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1
STUDI
Land Surface Change & Arctic Land Warming
Department of Geography
Jianmin WangThe Ohio State University
[email protected] 04/06/2015
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Two papers
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Background:Arctic summer warming
The Arctic-- a test bed to evaluate the consequences of
regional system dynamics. - a trend of arctic summer warming. - a large impact on the rates of water-
dependent processes.
Goals: - estimate recent and
potential future changes in atmosphere heating in arctic Alaska.
- figure out the causes. Data:- surface temperature records- satellite-based estimates of
cloud cover and energy exchange
- ground-based measurements of albedo and energy exchange
- field observations of changes in snow cover and vegetation
Fig. 1
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The causes?changes in atmospheric circulation:the Pacific North American Teleconnection, the Pacific Decadal Oscillation, El Nino Southern Oscillation
Loss of the extent of summer sea ice
Increase of summer cloud cover
Fig. 2
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The causes?Increase of summer cloud cover
Fig. 3
decrease in downwelling SW > increase in downwelling LW
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The causes?changes in atmospheric circulation:the Pacific North American Teleconnection, the Pacific Decadal Oscillation, El Nino Southern Oscillation
Loss of the extent of summer sea ice
Increase of summer cloud cover
Lengthening of the snowfree season
Fig. 2
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The causes?
Lengthening of the snowfree season
Snowmelt advance of 2.5 days decade-1
3.3 Wm-2 more energy absorbed or transferred=
A doubling of atmospheric CO2
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The causes?changes in atmospheric circulation:the Pacific North American Teleconnection, the Pacific Decadal Oscillation, El Nino Southern Oscillation
Loss of the extent of summer sea ice
Increase of summer cloud cover
Lengthening of the snowfree season
Expansion of shrubs and forests
Fig. 2
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The causes?
Since 1950, the cover of tall shrubswithin Alaska’s North Slope tundra has increased 1.2% decade-1.
11,600 km2 (2.3% of the treeless area) has been converted from tundra to forest in the past 50 years.
Expansion of shrubs and forests
(Sturm et al. 2001) (Van Bogaert et al. 2011)
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The causes? Table. 1
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Conclusions
• The longer snow-free season has contributed more strongly than vegetation changes to present summer land warming in the Alaska
• Improved understanding of the controls over rates of vegetation expansion would reduce the likelihood of unexpected surprises regarding the magnitude of high-latitude amplification of summer warming.
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Two papers
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Background:Arctic Sea Ice Loss
From NSIDC
Rapid sea ice loss events (RILEs)
9 Rapid Sea Ice Events (RILEs) are indentified in 21st century from the Community Climate System Model (CCSM3) 21st century A1B simulations
Goals: 1. The potential consequences
for adjacent land climate. 2. The impact on permafrost of
the timing of RILEs.
Methods: Community Land Model (CLM)
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Arctic Land Temperature Trends During Rapid Sea Ice Loss Events
Fig. 1
Composites are formed by averaging nine RILEs. Increased warmingrate during RILEs
The signal of enhanced warming can extend 1500 km inland
the warming trend during RILEs is 3.5 times greater than outside these periods
0.46 decade-1℃
1.60 decade-1℃
Sep Sea ice extent OND arctic land air temperature
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Arctic Land Temperature Trends During Rapid Sea Ice Loss Events
Warming over land is a response to sea ice loss
Inputs: 1. Sea ice conditions- 1980–1999 and 2080–2099 sea-ice conditions from CCSM3 A1B.2. SST – the same observed data.
Two 60-yr simulations with the CAM3 coupled to CLM3
Fig. 2
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Impact of Accelerated Warming on Permafrost
Fig. 3
Main parameter:1. Period 50 years2. Timing of warming: yrs 6–15 EARLY yrs 21–30 MID yrs 36–45 LATE None LINEAR3. initial permafrost states: -0.3 , -1.5 , -5.8 ℃ ℃ ℃
Permafrost: a thick subsurface layer of soil that remains frozen throughout the year, occurring chiefly in polar regions.
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Impact of Accelerated Warming on Permafrost
-0.3 -1.5 -5.8 ℃ ℃ ℃
DPT:Depth to permafrost table SHC: Soil heat content
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Conclusions
• Rapid sea ice loss forces a strong acceleration of Arctic land warming in CCSM3 (3.5-fold increase)
• Arctic land warming can trigger rapid degradation of currently warm permafrost.
rapid sea ice loss
Arctic land warming
Degradation of permafrost
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Future work
• The rate of shrub and forest expansion? • The impact of Arctic land warming on the sea
ice loss?
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References• https://biodilloversity.wordpress.com/2011/11/15/polar-bears-and-climate-change/• http://en.wikipedia.org/wiki/Arctic_sea_ice_decline• http://www.madrimasd.org/blogs/universo/2008/08/23/99331 • Lawrence, D. M., Slater, A. G., Tomas, R. A., Holland, M. M., & Deser, C. (2008). Accelerated
Arctic land warming and permafrost degradation during rapid sea ice loss. Geophysical Research Letters, 35(11).
• Chapin, F. S., Sturm, M., Serreze, M. C., McFadden, J. P., Key, J. R., Lloyd, A. H., ... & Welker, J. M. (2005). Role of land-surface changes in Arctic summer warming. science, 310(5748), 657-660.
• Sturm, M., Racine, C., & Tape, K. (2001). Climate change: Increasing shrub abundance in the Arctic. Nature, 411(6837), 546-547.
• Van Bogaert, R., Haneca, K., Hoogesteger, J., Jonasson, C., De Dapper, M., & Callaghan, T. V. (2011). A century of tree line changes in sub-Arctic Sweden shows local and regional variability and only a minor influence of 20th century climate warming. Journal of Biogeography, 38(5), 907-921.
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Thank you
Any questions?