glaciers and climate mass balance ela milankovic cycle albedo feedbacks quelcaya ice cap, peru
Post on 20-Dec-2015
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GLACIERS AND CLIMATE
• Mass balance
• ELA
• Milankovic cycle
• Albedo feedbacks
Quelcaya ice cap, Peru
Glacier Mass Balance
• area where ice accumulates
area where ice melts
Equilibrium line altitude (ELA) accumulation = ablationbalance = 0
Mass balance
• NEGATIVE: glacier gets smaller
• POSITIVE: glacier gets larger
• ZERO MASS BALANCE:– no change in glacier size (mass,volume)– GLACIER STILL MOVING FORWARD!!!
ELA and climate
• Positive Mass Balance -- ELA lower– Glacier gets larger
• Negative Mass Balance -- ELA higher– Glacier gets smaller
How does climate change affect glaciers?
• Climate change:– changes in temperature– changes in amount of moisture
Higher temperatures can cause glaciers to melt but the relationship is not straightforward,
Antarctica: higher temperature-->more evaporation from ocean ->air holds more water vapor ->more snowfall --> glaciers will grow!!!!
Ice ages• Ice ages return every 100,000 years
• Pleistocene = most recent ice age, that ended ~10,000 yrs ago
• Presently we are in an interglacial period
Glacial ages
• Little Ice Age: – 17th century - late 19th century
– consistently cool temperatures
– significant glacier advances.
ASTER Image courtesy of: NASA EROS
Data Center, Sept. 9, 2001
Indian HimalayasIndian Himalayas::
Glacier ablation at Glacier ablation at Gangotri, source ofGangotri, source ofthe holy Gangesthe holy Ganges
• glacier terminus retreated by glacier terminus retreated by 3km3km
Climate changes: a few facts
• strong warming over the last 50-200 yrs
• increasing CO2 levels
• Alpine glaciers have been experiencing rapid retreat
Ice-albedo (positive) feedback
Global warming
Glacial melt
Decrease in albedo
More energy absorbed
Decrease in surfaceof ice
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Glacier response to temperature changes
• winter temperature:– less snow– polar areas get little precip. (cold air)– if summer ablation same -- glacier retreats
• summer temperature:– more cloud cover– less summer ablation– if winter accumulation same -- glacier grows
Glacier response to changes in precipitation
• winter precipitation (snowfall)– if no change in temperature:– some snow survives over summer– glacier advances
Glacier response -summary
• Most alpine glaciers and ice caps expected to retreat under global warming scenario
• NOTE: Antarctica expected to grow due to possible increase in precipitation
Glaciers as records of climate
• Ice cores: – Detailed records of
temperature, precipitation, volcanic eruptions
– Go back hundred of thousands years
coming up on field
trip and Monday VIDEO