The accumulation pattern across Siple Dome, West Antarctica, inferred from radar-detected internal layers

Abstract The spatial distribution of accumulation across Siple Dome, West Antarctica, is determined from analysis of the shapes of internal layers detected by radio-echo sounding (RES) measurements. A range of assumed accumulation patterns is used in an ice-flow model to calculate a set of internal layer patterns. Inverse techniques are used to determine which assumed accumulation pattern produces a calculated internal layer pattern that best matches the shape of internal layers from RES measurements. All of the observed internal layer shapes at Siple Dome can be matched using a spatially asymmetric accumulation pattern which has been steady over time. Relative to the divide, the best-fitting accumulation pattern predicts 40% less accumulation 30 km from the divide on the south flank of Siple Dome and 15–40% more accumulation 30 km from the divide on the north flank. The data also allow the possibility for a small time variation of the pattern north of the divide. The mismatch between the calculated and the observed layer shapes is slightly reduced when the accumulation rate north of the divide is higher in the past (> 5kyr BP) than at present. Sensitivity tests show that the predicted change in the spatial accumulation pattern required to cause the slight Siple Dome divide migration (inferred from previous studies) would be detectable in the internal layer pattern if it persisted for > 2 kyr. Our analysis reveals no evidence that such a change has occurred, and the possible change in accumulation distribution allowed by the data is in the opposite sense. Therefore, it is unlikely that the Siple Dome divide migration has been caused by a temporal change in the spatial pattern of accumulation. This conclusion suggests the migration may be caused by elevation changes in Ice Streams C and D at the boundaries of Siple Dome.

[1]  T. Scambos,et al.  Changes in the margin of Ice Stream C, Antarctica , 2000, Journal of Glaciology.

[2]  R. Alley,et al.  Response of the East Antarctica ice sheet to sea-level rise , 1984 .

[3]  T. Scambos,et al.  Improving AVHRR Resolution Through Data Cumulation for Mapping Polar Ice Sheets , 1999 .

[4]  C. Hammer,et al.  Acidity of Polar Ice Cores in Relation to Absolute Dating, Past Volcanism, and Radio–Echoes , 1980, Journal of Glaciology.

[5]  R. Alley,et al.  The effect of ice-sheet thickness change on the accumulation history inferred from GISP2 layer thicknesses , 1995, Annals of Glaciology.

[6]  A. Gades,et al.  Bed properties of Siple Dome and adjacent ice streams, West Antarctica, inferred from radio-echo sounding measurements , 2000, Journal of Glaciology.

[7]  N. Reeh.  A Flow-line Model for Calculating the Surface Profile and the Velocity, Strain-rate, and Stress Fields in an Ice Sheet , 1988 .

[8]  R. Hindmarsh,et al.  Stochastic perturbation of divide position , 1996, Annals of Glaciology.

[9]  P. Mayewski,et al.  Seasonal variations of glaciochemical, isotopic and stratigraphic properties in Siple Dome (Antarctica) surface snow , 1999, Annals of Glaciology.

[10]  C. Raymond.  Deformation in the Vicinity of Ice Divides , 1983 .

[11]  R. Hindmarsh,et al.  Sensitivity of the divide position at Siple Dome, West Antarctica, to boundary forcing , 1998, Annals of Glaciology.

[12]  E. Waddington.  Accurate modelling of glacier flow , 1981 .

[13]  Robert W. Jacobel,et al.  Migration of the Siple Dome ice divide, West Antarctica , 1998 .

[14]  T. Scambos,et al.  Changes in the configuration of ice stream flow from the West Antarctic Ice Sheet , 1996 .

[15]  Gary D. Clow,et al.  Temperature, accumulation, and ice sheet elevation in central Greenland through the last deglacial transition , 1997 .

[16]  Dorthe Dahl-Jensen,et al.  Past accumulation rates derived from observed annual layers in the grip ice core from summit , 1993 .

[17]  David H. Bromwich,et al.  Snowfall in high southern latitudes , 1988 .

[18]  E. Steig,et al.  Using the sunspot cycle to date ice cores , 1998 .

[19]  C. Raymond,et al.  Predicted age-depth scales for Siple Dome and inland WAIS ice cores in west Antarctica , 1996 .

[20]  I. Willis,et al.  THE PHYSICS OF GLACIERS, third edition, by W. S. B. Paterson, Elsevier, Oxford, New York and Tokyo, 1994. No. of pages: ix + 480. Price £25.00. ISBN 0080379443. , 1996 .

[21]  E. Steig.  How well can we parameterize past accumulation rates in polar ice sheets , 1997 .

[22]  Constraints on holocene ice-thickness changes in central Greenland from the GISP2 ice-core data , 1995 .

[23]  W. Paterson,et al.  Estimated basal ice temperatures at Crête, Greenland, throughout a glacial cycle , 1986 .

[24]  C. H. Harrison.  Radio Echo Sounding of Horizontal Layers in Ice , 1973 .

[25]  P. Mayewski,et al.  Glaciochemical Studies at Siple Dome, West Antarctica, during the 1996–1997 Season , 1997 .

[26]  R. Alley,et al.  Abrupt increase in Greenland snow accumulation at the end of the Younger Dryas event , 1993, Nature.

[27]  D. Vaughan,et al.  Distortion of isochronous layers in ice revealed by ground-penetrating radar , 1999, Nature.

[28]  J. F. Nye.  A numerical method of inferring the budget history of a glacier from its advance and retreat , 1965 .

[29]  Eric W. Wolff,et al.  The chemical basis for the electrical stratigraphy of ice , 1992 .

[30]  G. Robin,et al.  Internal reflections in polar ice sheets , 1975 .

[31]  N. Nereson.  The flow history of Siple Dome and Ice Streams C and D, West Antarctica: Inferences from geophysical measurements and ice flow models , 1998 .