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Glacier Mass Balance (glacier + mass_balance)
Selected AbstractsImprovement and validation of a snow saltation model using wind tunnel measurementsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 14 2008Andrew Clifton Abstract A Lagrangian snow saltation model has been extended for application to a wide variety of snow surfaces. Important factors of the saltation process, namely number of entrained particles, ejection angle and speed, have been parameterized from data in the literature. The model can now be run using simple descriptors of weather and snow conditions, such as wind, ambient pressure and temperature, snow particle sizes and surface density. Sensitivity of the total mass flux to the new parameterizations is small. However, the model refinements also allow concentration and mass flux profiles to be calculated, for comparison with measurements. Sensitivity of the profiles to the new parameterizations is considerable. Model results have then been compared with a complete set of drifting snow data from our cold wind tunnel. Simulation mass flux results agree with wind tunnel data to within the bounds of measurement uncertainty. Simulated particle sizes at 50 mm above the surface are generally larger than seen in the tunnel, probably as the model only describes particles in saltation, while additional smaller particles may be present in the wind tunnel at this height because of suspension. However, the smaller particles carry little mass, and so the impact on the mass flux is low. The use of simple input data, and parameterization of the saltation process, allows the model to be used predictively. This could include applications from avalanche warning to glacier mass balance. Copyright © 2008 John Wiley & Sons, Ltd. [source] Mass balance of a slope glacier on Kilimanjaro and its sensitivity to climateINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2008Thomas Mölg Abstract Meteorological and glaciological measurements obtained at 5873 m a.s.l. on Kersten Glacier, a slope glacier on the southern flanks of Kilimanjaro, are used to run a physically-based mass balance model for the period February 2005 to January 2006. This shows that net shortwave radiation is the most variable energy flux at the glacier-atmosphere interface, governed by surface albedo. The majority of the mass loss (,65%) is due to sublimation (direct conversion of snow/ice to water vapour), with melting of secondary importance. Sensitivity experiments reveal that glacier mass balance is 2,4 times more sensitive to a 20% precipitation change than to a 1 °C air temperature change. These figures also hold when the model is run with input data representative of a longer term (1979,2004) mean period. Results suggest that a regional-scale moisture projection for the 21st century is crucial to a physically-based prediction of glacier retention on Africa's highest mountain. Copyright © 2007 Royal Meteorological Society [source] Near-surface-temperature lapse rates on the Prince of Wales Icefield, Ellesmere Island, Canada: implications for regional downscaling of temperatureINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 3 2007Shawn J. Marshall Abstract Screen temperatures were monitored from May 2001 to April 2003 in an array of 25 sites on the Prince of Wales Icefield, Ellesmere Island, Canada. The observational network covered an area of ca 15 650 km2 and spanned an altitude ranging from 130 to 2010 m above sea level. The spatial array provides a record of near-surface-temperature lapse rates and mesoscale temperature variability on the icefield. The mean daily lapse rate in the 2-year record is , 4.1° C km,1, with an average summer lapse rate of , 4.3° C km,1. Surface-temperature lapse rates in the region are therefore systematically less than the free-air lapse rates that are typically adopted for extrapolations of sea-level temperature to higher altitudes. Steep lapse rates, resembling moist adiabatic rates in the free air (,6 to , 7° C km,1), are more common in summer at our site and are associated with enhanced cyclonic activity (low-pressure and high relative vorticity) and southerly flow aloft. In contrast, northerly, anticyclonic flow prevails when summer lapse rates are weak (above , 2° C km,1). The low surface-temperature lapse rates and their systematic synoptic variability have important implications for applications that require downscaling or extrapolation of surface- or boundary-layer temperatures, such as modelling of glacier mass balance. We illustrate this in an analysis of observed versus modelled snowmelt on the icefield. Copyright © 2006 Royal Meteorological Society. [source] Detection of a possible change point in atmospheric variability in the North Atlantic and its effect on Scandinavian glacier mass balanceINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 14 2005Rowan Fealy Abstract Climate change, resulting from an increase in global temperatures, is likely to have a large impact on glaciers and glacier meltwater during the course of the present century resulting in significant contributions to sea level rise. Globally, glaciers are in retreat, partly as a response to the return to warmer conditions after the last neoglacial period during the Little Ice Age but also because of the almost continuous increases evident in global temperature since then. In contrast, Scandinavian glaciers, particularly maritime glaciers, were maintaining equilibrium or advancing over the closing decades of the last century possibly resulting from an increased moisture flux over the North Atlantic. While the more continental glaciers were still declining, the rate of decline diminished during the late 1980s. This coincides with an accelerated rate of increase evident on the maritime glaciers in southwestern Norway. A change point in atmospheric variability in the North Atlantic is identified as having occurred during this period. This change point is associated with an intensification of westerlies over Europe, particularly since the late 1980s, which significantly contributes to increases in temperature and precipitation