Author(s): G. Kirillin; C. Lhardt; S. Golosov; M. Lepparanta; N. Palshin; A. Terzhevik; G. Zdorovennova; R. Zdorovennov
Linked Author(s): Georgiy Kirillin
Keywords: No Keywords
Abstract: There is little known about seiches in ice-covered lakes though several recent reports suggest an appreciable contribution of the lakewide oscillations in the circulation under ice. Based on temperature records from the winter 2007-2008 in two ice covered lakes, P"a"aj"arvi in Finland and Vendyurskoe in Russia, we demonstrate a distinguished seiche signature in the isotherms displacements at periods from hourly to synoptic ones. The pattern of these lake-scale oscillations reveals several unique features suggesting their principal difference from the"normal"seiches in summer stratified lakes: In the deeper Lake P"a"aj"arvi, the oscillations develop on the background of specific"lenticular"thermal stratification with vertical spacing of the isotherms increasing from the near-shore areas to the central parts of the lakes. As a result, the oscillations take place at higher vertical modes with upper isotherms oscillating in the counterphase to lower ones. All dominating internal seiche periods exceed the inertial period for the lakes'latitudes, suggesting appreciable effect of the Coriolis force on the oscillations and, as a result, concentration of the seiche-produced oscillations currents in the near-shore areas in form of Kelvin waves-the typical feature of large-scale geophysical flows. In the shallower Lake Vendyurskoe, the internal seiches appear only intermittently, whereas a strong signature of external seiches persist in the temperature records at the bottom slope -- a feature specific for the strong near-bottom stratification in winter. These features make the spectrum of oscillations under ice much more manifold than that in the open waters, where usually only one vertical and one lateral mode dominate. The results have important implications for understanding the lateral mass transport from sediment and ice across the water column during the ice-covered season.
Year: 2010