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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 - PowerPoint PPT Presentation
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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.