Search results for "SNOW COVER"

Quantification des hauteurs de neige et des températures de l'air à la surface d'un glacier : du terrain à l'interpolation, confrontation de méthodes

2009

Quantifying snow cover and surface air temperature on a glacier is usually based on point data. The density of point measures is dependent on the local context. Interpolation brings the opportunity to generate a continuous surface. This surface can be used to derive a global measure for the whole glacier. These measures (total snow water equivalent, average thermal state) are integrated in glaciological and hydrological equations. Interpolation also renders the spatial variations of processes and provides information on inaccessible or not-monitored zones. Using the example of an arctic glacier, several interpolation methods were tested and compared. These methods were applied to snow drill…

High winter survival rate of acorn ants inside artificial nest sites (Hymenoptera: Formicidae)

2022

Although most species of ants overwinter underground to avoid low temperatures, the acorn ants of the genus Temnothorax remain in nests situated at ground level. During a field experiment, I studied the winter mortality of acorn ants in nest sites situated aboveground, as well as in sites experimentally buried in the soil. Despite the low air temperatures (even reaching –19°C, recorded 1.5 m above the ground), the survivorship was very high: all of the 18 queens used in the experiment survived, while the survival rate of workers was 61.9-100%, and for most colonies it exceeded 95%. The rate of survival in the nest sites aboveground and those experimentally buried in the soil was similar. Su…

2022

The quality of wintering habitats, such as depth of snow cover, plays a key role in sustaining population dynamics of Arctic lemmings. However, few studies so far investigated habitat use during the Arctic winter. Here, we used a unique long-term time series to test whether lemmings are associated with topographical and vegetational habitat features for their wintering sites. We examined yearly numbers and distribution of 22 769 winter nests of the collared lemming Dicrostonyx groenlandicus (Traill, 1823) from an ongoing long-term research on Traill Island, Northeast Greenland, collected between 1989 and 2019, and correlated this information with data on dominant vegetation types, elevatio…

Basal ice formation in snow cover in Northern Finland between 1948 and 2016

2018

Recent Change—Terrestrial Cryosphere

2015

This chapter compiles and assesses information on recent and current change within the terrestrial cryosphere of the Baltic Sea drainage basin. Findings are based on long-term observations. Snow cover extent (SCE), duration and amount have shown a widespread decrease although there is large interannual and regional variation. Few data are available on changes in snow structural properties. There is no evidence for a recent change in the frequency or severity of snow-related extreme events. There has been a decrease in glacier coverage in Sweden and glacier ice thickness in inland Scandinavia. The European permafrost is warming, and there has been a northward retreat of the southern boundary…

Size-related mortality during overwintering in cavity-nesting ant colonies (Hymenoptera: Formicidae)

2016

The ongoing process of climate change will result in higher temperatures during winter and therefore might increase the survival of overwintering invertebrates. However, the process may also lead to a reduction in snow cover and expose overwintering invertebrates to lower temperatures, which could result in higher mortality. During a field experiment, I investigated the effects of a reduction in snow cover on the survival of the ant Temnothorax crassispinus, which overwinters in nests located on the ground. Ant colonies differed in the survival rate of the workers in the experimental (from which snow cover was removed) and control group. In the control group, the survival rate was unrelated…

Basal ice formation in snow cover in Northern Finland between 1948 and 2016

2018

Abstract Basal ice formation in the terrestrial snow cover is a common phenomenon in northern circumpolar areas, one having significant impacts on ecosystems, vegetation, animals and human activities. There is limited knowledge on the spatial and temporal occurrence of basal ice formation because of the sparse observation network and challenges involved in detecting formation events. We present a unique dataset on the annual extent of ice formation events in northern Finland between 1948 and 2016 based on reindeer herders’ descriptions of the cold season in their management reports. In extreme years, basal ice can form over wide geographical extents. In approximately half of the herding dis…

Snowpack concentrations and estimated fluxes of volatile organic compounds in a boreal forest

2012

Abstract. Soil provides an important source of volatile organic compounds (VOCs) to atmosphere, but in boreal forests these fluxes and their seasonal variations have not been characterized in detail. Especially wintertime fluxes are almost completely unstudied. In this study, we measured the VOC concentrations inside the snowpack in a boreal Scots pine (Pinus sylvestris L.) forest in southern Finland, using adsorbent tubes and air samplers installed permanently in the snow profile. Based on the VOC concentrations at three heights inside the snowpack, we estimated the fluxes of these gases. We measured 20 VOCs from the snowpack, monoterpenes being the most abundant group with concentrations …

Labile nitrogen, carbon, and phosphorus pools and nitrogen mineralization and immobilization rates at low temperatures in seasonally snow-covered soi…

2006

Surface mineral horizons from four ecosystems sampled in the northwestern Italian Alps were incubated at −3 and +3°C to simulate subnivial and early thaw period temperatures for a seasonally snow-covered area. The soil profiles at these sites represent extreme examples of management, grazed meadow (site M) and extensive grazing beneath larch (site L) or naturally disturbed by avalanche and colonized by alder (site A) and the expected forest climax vegetation beneath fir (site F). Changes in labile pools of nitrogen (N) and phosphorus (P) were active at all sites at both temperatures during 14 days of laboratory incubation. Ammonium was the dominant inorganic form of total dissolved N (TDN),…

Changes in the seasonal snow cover of alpine regions and its effect on soil processes: A review

2007

Abstract At its maximum annual development, snow can cover more than half the Northern Hemisphere land area with one-third experiencing seasonal snow cover. The precise conditions that develop during the annual pattern of snowpack development formation have implications for: (i) soil microbiological activity and nutrient transformations; (ii) the capacity of the accumulating snowpack to retain atmospheric derived solutes; (iii) preferential elution and rapid runoff of solutes from the snowpack during periods of thaw; and (iv) leaching of solutes. Long-term records of annual snow accumulation suggest that substantial, regional scale shifts in snowpack characteristics have been occurring. The…