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

2018 ◽  
Vol 22 (12) ◽  
pp. 6493-6504 ◽  
Author(s):  
Georgiy Kirillin ◽  
Ilya Aslamov ◽  
Matti Leppäranta ◽  
Elisa Lindgren
Keyword(s):  
Heat Flux ◽  
Heat Transport ◽  
Turbulent Mixing ◽  
Ice Cover ◽  
The Arctic ◽  
Small Scale ◽  
Conductive Heat ◽  
Strong Wind ◽  
Dissipation Rates ◽  
Ice Water

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.

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

2018 ◽  
Author(s):  
Georgiy Kirillin ◽  
Ilya Aslamov ◽  
Matti Leppäranta ◽  
Elisa Lindgren
Keyword(s):  
Heat Flux ◽  
Heat Transport ◽  
Turbulent Mixing ◽  
Ice Cover ◽  
The Arctic ◽  
Small Scale ◽  
Conductive Heat ◽  
Strong Wind ◽  
Dissipation Rates ◽  
Ice Water

Abstract. We performed a field study on mixing and vertical heat transport under 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 heat budget of seasonal ice on inland and coastal waters.

scholarly journals Spatial variations in the winter heat flux at SHEBA: estimates from snow-ice interface temperatures

2001 ◽  
Vol 33 ◽  
pp. 213-220 ◽  
Author(s):  
Matthew Sturm ◽  
Jon Holmgren ◽  
Donald K. Perovich
Keyword(s):  
Heat Flux ◽  
Snow Depth ◽  
Heat Budget ◽  
The Arctic ◽  
Small Scale ◽  
Interface Temperature ◽  
Conductive Heat ◽  
Total Heat Loss ◽  
Melt Ponds ◽  
Ice Floes

AbstractThe temperature of the snow-ice interface was measured every 2.4 h throughout winter 1997/98 at 30 locations near the Surface Heat Budget of the Arctic Ocean (SHEBA) camp in the Beaufort Sea. Measurements were obtained from young ice, ridges, refrozen melt ponds and ice hummocks. Average snow depths at these locations were 567 cm, while mean interface temperatures ranged from −8° to −25°C, with minimums varying from −12° to −39°C. Interface temperatures were linearly related to snow depth, with increasing scatter at greater depths. The conductive heat flux during the winter, Fc, was estimated for each location using air and interface temperatures, snow depths and measured snow thermal conductivities. Fc was integrated to determine total heat loss for the winter at each site. Losses varied by a factor of four, with variations over short distances (10 m) as large as the variations between ice floes. Spot measurements along traverse lines confirm that large variations in interface temperature are common, and imply that small-scale spatial variability in the conductive flux is widespread. A comparison of the dependence of Fc on snow depth and ice thickness based on our observations with the dependence predicted by a one-dimensional theoretical model suggests that spatial heterogeneity may be an important issue to consider when estimating the heat flux over large aggregate areas. We suggest that the small-scale variability in the conductive flux arises because the combined snow and ice geometry can produce significant horizontal conduction of heat.

scholarly journals Oceanic Heat Flux as a Component of the Heat Budget of Sea Ice

1985 ◽  
Vol 6 ◽  
pp. 171-173 ◽  
Author(s):  
M. P. Langleben
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Latent Heat ◽  
Heat Budget ◽  
Average Rate ◽  
Ice Cores ◽  
Ice Cover ◽  
Energy Balance Equation ◽  
Conductive Heat ◽  
Oceanic Heat Flux

Heat budget studies of the sea ice cover near Pond Inlet, NWT, were made using data obtained at two locations in Eclipse Sound, one about 0.5 km from shore and the other about 7.5 km from shore. The observations at intervals of one week included ice temperatures at 10 cm separation in vertical profile, salinities of adjacent 2.5 cm-thick slices from vertical ice cores, and ice thickness. The time series analysed extend from three to six months in the six data sets obtained for three winters of observations. Values of oceanic heat flux have been determined as residuals in the energy balance equation applied to the ice cover. The results show that in Eclipse Sound the oceanic heat flux is a significant component of the heat budget of the ice cover. Its value over the winter is typically about 6 W m-2about half as large as the average rate of release of the latent heat of freezing. There does not appear to be any systematic variation in value of the 4 week-average oceanic heat flux during the season. Nor is there any apparent correlation of oceanic heat flux with rate of release of latent heat (ie ice growth rate), or with the severity of the winter as measured by the magnitude of the conductive heat flux.

scholarly journals Laboratory experiments on Internal Solitary Waves in ice covered waters 

2021 ◽  
Author(s):  
Magda Carr ◽  
Peter Sutherland ◽  
Andrea Haase ◽  
Karl-Ulrich Evers ◽  
Ilker Fer ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Solitary Waves ◽  
Ice Cover ◽  
The Arctic ◽  
Internal Solitary Waves ◽  
Small Scale ◽  
Lower Bounding ◽  
The Arctic Ocean ◽  
Wave Induced

