Thesis (M.A.)--University of Wyoming, 2008. / Title from PDF title page (viewed on August 6, 2009). Includes bibliographical references (p. 44-46).

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Rock glaciers are tongue-shaped or lobate masses of rock debris which occur below cliffs and talus in many alpine regions. They are best developed in continental alpine climates where it is cold enough to preserve a core or matrix of ice within the rock mass but insufficiently snowy to produce true glaciers. Previous reports have identified and briefly described several rock glaciers in the Olympic Mountains, Washington {Long 1975a, pp. 39-41; Nebert 1984), but no detailed integrative study has been made regarding the geomorphic character, age,and distribution of these features.

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This project investigates the near surface energy balance on the Murt`el-Corvatsch rock glacier in the Upper Engadine, Swiss Alps, using the 1D physical SNOWPACK model. A correct representation of the near surface energy balance is important to predict the long term evolution of permafrost below rock glaciers. This is of interest in the context of future water availability and management of water resources in a changing climate and also in the context of natural hazards. Some difficulties in modelling the thermal regime of rock glaciers are related to the large pore spaces between the blocks, which allow for different modes of heat transport. With this in mind, different modelling approaches were investigated: using the standard SNOWPACK (without advective heat flux, ventilation or canopy module), adding an advective heat flux, using the ventilation and canopy modules. The most promising results, i.e. the best match between measured and modelled temperatures, were obtained from the ventilation parameterisation. This parameterisation accounts for boundary-layer air penetrating into the blocky layer. Furthermore it was found that the most important input variables are the thickness of the the blocky layer, since this is where the additional modes of heat exchange take place, and the ice and void volume fraction together with the field capacity in the icy layer. The latter are particularly relevant for long term modelling as they determine the amount of ice melt and water transport in the icy layer. Measured and modelled temperatures at depths of 0.5 m, 2.5 m, 3.5 m and 7.5 m were compared. Generally good agreements between modelled and measured temperatures were obtained for the depths 0.5 m, 3.5 m and 7.5 m. The slight warming trend at the end of the modelled period (2012- 2016) that can be observed in the borehole data is also present in the modelled temperatures. The depth of 2.5 m shows the least agreement between modelled and measured temperatures with and overestimation during the snow free period and an underestimation during the snow covered period. However, agreement between modelled and measured temperatures improves for the snow covered period after a simulation period of about ten years.

Eliot Glacier is a small (1.6 km2), relatively well-studied glacier on Mount Hood, Oregon. Since 1901, glacier area decreased from 2.03 ± 0.16 km2 to 1.64 ± 0.05 km2 by 2004, a loss of 19%, and the terminus retreated about 600 m. Mount Hood's glaciers as a whole have lost 34% of their area. During the first part of the 20th century the glacier thinned and retreated, then thickened and advanced between the 1940s and 1960s because of cooler temperatures and increased winter precipitation and has since accelerated its retreat, averaging about 1.0 m a-1 thinning and a 20 m a-1 retreat rate by 2004. Surface velocities at a transverse profile reflect ice thickness over time, reaching a low of 1.4 m a-1 in 1949 before increasing to 6.9 ± 1.7 m a-1 from the 1960s to the 1980s. Velocities have since slowed to about 2.3 m a-1 , about the 1940 speed.

Continental-scale inventories of glaciers are available, but no analogous rock glacier inventories exist. We present the Portland State University Rock Glacier Inventory (n = 10,343) for the contiguous United States, then compare it to an existing inventory of contiguous United States glaciers (n = 853), identifying geographic and climatic factors affecting the spatial distributions observed. At least one rock glacier is identified in each of the 11 westernmost states, but nearly 90% are found in just five; Colorado (n = 3889), Idaho (n = 1723), Montana (n = 1780), Utah (n = 834), and Wyoming (n = 849). Glaciers are concentrated in relatively humid mountain ranges, while rock glaciers are concentrated in relatively arid mountain ranges. Mean glacier area (0.60 ± 0.073 km2) is significantly greater than mean rock glacier area (0.10 ± 0.002 km2), though total glacier area (507.70 km2) is lower than total rock glacier area (1008.91 km2). Glacier and rock glacier areas, as a percent of small watersheds containing them, are modeled using geographically weighted regression. Glacier percent area (R2 = 0.55) is best explained by elevation range and mean fall snowfall, while rock glacier percent area (R2 = 0.42) is best explained by mean spring dewpoint temperature and slope standard deviation. Finally, we compare riparian vegetation along meltwater streams draining glaciers and rock glaciers. Initial 500 m long meltwater stream reaches emanating from a total of 35 pairs of collocated glaciers and rock glaciers were delineated, allowing estimation of riparian vegetation cover and density. Rock glacier meltwater stream riparian vegetation cover (mean cover = 86.2% ± 9.3%) and density (mean NDVI = 0.30 ± 0.02) are significantly greater (p-value < 0.05) than glacier meltwater stream riparian vegetation cover (mean cover = 64.5% ± 10.9%) and density (mean NDVI = 0.13 ± 0.01). This study shows that while the spatial distributions of glaciers and rock glaciers are both generally influenced by a combination of geographic and climatic variables, the specific forcings and local magnitudes are distinct for each cryospheric feature type, and processes inherent to rock glacier cryospheric meltwater sourcing positively influence first-order meltwater stream vegetation patterns.

