Lecture 2

Question 1

What is an ice sheet?

Answer 1

A mass of glacier ice that covers a land area greater than 50 000 km2

Question 2

What is the largest Ice mass on Earth today?

Answer 2

The Antarctic Ice Sheet.

Question 3

How much of the Antarcitic continent does the Antarctic Ice Sheet cover?

Answer 3

98%

Question 4

What is the total ice volume of the Antarctic Ice Sheet?

Answer 4

58 m sea level equivalent
West A. 5 m
East A. 53 m

Question 5

How much of the fresh water on Earth does the Antarctic Ice Sheet contain?

Answer 5

61%

Question 6

Why is the Antarctic Ice Sheet mass more or less constant?

Answer 6

Because the mass loss from the West has been compensated by the mass gain of the East

Question 7

Acculmulation on glaciers?

Answer 7

Precipitation, rain, hail, freezing rain, snow, wind-blown snow, avalanching, hoar frost

Question 8

Surface ablation/output of glaciers?

Answer 8

Outputs such as wind-blown snow, avalanching, sublimation, surface-meltwater-runoff, subaerial melt, sublimation, calving, subaqueous frontal melt (meltwater, icebergs)

Question 9

What is the surface mass balance of a glacier?

Answer 9

Accumulation minus Surface ablation

Question 10

What is the mean ice thickness of the Antarctic Ice Sheet?

Answer 10

2 km

Question 11

What is the maximum thickness of the grounded ice on the Antarctic Ice Sheet?

Answer 11

5 km

Question 12

What is the grounding line?

Answer 12

It is the boundary between grounded and floating ice sectors

Question 13

How much mass has the Antarctic Ice Sheet lost?

Answer 13

Less than 1%
Major players: ocean (mass loss) and precipitation (mass gain)

Question 14

What causes the mass loss of the Antarctic Ice Sheet?

Answer 14

49 percent due to ice calving
50 percent due to melting under ice shelves
<0,5 percent due to subglacial melting under grounded ice sectors

Question 15

What is ice flow

Answer 15

The flow of ice sheets through deformation and sliding, which removes the ice from grounded sectors and into the ocean

Question 16

Where does the ice on an ice sheet flow the slowest?

Answer 16

On the thickest parts

Question 17

Where does the ice on an ice sheet flow the fastest?

Answer 17

On the ice shelves and the edges where rapidly flowing ice streams and outlet glaciers develop

Question 18

Where does ice sliding occur?

Answer 18

where the ice
1 melts at the base,
2 sits on top of hydrological systems or
3 is underlain by saturated, deformable sediment

Question 19

What causes ice flow on the Antarctic ice sheet?

Answer 19

Pressure melting point: Basal ice of ice sheets melts at negative temperatures due to the pressure of the overlying layers.

Geothermal heat warms the base of ice sheets and makes the ice base deform and melt.

Question 20

Geothermal heat

Answer 20

the heat rising from the deep Earth interior

Question 21

Topographically constrained flow

Answer 21

When basal sliding occurs, ice erodes subglacial bedrock through plucking and abrasion which forces rapid ice flow, and the locations of ice streams = facilitates further erosion

Question 22

Sub-shelf melting

Answer 22

Warm ocean currents penetrate under ice shelves and melt from below.

Question 23

How does ice calving occur?

Answer 23

Weakness and formation of cracks
combined with surface melt promote crack penetration, resulting in a break-off of a part of an ice shelf

Question 24

Second largest ice mass

Answer 24

The Greenland Ice Sheet

Question 25

How much of the freshwater does the Greenland Ice Sheet contain?

Answer 25

7-8%: 7.4 m s.l.e.

Question 26

Why is the Greenland ice sheet losing mass at an increasing rate?

Answer 26

An increase in air temperature drives surface melt

Question 27

Maximum thickness of Greenland Ice Sheet?

Answer 27

3.2 km

Question 28

Mean thickness of Greenland Ice Sheet?

Answer 28

2150 m

Question 29

What is the ice divide?

Answer 29

The highest point on the ice sheet surface.

Question 30

Why is the ice divide the best target for ice coring?

Answer 30

Because there is no horizontal movement in this area it gives the highest resolution of paleoclimate reconstructions

Question 31

What is sublimation on a glacier?

Answer 31

Sublimation is a process by which ice at the surface of a glacier can turn directly into water vapor and be carried away with the wind when the air temperature is below freezing and the air is very dry.