Multiphase formation of superimposed ice during a mass-balance year at a maritime high-Arctic glacier

Abstract

ABSTRACT. Meteorological and snow-temperature data from midtre Love¨nbreen, Spitsbergen, Svalbard, indicate two distinct annual phases of rapid snowpack warming and superimposed-ice formation in 1998/99. Short periods of positive air temperatures in early winter, lasting up to 36 hours and often coinciding with rainfall, caused rapid glacierwide melting. Percolating water froze to form superimposed ice on the lower half of the glacier, and wetted^refrozen snow and ice lenses at higher altitudes. The second period of superimposed-ice formation commenced in May/June 1999 and continued for 5 weeks at low altitudes and throughout the summer at high altitudes. These observations at midtre Love¨nbreen are typical of Spitsbergen glaciers and reflect the unique climatology of the region. They contrast with those from glaciers in more continental climatic settings where superimposed-ice formation is confined to a single period during summer. There are significant implications for glacier mass balance, with superimposed ice locally comprising up to 20% of winter balances and accounting for $16^25% of the annual accumulation. Since projected climatic warming is greatest during the winter months in Arctic regions, superimposed ice may become an increasingly important component of the winter, and potentially the net, balance of Spitsbergen glaciers.

Spatial mapping of multi-year superimposed ice on the glacier Kongsvegen, Svalbard

“…For this reason we restrict ourselves to stating that the long-term SI depth distribution shows a strong connection to: (1) the water pathways and thus topography; (2) elevation, snow depth and distance to the firn, all of which are highly correlated; and (3) cross-glacier gradient. This approach does not explain the physical reason for the differences in depth but instead confirms what Obleitner and Lehning (2004) and Wadham and Nuttall (2002), for example, have postulated.…”

“…The main difficulty in answering this question is that many of the parameters suggested in other studies (i.e. Wadham and Nuttall, 2002;Obleitner and Lehning, 2004) correlate with each other, thus hindering a quantitative analysis using regression of observed and derived parameters. For this reason we restrict ourselves to stating that the long-term SI depth distribution shows a strong connection to: (1) the water pathways and thus topography; (2) elevation, snow depth and distance to the firn, all of which are highly correlated; and (3) cross-glacier gradient.…”

Simulating melt, runoff and refreezing on Nordenskiöldbreen, Svalbard, using a coupled snow and energy balance model

“…Refreezing of percolating water is most pronounced in spring when low subsurface temperatures and the presence of a snow pack increase the potential for refreezing. During the melt season superimposed ice may form when percolating water accumulates a slush layer on top of the cold impermeable ice layer and refreezes (Wadham and Nuttall, 2002;Obleitner and Lehning, 2004;Wright et al, 2005). After the melt season, water trapped in pore spaces is subject to refreezing when a cold wave penetrates into the snow/firn pack (Pfeffer et al, 1991).…”

Modelling the long-term mass balance and firn evolution of glaciers around Kongsfjorden, Svalbard

“…As SI formation may constitute a substantial component of the mass budget (e.g. Wadham and Nuttall, 2002;Bøggild and others, 2005;Wright and others, 2007;Brandt and others, 2008), it is important to account for when converting stake height measurements into mass-balance estimates.…”