The thermal conductivity of seasonal snow

Abstract

Twenty-seven studies on the thermal conductivity of snow (Keff) have been published since 1886. Combined, they comprise 354 values ofKeff, and have been used to derive over 13 regression equation and predictingKeffvs density. Due to large (and largely undocumented) differences in measurement methods and accuracy, sample temperature and snow type, it is not possible to know what part of the variability in this data set is the result of snow microstructure. We present a new data set containing 488 measurements for which the temperature, type and measurement accuracy are known. A quadratic equation,whereρis in g cm−3, andKeffis in W m−1K−1, can be fit to the new data (R2= 0.79). A logarithmic expression,can also be used. The first regression is better when estimating values beyond the limits of the data; the second when estimating values for low-density snow. Within the data set, snow types resulting from kinetic growth show density-independent behavior. Rounded-grain and wind-blown snow show strong density dependence. The new data set has a higher mean value of density but a lower mean value of thermal conductivity than the old set. This shift is attributed to differences in snow types and sample temperatures in the sets. Using both data sets, we show that there are well-defined limits to the geometric configurations that natural seasonal snow can take.

Modeling the impediment of methane ebullition bubbles by seasonal lake ice

“…The snow's thermal conductivity was calculated from its density (Sturm et al, 1997), which was estimated from measurements of precipitation and snow depth (Sect. 2.2.8).…”

“…Methane is typically produced in anoxic bottom sediments by methanogenic microbes and can be released to the atmosphere by diffusion, vascular transport through aquatic plants, or ebullition (bubbling) (Rudd and Hamilton, 1978;Bastviken et al, 2004;Whalen, 2005). Methanogenesis in the oxic water column has been proposed as an additional CH 4 source in some lakes (Tang et al, 2014). In many lakes, ebullition from bottom sediments is the dominant mode of emission because gasphase CH 4 in bubbles is not subject to oxidation, whereas a significant proportion of dissolved CH 4 is typically oxidized by methanotrophic bacteria, including in the plant rhizosphere (Keller and Stallard, 1994;Casper et al, 2000;Bastviken et al, 2008).…”

Thermal diffusivity of seasonal snow determined from temperature profiles

“…In addition, latent heat transfer can also play a significant role in relatively warm snow [3]. However, latent heat transfer is also a diffusive mechanism which occurs along a temperature gradient, so its effects can be naturally lumped into an effective thermal diffusivity [18,15,17,3]. Several techniques exist for measuring thermal conductivity.…”

“…For thermal conductivity, several techniques exist which vary greatly in cost, ease of implementation, accuracy and spatial and temporal resolution. Some of these methods are described in Section 2, and a more rigorous summary and critique of several of the techniques was presented by Sturm et al [15]. Many of these methods require specialized, relatively expensive equipment in addition to requiring substantial effort to obtain measurements at high spatial and temporal resolution.…”

“…However, the Brandt and Warren [16] study is not representative of ephemeral, seasonal snow packs of hydrological importance because the diurnal solar forcing was atypical (polar night for 6 months) and snow temperatures were extremely low (6À40°C). In relatively warm snowpacks latent heat transfer can account for a significant portion of the overall heat transfer [15]. Due to these complications, it was unclear that the method used by Brandt and Warren [16] could be successful for relatively warm snowpacks with the strong diurnal forcing experienced by seasonal snow.…”