Late-Holocene glacier growth in Svalbard, documented by subglacial relict vegetation and living soil microbes

Abstract

Much renewed research interest in Arctic regions stems from the increasing concentration of atmospheric greenhouse gases and the alleged climatic sensitivity of high latitude areas. Glacier and permafrost changes are among a number of proxies used for monitoring past and present Arctic climate change. Here we present observations on frozen in situ soil and vegetation, found below cold-based glacier Longyearbreen (78813?N), 2 km upstream from the present glacier terminus. Dating of the relict vegetation indicates that the glacier has increased in length from about 3 km to its present size of about 5 km during the last c. 1100 years. The meteorological setting of non-surging Longyearbreen suggests this example of late-Holocene glacier growth represents a widespread phenomenon in Svalbard and in adjoining Arctic regions. In addition, we use the subglacial permafrozen soil system to evaluate microbial survival capacity over considerable time periods, and we present evidence for microbes having survived more than 1100 years in a subglacial, permafrozen state.

Observations: Cryosphere

“…Currently, the glacier terminus falls about midway between its maximum and minimum positions of the past three centuries, and Mackintosh et al report "the recent advance (1970Mackintosh et al report "the recent advance ( -1995 resulted from a combination of cooling and enhancement of precipitation." • Humlum et al (2005) evaluated the climate dynamics of high-latitude glaciers in the Svalbard Archipelago, especially the Longyearbreen glacier in arid central Spitzbergen (latitude 78°13'N). They found the Longyearbreen glacier "has increased in length from about 3 km to its present size of about 5 km during the last c. 1100 years," and they suggest this late-Holocene glacial growth is probably widespread in Svalbard and adjoining Arctic regions.…”

Thermal structure and drainage system of a small valley glacier (Tellbreen, Svalbard), investigated by ground penetrating radar

“…Such "cut-and-closure" conduits commonly form in lateral positions due to the convex shape of the ablation area (e.g. Longyearbreen: (Gulley et al, 2009a;Hansen, 2001;Humlum et al, 2005), although they can also occur close to the glacier centreline (e.g. Austre Brøggerbreen: (Vatne, 2001).…”

“…Cut-and-closure conduits can incise down to glacier beds and form subglacial channels in cold ice (e.g. (Gulley et al, 2009a;Humlum et al, 2005), although channels below depths of ∼20 m of ice are very susceptible to blockage, and water tends to be re-routed to shallower flow paths.…”

“…Cut-and closure conduits appear to be very widespread on uncrevassed parts of Svalbard glaciers (Gulley et al, 2009a, b), and have been observed in subglacial positions below thin ice near glacier termini. For example, cut-and-closure channels existed at the bed of the cold-based Longyearbreen between 2001 and 2003 (Humlum et al, 2005), although this channel subsequently became blocked and water was re-routed at a higher level within the glacier (Gulley et al, 2009a). Other examples have been observed near the termini of Scott Turnerbreen (Temminghoff, 2009) and Rieperbreen (Gulley, unpublished data).…”

Subglacial and Proglacial Ecosystem Responses to Climate Change

“…The amount of subglacial OM is heterogeneously distributed and relict soils (e.g. Humlum et al, 2005) and vegetation (e.g. Knudsen et al, 2008) may be preserved in situ beneath glaciers.…”