Ice-Atmosphere Interaction: Melting of Mountain Glaciers Rebecca Miller Atmospheric Sciences.
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Transcript of Ice-Atmosphere Interaction: Melting of Mountain Glaciers Rebecca Miller Atmospheric Sciences.
Ice-Atmosphere Interaction: Melting of Mountain Glaciers
Rebecca MillerAtmospheric 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 ice-core records
• Melting ImpactsoGlacierso Societies
Introduction: Ice Core • Paleoclimate record• Oxygen and hydrogen
isotopes, accumulation, dust
• Variability in precipitation, temperature, aridity, and atmospheric and oceanic circulation
Thompson in Guliya, China, 1992
Objective: “the acquisition of a global array of ice cores that provide high-resolution climatic and environmental histories that will contribute to our understanding of the complex interactions within Earth’s climate system”
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 greenhouse-gas-forced warming, upper-tropospheric humidity and water-vapor 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
• Enriched isotopic ratios occur during strong El Niño events
Dust
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
1000 year records of oxygen isotopes
Incre
asi
ng
Ele
vati
on
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 factoro Ice masses are sensitive to
temperature changeo 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 • persistent warming = ice loss
Ice cover• 86% disappeared since 1912• 27% of that present in 2000 is now gone
Impact On Water Resources
• Changes in water supplyo Hydroelectricityo Irrigationo Public water supply
• Floodingo Cropso 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 storageBlack – 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 Rhine River in Europe• 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
• 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 ImpactsHimalaya-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
• Capability of models• Inclusion of aerosols
and clouds
• Models predict warming
• Alterations of the hydrological cycle
• Earlier runoff• Insufficient reservoir
storage• Reduction in dry-
season water
What Happens Now?• More Research…• Better water management• Better models and predictions
Questions?