New Zealand Journal of Geology and Geophysics abstracts
Temperature and bathymetry of ice-contact lakes in
Mount Cook National Park, New Zealand
CHARLES R. WARREN
School of Geography & Geosciences
University of St Andrews
St Andrews, Fife KY16 9ST
Scotland, United Kingdom
MARTIN P. KIRKBRIDE
Department of Geography
University of Dundee
Dundee DD1 4HN
Scotland, United Kingdom
Abstract Several ice-contact lakes have formed in conjunction
with twentieth century glacier retreat in Mt Cook National Park. They occupy
overdeepened glacial valleys and are dammed by terminal moraines and/or outwash
heads. During the autumns of 1994 and 1995, the temperature and bathymetry of
"Maud lake", "Godley lake", and Hooker Lake were surveyed. The near-glacier
vertical water temperature profiles exhibited greater temperature variation
than those at the distal ends of the lakes. Thermal stratification existed in
Hooker Lake, whereas both Maud and Godley lakes were thoroughly mixed. Water
temperatures in the latter were consistently between 3 and 4.5deg.C, but most
parts of Hooker Lake were cooler than 2deg.C, with a minimum recorded
temperature of 0.2deg.C. These contrasts are important because melting of
submerged parts of glacier termini is significant for ablation rates and for
the dynamics of calving termini. All the lakes are steep sided and deep. Maud
and Godley lakes approach 100 m in depth, whereas Hooker Lake has a
maximum recorded depth of 136 m. Extensive flat floors in Maud and Godley
lakes probably reflect rapid sediment accumulation following glacier retreat.
Water depth at the termini of iceberg-calving glaciers is known to correlate
strongly with rates of iceberg production and hence the rate of glacier
retreat. However, given the substantial water depths through which these
glaciers (and also the neighbouring Tasman Glacier) have retreated, they appear
to be more stable than comparable glaciers in other countries. The subaqueous
geometry of all the glacier termini comprises a projecting ramp of glacier ice.
All the lakes are being enlarged by glacier retreat except Maud lake, which has
been reduced in size since 1995 by the advance of Maud and Grey Glaciers.
Keywords ice-contact lakes; lake temperature; bathymetry;
glacier retreat; calving; ice melt rates; Mount Cook; New Zealand
New Zealand Journal of Geology and Geophysics, 1998, Vol. 41: 133-143
0028-8306/98/4102-0133 $7.00/0 (c) The Royal Society of New Zealand
1998
PDF file of entire paper: medium quality (1224K); (scanned from paper original: notes about this process)
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