Radio-frequency probes of Antarctic ice at South Pole

• Published in: The Cryosphere
• Main Authors: Besson, David Zeke, Kravchenko, I.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Copernicus Publications on behalf of the European Geosciences Union. 2014
• Subjects: Antarctic; East Antarctica; South Pole; Antarc*; Antarctica; Ice Sheet; Norwegian Polar Institute; South pole; The Cryosphere
• Online Access: http://hdl.handle.net/1808/15840; https://doi.org/10.5194/tc-7-855-2013

Using hardware developed for the ARA (Askaryan Radio Array) particle astrophysics experiment, we herein report on the amplitude and temporal characteristics of polarized surface radar echo data collected in South Polar ice using radio sounding equipment with 0.5-ns echo-time sampling. We observe strong echoes at 6, 9.6, 13.9, 17, and 19 μs following vertical pulse emission from the surface, corresponding to reflectors in the upper half of the ice sheet. The synchronicity of those echoes for all broadcast azimuthal polarizations affirms the lack of observable birefringence over the upper half of the ice sheet. Of the five strongest echoes, three exhibit an evident amplitude correlation with the local surface ice flow direction, qualitatively consistent with measurements in East Antarctica. Combined with other radio echo sounding data, we conclude that observed birefringent asymmetries at South Pole are generated entirely in the lower half of the ice sheet. By contrast, birefringent asymmetries are observed at shallow depths in East Antarctica. The authors particularly thank Chris Allen and John Paden (University of Kansas), John Ralston (University of Kansas), Rebecca Boon (Pennsylvania State University), Joe MacGregor (University of Texas), and Kenny Matsuoka (Norwegian Polar Institute) for very helpful discussions, as well as our colleagues on the RICE and ANITA experiments. We also thank Andy Bricker of Lawrence High School (Lawrence, KS) for his assistance working with Lawrence High School students who performed essential antenna calibrations. This work was supported by the National Science Foundation’s Office of Polar Programs (grant OPP-0826747) and QuarkNet programs. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.