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Differential Heating Drives Downslope Flows that Accelerate Mixed‐Layer Warming in Ice‐Covered Waters
Author(s) -
Ulloa Hugo N.,
Winters Kraig B.,
Wüest Alfred,
Bouffard Damien
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl085258
Subject(s) - entrainment (biomusicology) , convection , gravity current , advection , mixed layer , geology , environmental science , boundary layer , atmospheric sciences , buoyancy , turbulence , mechanics , geophysics , oceanography , physics , internal wave , thermodynamics , rhythm , acoustics
In ice‐covered lakes, penetrative radiation warms fluid beneath a diffusive boundary layer, thereby increasing its density and providing energy for convection in a diurnally active, deepening mixed layer. Shallow regions are differentially heated to warmer temperatures, driving turbulent gravity currents that transport warm water downslope and into the basin interior. We examine the energetics of these processes, focusing on the rate at which penetrative radiation supplies energy that is available to drive fluid motion. Using numerical simulations that resolve convective plumes, gravity currents, and the secondary instabilities leading to entrainment, we show that advective fluxes due to differential heating contribute to the evolution of the mixed layer in waterbodies with significant shallow areas. A heat balance is used to assess the relative importance of differential heating to the one‐dimensional effects of radiative heating and diffusive cooling at the ice‐water interface in lakes of varying morphologies.