Corridor Aerogeophysics of the South East Ross Transect Zone (CASERTZ)

Principle Investigator: Don Blankenship, University of Texas
NSF Program: Office of Polar Programs, NSF Award Number  OPP-9120464, 9319369 (and 9319379)

(in collaboration with U.S. Geological Survey, Naval Research Laboratory and Lamont-Doherty Earth Observatory)
 

Download CASERTZ data

Background

The CASERTZ scientific objective was to understand the lithospheric framework across the West Antarctic rift system in order to determine the geological controls on the dynamics of the West Antarctic Ice Sheet, the last marine ice sheet. These experiments included a suite of aerogeophysical measurements made within carefully chosen corridors. These corridors covered the eastern portion of the Interior Ross Embayment and encompassed: 1) the initiation zone and catchment regions of ice streams B and C and all of ice stream D from the ice divide to the grounding line (IRE, BSB, and TKD, respectively); and 2) the boundary between the broadly extended portion of the West Antarctic rift system within the Interior Ross Embayment and the crustal provinces dominated by the Whitmore Mountains and the Byrd Subglacial Basin (IRE and BSB, respectively). The experimental objective was to characterize and correlate the distribution of sedimentary basins, volcanic rocks and important ice dynamical boundaries within these corridors.

Technical Development

To achieve these objectives, CASERTZ required a system capable of simultaneously measuring the precise surface elevation and ice thickness needed for ice sheet studies, as well as the potential field observations necessary for inferring subglacial geology. UTIG, as lead institution for CASERTZ, benefited substantially from the expertise of its collaborating institutions, which included the USGS as well as the Naval Research Laboratory and Lamont Doherty Earth Observatory (NRL/LDEO). Initially, the CASERTZ instrumentation focus was only ice-penetrating radar, laser altimetry and magnetics in collaboration with the USGS but ultimately, with the assistance of NRL/LDEO, UTIG successfully developed an integrated aerogeophysical platform that included airborne gravity with carrier-phase GPS to support kinematic differential positioning. UTIG also developed flight structures for these instruments including an antenna system for radar sounding, access ports for laser altimetry, a towed magnetometer system and flight-certified equipment racking systems that placed the gravimeter near the aircraft's center of gravity. In parallel with the instrument integration, we also designed and implemented a comprehensive data management system to tightly couple time/position with the integrated aerogeophysical observations. During the initial two field seasons in West Antarctica, UTIG, with the assistance of the USGS and NRL/LDEO, used this system to collect 50,000 line km of geophysical observations within the region shown as IRE the coverage map. Details of the instrumentation can be found here.

In 1994, in response to the science proposal to complete the CASERTZ corridors, the National Science Foundation's Office of Polar Programs requested that the aircraft and its integrated instrumentation package be operated as a facility with a mission of providing aerogeophysical observations to the broader Antarctic science community. This request led to a Cooperative Agreement between UTIG and NSF that created the Support Office for Aerogeophysical Research (SOAR).

Results

Volcano figure

Geological Controls on Ice Streams

Airborne geophysical results from the Interior Ross Embayment (IRE) from Blankenship et al., [2001]. (a) Surface topography from laser altimetry showing the steady downslope from the interior ice (along 105° W) to the onset regions of ice stream B and C branches B2, C1a, C1b and C2 as indicated by the white hatchure of crevasses identified by radar scattering. Superimposed with this figure are 50 and 100 kPa driving stress contours in blue and red, respectively. These bound the areas of ice stream onset; above 100 kPa ice flows by internal deformation, below 50 kPa rapid basal motion enabled by some process with an effectively weaker rheology than that of ice. (b) Bed elevation from radar sounding showing, in red, the Ellsworth-Whitmore Mountain Block and, in violet, troughs that locate the various ice stream tributaries. Contours of critical driving stress and the outline of the EWB from the subglacial topography are overlaid on maps of Bouguer gravity (c) and Magnetic field intensity (d).

From the analysis presented in Blankenship et al., [2001], we concluded that the only consistent control on the initiation of ice streaming in the IRE survey was the presence of a thin marine sediment drape that was deposited prior to West Antarctic glaciation. A follow-study by Studinger extended this conclusion to the BSB survey block as well.

WAISCORES site selection

Selected Publications

Morse, D. L., D. D. Blankenship, E. D. Waddington and T. A. Neumann. 2002. A site for deep ice coring in West Antarctica: Results from aerogeophysical surveys and thermo-kinematic modeling. Annals of Glaciology, 35, p. 36-44.

Studinger, M., R. E. Bell, C. A. Finn and D. D. Blankenship. Mesozoic and Cenozoic extensional tectonics of the West Antarctic rift system from high-resolution airborne geophysical mapping. In Gamble J.A., D.N.B Skinner, S. Henrys and R. Lynch, eds., Antarctica at the close of a millennium, Proceedings volume 8th International Symposium on Antarctic Earth Sciences, Royal Society of New Zealand Bulletin, vol. 35, p. 563-569 (2002).

Blankenship, D. D., D. L. Morse, C. A. Finn, R. E. Bell, M. E. Peters, S. D. Kempf, S. M. Hodge, M. Studinger, J. C. Behrendt, and J. M. Brozena. 2001, Geological controls on the initiation of rapid basalmotion for West Antarctic ice streams: A geophysical perspective including new airborne radar sounding and laser altimetry results. In Alley, R. B. and R. A. Bindschadler eds., The West Antarctic Ice Sheet: Behavior and Environment, American Geophysical Union, p. 105 - 121.

Sweeney, R. E., C. A. Finn, D. D. Blankenship, R. E. Bell and J. C. Behrendt. Central West Antarctica aeromagnetic data: a web site for distribution of data and maps. Open File Report 99-420, U. S. Geological Survey, (1999).

Bell, R.E., D.D. Blankenship, C.A. Finn, D.L. Morse, T.A. Scambos, J.M. Brozena and S.M. Hodge. Influence of subglacial geology on the onset of a West Antarctic ice stream from aerogeophysical observations. Nature, vol. 394, no. 6688, p. 58-62 (1998).

Behrendt, J.C., C.A. Finn, D.D. Blankenship and R.E. Bell. Aeromagnetic evidence for a volcanic caldera(?) complex beneath the divide of the West Antarctic ice sheet. Geophysical Research Letters, vol. 25, no. 23, p. 4385-4388 (1998).

Behrendt, J.C., D.D. Blankenship, D. Damaske, A.K. Cooper, C. Finn and R.E. Bell. Geophysical evidence for Late Cenozoic subglacial volcanism beneath the West Antarctic Ice Sheet and additional speculation as to its origin. In Rice, C.A., ed., The Antarctic Region: Geological Evolution and Processes, Terra Antarctica Publication, Siena, p. 539-546 (1997).

Behrendt, J.C., R. Saltus, D. Damaske, A. McCafferty, C.A. Finn, D.D. Blankenship and R.E. Bell. Patterns of late Cenozoic volcanic and tectonic activity in the West Antarctic rift system revealed by aeromagnetic surveys. Tectonics, vol. 15, no. 2, p. 660-676 (1996).

Bindschadler, R., P. Vornberger, D. Blankenship, T. Scambos and R. Jacobel. Surface velocity and mass balance of ice streams D and E, West Antarctica. Journal of Glaciology, vol. 42, no. 142, p. 461-475 (1996).