<p>Oceanic internal waves (IWs) propagate along density interfaces and are ubiquitous in stratified water. Their properties are influenced strongly by the nature and form of the upper and lower bounding surfaces of the containing basin(s) in which they propagate.<span>  </span>As the Arctic Ocean evolves to a seasonally more ice-free state, the IW field will be affected by the change. The relationship between IW dynamics and ice is important in understanding (i) the general circulation and thermodynamics in the Arctic Ocean and (ii) local mixing processes that supply heat and nutrients from depth into upper layers, especially the photic zone. This, in turn, has important ramifications for sea ice formation processes and the state of local and regional ecosystems.<span>  </span>Despite this, the effect of diminishing sea ice cover on the IW field (and vice versa) is not well established. A better understanding of IW dynamics in the Arctic Ocean and, in particular, how the IW field is affected by changes in both ice cover and stratification, is central in understanding how the rapidly changing Arctic will adapt to climate change.</p><p> </p><p>An experimental study of internal solitary waves (ISWs) propagating in a stably stratified two-layer fluid in which the upper boundary condition changes from open water to ice are studied for grease, level, and nilas ice. The experiments show that the internal wave-induced flow at the surface is capable of transporting sea-ice in the horizontal direction. In the level ice case, the transport speed of, relatively long ice floes, nondimensionalized by the wave speed is linearly dependent on the length of the ice floe nondimensionalized by the wave length. It will also be shown that bottom roughness associated with different ice types can cause varying degrees of vorticity and small-scale turbulence in the wave-induced boundary layer beneath the ice. Measures of turbulent kinetic energy dissipation under the ice are shown to be comparable to those at the wave density interface. Moreover, in cases where the ice floe protrudes into the pycnocline, interaction with the ice edge can cause the ISW to break or even be destroyed by the process. The results suggest that interaction between ISWs and sea ice may be an important mechanism for dissipation of ISW energy in the Arctic Ocean.</p><p> </p><p><strong>Acknowledgements</strong></p><p>This work was funded through the EU Horizon 2020 Research and Innovation Programme Hydralab+.</p>

scholarly journals Variations of ablation, albedo and energy balance at the margin of the Greenland ice sheet, Kronprins Christian Land, eastern north Greenland

1995 ◽  
Vol 41 (137) ◽  
pp. 174-182 ◽  
Author(s):  
Thomas Konzelmann ◽  
Roger J. Braithwaite
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Latent Heat ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Small Scale ◽  
Conductive Heat ◽  
Net Radiation ◽  
Conductive Heat Flux ◽  
North Greenland

AbstractA meteorological and glaciological experiment was carried out in July 1993 at the margin of the Greenland ice sheet in Kronprins Christian Land, eastern north Greenland. Within a small area (about 100 m2) daily measurements were made on ten ablation stakes fixed in “light” and “dark” ice and were compared to each other. Simultaneously, the components of the energy balance, including net radiation, sensible-heat flux, latent-heat flux and conductive-heat flux in the ice were determined. Global radiation, longwave incoming radiation and albedo were measured, and longwave outgoing radiation was calculated by assuming that the glacier surface was melting. Sensible-and latent-heat fluxes were calculated from air temperature, humidity and wind speed. Conductive-heat flux in the ice was estimated by temperature-profile measurements in the uppermost ice layer. Net radiation is the major source of ablation energy, and turbulent fluxes are smaller energy sources by about three times, while heat flux into the ice is a substantial heat sink, reducing energy available for ice melt. Albedo varies from 0.42 to 0.56 within the experimental site and causes relatively large differences in ablation at stakes close to each other. Small-scale albedo variations should therefore be carefully sampled for large-scale energy-balance calculations.

scholarly journals Oceanic Heat Flux as a Component of the Heat Budget of Sea Ice

1985 ◽  
Vol 6 ◽  
pp. 171-173
Author(s):  
M. P. Langleben
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Latent Heat ◽  
Heat Budget ◽  
Average Rate ◽  
Ice Cores ◽  
Ice Cover ◽  
Energy Balance Equation ◽  
Conductive Heat ◽  
Oceanic Heat Flux

Heat budget studies of the sea ice cover near Pond Inlet, NWT, were made using data obtained at two locations in Eclipse Sound, one about 0.5 km from shore and the other about 7.5 km from shore. The observations at intervals of one week included ice temperatures at 10 cm separation in vertical profile, salinities of adjacent 2.5 cm-thick slices from vertical ice cores, and ice thickness. The time series analysed extend from three to six months in the six data sets obtained for three winters of observations. Values of oceanic heat flux have been determined as residuals in the energy balance equation applied to the ice cover. The results show that in Eclipse Sound the oceanic heat flux is a significant component of the heat budget of the ice cover. Its value over the winter is typically about 6 W m-2 about half as large as the average rate of release of the latent heat of freezing. There does not appear to be any systematic variation in value of the 4 week-average oceanic heat flux during the season. Nor is there any apparent correlation of oceanic heat flux with rate of release of latent heat (ie ice growth rate), or with the severity of the winter as measured by the magnitude of the conductive heat flux.