over northern Europe while suppressing the penetration of warm, moist air into more southern European locations. Regional variations in temperature and precipitation from selected Scandinavian stations are also found to be consistent with the changes in the large-scale modes of atmospheric variability in the North Atlantic. Copyright © 2005 Royal Meteorological Society [source] Ages and inferred causes of Late Pleistocene glaciations on Mauna Kea, Hawai'i,JOURNAL OF QUATERNARY SCIENCE, Issue 6-7 2008Jeffrey S. Pigati Abstract Glacial landforms on Mauna Kea, Hawai'i, show that the summit area of the volcano was covered intermittently by ice caps during the Late Pleistocene. Cosmogenic 36Cl dating of terminal moraines and other glacial landforms indicates that the last two ice caps, called Older Makanaka and Younger Makanaka, retreated from their maximum positions approximately 23,ka and 13,ka, respectively. The margins and equilibrium line altitudes of these ice caps on the remote, tropical Pacific island were nearly identical, which would seem to imply the same mechanism for ice growth. But modelling of glacier mass balance, combined with palaeotemperature proxy data from the subtropical North Pacific, suggests that the causes of the two glacial expansions may have been different. Older Makanaka air atop Mauna Kea was likely wetter than today and cold, whereas Younger Makanaka times were slightly warmer but significantly wetter than the previous glaciation. The modelled increase in precipitation rates atop Mauna Kea during the Late Pleistocene is consistent with that near sea level inferred from pollen data, which suggests that the additional precipitation was due to more frequent and/or intense tropical storms associated with eastward-moving cold fronts. These conditions were similar to modern La Niña (weak ENSO) conditions, but persisted for millennia rather than years. Increased precipitation rates and the resulting steeper temperature lapse rates created glacial conditions atop Mauna Kea in the absence of sufficient cooling at sea level, suggesting that if similar correlations existed elsewhere in the tropics, the precipitation-dependent lapse rates could reconcile the apparent difference between glacial-time cooling of the tropics at low and high altitudes. Copyright © 2008 John Wiley & Sons, Ltd. [source] A geochronological approach to understanding the role of solar activity on Holocene glacier length variability in the Swiss AlpsGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 4 2006Anne Hormes ABSTRACT. We present a radiocarbon data set of 71 samples of wood and peat material that melted out or sheared out from underneath eight presentday mid-latitude glaciers in the Central Swiss Alps. Results indicated that in the past several glaciers have been repeatedly less extensive than they were in the 1990s. The periods when glaciers had a smaller volume and shorter length persisted between 320 and 2500 years. This data set provides greater insight into glacier variability than previously possible, especially for the early and middle Holocene. The radiocarbon-dated periods defined with less extensive glaciers coincide with periods of reduced radio-production, pointing to a connection between solar activity and glacier melting processes. Measured long-term series of glacier length variations show significant correlation with the total solar irradiance. Incoming solar irradiance and changing albedo can account for a direct forcing of the glacier mass balances. Long-term investigations of atmospheric processes that are in interaction with changing solar activity are needed in order to understand the feedback mechanisms with glacier mass balances. [source] Timing and style of Late Pleistocene glaciation in the Queer Shan, northern Hengduan Mountains in the eastern Tibetan Plateau,JOURNAL OF QUATERNARY SCIENCE, Issue 6 2010Liubing Xu Abstract Glacial landforms and sediments provide evidence for the existence of two Late Pleistocene major glacial advances in the Queer Shan, northern Hengduan Mountains in the eastern Tibetan Plateau. In the current study, optically stimulated luminescence and electron spin resonance dating results reveal that the two glacial advances occurred during Marine Isotope Stage (MIS) 3 and the Last Glacial Maximum (LGM) in MIS 2, respectively. Geomorphic evidence shows that the glacial advance during MIS 3 was more extensive than that in MIS 2. This glacial advance is synchronous with other glaciated areas in the Himalaya and Tibet, but contrasts with global ice volumes that reached their maximum extent during the LGM. Glaciers in the Queer Shan are of the summer accumulation type and are mainly fed by precipitation from the south Asian monsoon. Palaeoclimate proxies show that during MIS 3 the south Asian monsoon strengthened and extended further north into the Tibetan Plateau to supply more precipitation as snow at high altitudes. This in turn led to positive glacier mass balances and caused glaciers to advance. However, during the LGM, despite cooler temperature than in MIS 3, the weakened south Asian monsoon and the associated reduced precipitation were not as favourable for glacier expansion as in MIS 3. Copyright © 2010 John Wiley & Sons, Ltd. [source] Seasonal variability in velocity and ablation of Te Moeka o Tuawe/Fox Glacier, south Westland, New ZealandNEW ZEALAND GEOGRAPHER, Issue 1 2008Heather L. Purdie Abstract:, Seasonal variations in ablation and surface velocity were investigated on the lower Fox Glacier. Variations occur between summer and winter ablation, with surface velocity also showing marked seasonality. Recent advance has resulted in the glacier gaining around 200 m length since late 2004. Longer term, Fox Glacier appears linked to the Southern Oscillation Index, with positive glacier mass balances associated with negative Southern Oscillation Index (El Niño). An estimated glacier response time of approximately 9,14 years suggests the current terminus advance was linked to mass gains in the mid-1990s. Recent collapses at the terminal face continue to prove a hazard at this busy tourist destination. [source] | |||||||||||||