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Ice-Atmosphere Interaction: Melting of Mountain Glaciers Rebecca Miller Atmospheric Sciences Tropical glaciers, recorders and indicators of climate change, and disappearing globally Thompson et. Al. 2011 Picture: Thompson at Kilimanjaro , 1999 Introduction: Overview • Interaction of ENSO variability and warming trends recorded in icecore records • Melting Impacts o Glaciers o Societies Introduction: Ice Core • Paleoclimate record • Oxygen and hydrogen Objective: “the acquisition of aisotopes, global array of ice cores that provide high-resolution climatic and dust accumulation, environmental histories that will contribute to our • Variability understanding of the complex interactions in within precipitation, Earth’s climate system” temperature, aridity, and atmospheric and Thompson in Guliya, China, 1992 oceanic circulation Introduction: Warming • Earth’s average temperature has increased ~0.7°C since 1900 • Twice as much warming at higher elevations in the tropics than at Earth’s surface due to greenhousegas-forced warming, upper-tropospheric humidity and watervapor feedback Snow Melts, Ice Melts Darker land surface Absorption of radiation Increases Fig. 1 • Temperature • SST • Intense Precipitation • “Heat Engine” • Tropical disturbances distribute tropical energy pole-ward Tropical Ice-core Evidence of ENSO Dust • Enriched isotopic ratios occur during strong El Niño events Fig. 3 • Extended reconstruction of SST • (b) detrended – long term warming trend removed • Variability of ENSO through time • Changes in the tropical freezing level Fig. 4 Melting impacts the isotopic records • Meltwater homogenizes the seasonal changes Temperature is projected to increase more with higher elevation Increasing Elevation 1000 year records of oxygen isotopes Warming And Retreat Of Tropical Ice Fields • Rate at which a glacier responds to climate change is inversely proportional to its size • Temperature is a dominate factor o Ice masses are sensitive to temperature change o Exist very close to the melting point If the current rates continue or accelerate, many tropical ice caps may disappear within the first half of the 21st century Rate of ice loss per year Warming And Retreat Of Tropical Ice Fields Quelccaya • Rate of retreat is accelerating Warming And Retreat Of Tropical Ice Fields Tibetan Plateau, Himalaya, Naimona’nyi Kilimanjaro • surface temperature measurements • satellite observation studies Ice cover • persistent warming = ice loss • 86% disappeared since 1912 • 27% of that present in 2000 is now gone Impact On Water Resources • Changes in water supply o Hydroelectricity o Irrigation o Public water supply • Flooding o Crops o Grazing animals • Avalanches Conclusion • Warming trends across tropical glaciers • Rising temperatures more pronounced with increasing elevation • Melting is already effecting people who depend on the meltwater Qori Kalis Potential impacts of a warming climate on water availability in snow-dominated regions Barnett et. Al. 2005 Climate Research Division, Scripps Institution of Oceanography, California Introduction: Overview • Increasing temperature has consequences for the hydrological cycle • Changes in this cycle effect water supply from melting snow or ice • Earlier runoff in spring or winter, reduced flow in summer and autumn Global Distribution • 2000 – approximately 1/6th the world’s population lives within snowmelt-dominated and low-reservoir storage domain • Snowmelt dominated regions: o Greater than ~45° o Mountainous regions Red – snowmelt-dominated, inadequate reservoir storage Black – water availability is influence by snowmelt Evapotranspiration • Little agreement on direction and magnitude of evapotranspiration trends • Observations show pan evaporation has been decreasing 1. Increasing evapotranspiration • Cool and humid 2. Decreasing evapotranspiration • Reduced energy available for evaporation Impacts on regional water supply Western USA • Spring stream flow will come a month earlier • Not enough reservoir storage to handle this shift By 2050 the Columbia River system will not be able to accommodate both hydroelectricity and the summer releases for salmon Rhine River in Europe • Increasing temperature = rainfall-dominated • Reduction in water availability, increase of low flow days Ships will not be able to travel the river, decrease in hydroelectricity, shortened ski season Impacts on regional water supply Canadian Prairies • … earlier snowmelt → decrease in soil moisture • Increase in frequency and severity of drought • Sensitive to drought due to irrigation needs Glacier Impacts Himalaya-Hindu Kush South American Andes • Melting rate is increasing → runoff • Water shortage is not being experienced yet but will arrive more abruptly • Glacier covered area reduced 25% in last three decades • Current dry season water resources will be depleted once glaciers have disappeared Conclusion Uncertainties • Models predict warming • Alterations of the hydrological cycle • Earlier runoff • Insufficient reservoir storage • Reduction in dryseason water • Capability of models • Inclusion of aerosols and clouds What Happens Now? • More Research… • Better water management • Better models and predictions