Permafrost slopes

Question 1

Describe an effect of + feedback systems on a geomorphic system

Answer 1

eg. thermokarsts like active layer detachment slides and retrogressive thaw slumps
–> thermal removal of excess ice, initiated by a thermal disturbance

These are positive feedbacks: disturbance –> exposes ice-rich permafrost –> thaw –> mass movement (which is another disturbance) –> exposes ice- rich permafrost……

Effect:
permafrost that is otherwise resilient, and has probably been present for a very long time, is very susceptible to thermal disturbances because of the positive feedback effect that comes with it

Question 2

Where might you expect to see more thermokarst activity:
a) an area that burned somewhat recently
b) an area with little thermal disturbance

Answer 2

a) because a burn= thermal disturbance= leads to thermokarsts

Question 3

How might thermokarsts impact the biogeochemistry of a little headwater stream? What about in a larger system like the north sask river?

Answer 3

In a little stream, thaw slumps impacts the biogeochemistry by adding metals like mercury to the water

In a larger system though, there does not seem to be much of an effect because the mercury gets diluted

Question 4

T/F

it’s impossible to directly date relic permafrost ice using stratigraphic principles because it doesn’t last long enough

Answer 4

false
In rare cases, it’s possible!
permafrost is sensitive to disturbance, but it you leave it alone it can persist for a very long time

Question 5

ice wedge cast=

Answer 5

sedimentary evidence for the existence of past permafrost that that thawed

Question 6

In central yukon, ice wedge casts mark the onset of ____ at the same time as the onset of ____, which is a neat linkage!

Answer 6

permafrost
glaciation

Question 7

permafrost warming facilitates ___ and ___genesis as previously frozen organic C thaws

Answer 7

respiration
methanogenesis

Question 8

There is not a huge difference in CO2 and methane in interglacial vs glacial periods –> big mystery. What are 2 possible explanations?

Answer 8

1. maybe there is less carbon stored in permafrost than we thought
2. maybe there used to be a very effective carbon sink that removed it from the atmosphere quickly

Question 9

1500ka-500ka, interglacial thaw has been inferred from caves. How?

Answer 9

Period of lots of speleothem formation

Question 10

Speleothem=

Answer 10

precipitated cave deposits
- they form growth layers over time like trees

Question 11

explain the speleothem-permafrost proxy for cold vs warm enviros

Answer 11

cold enviro: when permafrost is present above a cave, waters cannot seek through materials above the cave, so speleothems will not form

warm enviro: when permafrost thaws above a cave, speleothem formation is possible because waters can now migrate through the materials above the cave

Question 12

Ice-rich permafrost is thaw-susceptible –> excess ice when thawed leads to ground ____

Answer 12

instability

Question 13

There are 2 general ways to resolve the issue of building in ice-rich areas:

Answer 13

1. avoid ice-rich areas and build somewhere else (that would mean no civilization in a lot of the arctic)
2. keep heat out of the ground, or transfer the heat out (then can build on top of that)

Question 14

List 4 methods of reducing disturbance of ice-rich areas when building

Answer 14

1. thermosiphons
2. raise buildings (stilts)
3. thick gravel pads
4. avoid disturbance during construction, like using very wide tires to distribute weight & construction in winter when ground is frozen

Question 15

How do thermosiphons work?

Answer 15

they pump heat out of the ground and into the atmosphere because of the dramatic difference between air and ground temps
*draw a thermosiphon

Question 16

Building houses on stilts allows:
1
2

Answer 16

1. cold winter air to cool the ground
2. separates the ground from warm buildings

Question 17

Why is it beneficial to build on a thick gravel pad (instead of a sand pad or directly on the ground) in an ice-rich area

Answer 17

gravel= no excess ice! convection is possible: move heat from ground into air

sand/ silt= has high unfrozen water content, which facilitates ice lens growth –> excess ice. No convection + excess ice= not effective

Question 18

Give 2 ways that you could avoid disturbing the landscape during construction in the arctic

Answer 18

1. construct in the winter when the ground is frozen
2. use very wide tires to spread the weight of equipment