into a measure of the materials' electrical "conductivity," which is a measure of how well the materials conduct electricity. Good electrical conductors such as salty seawater have high conductivity values, while poor conductors such as ice--out of which the salt has been extruded during the freezing process--have low conductivity values.
The EM-31 is a low-power unit and thus will register interference only from materials nearby. The unit sends out these waves unequally in two directions, allowing the operator to rotate the instrument about its long axis and record average conductivity values of the subsurface materials to average depths of 3 meters and 6 meters. This gives an idea of any layered structure in the subsurface.
While at the pole, we will drill narrow boreholes through the ice in several places to measure the ice thickness directly. Then, these known values will be correlated to the conductivity readings of the EM-31. Assuming a simple two-layer structure of relativity thin, poorly conducting ice on top of the underlying strongly conducting seawater, the conductivity values should vary with the ice thickness. From this data, we will construct a calibration curve from which subsequent EM-31 readings will be related to ice thickness without having to drill any more boreholes.
The ultimate goal of this mission is to correlate the readings of ice thickness that we measure with measurements taken from NASA's and NOAA's satellites that fly over the pole. These satellites take their readings with various instruments, but no one knows exactly how those readings translate into a definite (within known error bars) ice thickness. NASA calls this process "validation" of their remote sensing satellites. Thus, the steps in this particular validation are (1) measure the ice thickness directly at a few points by drilling; (2) measure the ice thickness indirectly over a large area--large enough to be measured by satellites--through our EM-31 readings and the calibration curve; and (3) match our direct/indirect readings with the satellite readings so that, in the future, NASA can measure ice thickness remotely (and accurately) using these satellites.
R.U. F.R.E.E.Z.I.N.G. North Pole 2003: Trip Itinerary
Geophysical survey plan for this trip
The University Centre on Svalbard, where we'll be staying for part of this trip.
RU science explores the arctic, Tartan Article
NASA's SPI Office FRIGID Home page
Bay Mills Community College: The Great North Pole Waasnoodeg Expedition
American International College (AIC) Springfield, MA