Ice–water heat exchange during ice growth in Lake Baikal

ABSTRACTTwo non-invasive optical Schlieren methods have been adapted to visualize brine channel development and convective processes in experimentally grown sea ice obtained when a NaCl aqueous solution is cooled from above in a quasi-two-dimensional Hele–Shaw cell. The two different visualization methods, i.e. traditional and synthetic Schlieren optical imaging, produce high spatial resolution images of transport processes during ice growth, without any external perturbation. These images allow observations of the flow dynamics simultaneously within the ice layer, around the ice/water interface, and in the liquid water layer, revealing connections between the processes occurring within the two phases. Results from these methods show that desalination of the growing ice layer occurs by two concurrent, yet independent, mechanisms: (1) boundary layer convection persisting throughout the ice growth period, with short fingers present just below the ice/water interface, and (2) gravity-driven drainage from the brine channels producing deep penetrating convective streamers, which appear after a given time from the beginning of ice growth. The improved visualization and qualitative characterization of these processes show that Schlieren optical methods have exciting potential applications for future study of convective processes during sea-ice growth.

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A new similarity model for the stratified under-ice boundary layer in lakes and its application to ice-covered Lake Baikal

10.5194/egusphere-egu2020-7478 ◽

2020 ◽

Author(s):

Georgiy Kirillin ◽

Ilya Aslamov ◽

Nikolai Granin ◽

Roman Zdorovennov

Keyword(s):

Boundary Layer ◽

Heat Flux ◽

Lake Baikal ◽

Strong Dependence ◽

Shear Velocity ◽

Ice Cover ◽

Heat Fluxes ◽

Solid Boundary ◽

Buoyancy Frequency ◽

Ice Water

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 propose a model of the turbulent energy budget in the stably stratified boundary layer under ice, based on the length scale incorporating the dissipation rate and the buoyancy frequency (Dougherty-Ozmidov scaling). The model was verified on fine-scale measurements in Lake Baikal and demonstrated a good agreement with data. The measured ice-water heat fluxes in were among the largest reported in lakes (up to 40&#8201;W&#8201;m&#8722;2) and scaled well against the proposed relationship. The model yields a scaling relationship for the ice-water heat flux as a function of the shear velocity squared that suggests the traditional bulk parameterizations may significantly underestimate the ice-water heat flux, especially at strong under-ice current velocities. The ultimate result consists in a strong dependence of the water-ice heat flux on the shear velocity under ice.&#160;

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Environmental record of layers of bubbles in natural pond ice

Journal of Glaciology ◽

10.1017/jog.2018.73 ◽

2018 ◽

Vol 64 (248) ◽

pp. 866-876 ◽

Cited By ~ 2

Author(s):

JOLANA HRUBA ◽

GUNTHER KLETETSCHKA

Keyword(s):

Heat Flux ◽

Growth Rates ◽

Natural Waters ◽

Gas Bubbles ◽

Ice Thickness ◽

Cooling Rates ◽

Ice Growth ◽

Order Of Magnitude ◽

Concentration Changes ◽

Ice Water

ABSTRACTAutonomous temperature data loggers were used to measure the temperature profile within a growing ice cover and in the water below. The ice formed under natural conditions over the pond. We observed the presence of distinct layers of gas bubbles throughout the ice thickness. Temperature measurements allowed us to determine growth rates (μm s−1) and cooling rates (°C s−1) of the ice and demonstrated that these bubble layers formed during the peak ice growth rates from 0.58 to 0.92 µm s−1. The growth rates, leading to the formation of layers of bubbles, were more than an order of magnitude lower than for bubbles produced in controlled laboratory conditions (from 3 to 80 µm s−1). This observation introduces the possibility that solid impurities play a role in natural waters and that they must lower the limit of growth rates required for bubble occurrence. Data revealed a decrease in ice growth rates while cooling rates increased. We interpret this observation as an effect of the heat flux from the water to the ice (8.34–34.11 W m−2), and of gas concentration changes in the water below. Calculations of the ice thickness using traditional methods showed the necessity to include the heat flux from the water to the ice and the effect of gas bubbles within the ice and near the ice–water interface.

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Interconnection of bacterial and phytoplanktonic communities with hydrochemical parameters from ice and under-ice water in coastal zone of Lake Baikal

Scientific Reports ◽

10.1038/s41598-020-66519-3 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Yu. S. Bukin ◽

N. A. Bondarenko ◽

I. I. Rusanov ◽

N. V. Pimenov ◽

S. V. Bukin ◽

...

