Lecture 1: Glaciers in time/ space

Question 1

What are glaciers? And where can they terminate?

Answer 1

Masses of snow/ice which, if accumulate to sufficient thickness, deform under their own weight and flow. Can terminate on land, in sea or lakes.

Question 2

What is firnification? What does further melting and compaction of its product form?

Answer 2

The compaction of snowflakes to form granular snow, and the melting and refreezing of this creates glacier ice.

Question 3

What determines snow’s survival over summer?

Answer 3

Sun’s angle and climate. Therefore determined by position on the earths surface and so more snow at poles.

Question 4

What does the direction of ice flow show, and what doesnt it?

Answer 4

reflects size and shape of glacier, not shape of ground.

Question 5

Where do ice caps form and how do they differ from ice sheets?

Answer 5

Ice caps form in polar / sub-polar regions in high/flat areas. Ice sheets are ice caps of >50,000km

Question 6

Describe an ice shelf - its formation, accumulation and wastage.

Answer 6

Ice shelf is a floating ice sheet loosely constrained by shape of the coastline. May have formed by ice sheet deforming under own weight. Nourished by snow accumulation their flat surface, and wastage occurs by calving and bottom melting.

Question 7

Ice domes domes are built symmetrically over land and steepen towards their edges - describe the periphery of them.

Answer 7

Radiating pattern of outlet glaciers in depressions. Also a zone of rapidly moving ice bordered by crevasses.

Question 8

What are the main means of ice evacuation from ice sheets/caps?

Answer 8

Sheet flow in ice dome regions and stream flow in outlet glaciers.

Question 9

Describe a cirque.

Answer 9

small, wide, armchair shaped hollow in bedrock that filled with snow and ice. Has a steep side and backwall - hang on side of valleys at lower altitudes than might be expected.

Question 10

What characterizes a valley glacier?

Answer 10

present in mountainous areas, active, fast flowing, may originate from icefield / cirque. 10-30km in size, where size reflects importance in hierarchy of the drainage basin.

Question 11

How are piedmont glaciers formed?

Answer 11

Ice flows unconstrained over coastal plain from mountain belt.

Question 12

Tidewater glaciers are a major outlet, and form the main mass transfer from ice sheets, but how are they formed?

Answer 12

Chunks of ice break off tidewater tongues by calving to form glaciers.

Question 13

Moving down the mountains altitude, put these in order: Valley, Piedmont, Cirque?

Answer 13

Cirque, Valley, Piedmont.

Question 14

When did Larson A and B collapse?

Answer 14

A - 1995

B -2002

Question 15

A glaciers thermal regime affects the destination of surface meltwater. Give an example of temperate glaciers and what characterises them?

Answer 15

Mountain glaciers at P.M.P.

Question 16

Cold glaciers are often small, thin polar glaciers below p.m.p - what does this mean for adhesion, and therefore deformation and erosion?

Answer 16

Adhesion to ice/rock interface greater than at other levels in the ice, therfore deformation occurs immediately above the bed (as oppossed to between rock and ice). Erosion therfore depends on pressure of debris in basal ice (as when basal ice thins to bypass an obstacle on bed, rock fracture and deformation may occur.

Question 17

Describe polythermal glaciers. What are they also known as?

Answer 17

aka subpolar glaciers. Reach p.mp. at depth.

Question 18

Why is understanding the thermal regime of a glacier important?

Answer 18

Response / influence to climate.
Hazards such as jokullhaup outburst floods, ice avalanches and frontal advance.
Mechanical and chemical erosion and contribution to biogeochemical cycles.
Habitats - viability of life?

Question 19

Bacterial populations at the glacier bed may contribute to what?

Answer 19

Rock weathering and carbon cycling.

Question 20

A new paradigm of viable life in glacier ecosystem sustained by what properties of the environment?

Answer 20

biotic processes
oxic at surface, anoxic at bed
Liquid water present locally - Snow/ice insulates whilst sediments supply nutrients.

Question 21

What life might glacier surfaces support and how?

Answer 21

Microbial microcosms in cryoconite holes - debris provide nutrients and organic carbon. Photosynthesis drives bio-accumulation of 10^7-10^8 cells per gram.

Question 22

The sub-glacial environment supports anaerobes and chemo-lithoautotrophes with cell concentrations of 10^6 cells/gram. What of their properties support this?

Answer 22

Dark, liquid water from surface and basal melting, anoxic, sediment supplies nutrients and carbon, bacteria involved in redox reactions.

Question 23

How do oxygen isotope ratios provide evidence for past glaciations?

Answer 23

More global ice = less O^16 in the oxygen.

Question 24

How can deep ocean cores provide evidence of glaciations?

Answer 24

CO2 levels are low during glaciation

Question 25

How can dust in ice cores show past glaciations?

Answer 25

Dust increases during glaciations due to rock flour in the outwash plains.

Question 26

What supports the milankovitch theory of eccentricity+obliquity=precession of the equinoxes cycles?

Answer 26

Similarity between oxygen isotope data and orbital predictions.

Question 27

Milankovitch theory may only be able to explain small differences in temperature and changes to cyclicity of glacials, what might amplify their effect?

Answer 27

Sea level change, increased surface albedo, increased GHGs and ocean circulation.