GPS surveying to obtain ice flow velocities for the southern McMurdo Ice Shelf, Antarctica, 2002-2005.

In the 2002/03 field season (event K114), 34 marker poles were established in a
2.5 km-spaced grid over the southern McMurdo Ice Shelf (SMIS), and these were
positioned using differential GPS. These poles were subsequently resurveyed in
the 2003/04 field season (event K001W), when a further 10 poles were added to
the survey grid. The resultant motion vectors support sparse measurements made
in the 1960s (Swithinbank, 1970), indicating that the SMIS is moving ~2-7 m/yr;
to the W/NW between Black Island and Mount Discovery, and to the W/SW south of
Black and White Islands. A third occupation of the poles at the end of the
2003/04 season provided a one month interval check on the annual movement
figures, confirming that motion is fastest south of Black Island, and is slower
further north. The poles added in the 2003/04 season were resurveyed in January
2005 (event K065) to increase the reliability of the annual movement vectors.
This data set serves to show that the SMIS is essentially stagnant compared to
the northern McMurdo Ice Shelf and the Ross Ice Shelf (RIS), which are moving
up to two orders of magnitude faster than the SMIS. The data affect
interpretation of the origin, mass balance and processes of the SMIS, with
implications for understanding the dynamics of the transition zone between the
SMIS and the adjacent RIS.