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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 22, issue 12
Hydrol. Earth Syst. Sci., 22, 6493-6504, 2018
https://doi.org/10.5194/hess-22-6493-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue: Modelling lakes in the climate system (GMD/HESS inter-journal...

Hydrol. Earth Syst. Sci., 22, 6493-6504, 2018
https://doi.org/10.5194/hess-22-6493-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 14 Dec 2018

Research article | 14 Dec 2018

Turbulent mixing and heat fluxes under lake ice: the role of seiche oscillations

Georgiy Kirillin1, Ilya Aslamov2, Matti Leppäranta3, and Elisa Lindgren4 Georgiy Kirillin et al.
  • 1Department of Ecohydrology, Lebiniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany
  • 2Limnological Institute, Siberian Branch of Russian Academy of Science (LIN SB RAS) Irkutsk, Russia
  • 3Institute of Atmospheric and Earth Sciences, University of Helsinki, Helsinki, Finland
  • 4Department of Physics, University of Helsinki, Helsinki, Finland

Abstract. We performed a field study on mixing and vertical heat transport under the ice cover of an Arctic lake. Mixing intensities were estimated from small-scale oscillations of water temperature and turbulent kinetic energy dissipation rates derived from current velocity fluctuations. Well-developed turbulent conditions prevailed in the stably stratified interfacial layer separating the ice base from the warmer deep waters. The source of turbulent mixing was identified as whole-lake (barotropic) oscillations of the water body driven by strong wind events over the ice surface. We derive a scaling of ice–water heat flux based on dissipative Kolmogorov scales and successfully tested against measured dissipation rates and under-ice temperature gradients. The results discard the conventional assumption of nearly conductive heat transport within the stratified under-ice layer and suggest contribution of the basal heat flux into the melt of ice cover is higher than commonly assumed. Decline of the seasonal ice cover in the Arctic is currently gaining recognition as a major indicator of climate change. The heat transfer at the ice–water interface remains the least studied among the mechanisms governing the growth and melting of seasonal ice. The outcomes of the study find application in the heat budget of seasonal ice on inland and coastal waters.

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We have discovered transient appearances of strong turbulent mixing beneath the ice of an Arctic lake. Such mixing events increase heating of the ice base up to an order of magnitude and can significantly accelerate ice melting. The source of mixing was identified as oscillations of the entire lake water body triggered by strong winds over the lake surface. This previously unknown mechanism of ice melt may help understand the link between the climate conditions and the seasonal ice formation.
We have discovered transient appearances of strong turbulent mixing beneath the ice of an Arctic...
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