Land surface phenology (LSP) and vegetation growth of the circumpolar north are changing in response to more
pronounced warming in the region. We here provide phenology index (PI) based vegetation dynamics
product, comprising start (SOS), end (EOS), length of growing season (LOS), and growing season integrated annual
normalized difference vegetation index (NDVI), specifically designed for the entire circumpolar north
(N45°N) using SPOT VGT data starting from 1999. PI combines the merits of NDVI and normalized difference infrared
index (NDII) by taking the difference of squared greenness (from NDVI) and wetness (from NDII) to remove
the soil and snow cover dynamics from key vegetation LSP cycles. Validation based on North
American and European deciduous broadleaf, evergreen needleleaf and mixed forests, and wetland flux tower
sites shows good agreements between the LSP dates from the circumpolar vegetation dynamics and ground phenology
estimates from CO2 flux measurements. The validation also proves that the circumpolar vegetation dynamics
product is an improvement over the operational global MODIS Combined Land Cover Dynamics
(MCD12Q2) product for the circumpolar region. The results are further compared with the interannual variability
of sea ice extent and leading teleconnection patterns in the region. The circumpolar averaged results show that,
the growing season integrated annual NDVI is significantly increasing (0.68% year-1 , p = 0.006) and well correlated with the growing season sea ice extent trend (p = 0.007). The circumpolar vegetation dynamics is more
related to Polar/Eurasia pattern (i.e., indicator of circumpolar vortex) than to Scandinavian Pattern (SCA) and
North Atlantic Oscillation (NAO). In view of the considerable scientific and policy importance of the circumpolar
region, particularly the arctic ecosystems, the presented circumpolar vegetation dynamics product will greatly
contribute to study changes in plant growth, phenology, photosynthetic capacity, and associated feedbacks
under climate change