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that the ice did not melt out and had a thickness of 2m in November (Laybourn-Parry et
al., 2002), indicating inter-annual variation in ice thickness. The increase could be due to
lower temperatures for the 2000 winter compared to the 1999 winter. The 1999 winter
was considered to be unusually mild. As previously mentioned, the Vestfold Hills saw
unusually high precipitation throughout 1999 and 2000 (information courtesy of the
Bureau of Meteorology, Melbourne, Australia).
Epilininion
Ice
Anoxic Sump
Figure 3.19 -
Diagrammatic representation of the profile of Pendant Lake indicating the anoxic
sump.
The annual water temperatures in Pendant Lake (Fig. 3.2b) were, on average,
higher than those in Ace Lake. This may be due to the near complete mixing of the water
column during the winter compared to the permanently stratified Ace Lake. Ace Lake
had a higher summer temperature (Laybourn-Parry et al., 2002), possibly due to solar
heating through the thinner ice cover and surrounding rocks, compared with the relatively
thick ice cover on Pendant Lake which, due to whitening of the ice (produced by repeated
freeze/thaw during summer), would act as a reflective barrier to solar heating.
Salinity (Fig 3.4b) was on average lower in Pendant Lake (17.75ppt) than the
mixolimnion
of Ace Lake (19.66ppt). Also, salinity throughout the water column was
generally more uniform, with only a small increase at l Om where the sampling bottle
collected some water from the more saline anoxic sump. An exception was in November,
2000, when there was a small decrease in salinity with depth, which could be caused by
an increase in salinity in the surface waters due to exclusion of brine through increased
ice formation (Gibson, 1999; Rankin et al., 1999). The salinity profile during February
shows the opposite trend, with fresher water at the surface due to ice melt (Fig 3.1 b;
Laybourn-Parry et al., 2002). 98