Local effects of depth-dependent water content of ice and snow and firn layers temperature on a conjectured subglacial lake below Amundsenisen Icefield (Svalbard)

It is known that the Amundsenisen Icefield in Southern Spitzbergen (Svalbard achipelago) is temperate with an upper layer of snow and firn. It is an accumulation area and, though ice/water mass balance is clearly subject to time evolution, observation data on the long-term elevation changes over the past 40 years (Nuth et al., 2010) allow to assume constant icefield surface. Within our study of the plausibility of a subglacial lake (Glowacki et al., 2007), here, we focus on the sensitivity of the system to the thermal effect of the firn and snow layers.

Plausibility of a subglacial lake under Amundsenisen Icefield (Svalbard): spatially variable water content and sensitivity to thermal effect of snow and firn layers

Within our study of the plausibility of a subglacial lake under the Amundsenisen Icefield in Southern Spitzbergen, Svalbard achipelago (Glowacki et al., 2007), here we focus on the sensitivity of the system to the thermal effect of the firn and snow layers. Rough heat balance analysis shows that the firn layer plays an important role by driving the heat release to the atmosphere, so that its influence on the ice-water phase transition cannot be neglected (Bucchignani et al., 2012).

Short Communication Over-Winter Channel Bed Temperature Regimes Generated by Contrasting Snow Accumulation in a High Arctic River

We report experimental results of near-surface winter temperatures along and adjacent to the channel bed of a High Arctic river on Melville Island, Canada. Temperature loggers 5cm below the ground surface in areas where the terrain suggests varying snow accumulation patterns revealed that the maximum winter difference between air and near-surface temperatures ranged from 0 to +30°C during the winter of 2012–13, and that shallow near-surface freezing conditions were delayed for up to 21 days in some locations. Cooling to -10°C was delayed for up to 117 days. Modelled temperature at the top of permafrost indicates that permafrost at locations with thick snow can be up to 8°C warmer than those with thin snow. This thermal evidence for an ameliorated surface environment indicates the potential for substantial extended microbial and biogeochemical cycling during early winter. Rapid thaw of the bed during initiation of snowmelt in spring also indicates a high degree of hydrological connectivity. Therefore, snow-filled channels may contribute to biogeochemical and aquatic cycling in High Arctic rivers.

Europe and the World or Snow White and the Seven Fallacies. Egmont Paper No. 61, October 2013

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Lake-effect snow as the dominant control of mesic-forest distribution in Michigan, USA

1Recent studies demonstrated the sensitivity of northern forest ecosystems to changes in the amount and duration of snow cover at annual to decadal time scales. However, the consequences of snowfall variability remain uncertain for ecological variables operating at longer time scales, especially the distributions of forest communities. 2The Great Lakes region of North America offers a unique setting to examine the long-term effects of variable snowfall on forest communities. Lake-effect snow produces a three-fold gradient in annual snowfall over tens of kilometres, and dramatic edaphic variations occur among landform types resulting from Quaternary glaciations. We tested the hypothesis that these factors interact to control the distributions of mesic (dominated by Acer saccharum, Tsuga canadensis and Fagus grandifolia) and xeric forests (dominated by Pinus and Quercus spp.) in northern Lower Michigan. 3We compiled pre-European-settlement vegetation data and overlaid these data with records of climate, water balance and soil, onto Landtype Association polygons in a geographical information system. We then used multivariate adaptive regression splines to model the abundance of mesic vegetation in relation to environmental controls. 4Snowfall is the most predictive among five variables retained by our model, and it affects model performance 29% more than soil texture, the second most important variable. The abundance of mesic trees is high on fine-textured soils regardless of snowfall, but it increases with snowfall on coarse-textured substrates. Lake-effect snowfall also determines the species composition within mesic forests. The weighted importance of A. saccharum is significantly greater than of T. canadensis or F. grandifolia within the lake-effect snowbelt, whereas T. canadensis is more plentiful outside the snowbelt. These patterns are probably driven by the influence of snowfall on soil moisture, nutrient availability and fire return intervals. 5Our results imply that a key factor dictating the spatio-temporal patterns of forest communities in the vast region around the Great Lakes is how the lake-effect snowfall regime responds to global change. Snowfall reductions will probably cause a major decrease in the abundance of ecologically and economically important species, such as A. saccharum.

Halogen deposition in polar snow and ice

The atmospheric chemistry of iodine and bromine in polar regions is of interest due to the key role of halogens in many atmospheric processes, particularly tropospheric ozone destruction. Bromine is emitted from the open ocean but is enriched above first-year sea ice during springtime bromine explosion events, whereas iodine is emitted from biological communities hosted by sea ice. It has been previously demonstrated that bromine and iodine are present in Antarctic ice over glacial-interglacial cycles. Here we investigate seasonal variability of bromine and iodine in polar snow and ice, to evaluate their emission, transport and deposition in Antarctica and the Arctic and better understand potential links to sea ice. We find that bromine enrichment (relative to sea salt content) and iodine concentrations in polar ice do vary seasonally in Arctic snow and Antarctic ice and we relate such variability to satellite-based observations of tropospheric halogen concentrations. Peaks of bromine enrichment in Arctic snow and Antarctic ice occur in spring and summer, when sunlight is present. Iodine concentrations are largest in winter Antarctic ice strata, contrary to contemporary observations of summer maxima in iodine emissions.

(Table 1) Stable oxygen isotopic ratios and yearly snow accumulation of firn and ice cores from Svalbard

We analyse ice cores from Vestfonna ice cap (Nordaustlandet, Svalbard). Oxygen isotopic measurements were made on three firn cores (6.0, 11.0 and 15.5 m deep) from the two highest summits of the glacier located on the SW-NE and NW-SE central ridges. Sub-annual d18O cycles were preserved and could be counted visually in the uppermost parts of the cores, but deeper layers were affected by post-depositional smoothing. A pronounced d18O minimum was found near the bottom of the three cores. We consider candidates for this d18O signal to be a valuable reference horizon since it is also seen elsewhere in Nordaustlandet. We attribute it to isotopically depleted snow precipitation, which NCEP/NCAR reanalysis shows was unusual for Vestfonna, and came from northerly air during the cold winter of 1994/95. Finding the 1994/95 time marker allows establishment of a precise depth/age scale for the three cores. The derived annual accumulation rates indirectly fill a geographical gap in mass balance measurements and thus provide information on spatial and temporal variability of precipitation over the glacier for the period spanned by the cores (1992-2009). Comparing records at the two locations also reveals that the snow net accumulation at the easternmost part of Vestfonna was only half of that in the western part over the last 17 years.