| PI | Institute/Department | |
|---|---|---|
| Hindmarsh, Richard |
British Antarctic Survey, Physical Sciences Division
|
| Program Manager | Funding Agency | |
|---|---|---|
| Crain, Ms. Renee |
NSF, Office of Polar Programs
|
The rate at which ice flows into the sea from the large ice sheets directly affects sea level. The forces that drive this flow are controlled by the increasingly well-known geometry of the ice-sheets, but the resistance to flow depends upon the viscous properties of ice. Ice has the peculiar property that the viscosity depends upon the rate at which the ice is deforming. This sensitivity is usually described with the Glen index. Recent theoretical studies have shown that our knowledge of the Glen index is not sufficiently developed to accurately predict very basic outcomes of marine ice-sheet change during glacial cycles; and predict the spatial dimensions of surface response in ice streams to a better accuracy than current satellite measurements. In many field measurements it is difficult to characterize the stresses very well and to know how the provenance of the ice has affected measurements. The researchers will go to divide locations where the stress field can be characterized well and the provenance is very well constrained. Radar layers provide markers within the ice, and their vertical displacement over relatively short time periods can be measured using interferometric phase-sensitive radar techniques. This will provide instantaneous vertical velocity fields and strain-rate fields in the upper third to a half of the ice field. GPS techniques will also be used to measure surface strain-rates, which can be compared with the vertical strain-rates derived from the radar. Measurements will be made at GRIP (Greenland) and at Dome C (Antarctica). At divide locations the velocity field is especially sensitive to the Glen index, and this is particularly the case in the upper part of the ice. The researchers will use full-system modeling to determine the Glen index that best fits the data, and thereby measure the Glen index in the field in a well-controlled location.
With this NERC-funded project, a research team will conduct radar studies during two field seasons at the site of a former deep core-drilling project called GRIP, in Greenland; and at Dome C in Antarctica. This database carries information on the arctic work only. During two consecutive field seasons starting in 2008, a field team will travel to Summit Station, Greenland, via the NSF logistics chain from Kangerlussuaq. They will base at the station for about two weeks each season and travel via snowmachine to the study site, GRIP, which is about 30 km from Summit. There, they will use a stationary radar to survey a transect about 10 km long. They will take data about every 200m. The work should be finished in about five days (additional time is built in to the schedule for weather delays). In 2008, a team of three will travel to Summit from Europe early in May. The PI will work on the ice cap for about one week; his two team members will remain after his departure for the rest of the month to complete the field work. The researchers will both tent camp and make day trips to their field site. The field plan amounts to about 700 km of snowmachine travel. In addition to the radar survey, the team will make a topographic survey of the radar survey area to cover the footprint of a Danish survey over-flight. This will involve traversing parallel tracks into the radar survey area and a small additional survey grid. The four elements of the survey in order of priority are: (1) Do the five lines (five days). The most northerly line (5H north of Divide) will be done first. (2) Repeat the first line (the most northerly line) as late as possible. (3) Do CMP work. (4) Do polarimetric measurements. In 2009, a team of 2 will return to Summit Station for 2-3 weeks of measurements in May.
For each year of the grant, CPS will provide transport to and from Summit for personnel and cargo, Kangerlussuaq and Summit user days, use of on-site Summit facilities and equipment, including snowmachines a sled, fuel, and a generator. CPS will provide this support on a cost-reimbursable basis. All other support will be arranged by the PI and paid from the grant.
| Season | Field Site | Date In | Date Out | #People |
|---|---|---|---|---|
|
2008
|
Greenland - Summit
|
|
|
3
|
|
2009
|
Greenland - Summit
|
|
|
2
|