Understanding drivers of recent Arctic tundra vegetation changes.

Greening of the Arctic:
Understanding drivers of recent Arctic
A “planet-to-plant” analysis of vegetation ch
tundra vegetation changes.
US Bhatt1, DA Walker1, MK Raynolds1, P. A. Bieniek, HE Epstein3, JC Comiso5, JE Pinzon5,
CJ Tucker5, IV Polyakov1, Y Liu9, R Gens1 CE Tweedie6, PJ Webber7, M. Steele8, G Jia4
1UAF, 3UVA, 4CAS
China, 5NASA GSFC, 6UTEP, 7Mich State U, 8U Wash, 8U Wisc,
Greening/Sustainable Arctic III, GC54A, 3001 (Moscone West)
Friday 17 December 2010, AGU, San Francisco
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•
Main Findings
D.A. Walker, H.E. Epstein, U.S. Bhatt, M.O. Leib
Arctic vegetation has become
M.K. Raynolds,
G. Jia, G.V.
‘greener’
& is linked
to Frost,
ice A.V. Khom
Moskalenko, P. Orekhov, G. Matyshak, P.J.
This
greening
hasJ. varied
Tweedie,
W.A. Gould,
Mercado,in
C.A. Mung
J. Comiso,
J.E. Pinzon, C.J.the
Tucker,
N.G. Ukra
strength
throughout
Arctic
Drozdov, A.A. Gubarkov, E. Kaarlejarvi, O. K
tundra & causes
complex!
V.E.are
Romanovsky,
Q. Yu
Mean MaxNDVI (82-10) linked to Mean Sea Ice
Circumpolar
Arctic
Vegetation
Map
80% of the
Arctic
tundra (3.2
million
km2) <
100km from
ocean
Remote sensing data & methods
Data: 1982-2010 (29 yrs, weekly)
• Passive Microwave Sea Ice Concentration (25km)
• AVHRR Land Surface Temp. (25-km)
• Gimms NDVI 3g (Max and Integrated) (14-km)
New version that is corrected for Arctic
Russia
Alaska
Canada
• Divided Arctic Ocean
(Treshnikov, 1985) to
examine trends and
variability in 50/100-km
ocean - full tundra land
domains
Trends 1982-2010 indicate:
More Open Water in Summer ==> Higher NDVI
Open water area May-August trend:
Time
TimeIntegrated
IntegratedNDVI
NDVI%%change
change
Summer Warmth Index % change
[Updated from Bhatt et al. 2010]
Contrasting NDVI Seasonality/Trends in Beaufort and W. Kara
Beaufort
W. Kara
1982-2010
Bi-weekly
MaxNDVI
Weekly
Sea ice
Weekly
T surface
Contrasting NDVI Variability/Trends in Beaufort and W. Kara
W. Kara
Beaufort
Maximum
NDVI
Time Integrated
NDVI
Spring 100km
coastal sea ice
Summer
Warmth Index
SWI anomalies in 2009 and 2010
Open Water & SWI Correlations Vary with Basin
W. Kara
Laptev
Beaufort
• W. Kara & Laptev: More open water, nearby land
warmest
• Beaufort: More open water, nearby ocean warm,
land temperatures mixed
Temperature anomaly as a function of the
distance from coast shows maximum
warming near coast during ice retreat
FALL
866
867
868
869
870
Figure 9. (Left) Year (x-axis) versus distance from the coast (y-axis, with zero at the coast and genera
southward increase of distance from the Arctic Ocean) arctic autumnal SAT anomalies. Po
amplification is evident during extended warm periods in the 1930–40s and recent decade. (Rig
Long-term (1900–2008) trend as a function of distance from the coast.
871
872
873
874
875
g locations of meteorological stations. Insert 876
shows the number
877
ce 1800.
878
[Bekrayev et al 2010 & I. Polyakov]
879
880
881
882
SUMMER
of active
mmer months of June–August of 1995. Blue (red) squares indihly mean ice extent (represented by gray plus red areas).
Specified sea ice GCM studies suggest
reduced ice warms adjacent land SAT
• Lawrence et al. 2008, Deser et al. 2010, Bhatt et al. 2008
Fall more than summer!
Aug 1995 - CCM3 T42
[Bhatt et al. 2008]
s latent plus longwave) felt by the atmosphere and (b) surface air
k (light) red or blue indicates statistical significance at the 99%
Jul 2007 - CAM3 T85
[Damman et al. in prep]
What is the plan?
• Synthesize observational analysis
• Develop clearer hypothesis of what is
happening in each region. (e.g. Snow,
clouds, & plant processes related to
delayed response)
• Regional scale modeling
• Test hypothesis for individual domains
Conclusions
1. Ice is linked to the terrestrial changes. More
analysis needed.
2. Arctic trends/anomalies vary spatially!
3. Ice probably key driver in some regions but
not all.
Thank you for your
attention!
Acknowledgments
Typical subzone A zonal vegetation at Isachsen,
Ellef Ringnes Island, Nunuvut, Canada. Yellow
flowers are Papaver polaris. Photo: D.A. Walker.
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This work was supported by NSF and
NASA.
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This project is part of the Greening of
the Arctic project of the International
Polar Year and NEESPI.