Antarctic Surface Accumulation and Ice Discharge

Project Description
Short Title: ASAID
Proposal URL: http://classic.ipy.org/development/eoi/proposal-details.php?id=88

This project makes use of the unique focus of IPY cooperation to synthesize, collect, analyze and produce comprehensive data sets on the spatial and temporal patterns of accumulation of snow and the perimeter discharge of ice from the Antarctic ice sheet. The work can be subdivided into three major activities, each requiring a distinctly different approach.

1) Spatial and Temporal Pattern of Net surface Accumulation. Various successful ITASE traverses of the Antarctic over the past decade have begun the process of collecting high-frequency radar soundings that, when tied to dated ice cores, provide a continuous transect of accumulation history by following dated radar horizons. We will expand these observations in two ways: by encouraging the collection of more data as part of any IPY or post-IPY traverse across Antarctica including identifying commercially available equipment that can be used to begin standardizing the international data set; and by collecting additional data with an existing airborne high-frequency radar system flown in areas that both fill in major gaps in coverage and increase the number of intersecting transect tie-points. The distributed product from this activity will be a three-dimensional mapping of numerous isochrones that represent the spatial and temporal variability of Antarctic accumulation at an unprecedented level of detail.

2) Position and Velocity at the Grounding Line. These will be determined exclusively from satellite data using proven techniques. Interferometric SAR analysis has already determined many segments of the grounding line and SAR data are presently being analyzed to determine surface ice velocity over the region north of 72S. Two other satellite data sets will assist in this analysis: Landsat data, made available through a planned map mosaicing activity, will be examined to help in the delineation of the grounding line and flow rate; and satellite altimetry will provide additional indications of the grounding line transition. These data provide an earlier epoch measurement. It is hoped that a new collection of interferometric quality SAR data will be part of IPY to allow a common epoch for the data sets of surface velocity and ice thickness. The comparison of this new velocity data with the previous large-scale mapping of ice speed, as well as a wealth of isolated older measurements, will provide useful indications of the temporal variation of ice discharge and grounding line position along large portions of the Antarctic's grounded perimeter.

3) Ice Thickness at the Grounding Line. These data are required to complete the calculation of ice discharge. Our goal is to make direct measurements as nearly coincident with the flow measurements, as possible. This is a very challenging task. Negotiations are continuing in countries that have operational airborne ice penetrating radars that can measure ice thickness of more than one kilometer. Some other IPY programs (e.g., ACE, PET and GIGAGAP) have indicated a willingness to include needed measurements as part of their field program. Where new measurements are not possible during IPY, or perhaps immediately thereafter, older measurements will be used. There are many existing data sets for portions of the Antarctic perimeter - the largest being from the Italian program. Additionally, we will develop the means to use satellite altimetry (ICESat and possibly Cryosat) to provide more widely spaced measurements of ice thickness inferred from surface elevations on floating ice immediately adjacent to the grounding line.