met 112 global climate change- lecture 12 glaciers, ice sheets, and the cryosphere dr. craig...

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MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

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Page 1: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

MET 112 Global Climate Change- Lecture 12

Glaciers, Ice Sheets, and the Cryosphere

Dr. Craig ClementsSan Jose State University

Page 2: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Definitions

Glacier- is a body of moving ice that has been formed on land by compaction and recrystallization of snow.

Two requirements must be met before a mass of ice can be called a glacier. (1) ice must be moving, either internally or as a sliding block. (2) the mass must be due to the accumulation and metamorphism of snow.

In any region a specific elevation exists called the snowline or firn line, above which some snow remains on the ground perennially and permits the formation of a glacier.

In polar climates, snowlines are usually near or at sea level and gradually increase in elevation in climatic zones with a higher annual temperatures.

Page 3: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Mass Balance: an accounting or budgeting of the gains and losses of snow that occur on a glacier during a specific time interval.

Definitions

Accumulation- the water equivalent of ice and snow added to a glacier during a period (annual, called budget year).

Ablation- processes that remove snow or ice including melting evaporation, wind erosion, sublimation or breaking off of large blocks into standing water, called calving.

Page 4: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Accumulation Zone (+)

Ablation Zone (-)

Equilibrium line

Glacier Mass Balance

ice

Page 5: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Definitions

Glaciers can be placed in three broad categories:

Cirque glaciers, valley glaciers, and ice sheets.

Ice sheet- a dome-shaped mass of glacier ice that covers surrounding terrain and is greater than 50,000 square kilometers (12 million acres) (e.g., the Greenland and Antarctic ice sheets).

Valley glacier- a mountain glacier whose flow is confined by valley walls.

A cirque glacier is formed in a cirque, bowl-shaped depressions on the side of mountains. Snow and ice accumulation in corries often occurs as the result of avalanches from higher surrounding slopes.

Page 6: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Cirque Glacier: Teton Glacier

Photographer unknown

Page 7: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University
Page 8: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Glacier

Ablation zone

Horn: a peak that is shaped by multiple cirques

Accumulation zone

22-km long, Grosser Aletshglescher, Switzerland

Page 9: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

An ice shelf is a thick, floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface.

Ice shelves are found in Antarctica, Greenland and Canada only.

Definitions

Ice shelves of Antarctica

Page 10: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Russel Glacier, Greenland ice sheet, June 2008

Page 11: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Ice Sheet: Greenland

Page 12: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Melt ponds on the surface of Greenland’s ice sheet.

Page 13: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Moulin: a narrow, tubular chute, hole or crevasse through which water enters a glacier from the surface.

Page 14: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Sea ice is formed from ocean water that freezes. Because the oceans consist of saltwater, this occurs at about -1.8 °C (28.8 °F)

Land-fast ice, or simply fast ice, is sea ice that has frozen along coasts ("fastened" to them) or to the sea floor over shallow parts of the continental shelf, and extends out from land into sea. Unlike drift ice, it does not move with currents and wind.

Sea ice may be contrasted with icebergs, which are chunks of ice shelves or glaciers that calve into the ocean. Icebergs are compacted snow and hence fresh water.

Definitions

Drift ice is ice that floats on the surface of the water in cold regions, as opposed to fast ice, which is attached ("fastened") to a shore. Usually drift ice is carried along by winds and sea currents, hence its name, "drift ice".

Page 15: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Aerial view of the pack ice at the east coast of Greenland , drifting southward in the East Greenland current. July 1996.

Page 16: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Sea ice climatologies: Arctic and Antarctic sea ice concentration climatology from 1979-2000, at the approximate seasonal maximum and minimum levels based on passive microwave satellite data.

Image provided by National Snow and Ice Data Center, University of Colorado, Boulder.

Page 17: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University
Page 18: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University
Page 19: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Glacial Landforms

Cirque: a small basin or bowl at the head of a glacial valley

Arete: a sharp ridge separating two glacial valleys

Moraine: a ridge of debris (broken rocks) found at glacier edges

Page 20: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Glacier Flow and erosion (plucking and abrasion)

Landform called: Roche Montanée

Page 21: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Lembert Dome, Tuolumne Meadows, Yosemite National Park, Sierra Nevada, California

Roche Montanée

Page 22: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Melting of Yosemite’s Glaciers

Photographer unknown

Page 23: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Mt. Lyell Glacier, Yosemite National Park

Photographer unknown

Page 24: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

What will happen when the snow and glaciers melt in California or around the world?

Who will it affect?

Page 25: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Water Resources?

Page 26: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

What effect will this have on the oceans?

Melting glaciers can affect the ocean currents.

How and what will this affect?

Page 27: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Oceans and Climate

Oceans act on the climate:

1. Behave strongly as a coupled system

2. Evaporation from the oceans provides the main source of atmospheric water vapor—latent heat of condensation in clouds– provides the largest single heat source for the atmosphere.

3. The atmosphere, in turn, acts through wind stress on the ocean surface as the main driver ocean circulation.

Page 28: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Oceans Oceans transport heat around the globe

Large heat capacity = large quantity of heat is needed to raise the

temperature of the oceans only slightly

Entire heat capacity of the atmosphere = 3 m deep in ocean (surface layer of ocean)

Internal circulations of the oceans redistribute heat throughout climate system

Even small changes in the regional heat transport by oceans could have large implications for climate change.

Page 29: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Oceans Heat Capacity

Total heat transported by the north Atlantic Ocean is over 1000 Terawatts

1 Terawatt = 1 million million watts (1012 W)

A typical power station provides 1000 million watts (109 W)

Total amount of commercial energy produced produced globally = 12 Terawatts.

Page 30: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Thermohaline Circulation

In polar regions, seawater at the surface of the ocean is intensively cooled by the wind. Wind moving over the water also produces a great deal of evaporation, leading to a decrease in temperature, called evaporative cooling.

Evaporation removes only molecules of pure water, resulting in an increase in the salinity of the seawater left behind, and thus an increase in the density of the water mass.

To sink deep, ocean water needs to be dense, cold and salty (North Atlantic, Antarctica)

Page 31: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

The Great Conveyor Belt

Page 32: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University
Page 33: MET 112 Global Climate Change- Lecture 12 Glaciers, Ice Sheets, and the Cryosphere Dr. Craig Clements San Jose State University

Thermohaline Circulation (THC)

Melting of ice leads to the ocean surface to become less salty (lower salinity) and therefore, less dense. It will not sink so easily—

THC weakens and less heat will flow northward from tropics.

GCMs show this occurring.

THC shutting off completely after 2 or 3 centuries.

Severe Cooling