Rock glacier characteristics serve as an indirect record of multiple alpine glacier advances in Taylor Valley, Antarctica

Abstract

Abstract. The geomorphic record indicates that alpine glaciers in the McMurdo Dry Valleys of southern Victoria Land, Antarctica, appear to advance during interglacial periods in response to ice-free conditions in the Ross Sea. Few records of these advances are preserved and/or subaerially exposed, complicating the interpretations of regional glacier response to climate changes. Here, we present geophysical and geochemical analyses of a rock glacier that originates from icefalls fed by alpine Doran Glacier in central Taylor Valley. The rock glacier exhibits a trend of increased weathering of granitic clasts via ventifaction and grussification down-flow. Meltwater ponds on the rock glacier exhibit variable salinity that ranges from freshwater to higher than seawater, with the highest salinity pond near the rock glacier toe. Ground-penetrating radar analyses reveal the feature to possess a primarily clean ice interior, with layers of englacial debris. Stable isotopic data from three ice cores support a glacial origin for the ice within the rock glacier. These data suggest that the current morphology of the rock glacier is the result of multiple events of increased ice contribution caused by advances of Doran Glacier, which is the main source of ice to the rock glacier. We therefore demonstrate the potential of ice-cored rock glaciers to record multiple advances and retreats of Dry Valley glaciers, permitting the interpretation of glacial responses to Pleistocene and Holocene climate change even where direct records are not present.

Summary and synthesis of Changing Cold Regions Network (CCRN) research in the interior of western Canada – Part 2: Future change in cryosphere, vegetation, and hydrology

“…Even in the absence of further warming, many of these glaciers are out of balance with the current climate, given their present configuration (Zemp et al, 2015;Marzeion et al, 2018). This indicates that they will further recede to adjust their geometry to the current climate, with a typical response time of several decades for glaciers in western Canada (Marshall et al, 2011;Marzeion et al, 2018). Ongoing climate change is expected to further exacerbate the current imbalance and lead to additional retreat (Clarke et al, 2015).…”

“…Dust, impurities, and algae in the snow and ice become more concentrated on glacier surfaces as a consequence of high melt rates, in turn reducing the albedo and further enhancing melt (Williamson et al, 2019;DeBeer et al, 2020). There may also be an interaction with wildfire in western Canada, with deposition of black carbon and forest-fire fallout further reducing glacier albedo and providing nutrients to microbial communities (e.g., Marshall and Miller, 2020). High thinning rates in the upper accumulation area of many glaciers in western Canada indicate that these processes are well under way (Anderson, 2017;Pelto et al, 2019;Ednie and Demuth, 2018), while reductions in accumulation zone extent can lead to rapid glacier disintegration, and even complete disappearance.…”

“…The presence of glacial ice helps to regulate local climates and preserve cold conditions. As reduced snow accumulation leads to a reduction in glacier mass balance, so a reduction in glacier extent leads to a reduction in snow accumulation, given that the glacier surface, which is ≤ 0 • C, helps retain snow cover (Marshall et al, 2011).…”

Summary and synthesis of Changing Cold Regions Network (CCRN) research in the interior of western Canada – Part 2: Future change in cryosphere, vegetation, and hydrology

“…Dust, impurities, and algae in the snow and ice become more concentrated on glacier surfaces as a consequence of high melt rates, in turn reducing the albedo and further enhancing melt (Williamson et al, 2019;DeBeer et al, 2020). There may also be an interaction with wildfire in western Canada, with deposition of black carbon and forest-fire fallout further reducing glacier albedo and providing nutrients to microbial communities (e.g., Marshall and Miller, 2020). High thinning rates in the upper accumulation area of many glaciers in western Canada indicate that these processes are well under way (Pelto et al, 2019), while reductions in accumulation zone extent can lead to rapid glacier disintegration, and even complete disappearance.…”

“…Process algorithms cover a wide range of phenomena specific to cold regions hydrology, which are then linked together to represent specific elements of the hydrological system and cycling over distinct landscape units termed "hydrological response units" (HRUs). Process studies and model developments focused on blowing snow transport and sublimation over complex terrain Pomeroy, 2018, 2020); snowmelt in disturbed forests and on slopes; water flow through snowpacks Pomeroy, 2017, 2019); glacier snow, firn and ice melt (Samimi and Marshall, 2017;Marshall and Miller, 2020;Pradhananga, 2020); snow avalanching; soil moisture and hydraulic conductivity (Zwieback et al, 2019a); and freezing and thawing of soils (Krogh et al, 2017;Williamson et al, 2018;Rowlandson et al, 2018;Lara et al, 2020). CRHM was applied at a number of the WECC observatories as well as other sites in western North America and run for historical periods using local meteorological observations, ERA-Interim (Dee et al, 2011), and/or bias-corrected WATCH (http://www.eu-watch.org/) forcing data.…”