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!!!

Where is the ELA?

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

Causes of ice ages? Milankovic cycles

long term variations in Earth’s orbit around the Sun:

Glacial ages

• Little Ice Age: – 17th century - late 19th century

– consistently cool temperatures

– significant glacier advances.

Kilimanjaro, East Africa (5895 m)

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

What’s the culprit?

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

Glacier retreat reveals mummies: next week!!

500-year old mummy found in Peruvian Andes

Otzi- 5,000 year old mummy found in Tyrolean Alps.