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

Kirillin, Georgiy; Aslamov, Ilya; Leppäranta, Matti; Lindgren, Elisa

doi:10.5194/hess-22-6493-2018

Cited by 35 publications

(51 citation statements)

References 29 publications

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“…3): under ice, the water temperatures slightly increased with depth. The mean vertical gradient of 0.6 • C over the upper 10 m of the water column was about an order of magnitude weaker than those typically observed in shallow ice-covered lakes (Kirillin et al, 2018). Below 10 m depth the water column was well mixed vertically down to 30 m. Closer to the ice base, two horizontal layers could be distinguished: a < 0.5 m thin layer adjacent to the ice with a temperature difference of ≈ 0.3 • C across it.…”

Section: Mean Currents Temperatures and Stratificationcontrasting

confidence: 54%

“…The fluxes were apparently related to the surface water circulation pattern beneath the ice cover (Zhdanov et al, 2017). The observed ice-to-water heat fluxes exceeded fluxes measured in small lakes (Kirillin et al, 2018) by up to an order of magnitude. Free convection due to penetrating solar radiation was not strong enough to produce upward heat release at these rates.…”

Section: Introductionmentioning

confidence: 64%

“…(21); the ε values from three beams were compared for similarity and averaged. The detailed procedure of data postprocessing and the quality check is described by Kirillin et al (2018) and Volkov et al (2019).…”

Section: Study Site and Field Methodsmentioning

confidence: 99%

“…The strong stratification in the IL prevents convective mixing despite the negative buoyancy production by the decrease of the solar radiation with depth and reduces convective transport of heat to the ice-water interface. As a result, only a small amount of the heat is available for ice melt, despite strong convection in the SML (Kirillin et al, 2018). The situation is akin to formation of a stably stratified layer (SL) beneath the ice base and the near-surface temperature maximum in marginal polar seas, driven by freshening of the surface waters due to runoff or accelerated sea ice melt (Jackson et al, 2010(Jackson et al, , 2012.…”

Section: Introductionmentioning

confidence: 99%

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Turbulence in the stratified boundary layer under ice: observations from Lake Baikal and a new similarity model

Kirillin

Aslamov

Козлов

et al. 2020

Hydrol. Earth Syst. Sci.

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Seasonal ice cover on lakes and polar seas creates seasonally developing boundary layer at the ice base with specific features: fixed temperature at the solid boundary and stable density stratification beneath. Turbulent transport in the boundary layer determines the ice growth and melting conditions at the ice-water interface, especially in large lakes and marginal seas, where large-scale water circulation can produce highly variable mixing conditions. Since the boundary mixing under ice is difficult to measure, existing models of ice cover dynamics usually neglect or parameterize it in a very simplistic form. We present the first detailed observations on mixing under ice of Lake Baikal, obtained with the help of advanced acoustic methods. The dissipation rate of the turbulent kinetic energy (TKE) was derived from correlations (structure functions) of current velocities within the boundary layer. The range of the dissipation rate variability covered 2 orders of magnitude, demonstrating strongly turbulent conditions. Intensity of mixing was closely connected to the mean speeds of the large-scale under-ice currents. Mixing developed on the background of stable density (temperature) stratification, which affected the vertical structure of the boundary layer. To account for stratification effects, we propose a model of the turbulent energy budget based on the length scale incorporating the dissipation rate and the buoyancy frequency (Dougherty-Ozmidov scaling). The model agrees well with the observations and yields a scaling relationship for the ice-water heat flux as a function of the shear velocity squared. The ice-water heat fluxes in the field were the largest among all reported in lakes (up to 40 W m −2 ) and scaled well against the proposed relationship. The ultimate finding is that of a strong dependence of the water-ice heat flux on the shear velocity under ice. The result suggests large errors in the heat flux estimations when the traditional "bulk" approach is applied to stratified boundary layers. It also implies that under-ice currents may have much stronger effect on the ice melt than estimated by traditional models.

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Section: Mean Currents Temperatures and Stratificationcontrasting

confidence: 54%

Section: Introductionmentioning

confidence: 64%

Section: Study Site and Field Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Turbulence in the stratified boundary layer under ice: observations from Lake Baikal and a new similarity model

Kirillin

Aslamov

Козлов

et al. 2020

Hydrol. Earth Syst. Sci.

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“…Changes to the thermal regime of ice-covered lakes can have diverse impacts, ranging from the loss of physical and cultural ecosystem services to the amplification of greenhouse gas emissions (Downing, 2010;DelSontro et al, 2018;Sharma et al, 2019). Nevertheless, the processes controlling heat fluxes, lateral transport, and temperature distribution in ice-covered waterbodies remain only partially characterized (Huang et al, 2019;Kirillin et al, 2018;Leppäranta, 2009). This issue poses a serious challenge for assessing the fate of polar aquatic systems in global warming scenarios.…”

Section: Introductionmentioning

confidence: 99%

Differential Heating Drives Downslope Flows that Accelerate Mixed‐Layer Warming in Ice‐Covered Waters

Ulloa

Winters

Wüest

et al. 2019

Geophysical Research Letters

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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. Plain Language SummaryLake ice cover is one of the essential climate variables defined by the World Meteorological Organization. Its evolution is affected by direct meteorological forcing and by ice-penetrating radiation that heats near-surface waters and excites buoyancy-driven fluid motions. Both effects regulate water-to-ice heat transfer and thus the ice melting rate. We show how the warming of under-ice water is impacted by differential heating of the lake shallows and the resultant transport and mixing. We present a scaling analysis that quantifies how the rate of under-ice, mixed-layer warming depends on geometrical properties of the lake morphology. Accounting for differential heating and lateral transport is essential for processed-based models of ice-covered waterbodies that go beyond one-dimensional balances.

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Barotropic seiches in a perennially ice‐covered lake, East Antarctica

Castendyk

Dugan

Gallagher

et al. 2021

Limnol Oceanogr Letters

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This work contributes to a growing body of observations on currents and seiches in ice-covered lakes. Under-ice currents play an important role in the biology of ice-covered lakes, and are especially important for redistributing nutrients in perennially ice-covered, polar lakes. This manuscript provides evidence of barotropic seiches below a 4-m-thick ice cover with consistent 10.5-min periods in Lake Hoare in the McMurdo Dry Valleys of East Antarctica. The period of the seiche seasonally lengthened to 13 min following the arrival of summer melt. During winter, there is a strong relationship between surface winds >5 m s À1 and seiche activity, indicating that seiches are caused by flexural vibrations of the permanent ice cover. Our manuscript provides new information that will benefit those studying under-ice water movements. Firstly, Lake Hoare is much smaller and has a much thicker ice cover than previous studies. Secondly, our data include a much longer time-series. Lastly, our data cover an important period when the lake transitions from winter fast ice to summer floating ice.

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

Cited by 35 publications

References 29 publications

Turbulence in the stratified boundary layer under ice: observations from Lake Baikal and a new similarity model

Turbulence in the stratified boundary layer under ice: observations from Lake Baikal and a new similarity model

Differential Heating Drives Downslope Flows that Accelerate Mixed‐Layer Warming in Ice‐Covered Waters

Barotropic seiches in a perennially ice‐covered lake, East Antarctica

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