This thesis provides a contribution to the knowledge on the effects of deglaciation on alpine stream ecosystems, taking into account also the hydroecological influence of thawing permafrost and paraglacial features. With a focus on the European Alps, a review is provided on the climate changes and shifts in the cryosphere (snow, glaciers, permafrost), the related changes in hydrology, geomorphic processes and the physical and chemical habitat of alpine river networks, and the consequent shifts in stream communities and food webs. A conceptual model is provided to summarize the complex interactions and the cascading effects triggered by deglaciation on hydrology, habitat and biota of alpine streams, that can be useful for educational purposes and to help the scientific community to contextualize these issues to other alpine areas. Deglaciation induces homogenisation of river networks, loss of biodiversity, and shifts in primary and secondary production, functional diversity and food webs. The scarce published studies on streams influenced by permafrost provide hints on the role of thawing rock glaciers (i.e. evident form of mountain permafrost) in shaping the ecology of freshwaters, and reveal important research gaps. To increase the knowledge on this topic, different alpine streams fed by waters of different origin were selected in two subcatchments (Zay, Solda) of a deglaciating area of the Central Italian Alps (Solda Valley), and their habitat conditions and benthic invertebrate communities were investigated over a two-year period. Rock glacier-fed streams could be distinguished from those fed by glaciers, groundwater and those of mixed origin because of their constantly clear and very cold waters, stable channels, and high concentrations of ions and trace elements that increased as summer progressed. Furthermore, the Zay rock glacier strongly influenced the glacier-fed stream through an intense export of solutes, which become progressively more relevant towards the end of summer. This influence was also due to the contribution of a proglacial lake and a moraine body, that both strongly decreased the glacial influence along the glacier-fed stream before its confluence with the rock glacier outflow. The wide range of habitat conditions revealed to strongly influence the benthic invertebrate communities in the study area. Channels with groundwater (krenal) and mixed (glacio-rhithral) exhibited a higher taxa richness and diversity. Peaks of abundance and biomass in the catchment were recorded just downstream the talus body, in the upper glacio-rhithral channel. Chironomidae from the cold-adapted genus Diamesa were dominant in the proglacial sections (upper kryal) of the glacier-fed streams. The proglacial lake, the moraine body and the rock glacial tributary at Zay contributed to the amelioration of the environmental features of the glacier-fed stream (lower kryal), boosting high invertebrate biomass and abundance and causing shifts in the community composition (e.g. increased Orthocladiinae and other Diamesinae chironomids, abundant Trichoptera). The two rock glacial communities differed considerably between each other. In fact, the community of the Zay rock glacial stream was partially influenced by the seepage of glacier waters, and resembled those of the surrounding lower kryal. On the contrary, the Solda rock glacial stream, detached from any glacier influence, hosted a rich and diverse community which resembled those of glacio-rhithral and krenal, even though with a higher abundance of Diamesa. Overall, the results of this thesis showed that in the advanced phases of glacier retreat, paraglacial landforms and permafrost can increasingly contribute to the riverscape diversity and shape the ecology of river networks. Because of their unique environmental settings, rock glacial streams should be considered a distinct alpine stream habitat, acting in deglaciating catchments as stepping stones that enhance the upstream colonisation of non-glacial communities following glacier retreat. At the same time, they might represent cold refugia for cold-stenothermal and/or typically glacial taxa when glaciers will be disappeared, because of the slower thawing rate of rock glacier ice. In this context, the presence of Diamesa kryal specialist species in rock glacial streams deserves further investigation, in order to understand the potential conservation value that these habitats may have in buffering the β-diversity reduction which is predicted in alpine areas as a consequence of glacier loss.