Draft Proposal 2004 - page 9

US ITASE Objectives

Changes in the Antarctic environment have the potential to exert major controls on the global environmental system. US ITASE activities developed thus far and in this proposal will provide important focus to the determination of the significance of environmental change in both West and East Antarctica.

During the 1999-2003 US ITASE program, science was conducted along ground-based traverses near the ice divides of the West Antarctic Ice Sheet and adjacent regions, satellite traverses into major ice drainage basins entering the Ross Sea by way of Siple Coast ice streams entering the Ross Ice Shelf, and into the Amundsen Sea by way of ice streams entering Pine Island Bay, and traverses from West Antarctica to the South Pole.

For the period 2005-2007, US ITASE proposes traverses along the interior margin of the Transantarctic Mountains of East Antarctica. The sum of these traverses (1999-2007) will provide environmental records (e.g., change in temperature and atmospheric circulation, ice accumulation rates, ice thickness, and internal radio-echo horizons) for the region surrounding the Ross Sea Embayment and through collaboration with Italian, French, and Australian ITASE colleagues north and west through Northern Victoria Land and Wilkes Land.

The US ITASE objectives listed below represent a combination of ideas developed by current US ITASE researchers and several additional researchers who are interested in submitting proposals for involvement in future US ITASE activities or in collaborating. They include: R. Ackert (WHOI), M. Albert (CRREL), S. Arcone (CRREL), R. Bales (Arizona), H. Borns (Maine), D. Bromwich (Ohio State), F. Carsey (JPL), D. Qin (Academia Sinica), M. Fily (France), M. Frezzotti (Italy), I. Goodwin (Australia), T. Gow (CRREL), B. Hall (Maine), G. Hamilton (Maine), T. Hughes (Maine), B. Jacobel (St Olaf), K. Kreutz (Maine), P. Mayewski (Maine), J. McConnell (DRI), D. Meeker (UNH/Maine), D. Meese (CRREL). C. Shuman (NASA), T. Scambos (Colorado), E. Steig (Washington), K. Taylor (DRI), B. Welch (St. Olaf), and J. White (Colorado). Additional input and involvement is always invited.

US ITASE science objectives that can be investigated through the information developed from a Ross Sea Embayment-Wilkes Land wide investigation that combines 1999-2003 US ITASE activities in West Antarctica plus proposed 2005-2007 activities in the region between Taylor Dome and South Pole include, but are not confined to the following:

  1. What is the current rate of change in mass balance over the Ross Sea Embayment region?
    The accumulation rate over Antarctica is an important parameter in understanding both the stability of the Antarctic ice sheet and change in climate (Giovinetto and Bull, 1987; Bentley and Giovinetto, 1992; Bindschadler, 1992; Jacobs and Hellmer, 1992). Numerical models of the ocean/atmosphere system (Manabe et al., 1992) suggest that increases in atmospheric CO2 may dramatically increase the precipitation at extreme southern latitudes. As an example, results from Wilkes Land in East Antarctica (Morgan et al., 1991) have already detected increases in snow accumulation since 1960 on the order of 20% above the long-term mean (1806-present). Results from US ITASE activities in Antarctica reveal significant complexity as a consequence of distance from the ocean, topography and change in climate (Spikes et al., in press 2004; Kaspari et al., in press 2004).

    The East Antarctic Ice Sheet (EAIS) stores a considerably larger volume of potential sea level rise than the West Antarctic Ice Sheet, yet is far less explored. Measurements of the rates of ice sheet thickness change are being conducted at only three sites in EAIS: South Pole, Taylor Dome and Vostok. Additional measurements are required to assess spatial variability in ice sheet change. One hypothesis is that interior portions of EAIS are close to mass balance (as suggested by results from South Pole), but this needs to be tested at other interior sites. More recent work on Byrd Glacier using satellite imagery suggests that important changes are underway on this large outlet glacier (Stearns and Hamilton, submitted). Ground-based measurements are particularly necessary in interior EAIS because ICESat (launched in 2003 to study ice sheet elevation changes) does not include coverage of the ice sheet south of 86 degrees and is also experiencing a scaled-back measurement program because of technical difficulties.

    Modern rates of thickness change along an ice sheet transect bordering the Transantarctic Mountains will be important for deciphering the deglacial history contained in bedrock rebound rates. Very precise measurements of rock motions are underway as part of TAMDEF (T. Wilson, Ohio State). Once the present day ice sheet contribution is accounted for, these rebound rates will be used to constrain past ice sheet volume.
  2. What is the ice dynamics history of the Ross Sea Embayment?
    US ITASE traverses (1999-2003) provided glaciological data (e.g., ice accumulation rates, ice thickness, and internal radio-echo horizons) needed to model West Antarctic ice draining north into Pine Island and west into the Ross Ice Shelf, in addition to ice entering from the south through the Bottleneck between the East and West Antarctic Ice Sheets. The Taylor Dome to South Pole traverse will provide these data for ice entering the Ross Sea Embayment from the south and west, with remote sensing investigations and proposed traverses to the Transantarctic Mountains between and along the major ice streams (notably Beardmore Glacier, Nimrod Glacier, Byrd Glacier, Mullock Glacier, and David Glacier). The imagery and traverses will provide glaciological data needed to study the transitions from sheet flow to stream flow and glacial geological data needed to determine the former elevation of East Antarctic ice before the Ross Sea Embayment formed. As the 2005-2006 US ITASE traverse moves south from Taylor Dome, it will leave a region that shows widespread evidence of extensive glacial collapse reported by Mayewski et al. (1979) (e.g., hanging glaciers), and where Anderson (pers. comm.) has mapped deep submarine glacial troughs that were eroded by former ice streams. This is evidence of enhanced gravitational collapse of the East Antarctic Ice Sheet in this region that took place when ice streams became unbuttressed by ice shelves that disintegrated during late glacial climate warming and rising sea level. Understanding this deglaciation history will provide insights on how the West Antarctic Ice Sheet may experience accelerated gravitational collapse as modern ice streams surge into regions such as Pine Island Bay.
  3. What is the detailed subglacial structure of the ice streams entering the Ross Sea Embayment and how do these ice streams form?
    Early results from the first RADARSAT Antarctic Mapping Mission revealed that major outlet glaciers draining through the Transantarctic Mountains are supplied with ice from feeder ice streams that converge in the main trunk outlet glaciers, and that these feeder ice streams probably follow bedrock channels that branch from the fjord occupied by the outlet glacier. In some cases these feeder branches are hundreds of kilometers long, so that stream flow develops far into the interior of the East Antarctic ice sheet. The proposed traverse will cross the upper reaches of many of these feeder ice streams that converge on major outlet glaciers in the Transantarctic Mountains and follow several ~200 km inland. Radar sounding along the traverse route, combined with surface measurements of ice accumulation, velocity, slope and temperature, allow modeling of changing sheet flow to stream flow at the heads of these feeder streams. Surface velocity and slope could be related to bed topography and bed deformability, allowing an assessment of the mobility of feeder streams. In addition, deep radar could:
    1. define the catchment areas feeding the glaciers running through the Transantarctic Mountains and
    2. show paleo changes (from internal layers) in the boundaries of these regions. Bedrock topography would give a first cut at geologic controls on the outflow, and internal layers would depict changes.
  4. What is the history of blue ice areas?
    The distribution of blue ice areas can be mapped using satellite imagery, but requires ground truth for verification. On the ground, these regions may display unconformities in the internal layers, as mapped using high-resolution radar, suggesting changes in their former location and extent.

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