International Polar Year 2007–2008 - WMO

most strongly along ponds and streams and areas with
abundant moisture and nutrients. Similar changes
have been observed by the BTF researchers in wetland
vegetation of East Greenland, but changes in productive
habitats in West Greenland over the past 42 years
were not so dramatic. Changes in more barren rocky
landscapes are less obvious in Canada, although there
is strong increase in lichen cover that cause increased
NDVI on these surfaces as well. A new satellite-derived
data set (AVHRR GIMMS NDVI data) has permitted IPY-
GOA to make the first analysis of NDVI trends in the
High Arctic (north of 72°). Dry, unproductive sites in
West Greenland and Svalbard re-visited after 70 years
(Prach, 2010; Fig. 2.9-5) were also much smaller than
those in the more productive habitats.
In the Low Arctic, several GOA studies indicate
that change is occurring most rapidly in areas
Fig. 2.9-3. Mean monthly
surface-air-temperature
pattern for the Abisko
region for different periods:
(a) August 1913-2008, (b)
August 2000-2008, (c)
January 1913-2008, (d)
January 2000-2008. For the
August data, growth days
above 5°C (GDD5) are used
because of their importance
for climate-impacts
research.
(From Yang et al., in press)
where disturbance is most frequent. In the central
Yamal Peninsula in West Siberia, Russia greening is
concentrated in riparian areas and upland landslides
associated with degrading massive ground ice, where
low-willow shrublands replace the zonal sedge, dwarfshrub
tundra growing on nutrient-poor sands (Walker
et al., 2009; Walker et al., 2010 in press). Analysis of
annual growth rings in the Varendei tundra of the
Nenets Autonomous Okrug, Russia shows that willow
growth is closely linked to the temperature record and
increasing NDVI, demonstrating a clear relationship
between deciduous shrub growth and Arctic warming
(Forbes et al., 2009).
In sub-Arctic Sweden, site re-visits under the
BTF project over the past three decades showed
dramatic changes in birch tree growth by a factor
of six (Rundqvist et al., in press), recent invasion of
s C I e n C e P r o g r a m 299