Transcript PowerPoint 演示文稿 - Ohio State University

STUDI
Land Surface Change &
Arctic Land Warming
Department of Geography
Jianmin Wang
The Ohio State University
[email protected]
04/06/2015
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Two papers
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Background:
Arctic summer warming
The Arctic-
Goals:
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a test bed to evaluate the consequences of
regional system dynamics.
a trend of arctic summer warming.
a large impact on the rates of waterdependent processes.
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estimate recent and
potential future changes in
atmosphere heating in arctic
Alaska.
figure out the causes.
Data:
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Fig. 1
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
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The causes?
changes in atmospheric circulation:
the Pacific North American Teleconnection,
the Pacific Decadal Oscillation,
El Nino Southern Oscillation
Fig. 2
Loss of the extent of summer sea ice
Increase of summer cloud cover
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The causes?
Increase of summer cloud cover
decrease in downwelling SW > increase in downwelling LW
Fig. 3
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The causes?
changes in atmospheric circulation:
the Pacific North American Teleconnection,
the Pacific Decadal Oscillation,
El Nino Southern Oscillation
Fig. 2
Loss of the extent of summer sea ice
Increase of summer cloud cover
Lengthening of the snowfree season
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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
Fig. 2
Loss of the extent of summer sea ice
Increase of summer cloud cover
Lengthening of the snowfree season
Expansion of shrubs and forests
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The causes?
Expansion of shrubs and forests
(Sturm et al. 2001)
Since 1950, the cover of tall shrubs
within Alaska’s North Slope tundra has
increased 1.2% decade-1.
(Van Bogaert et al. 2011)
11,600 km2 (2.3% of the treeless area) has
been converted from tundra to forest in the
past 50 years.
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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 highlatitude amplification of summer warming.
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Two papers
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Background:
Arctic Sea Ice Loss
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)
Rapid sea ice loss
events (RILEs)
From NSIDC
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Arctic Land Temperature Trends
During Rapid Sea Ice Loss Events
Sep Sea ice extent
OND arctic land
air temperature
Composites are formed
by averaging nine RILEs.
Increased warming
rate during RILEs
the warming trend
during RILEs is 3.5
times greater than
outside these periods
1.60 ℃decade-1
The signal of enhanced
warming can extend
1500 km inland
0.46 ℃decade-1
Fig. 1
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Arctic Land Temperature Trends
During Rapid Sea Ice Loss Events
Warming over land is a response to sea ice loss
Two 60-yr simulations with
the CAM3 coupled to CLM3
Inputs:
1. Sea ice conditions1980–1999 and 2080–2099 sea-ice
conditions from CCSM3 A1B.
2. SST –
the same observed data.
Fig. 2
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Impact of Accelerated Warming
on Permafrost
Permafrost: a thick subsurface layer of soil that remains frozen
throughout the year, occurring chiefly in polar regions.
Main parameter:
1. Period
50 years
2. Timing of warming：
yrs 6–15
EARLY
yrs 21–30
MID
yrs 36–45
LATE
None
LINEAR
3. initial permafrost states：
-0.3 ℃, -1.5 ℃, -5.8 ℃
Fig. 3
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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
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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), 657660.
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?
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