Keyword(s):

Coastal Zone ◽

Lake Baikal ◽

Hydrochemical Parameters ◽

Ice Water

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

Hydrology and Earth System Sciences ◽

10.5194/hess-24-1691-2020 ◽

2020 ◽

Vol 24 (4) ◽

pp. 1691-1708 ◽

Cited By ~ 2

Author(s):

Georgiy Kirillin ◽

Ilya Aslamov ◽

Vladimir Kozlov ◽

Roman Zdorovennov ◽

Nikolai Granin

Keyword(s):

Boundary Layer ◽

Heat Flux ◽

Lake Baikal ◽

Dissipation Rate ◽

Large Scale ◽

Shear Velocity ◽

Ice Cover ◽

Solid Boundary ◽

Buoyancy Frequency ◽

Ice Water

Abstract. 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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Estimate of heat flux at the ice-water interface in Lake Baikal from experimental data

Doklady Earth Sciences ◽

10.1134/s1028334x14080017 ◽

2014 ◽

Vol 457 (2) ◽

pp. 982-985 ◽

Cited By ~ 5

Author(s):

I. A. Aslamov ◽

V. V. Kozlov ◽

I. B. Misandrontsev ◽

K. M. Kucher ◽

N. G. Granin

Keyword(s):

Experimental Data ◽

Heat Flux ◽

Lake Baikal ◽

Water Interface ◽

Ice Water

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Ice Growth and Platelet Crystals in Antarctica

10.26686/wgtn.16984669.v1 ◽

2021 ◽

Author(s):

◽

Jonathan Crook

Keyword(s):

Sea Ice ◽

Single Crystal ◽

Ice Cores ◽

The Arctic ◽

First Year ◽

Water Interface ◽

Ice Growth ◽

Brine Rejection ◽

Ice Water ◽

The Antarctic

First-year land-fast sea ice growth in both the Arctic and the Antarctic is characterised by the formation of an initial ice cover, followed by the direct freezing of seawater at the ice-water interface. Such growth usually results, through geometric selection, in congelation ice. This is, in general, the typical crystal structure observed in first-year ice growth in the Arctic. However, in certain regions of the Antarctic, platelet crystals are observed to contribute significantly to the ice growth, beyond a depth of 1 m. This thesis will investigate a number of ideas as to why the platelet crystals only appear in the ice after a significant amount of congelation growth has occurred. One of the key premises will be that platelet ice forms when smaller frazil crystals, beneath the ice, rise up and attach to the interface. They are then incorporated into the ice cover and become the platelets seen in ice cores. The Shields criterion is used to find the strength of turbulence, associated with tidal flow, required to keep a frazil crystal from adhering to the interface. It is shown that the sub-ice flow is sufficient to keep most crystals in motion. However, this turbulence may weaken or dissipate completely as the tide turns. The velocity associated with brine rejection is suggested as an alternative to keep the crystals in suspension during these periods of low shear turbulence. Brine rejection occurs as the sea ice grows, rejecting salt into the seawater below. By comparing this velocity with a model for the frazil rise velocity it is shown that brine rejection has sufficient strength to keep crystals in suspension. This effect weakens as the ice gets thicker, allowing larger frazil crystals to rise to the interface. The early work in this thesis shows that a flow can keep a single crystal from adhering to the interface. This can be regarded as the competence of a flow to keep a crystal in suspension. However, of equal importance is the capacity of a flow to keep a mass of crystals in suspension. It is shown that, given a sufficiently large mass of crystals beneath the ice, the same flow that can hold a single crystal in suspension will not be able to keep all the crystals in motion. The deposition of crystals is predicted to occur in a gradual manner if there is a steady build-up of crystals beneath the ice. The largest crystals, close to the interface, will settle against the ice as the flow is unable to support the entire mass of crystals Also considered is whether frazil crystals may be similar to cohesive sediments. If this is the case, a sudden influx of crystals from outside of the system may lead to the formation of a layer of unattached crystals beside the ice-water interface. This can cause a critical collapse of the turbulent field, resulting in the settling of a large quantity of frazil crystals. Though the emphasis of much of this thesis is on the effect of the flow on the crystals, it is also found that a mass of crystals can have a stabilising effect on the flow. The change in the density profile induced by an increase in the frazil concentration towards the ice-water interface (and hence a decrease in the density of the ice-water mixture) damps the turbulence produced by shear. The mass and size of crystals in suspension play major roles in the strength of stabilisation. Measurements of turbulence and the suspension of frazil crystals beneath sea ice are difficult to make. This thesis aims to present and analyse a number of models which may explain the platelet puzzle - the delayed appearance of the platelet crystals in ice cores. These are compared with the observations which are available, and conclusions made on the validity of the theories presented.

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

10.5194/hess-2019-608 ◽

2019 ◽

Author(s):

Georgiy Kirillin ◽

Ilya Aslamov ◽

Vladimir Kozlov ◽

Roman Zdorovennov ◽

Nikolai Granin

Keyword(s):

Boundary Layer ◽

Heat Flux ◽

Lake Baikal ◽

Dissipation Rate ◽

Strong Dependence ◽

Shear Velocity ◽

Ice Cover ◽

Solid Boundary ◽

Buoyancy Frequency ◽

Ice Water

Abstract. 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 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 under-ice currents, the latter being of geostrophic origin and having lake-wide scales. 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 result consists in 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.

Download Full-text