摘要：Key observational indicators of climate change in the Arctic, most spanning a 47 year period (1971–2017)
demonstratefundamental changes among nine key elements of the Arctic system.We find that, coherent
with increasing air temperature, there is an intensification of the hydrological cycle, evidentfrom increases
in humidity, precipitation, river discharge, glacier equilibrium line altitude and land ice wastage.
Downward trends continue in sea ice thickness(and extent) and spring snow cover extent and duration,
while near-surface permafrost continues to warm. Several of the climate indicators exhibit a significant
statistical correlation with air temperature or precipitation, reinforcing the notion that increasing air
temperatures and precipitation are drivers of major changes in various components of the Arctic system.
To progress beyond a presentation of the Arctic physical climate changes, we find a correspondence
between air temperature and biophysical indicators such as tundra biomass and identify numerous
biophysical disruptions with cascading effects throughout the trophic levels. These include: increased
delivery of organic matter and nutrients to Arctic near‐coastal zones; condensed flowering and pollination
plant species periods; timing mismatch between plant flowering and pollinators; increased plant
vulnerability to insect disturbance; increased shrub biomass; increased ignition of wildfires; increased
growing season CO2 uptake, with counterbalancing increases in shoulder season and winter CO2
emissions; increased carbon cycling, regulated by local hydrology and permafrost thaw; conversion
between terrestrial and aquatic ecosystems; and shifting animal distribution and demographics. The Arctic biophysical system is now clearly trending awayfrom its 20th Century state and into an unprecedented
state, with implications not only within but beyond the Arctic. The indicator time series of this study are
freely downloadable at AMAP.no.
