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?