Basal sliding of Ice Stream D
measured with a tethered stake in till at the bottom of borehole 3.
Borehole coordinates: S 81o 4' 25"; W 140o 0' 20"
Details of similar measurements on Ice Stream B are found in Hermann
Engelhardt and Barclay Kamb. 1998. Basal Sliding of Ice Stream B, West
Antarctica. Journal of Glaciology, Vol. 44, No. 147, p. 223-230.
Ice Stream D is flowing from East to West. The surface
velocity near our boreholes was measured along two profiles using repeat
GPS positioning, Bjorn Johns and Oivind Ruud from UNAVCO assisting:
a. North to South profile
across the ice stream, 7.8 km long beginning at
coordinate S 81o 1' 1"; W 139o 59' 10" and
ending at coordinate S 81o 5' 19"; W 139o 59'
b. East to West profile
parallel to ice stream flow, 11.2 km long beginning
in the East at coordinate S 81o 3' 59"; W 139o
39' 10" and ending downstream at coordinate S 81o 3' 59";
W 140o 19' 1".
The vertical temperature
profile of Ice Stream D compared with the Siple Dome temperatures and
the Ice Stream C temperatures shows that D is almost as cold as C but
much colder than Siple Dome. The basal temperature is at the pressure
melting point at -0.83oC. The basal temperature gradient in
ice is 53 K/km.
Our airplane broke through a 2 m
snow bridge and fell into a
crevasse. The recovery of the
damaged plane took 6 weeks. One engine
and two propellers needed replacement. The crevasse under the plane
had been filled in before work started. The
LC-130 was finally winched out of its precarious position. The
recovery crew could celebrate:
Frank Madia, Joe Butler, Charlie Lucia, Ron Sacco, Jeff Brueck,
Jack Brown, Chuck Shannon, Terry Schild, Michael Kemp, Jim Jenkins,
Chris McIntosh, Graeme Howden, Robert Melden, Andrew Svendsen,
Robert Thivierge, Mark Sellers, Gregory Lambert, Steve Dunbar,
Michael McCarthy, Scott (Snackbar) Konu, Steve Zebroski, Nancy
Pfeiffer, David and Tanya Zastrow, Leslie Conway, John Britt,
Christopher Parrish, David Gurnyski, Bill Mathews, Maj. Kolt,
Tim Thomson, Tim Putman, DJ Jones, Sheila Connolly
and many more behind the scenes.
The BIG X on the image of Ice Stream D marks
the place of the accident. The recovery camp was established nearby,
not very far from the big snow-bridged crevasses. It was later used as
our drilling camp. Our original plan was to land and drill in the
middle of the non-crevassed part of the ice stream, about 4 km to the
North of the heavily crevassed shear zone.
Because of this accident, our drilling season was reduced to 8 days,
lasting from 17 to 25 January 1999.
During these 8 days we drilled 6 boreholes, 1100 m deep each to the
bed of the ice stream.
The participants in the field work on Ice Stream D were Ginny Catania,
Shulamit Gordon, Beth Pratt, Barclay Kamb, Robin Bolsey, Ben Farrow, Greg Gerbi,
Hans Schwaiger, Matt Bachmann, and Hermann Engelhardt.