Spatial and temporal variations in albedo on Storglaciären, Sweden

Abstract

Extensive albedo data from Storglaciären, Sweden, during nine summers are analyzed, focusing on the effect of surface slope on measurements and on the influence of clouds on albedo of both snow and ice surfaces. On clear-sky days, albedo continuously dropped throughout the day by > 0.3 when derived from measurements in a horizontal plane over the slightly sloping surface. When we correct for the tilt effect, over frozen surfaces the apparent decrease in albedo largely disappeared, while over melting surfaces it became significantly less pronounced. This emphasizes the need to correct horizontally measured data for slope when they are used, for example, as ground truth for satellite-derived albedo, or in high-resolution glacier melt runoff models. Albedo varied by > 0.1 due to cloud fluctuations. To quantify cloud effects, albedo changes between successive (half-)hourly and daily data were regressed against corresponding changes in cloudiness expressed by the ratio of global radiation to top-of-atmosphere solar radiation. The resulting relationship over snow explains 66% of oberved albedo changes using hourly, and 42% using daily, time-steps. Over ice, the corresponding values are 28% and 0%. Hence, cloudiness is a dominating factor in determining short-term variability of albedo over snow, whereas over ice the observed large day-to-day variability ( > 20%) is mainly attributed to changes in the physical characteristics of the weathering crust. Results suggest that cloud effects should be incorporated into models treating snow and ice surfaces separately.

Meteorological drivers of ablation processes on a cold glacier in the semi-arid Andes of Chile

“…As clouds have been found to significantly augment the albedo at this site (Abermann et al, 2013), and elsewhere (e.g. Jonsell et al, 2003), the negative correlation between albedo and sublimation must partly reflect the effect of clouds, and the lower correlation between sublimation and snowfall (r = −0.22) tends to confirm this. A negative correlation with the east-west component of the wind (u-wind, r = 0.33) implies that sublimation is somewhat enhanced when the wind originates from a more westerly direction.…”

Assessing the retrieval of cloud properties from radiation measurements over snow and ice

“…Brock et al (2000) found no correlation between ice albedo and θ 0 or cloud cover. Jonsell et al (2003) also observed only a very weak albedo change under cloudy skies.…”

Sensitivity of a distributed temperature-radiation index melt model based on AWS observations and surface energy balance fluxes, Hurd Peninsula glaciers, Livingston Island, Antarctica

“…The daily mean α will be the same regardless of using S i , S d or S c as incoming short-wave flux. Jonsell et al (2003) found only a limited effect of clouds on α during ice conditions, probably because the multiple reflection of radiation will be limited due to lower α. The location of the AWS was snow covered during the period of data collection, with the exception of a few days at the end of the melt season 2006/07, but still with α exceeding 0.55, and therefore we applied Eqs.…”

“…A high sensitivity of the mass balance to changes in T air for glaciers on the nearby KGI was pointed out by Knap et al (1996) from the results of running a simple ice-flow model forced by an energy-balance model, after perturbating T air , until a new equilibrium state was reached. An energybalance model based on single-point measurements on Ecology glacier, KGI, produced an increase in ablation by 15 % in response to a 1 K temperature increase (Bintanja, 1995).…”