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

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Kirillin , G , Aslamov , I , Leppäranta , M & Lindgren , E 2018 , ' Turbulent mixing and heat fluxes under lake ice : the role of seiche oscillations ' , Hydrology and Earth System Sciences , vol. 22 , no. 12 , pp. 6493-6504 . https://doi.org/10.5194/hess-22-6493-2018

Title: Turbulent mixing and heat fluxes under lake ice : the role of seiche oscillations
Author: Kirillin, Georgiy; Aslamov, Ilya; Leppäranta, Matti; Lindgren, Elisa
Contributor: University of Helsinki, Institute for Atmospheric and Earth System Research (INAR)
University of Helsinki, Department of Physics
Date: 2018-12-14
Language: eng
Number of pages: 12
Belongs to series: Hydrology and Earth System Sciences
ISSN: 1027-5606
URI: http://hdl.handle.net/10138/285173
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.
Subject: VARIABILITY
CONVECTION
114 Physical sciences
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