Measurement of the specific surface area of 176 snow samples using methane adsorption at 77 K

Abstract

[1] To help quantify exchanges between the atmosphere and the snow cover, we have measured the specific surface area (SSA) of 176 snow samples taken from the seasonal snowpack in the Alps, Svalbard, and the Canadian high Arctic around Alert. A volumetric method was used, and the adsorption isotherm of CH 4 on snow at 77 K was recorded. The data were analyzed by the Brunauer-Emmett-Teller method to yield SSA and ÁQ CH4 , the mean heat of adsorption of the first CH 4 monolayer. SSA values obtained were between 100 and 1580 cm 2 /g. The reproducibility of the method is estimated at 6%, and the accuracy is estimated at 12%. We propose that ÁQ CH4 = 2240 ± 200 J/mol should be used as a criterion of reliability of the measurement. The method is described in detail to promote its use. Aged snow samples have lower SSA than fresh ones. The lowest values were found for faceted crystals and depth hoar, and the highest values were found for fresh rimed dendritic snow. A method that field investigators can use to estimate SSA from a visual examination of the snow and from a density measurement is suggested. Snow samples are classified into 14 types based on snow age and crystal shapes. Within each type, a density versus SSA correlation is determined. Our data indicate that, depending on snow type, SSA can then be estimated within 25 to 40% at the 1s confidence level with the method proposed. Preliminary data suggest that SSA spatial variability of a given snow layer is low (<5%), but metamorphism can increase it.

Simulation of the specific surface area of snow using a one-dimensional physical snowpack model: implementation and evaluation for subarctic snow in Alaska

“…(9) and (10) were performed in the same snowpack at Fairbanks (Taillandier et al, 2007). The comparison indicates a reasonable agreement between the simulations and the observations considering that the accuracy of the SSA measurements was estimated to be 12% (Legagneux et al, 2002). Nevertheless, the simulated SSA values are generally higher than the observed values.…”

“…The horizontal resolution is 0.3 degrees (approximately 32 km) and data from the grid including the field site were selected. Previous investigations revealed that the NARR re-analysis delivers reliable input data for snowpack modeling (Langlois et al, 2009).…”

“…It represents the surface area of snow crystals that is accessible to gases per unit mass of snow (Hanot and Dominé, 1999). Therefore, it can be measured directly by the gas adsorption technique (Hanot and Dominé, 1999;Legagneux et al, 2002) or stereology (Arnaud et al, 1998). However, both techniques are time-consuming and the number of measurements in the field or in the laboratory obtained with these techniques…”

Acetaldehyde in the Alaskan subarctic snowpack

“…The original method is detailed in Legagneux et al (2002), with subsequent improvements detailed in Domine et al (2007b). A mathematical treatment was applied to the adsorption isotherm to derive the SSA.…”

Comparison of different methods to retrieve optical-equivalent snow grain size in central Antarctica

“…SSA (in units of m 2 kg −1 ) is measured with techniques such as methane adsorption (e.g., Domine et al, 2001;Legagneux et al, 2002), stereology (e.g., Matzl and Schneebeli, 2010), and X-ray microtomography (e.g., Flin et al, 2005;Kaempfer and Schneebeli, 2007). Those methods are difficult to employ in the field.…”