| Rhodamine
WT was added to Toolik Lake at depths at which intrusions had been detected
in the South West Basin. Some of the intrusions were of warm, high
conductivity water; some were of cool, low conductivity water.
We hypothesized that the intrusions were due to seepage of waters above the permafrost or were due to flow of water through thawed portions of the permafrost. In the latter case, the water would have originated from a dammed river valley to the South of Toolik Lake. The Rhodamine was injected at several depths in the thermocline and did reach the central portion of the South West basin within a few days. |
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The profile of temperature and conductivity from 21 July 1999 shows evidence for both hypotheses. The layer of high conductivity water at 5m depth indicates groundwater flowing into the lake above the permafrost. This water may have originated from a dammed river valley above the lake. A rainstorm several days priorto our measurements increased the head of water in the overall groundwater system and accentuated the flow through the permafrost. |
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Subsequent examination of isotherm displacements
from the South West Basin (area = 0.2 km2)
indicated the difficulty in doing tracer studies even in small lakes.
High frequency waves with amplitudes of 1 m were common in the pycnocline.
These waves were initiated by moderate winds. Amplitudes at the base
of the pycnocline reached 3 m. Following the movement of a tracer
at one depth would be confounded by the extensive wave activity.
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last modified: February 14, 2000
Comments: brice@icess.ucsb.edu