Assessing the Resilience and Vulnerability of Permafrost Landscapes to Environmental Change

Torre Jorgenson,

Yuri Shur,

Mikhail Kanevskiy,

Matt Dillon, and

Eva Stephani

Approach to Assessing Permafrost Stability

• Define permafrost in relation to climate and ecosystems

• Determine ground ice characteristics in relationships to terrain units

• Assess magnitude of positive and negative feedbacks related to vegetation and water

• Compare permafrost stability in relation to terrain

Redefined Permafrost in Terms of Climate-Ecosystem Relationships

Shur, Y. L. and Jorgenson, M. T. 2007. Patterns of permafrost formation and degradation in relation to climate and ecosystems. Permafrost and Periglacial Processes 18: 7-19.

Ecologically mediated ice aggradation increases vulnerability to degradation

Climate-driven, Ecosystem-modified Permafrost

Vegetation-soil processes in the thinning active layer allow accumulation of 2-3 m of excess ice during floodplain evolution. Buildup of excess ice in upper permafrost form conditions for development of thaw lakes, even under cold climates

Floodplain evolution

Thermokarst lake development at MAATs of -12 C

Ecosystem-Driven Permafrost

Ground ice aggradation in relation to Sphagnum growth

Soil drainage after permafrost degradation

Naknek LakeMAAT +1.5 C

Fish CreekMAAT -11.5 C

Ecosystem-Protected Permafrost

Ataxitic ice in syngenetic permafrost formed in cold climates

Layered ice in epigenetic permafrost formed in “warm” climates

A New Permafrost Map for Alaska

From Jorgenson et al. 2008. Permafrost Characteristics of Alaska. NICOP Proceedings

Map based on terrain units and climate

From Jorgenson et al. 2008. Permafrost Characteristics of Alaska. NICOP Proceedings

Relating Ground Ice to Terrain UnitsGlaciomarineKanevskiy et al. submitted

Loess Kanevskiy et al. submitted

Colluvium

Ice Volume in Relation to

Terrain Units

0 20 40 60

A lluvial-m arineDepos it

Thaw B as in, Ic e-Ric h Center

Thaw B as in, Ic e-Ric h M argin

Thaw B as in, Ic e-P oor M argin

E olian S and

Ter

rain

Uni

t

E x c es s S egregated Ic e V olum e (% )

ThawStrain

MeanV is ib leIc e

Eolian Sand

Lacustrine Organic Silt

Buried Glacier Ice

Basal IceMatanuska Glacier

Basal Ice Barter Island

Kanevskiy, M., T. Jorgenson, Y. Shur, and M. Dillon (2008), Buried glacial basal ice along the Beaufort Sea Coast, Alaska, Eos Trans. 89, 53, C11D-0531.

Abundant in Wisconsin and Little Ice Age Moraines

Toolik Lake, NE14

Barter Island

Generalized ice profiles for common types of permafrost

Jorgenson, M. T., Romanovsky, V., Harden, J., Shur, Y., O’Donnell, J., Schuur, E. A. G. and Kanevskiy, M. 2010. Resilience and Vulnerability of Permafrost to Climate Change. Canadian J. Forest Research.

Resilience and vulnerability of permafrost depends on type and amount of ground ice

Conceptual model by M. Kanevskiy

Feedbacks Strongly Affect Permafrost Stability

Permafrost can degrade at MAATs of -20 C due to surface water

Permafrost can persist at MAATs of +2 C due to protection by vegetation and organic soil

Jorgenson, M. T., Romanovsky, V., Harden, J., Shur, Y., O’Donnell, J., Schuur, E. A. G. and Kanevskiy, M. 2010. Resilience and Vulnerability of Permafrost to Climate Change. Canadian J. Forest Research.

Effects of Vegetation-Soil and Water on Ground Temperatures

•Vegetation and soil reduce permafrost temperatures by 7 deg. C.•Water can raise ground temperatures by 12 deg. C.•Positive and negative feedback effects are larger than predicted climate warming

Jorgenson, M. T., Romanovsky, V., Harden, J., Shur, Y., O’Donnell, J., Schuur, E. A. G. and Kanevskiy, M. 2010. Resilience and Vulnerability of Permafrost to Climate Change. Canadian J. Forest Research.

Thermal modeling by V. Romanovskiy in:

Negative Feedback from Vegetation-Soils

Positive Feedback from Water

Gravel Riverbed

Upland Wet

Needleleaf Forest

Alpine Rocky Dry Dwarf Scrub

Upland Moist

Broadleaf Forest

Upland Moist Needleleaf

ForestLowland

Wet Forest Lowland

Wet Low Scrub

Upland Moist Tall

Scrub

Loess

Perm

afro

st

Thick Peat

Retransported Silt

Bedrock

Stratified Silt and Sand

Riverine Barrens

Lowland Bog

Meadow Lowland Fen

Meadow

Lowland Tussock

Bog

PF

Lowland Broadleaf

Forest

Lake

Landform–Soil–Vegetation-Permafrost Relationships

Upland LowlandL

oam

y

R

ock

y

Resilience of Silty Uplands

•Slopes shed water, reduce positive feedback

High ice content and latent heat slow thawing

Vegetation recovery after fire, allow negative feedbacks to stabilize permafrost. Ice-poor silt freezes back.

High Vulnerability

of Silty Lowlands

Innoko Toposequence

26

27

28

29

30

31

32

33

34

35

36

37

38

0 100 200 300 400 500 600 700

Distance (m)

Ele

vation (

m)

Ground Surface

Water Surface

Permafrost Table

Unfrozen Depth

Flat terrain allows water to impound, creating positive feedback to ground temperatures

Innoko Flats

Gravelly Lowlands with Thaw Lake Sinks

Yukon Flats

Lake drainage after losing permafrost curtain?

CONCLUSIONS• Large climate gradient across Alaska creates

range of permafrost temperatures and ground ice conditions

• Ground ice develops in response to temperature, soil texture, and ecology

• Permafrost can be highly resilient due to vegetation-soil development, yet highly vulnerable due to water

• Permafrost degradation sensitive to many interacting factors but can be broadly grouped by topography and soils.