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WAISCORES: Deep Ice Coring in West Antarctica

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Electrical Measurements on the Siple Dome, Antarctica Ice Core

Principal Investigator: Kendrick Taylor

This project measured the Electrical Conductivity (ECM) and Complex Conductivity (a.k.a CC, which is a measure of the total ions in the ice) along the main core from a depth of 0 to 800m. Poor core quality precluded measurements below 800 m. The project also measured ECM and Dielectric Properties (a.k.a. DEP, also a measure of the total ions in the ice but with lower spatial resolution than the Complex Conductivity measurement) on the shallow cores. Albedo measurements where made on the shallow cores and the main core to a depth of 391 m. Use of the albedo system was discontinued below 391 meters because it proved not to be effective.

A new method was developed that produces images showing the electrical conductivity of a vertical section of the core. This method (a.k.a multitrack ECM) allows the stratigraphy of the core to be observed in a quantitative way. Features such as discontinuous and incline layers can be observed, visually enhanced, and documented electronically.

The most significant use of the electrical methods was to date the top 11,920 years of the core. A computer algorithm was developed to identify annual layers and count them. This algorithm was trained using manual interpretations and was tuned such that features in the methane stratigraphy have the same age at Siple Dome as at GISP2. The computer algorithm was more consistent that manual interpretation methods. The time scale developed by this method is the basis for interpretation of all the records spanning last 11,920 years.

At the 43 depths the multitrack ECM was used, it demonstrated that down to a depth of ~850 m the stratigraphy did not have abnormal layering such as pitchouts and steeply inclined layering, except at one depth when there was an accumulation hiatus. Below 850 m regular layering was not found, possibly due to diffusion of the chemistry. This method should be utilized more in the future to search for stratigraphy irregularities.

Publications:

Taylor, K.C., R.B. Alley, D.A. Meese, M.K. Spencer, E.J. Brook, N.W. Dunbar, R. Finkel, A.J. Gow, A.V. Kurbatov, G.W. Lamorey, P.A. Mayewski, E. Meyerson, K. Nishiizumi, G.A. Zielinski. 2004. Dating the Siple Dome, Antarctica Ice Core by Manual and Computer Interpretation of Annual Layering. Submitted to Journal of Glaciology.

Taylor, K.C., J.W.C. White, E. Brook, J.P. Severinghaus, R.B. Alley, E.J. Steig, M.K. Spencer, E.A. Meyerson, D. Meese, P.A. Mayewski, Grachev, P.B. Price, A.J. Gow, G.W. Lamorey, R.C. Bay, and B. Barnet. Abrupt late glacial climate change in the Pacific sector of Antarctica. Science.

This paper presents all the Siple Dome evidence for two abrupt climate changes in the Ross sea area during the deglacial. The exciting thing is that the Southern most Pacific is capable of abrupt climate changes with the same magnitude as we saw in Greenland. This means that the Southern Pacific is probably as important in controlling abrupt climate changes as the North Atlantic.

Taylor, K.C., R.B. Alley, M.K. Spencer, D. Meese, and A.J. Gow. Automatic dating of ice cores by identification of annual layers. Journal of Geophysical Research.

This paper describes how the SDM core was dated with annual layers. It is not an exciting a topic, but it is the foundation for publications by other investigators. It has been delayed because the methane stratigraphy that provides the tie to GISP2 only became available in January 2002.

Taylor, K.C. Electrical stratigraphy of the Siple Dome, Antarctica ice core. Journal of Glaciology.

This paper discusses the Complex Conductivity and multitrack methods. And shows how the multitrack ECM method can identify disturbed stratigraphy.