Transcript Assessing the Resilience and Vulnerability of Permafrost

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.
Climate-driven, Ecosystem-modified Permafrost
Ecologically mediated ice aggradation increases vulnerability to degradation
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
Thermokarst lake development at MAATs of -12 C
Ecosystem-Driven Permafrost
Ground ice
aggradation in
relation to
Sphagnum
growth
Soil drainage
after
permafrost
degradation
Ecosystem-Protected Permafrost
Fish Creek
MAAT -11.5 C
Ataxitic ice in
syngenetic
permafrost
formed in
cold climates
Naknek Lake
MAAT +1.5 C
Layered ice
in epigenetic
permafrost
formed in
“warm”
climates
A New Permafrost Map for Alaska
Map based on
terrain units
and climate
From Jorgenson et al. 2008. Permafrost Characteristics of Alaska. NICOP Proceedings
Relating Ground Ice to Terrain Units
Glaciomarine
Kanevskiy et al.
submitted
Loess
Kanevskiy et al.
submitted
Colluvium
From Jorgenson et al. 2008. Permafrost Characteristics of Alaska. NICOP Proceedings
Ice Volume in
Relation to
Terrain Units
Terrain Unit
Alluvial-marine
Deposit
Thaw Basin, IceRich Center
Lacustrine
Organic Silt
Thaw Basin, IceRich Margin
Thaw Basin, IcePoor Margin
Thaw
Strain
Eolian Sand
Mean
Visible
Ice
0
20
40
60
Excess Segregated Ice Volume (%)
Eolian Sand
Buried
Glacier Ice
Barter
Island
Abundant in Wisconsin and
Little Ice Age Moraines
Toolik Lake, NE14
Basal Ice
Matanuska 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.
Generalized ice profiles for common types of permafrost
Resilience and
vulnerability of
permafrost depends
on type and amount
of ground ice
Conceptual model by
M. Kanevskiy
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.
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
Negative Feedback from
Vegetation-Soils
Positive
Feedback
from Water
•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
Thermal modeling by V. Romanovskiy in:
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.
Landform–Soil–Vegetation-Permafrost Relationships
Alpine Rocky Dry
Dwarf Scrub
Upland
Moist
Tall
Scrub
Upland
Wet
Needleleaf
Forest
Bedrock
Upland
Moist
Broadleaf
Forest
Upland Moist
Needleleaf
Forest
Lowland
Wet
Loess
Forest Lowland
Wet Low
Scrub
Retransported Silt
Riverine
Barrens
Lowland
Bog
Meadow
Lowland
Tussock
Bog
Lake
Thick Peat
Stratified Silt and Sand
Lowland
Lowland Broadleaf
Forest
Fen
Meadow
Gravel
Riverbed
PF
Loamy
Rocky
Upland
Lowland
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 Flats
38
Innoko Toposequence
Ground Surface
37
Water Surface
Permafrost Table
36
Unfrozen Depth
35
Flat terrain allows water to
impound, creating positive
feedback to ground
temperatures
Elevation (m)
34
33
32
31
30
29
28
27
26
0
100
200
300
400
Distance (m)
500
600
700
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.