scholarly journals Controlled meteorological (CMET) free balloon profiling of the Arctic atmospheric boundary layer around Spitsbergen compared to ERA-Interim and Arctic System Reanalyses

2016 ◽  
Vol 16 (19) ◽  
pp. 12383-12396
Author(s):  
Tjarda J. Roberts ◽  
Marina Dütsch ◽  
Lars R. Hole ◽  
Paul B. Voss
Keyword(s):  
Boundary Layer ◽  
Wind Shear ◽  
Marine Boundary Layer ◽  
Temperature Inversion ◽  
The Arctic ◽  
Small Scale ◽  
Strong Wind ◽  
Free Atmosphere ◽  
Free Region ◽  
Temperature And Humidity

Abstract. Observations from CMET (Controlled Meteorological) balloons are analysed to provide insights into tropospheric meteorological conditions (temperature, humidity, wind) around Svalbard, European High Arctic. Five Controlled Meteorological (CMET) balloons were launched from Ny-Ålesund in Svalbard (Spitsbergen) over 5–12 May 2011 and measured vertical atmospheric profiles over coastal areas to both the east and west. One notable CMET flight achieved a suite of 18 continuous soundings that probed the Arctic marine boundary layer (ABL) over a period of more than 10 h. Profiles from two CMET flights are compared to model output from ECMWF Era-Interim reanalysis (ERA-I) and to a high-resolution (15 km) Arctic System Reanalysis (ASR) product. To the east of Svalbard over sea ice, the CMET observed a stable ABL profile with a temperature inversion that was reproduced by ASR but not captured by ERA-I. In a coastal ice-free region to the west of Svalbard, the CMET observed a stable ABL with strong wind shear. The CMET profiles document increases in ABL temperature and humidity that are broadly reproduced by both ASR and ERA-I. The ASR finds a more stably stratified ABL than observed but captured the wind shear in contrast to ERA-I. Detailed analysis of the coastal CMET-automated soundings identifies small-scale temperature and humidity variations with a low-level flow and provides an estimate of local wind fields. We demonstrate that CMET balloons are a valuable approach for profiling the free atmosphere and boundary layer in remote regions such as the Arctic, where few other in situ observations are available for model validation.

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

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

<p>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 W m<sup>−2</sup>) 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. </p>

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

2020 ◽  
Vol 24 (4) ◽  
pp. 1691-1708 ◽  
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.

Three-dimensional vorticity, momentum and heat transport in a turbulent cylinder wake

2016 ◽  
Vol 809 ◽  
pp. 135-167 ◽  
Author(s):  
J. G. Chen ◽  
Y. Zhou ◽  
T. M. Zhou ◽  
R. A. Antonia
Keyword(s):  
Heat Flux ◽  
Heat Transport ◽  
Large Scale ◽  
Three Dimensional ◽  
Heat Diffusion ◽  
Small Scale ◽  
Stream Velocity ◽  
Streamwise Vorticity ◽  
Spanwise Vortex ◽  
D 20

The transport of momentum and heat in the turbulent intermediate wake of a circular cylinder is inherently three-dimensional (3-D). This work aims to gain new insight into the 3-D vorticity structure, momentum and heat transport in this flow. All three components of the velocity and vorticity vectors, along with the fluctuating temperature, are measured simultaneously, at nominally the same point in the flow, with a probe consisting of four X-wires and four cold wires. Measurements are made in the ($x$,$y$) or mean shear plane at$x/d=10$, 20 and 40 at a Reynolds number of$2.5\times 10^{3}$based on the cylinder diameter$d$and the free-stream velocity. A phase-averaging technique is developed to separate the large-scale coherent structures from the remainder of the flow. It is found that the effects of vorticity on heat transport at$x/d=10$and$x/d=20{-}40$are distinctly different. At$x/d=10$, both spanwise and streamwise vorticity components account significantly for the heat flux. At$x/d=20$and 40, the spanwise vortex rollers play a major role in inducing the coherent components of the heat flux vector, while the ribs are responsible for the small-scale heat diffusion out of the spanwise vortex rollers. The present data indicate that, if the spanwise-velocity-related terms are ignored, the estimated values of the production can have errors of approximately 22 % and 13 % respectively for the turbulent energy and temperature variance at$x/d=40$, and the errors are expected to further increase downstream. A conceptual model summarizing the 3-D features of the heat and momentum transports at$x/d=10$is proposed. Compared with the previous two-dimensional model of Matsumura & Antonia (J. Fluid Mech., vol. 250, 1993, pp. 651–668) or MA, the new model provides a more detailed description of the role the rib-like structures undertake in transporting heat and momentum, and also underlines the importance of the upstream half of the spanwise vortex rollers, instead of only one quadrant of these rollers, as in the MA model, in diffusing heat out of the vortex.

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