Alaskan Tundra Case Study

Question 1

How large is the Alaskan tundra?

Answer 1

8 million square kilometres across northern Canada, Alaska and Siberia.

Question 2

What is the mean temperature in the Alaskan tundra, and how low can temperatures get?

Answer 2

The mean is below -15 degrees celsius, and temperatures can go as low as -40.

Question 3

How many months in a year does the Alaskan tundra have a negative heat balance?

Answer 3

8 or 9 depending on the year.

Question 4

How much annual precipitation does the Alaskan tundra get?

Answer 4

Less than 100mm.

Question 5

Why does the Alaskan tundra have low atmospheric moisture?

Answer 5

The low temperatures cause the absolute humidity to be very low.

Question 6

How long is the growing season in the Alaskan tundra?

Answer 6

3 months.

Question 7

For what two reasons are evaporation rates low in the Alaskan tundra?

Answer 7

• Most solar energy goes towards melting snow.
• Surface and soil water are frozen for most of the year.

Question 8

Why are groundwater stores limited in the Alaskan tundra?

Answer 8

Permafrost prevents infiltration, percolation, recharge and groundwater flow from occuring.

Question 9

How much carbon does permafrost hold globally?

Answer 9

1600 gigatonnes.

Question 10

For what two reasons is carbon flux in the Alaskan tundra concentrated in the summer months?

Answer 10

• The active layer thaws, releasing stored carbon.
• Small plants and mosses grow rapidly.

Question 11

What is the NPP in the Alaskan tundra?

Answer 11

Less than 200 grams per square meter per year.

Question 12

When was oil and gas discovered at Prudhoe bay in Alaska?

Answer 12

1968.

Question 13

What two reasons led the US to start collecting oil and gas from Prudhoe bay?

Answer 13

• Global energy prices were high.
• The US aimed to reduce dependence on oil imports.

Question 14

In what three ways did oil and gas production cause localised permafrost melting in Alaska?

Answer 14

• Heat was released by machinery and infrastructure.
• Vegetation cover was removed for construction.
• Dust deposited along roadsides caused increased sunlight absorption.

Question 15

How much are carbon dioxide and methane losses from the permafrost estimated to be on the Alaskan North Slope.

Answer 15

Carbon dioxide varies from 7 to 40 million tonnes per year, whilst methane varies from 24,000 to 114,000 tonnes per year.

Question 16

How much are carbon dioxide emissions from permafrost in the Alaskan North Slope estimated to have increased since 1975?

Answer 16

73%.

Question 17

In what two ways is water drainage affected by human activity in the Alaskan tundra?

Answer 17

• Strip mining of aggregates for construction creates artificial lakes which expose the permafrost to additional melting.
• Road construction and seismic explosions used to prospect for oil and gas disrupt water drainage.

Question 18

In what five ways are impacts on the water and carbon cycles in the Alaskan tundra reduced?

Answer 18

• Roads and infrastructure can be built on insulating ice or gravel pads to reduce melting the permafrost below.
• Infrastructure can be built on piles to allow cold air to circulate and provide insulation for the permafrost.
• New drilling techniques such as Shell’s ‘snake drill’ allow for oil and gas to be accessed from several kilometres away, reducing the amount of drilling sites and required infrastructure.
• 10% of supercomputers are used to process data for the oil industry, reducing the amount of required exploration wells.
• The Trans-Alaska pipeline has refrigerated supports to stabilise the temperature of the permafrost around it.