Transcript Ice-Atmosphere Interaction: Melting of Mountain Glaciers

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