GLACIERS AND CLIMATE CHANGE

Objectives Distinguish between several different kinds of glaciers and ice formations. Describe how ice in a glacier changes form, accumulates, ablates, and moves. Explain how geologists learn about past climatic conditions. Examine evidence for anthropogenic climate change.

Glaciers and Ice Sheets Cryosphere –The perennially frozen part of the hydrosphere Components of the cryosphere –Glaciers A semi-permanent or perennially frozen body of ice, Consists largely of re-crystallized snow Moves under the pull of gravity –Temperate glaciers –Polar glacier –Ice sheets –Ice shelves, ice bergs

Glaciers and Ice Sheets Components of the cryosphere –Glaciers types Temperate glaciers –Ice is near melting point throughout the interior –Dominated by meltwater –Form in low and middle latitudes Polar glacier –Little melting occurs (cold temperatures) –Form in high latitude or altitude regions

Glaciers and Ice Sheets Components of the cryosphere –Glaciers types

Glaciers and Ice Sheets

How glaciers form –Snow that survives for more than a year gradually becomes denser until it is no longer penetrable by air and becomes glacier ice. –Further changes happen as the glacial ice is buried deeper (increasing pressure)

Glaciers and Ice Sheets How glaciers grow and shrink –A glacier is measured using the amount of snow (winter) and the amount of melting (summer). –The difference between accumulation and ablation is a measure of the glacier’s mass balance

Glaciers and Ice Sheets

How glaciers move –Glaciers move because of the pull of gravity –Ice in the central part of the glacier moves faster then the sides, and the uppermost moves faster than the lower layers

Glaciers and Ice Sheets

Internal flow –Ice moves in a glacier through a combination of ductile deformation at depth and brittle deformation at the surface –Crevasse A deep gaping fissure in the upper surface of a glacier

Glaciers and Ice Sheets Basal sliding –Ice at the bottom of a glacier slides across its bed (the rock or sediment which the glacier rests on) –The glacial landscape Glacier acts like a file, sled, and plow

Glaciers and Ice Sheets

Glacial erosion –Glacial striations –Glacial grooves –Cirques

Glaciers and Ice Sheets Glacial deposition –Till A mixture of crushed rock, sand, pebbles, cobbles, and boulders deposited by a glacier –Moraine A ridge or pile of debris that has been, or is being, transported by a glacier

Glaciers and Ice Sheets

Periglacial landforms –Tundra –Permafrost Ground that is perennially below the freezing point of water –Ice wedges –Patterned ground Produced by freeze- thaw cycle

Global Climate Change Global warming –A profound change in the worlds climate Climate change in the past –Glaciation A period when global temperature drops by several degrees, Expansion of continental ice sheets

Global Climate Change

Study of past climates –Paleoclimatology Causes of climate change –Geographic changes resulting from tectonism –Astronomical factors –Green house effect

Global Climate Change

Present day changes –What we know Anthropogenic –Produced by human activities

Global Climate Change Present day changes –What we think General circulation models allow us to estimate impact of burning fossil fuels or make projections

Global Climate Change

Critical Thinking How can you tell the age of the “fossil air” inside an ice core? Can you think of any other natural environments that have hexagonal patterns similar to patterned ground associated with periglacial landforms? Does you city, state, province, or country have goals for the reduction of carbon dioxide emissions to limit its contribution to global warming?