Victoria University Antarctic Research Expedition Science and Logistics Reports 2007-08: VUWAE 52
Submergence Velocity Measurements at Victoria Lower and Evans Piedmont Glaciers
Submergence Velocity Measurements at Victoria Lower and Evans Piedmont Glaciers
During the 1999/2000 season three submergence velocity devices (Hamilton & Whillans, 2000) for mass balance measurements in the McMurdo Dry Valleys were installed. During the 2004/2005 season two submergence velocity devices have also been installed at EPG. This method is used to determine mass balance by comparing vertical velocity of a marker in firn or ice with long-term, average snow accumulation rates. The movement of the marker is the result of three motions: firn compaction, gravitational glacial flow, and changes in mass balance. High precision GPS measurements are used to determine absolute position of the tracking point during subsequent years. Trimble 5700 base station and rover unit were used to measure the absolute position of the tracking point of the mass balance devices.
The rate of thickness change H, can then be calculated using (Hamilton et al., 1998):
H=rate of thickness change (myr
−1)
b
m=accumulation rate (Mgm
−2yr
−1)
ρ=density at marker depth (Mgm
−3)
z=vertical component of ice velocity(myr
−1)
α=surface slope (radians)
u=horizontal velocity (myr
−1 with azimuth)
.jpg)
Fig. 8 Cartoon of the 'coffee can' submergence mass balance device (modified after Hamilton and Whillans 2000)and picture of coffee can device deployed at Victoria Lower Glacier.