GLACIERS AND CLIMATE Mass balance ELA Pleistocene glaciation Milankovic cycle Albedo feedbacks Quelcaya ice cap, Peru

Geographical and Climatic conditions high snowfall in winter cool temperatures in summer Moisture important!!! Eg: Siberia and parts of Antarctica: low temperatures meet glacier growth requirements, but lack of adequate precipitation prevents glacier development

Annual Glacier Mass Balance (Net)Accumulation zone = area where ice accumulates (Net) Ablation zone= area where glacial ice melts Equilibrium line where accumulation=ablation balance = 0 (at equilibrium)

Equilibrium Line Altitude

Where is the ELA?

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 do glaciers reflect climate change? changes in temperature changes in amount of moisture Glaciers sensitive to temperature fluctuations climate change can cause glaciers to melt but the relationship is not straightforward, eg. Antarctica:climate change-->warmer-->more evaporation from ocean ->more water vapor -> more snowfall!

Ice ages Ice ages return every 100,000 years approx. 20 ice ages Pleistocene = most recent ice age, that started about 2 million years ago and ended ~10,000 yrs ago 4 major advances of ice, most recent ones: Laurentide: ended 20,000 yrs ago Wisconsin: ended 100,000 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 During the last Ice Age, glaciers covered 32% of the total land area. Little Ice Age: 17th century - late 19th century consistently cool temperatures significant glacier advances.

Earth’s climate record

Glaciers sensitive to climate changes: a few facts strong warming over the last 50-200 yrs increasing CO2 levels Alpine glaciers have been experiencing rapid retreat Ice cap on Mt. Kilimanjaro has been decreasing by 82% in the last 88 years Glaciers in the Alps decreased by 50% in volume

Ice-albedo (positive) feedback Global warming + + Glacial melt More energy absorbed + Decrease in surface of ice + + Decrease in albedo

Climatic responses- scenarios winter temperature: less, not more, 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

Climatic response (cont’d) winter precipitation (snowfall) if no change in temperature some snow survives over summer glacier advances temperature crucial factor-

Glacier response -summary Alpine glaciers and N.Hem. Ice caps expected to retreat under global warming scenario NOTE: Antarctica expected to grow due to possible increase in humidity

Aster image, Patagonia, Chile

Indian Himalayas: Glacier ablation at Gangotri, source of the holy Ganges glacier terminus retreated by 3km ASTER Image courtesy of: NASA EROS Data Center, Sept. 9, 2001

Summary: GLACIERS AND CLIMATE Mass balance ELA Pleistocene glaciation Milankovic cycle Albedo feedbacks Quelcaya ice cap, Peru