Florent Domine Georg Lackner Maria Belke-Brea Daniel NadeauPowerPoint Presentation Author: fdomine...
Transcript of Florent Domine Georg Lackner Maria Belke-Brea Daniel NadeauPowerPoint Presentation Author: fdomine...
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Does shrubs expansion in the high-Arctic lead to permafrost warming?
Takuvik, Université Laval and CNRS, Québec, CanadaUniversité laval, CEN, Québec, Canada
Florent Domine Georg Lackner
Maria Belke-Brea Denis SarrazinDaniel Nadeau
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Salix richardsonii on Bylot Island, 73°N 80°W
Shrubs are expanding on Arctic tundra
Bylot Island
Eastern Canadian Arctic
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Summary of conventional wisdom
In winter shrubs trap snow and limits heat loss.
In summer shrubs shade ground and limit heat gain
Permafrost T ↑
Permafrost T ↓
Impact of shrubs on permafrost thermal regime ?
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Sites in Qarlikturvik valley, Bylot Island
We compare 2 nearby sites without any manipulation
Herb tundra Shrub tundra
Monitor for 3 years Air T and RHWind speedRadiation
Snow depthSnow TSnow thermal conductivity
Soil TSoil water fractionSoil thermal conductivity
9 km
Salix richardsonii, 35 cm high
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Ground temperature at 15 cm depth: comparison
Year round Twillow – Ttundra= +2.3°C July-August: Twillow – Ttundra= +1.6°C
Air T: Twillow – Ttundra= +0.6°C
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Simulations to quantify terms of energy budget
Use Surfex V8 LSM with Crocus snow scheme, Arctic version
2- Investigate effects of : Differences in air TDifferences in surface roughnessDifferences in surface albedo
Differences in wind speed*Differences in snow compaction
a- Non-snow effects
b- Snow effects
1- Test model on tundra data
*lower at willlows⇒less snow compaction
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1- Test model on tundra data
RMSE = 2.00°C Bias (Surfex-Tundra) = +0.46°C
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Essentially, increased surface roughness leads to ground cooling
2- Investigate effects of: (a) non-snow effects: Temperature, roughness, albedo
T change= -1.32°C
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Essentially, decreased snow compaction leads to ground warming
2- Investigate effects of: (b) snow effects: Wind speed, snow compaction*
*reduced in shrubsT change= +1.43°C
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SURFEX simulates winter warming but not summer warming
2- ALL EFFECTS
T change, measure= +2.30°CT change, sim= +0.55°C
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Conclusions
At Bylot Island, ground at -15 cm under willows is 2.3°C warmer than under herb tundraWarming is observed in both summer and winter
Increased surface roughness due to shrubs produce cooling
Simulations with SURFEX indicate that:
Decreased snow compaction in shrubs produce warming
Remaining issues:
Summer warming under shrubs not simulated. Work on soil properties
Simulated zero curtain too short