Snow accumulation and compaction derived from GPR data near Ross Island, Antarctica

• Published in: The Cryosphere
• Main Authors: Kruetzmann, NC, Rack, W, McDonald, AJ, George, SE
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2011
• Subjects: Earth Sciences; Climate change science; Climatology; McMurdo Ice Shelf; Ross Island; Scott Base; Antarc*; Antarctica; Ice Shelf; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-5-391-2011; http://ecite.utas.edu.au/77810

We present an improved method for estimating accumulationand compaction rates of dry snow in Antarcticawith ground penetrating radar (GPR). Using an estimate ofthe emitted waveform from direct measurements, we applydeterministic deconvolution via the Fourier domain to GPRdata with a nominal frequency of 500 MHz. This revealsunambiguous reflection horizons which can be observed inrepeat measurements made one year apart. At two measurementsites near Scott Base, Antarctica, we extrapolatepoint measurements of average accumulation from snow pitsand firn cores to a larger area by identifying a dateable dustlayer horizon in the radargrams. Over an 800mx800m areaon the McMurdo Ice Shelf (77degree45' S, 167degree17' E) the averageaccumulation is found to be 269+-9 kgm-2 a-1. Theaccumulation over an area of 400mx400m on Ross Island(77degree40' S, 167degree11' E, 350ma.s.l.) is found to be higher(404+-22 kgm-2 a-1) and shows increased variability relatedto undulating terrain. Compaction of snow between2m and 13m depth is estimated at both sites by trackingseveral internal reflection horizons along the radar profilesand calculating the average change in separation of horizonpairs from one year to the next. The derived compaction ratesrange from 7 cmm-1 at a depth of 2 m, down to no measurablecompaction at 13m depth, and are similar to publishedvalues from point measurements.