Arctic Report Card 2020: Tundra Greenness Tundra Greenness

The Arctic tundra biome occupies Earth's northernmost landmasses and forms a "wreath" of treeless vegetation that encircles the Arctic Ocean. Arctic tundra ecosystems are strongly influenced by warming air temperatures (Bjorkman et al. 2020), and thus have become a focal point of global environmental change. One of the most conspicuous impacts of a warming Arctic climate and declining sea ice has been an increase in the productivity, or "greenness" of tundra vegetation (Lawrence et al. 2008; Bhatt et al. 2010; see essays Surface Air Temperature and Sea Ice). Tundra greenness has been monitored by Earth-observing satellites since the early 1980s and was identified as a key vital sign of the Arctic in the first Arctic Report Card published in 2006 (Richter-Menge et al. 2006). Satellites continue to monitor tundra greenness to the present day, although at the time of writing the record is only available through the 2019 growing season due to data processing requirements. Arctic greening has continued but interannual variability in greenness has increased over the past decade and trends have not been uniform from place to place or from year to year (Bhatt et al. 2013; National Academies of Sciences, Engineering and Medicine 2019; Myers-Smith et al. 2020). This interannual variability results from the dynamic linkages that connect the vegetation, atmosphere, sea ice, permafrost, seasonal snow, soils, disturbance processes, and wildlife of the Arctic (Duncan et al. 2020).