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Paleo Slide Set: Polar Ice Cores
Electrical Conductivity Measurements (ECM) being conducted on the entire length of the core
A total of 42 types of measurements comprise the GISP2 research effort. These include: CO2, O, and NOx in air bubbles trapped in the ice; concentrations of major ions (Na+, NH4+, K+, Mg++, Ca++, Cl-, NO3-, SO42-); cosmogenic isotopes ; stable isotopes; dust; electrical conductivity; and physical properties like crystal characteristics. The amount of data collected from the GISP2 core is truly astronomical, and it is possible in this presentation to introduce only a fraction of the body of knowledge gained during this massive effort.

Analyses that are costly or time-consuming can only be performed on selected segments of ice. Others like Electrical Conductivity Measurements (ECM, pictured here) are done on the entire length of the core. ECM is a fast and high-resolution way of measuring ice acidity. Two electrodes are drawn along the surface of the ice core while the electrical resistance (which varies as a function of acidity) between them is measured.

ECM is important for three reasons. First, it is well suited to detecting volcanic events in the core record. Volcanic eruptions emit large amounts of sulfur gases that react in the atmosphere with water to produce sulfuric acid (H2SO4). Given the right atmospheric conditions, some of this acid-enriched moisture may be transported to Greenland and precipitated onto the Greenland Ice Sheet, where it is incorporated into the glacier. These volcanic events often appear in the ECM record as large values reflecting high acid content because of the SO42-. Secondly, ECM is relatively easy to measure and is performed on the entire length of the core at a resolution of a few millimeters. Scientists look at ECM data to determine the location of interesting or significant climatic events that warrant further analyses, which ensures that researchers spend their time and money as effectively as possible. Finally, ECM varies seasonally, providing a high-resolution dating mechanism that, in conjunction with measurements of dust concentration and visual counting of annual dust bands (visual stratigraphy), allows the GISP2 core to be dated with unprecedented accuracy.

Photo Credits:
Mark Twickler
GISP2 SMO, University of New Hampshire.

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Last Modified: 12 October 2001

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