Evidence for regional climate change in the recent evolution of a high latitude pro-glacial lake

Abstract

Lake Wilson, a perennially ice-capped, deep (>lo0 m) lake at 80"s in southern Victoria Land was investigated in January 1993. Water chemistry and physical structure showed three distinct layers; an upper c. 35 m mixed layer of low salinity, moderately turbid water; a less turbid mid layer, 20 m thick of slightly higher salinity and supersaturated with oxygen; and a deep 20 m brackish layer (conductivity c. 4000 pS cm") with anoxic conditions in the lower 5 m. Extreme supersaturation of N,O (up to 400 times air saturation) together with high nitrate concentration (4000 mg m") was recorded in the deep layer. Phytoplankton biomass and photosynthetic activity was confined to the upper mixed layer and the band of supersaturated dissolved oxygen located at 40-55 m appears to represent a relict layer from when the lake level was lower. The evidence from a comparison of profiles between 1975 and 1993 suggests that Lake Wilson has risen 25 m since 1975, synchronous with a period of lake level rise in the McMurdo Dry Valleys lakes to the north at 77"s. Geochemical diffusion models indicate that Lake Wilson had evaporated to a smaller brine lake about 1000 yrs BP, which also fits the pattern shown by the McMurdo Dry Valleys lakes. Climate changes influencing lake levels have thus covered a wide area of southern Victoria Land.

The Saline Lakes of the McMurdo Dry Valleys, Antarctica

“…4.3 Lake Levels Shacat et al (2004) compared the depth of the halocline in Lake Joyce with that reported by Green et al (1988) and noted that between 1983 and 2000 there had been a rise in lake level amounting to approximately 4 m. Rising lake levels in parts of the MCM have been noted by Spigel and Priscu (1998) and by Webster et al (1996), but Chinn (1993) has pointed that lake levels are notoriously difficult to correlate with temperature alone. The trend of increasing lake levels discussed by Chinn (1993) for the period 1970-1990 does, however, suggest an increase in meltwater output from regional glaciers through the early to mid 1990s.…”

Biodiversity in extreme aquatic environments: Lakes, ponds and streams of the Ross Sea sector, Antarctica

“…Studies have recently begun on Lake Wilson, a similar but deeper (100 m) lake 300 km to the south of the Dry Valleys in the Darwin Glacier region (Webster et al, 1996). All of these systems are permanently capped by thick (3.5-5.5 m) ice, however a 1-10 moat of open water melts out for 1-2 months each year around the periphery of these lakes.…”

Reactivation of a cryptobiotic stream ecosystem in the McMurdo Dry Valleys, Antarctica: A long-term geomorphological experiment

“…Although the streams flow for only 6-12 weeks during the austral summer, they are important hydrologic and ecological features, carrying water, solutes and sediment to the lakes on the valley floors. Due to increasing stream flow during this century, lake levels have increased by several meters to as much as 25 m (Chinn, 1993;Webster et al, 1996;Bomblies et al, 2001). The presence of salt crusts in lake sediments indicates that cold dry climatic conditions have occurred repeatedly over the past 20,000 years and low stream flows have caused the lakes to become dry (Hendy et al, 1979;Doran et al, 1994).…”