W3-1 Cryosphere

• The cryosphere is the part of Earth's surface that remains perennially frozen.
• Sea ice, glaciers, and frozen ground are components of the cryosphere.
• Glaciers cover 10% of Earth's land surface.
• Frozen ground constitutes 20% of Earth's land.
• Almost 1/4 of the land in the Northern Hemisphere is covered by snow and frozen ground during the winter.
• The accumulation of snowfall greater than seasonal melt is a primary factor in glacier and ice cap formation.
• Highly reflective surfaces bounce sunlight back into space, which reduces surface air temperature.

Glaciers

• A glacier's advance or retreat depends on the balance between accumulation and ablation.
• Accumulation refers to added snow and ice.
• Ablation refers to lost snow and ice.
• The upper zone of a glacier is the accumulation area.
• The ablation area is below the accumulation area.
• The equilibrium line separates the accumulation and ablation areas.
• The terminus is the front of the glacier.
• The terminus responds to changes in mass balance.
• Glacial ice moves via internal flow and basal sliding.
• Internal flow happens when ice at critical thickness deforms and moves downslope due to gravity.
• Glacial ice deforms within individual ice crystals under stress.
• The surface is brittle, forming crevasses under tension to depths of <50 m.
• Glaciers form when gravity pulls a thick mass of snow and ice, causing it to move.
• Cirque glacier: The smallest glacier type.
• Valley glacier: A glacier extends down from a cirque.
• Ice cap: These cover mountain highlands or low-lying land at high latitudes and flow outward radially.
• Fjord glacier: A glacier located in a fjord.
• Piedmont glacier: A glacier that spreads out from a valley glacier.
• Earth's high mountain ranges contain glacier systems that extend tens of kilometers.
• Continent-sized ice sheets overwhelm land within their margins.
• Greenland and Antarctica hold 95% of Earth's glaciers.
• Glaciers in Greenland and Antarctica can reach 3000 m thick.
• Ice shelves, hundreds of meters thick, are in Antarctica's embayments.
• Glaciers originate from accumulated snow that is compacted until it has a density that prevents air from penetrating.
• Glacier ice is classified as a rock.
• Ice grains recrystallize at depth within glaciers, growing to 1 cm near the base.
• Glaciers can form wherever snow and ice have the ability to accumulate.
• High latitudes and high mountains at low latitudes are common.
• Ice temperatures vary among different glaciers.
• Warm (temperate) glaciers exist at the pressure melting point and can coexist with water.
• Cold (polar) glaciers are below the pressure melting point.

Glaciation

• Glacial erosion sculpts landforms such as cirques, aretes, U-shaped valleys, fjords and drumlins.
• Glaciers carry debris that is eventually deposited.
• Till is unsorted glacial debris that is deposited by glacial ice.
• Outwash is debris that is reworked, transported, and deposited by meltwater.
• Moraines are glacially bulldozed ridges of sediment.
• Eskers are curved ridges of sand and gravel.
• Kettles are closed basins.
• Land beyond the limit of glaciers is called periglacial and is mainly found in circumpolar regions.
• Periglacial regions are characterized by permafrost.
• The active layer of permafrost thaws in summer, becomes unstable, and refreezes in winter.
• When the active layer melts, the ground collapses.
• Patterned ground refers to ice-wedge polygons.
• Pingoes are frost-heaved hills.
• Gelifluction is mass wasting.
• Evidence of local and global environmental conditions is trapped in the snow that accumulates each year on a glacier.
• The oldest ice in most cirque and valley glaciers is several hundred to several thousand years old.
• Large ice sheets contain ice that dates far back into the ice ages.
• This can be examined through ice cores.

Sea Ice

• Sea ice forms by the solidification of fresh water at the ocean surface.
• Sea ice formation is not due to precipitation.
• Salt crystals are excluded during sea ice formation.
• Oceans become saltier in glacial periods and less salty when sea ice melts.
• Two thirds of Earth's persistent ice cover floats as a thin veneer on polar oceans.
• Sea ice comprises 1/1000 of Earth's total ice volume.
• When the ocean surface cools to the freezing point of sea water, additional cooling forms ice.
• Frazil refers to the first small platelets or needles that form.
• After frazil a soupy mixture forms at the surface.
• Without waves, crystals freeze together as a 1-10 cm thick ice blanket.
• With waves, crystals form 3 cm diameter pancake-like ice masses.
• Sea ice is distributed differently between the two hemispheres due to geography.
• Antarctica is covered by a vast, thick ice sheet, with sea ice forming a ring around it.
• The North Pole is within the deep Arctic Ocean, which is mostly covered by sea ice.
• Sea ice is in constant motion and constantly changing.
• Interactions among ice, water, and atmosphere influence ocean structure, salinity, and circulation.
• Sea ice is sensitive to temperature change.
• Salt exclusion during sea ice formation leads to the production of dense, cold saline water on the continental shelves.
• This production of dense, cold saline water produces deep-bottom ocean water.
• Floating ice isolates the ocean surface from the atmosphere, cutting off heat exchange.
• Ice has high albedo, reflecting incoming solar radiation rather than absorbing it.
• This results in a steep temperature gradient between the equator and poles, which drives atmospheric circulation.
• If the climate became colder and ice expanded, the result is a positive feedback due to raised albedo.
• If the climate warms and ice shrinks, a similar but opposite effect of positive warming occurs as overall albedo decreases.
• Melting sea ice doesn't contribute much to ocean levels, but melting land ice contributes a lot to water volume.
• Melting sea ice and land ice would drastically affect ocean salinity.