How Lakes Change Lakes on the Old Crow Flats are constantly changing in gradual response to weather conditions and the growth and decay of ground ice. The larger lakes tend to be oriented at right angles to the prevailing winds from the northeast. The permafrost in the Old Crow area is only about 60 meters thick and there is no permafrost under most of the permanent lakes.
Lakes sometimes change dramatically over just a few years.
The most obvious cause for rapid change is catastrophic draining into a neighbouring lake or stream at lower elevation. Extremely shallow lakes and those that have recently drained are very sensitive to further drying from increased evapotranspiration caused by pioneering vegetation, or if the weather is warmer and drier than normal. Once drained, forb and graminoid vegetation invades, followed by shrubs. Eventually permafrost invades the lake basin and the rising water table kills the shrubs. As time goes on the basin may gradually refill with water.