(Table 1) Normalized difference vegetation index in control and warming plots, Abisco Research Station

Extreme winter warming events in the sub-Arctic have caused considerable vegetation damage due to rapid changes in temperature and loss of snow cover. The frequency of extreme weather is expected to increase due to climate change thereby increasing the potential for recurring vegetation damage in Arctic regions. Here we present data on vegetation recovery from one such natural event and multiple experimental simulations in the sub-Arctic using remote sensing, handheld passive proximal sensors and ground surveys. Normalized difference vegetation index (NDVI) recovered fast (2 years), from the 26% decline following one natural extreme winter warming event. Recovery was associated with declines in dead Empetrum nigrum (dominant dwarf shrub) from ground surveys. However, E. nigrum healthy leaf NDVI was also reduced (16%) following this winter warming event in experimental plots (both control and treatments), suggesting that non-obvious plant damage (i.e., physiological stress) had occurred in addition to the dead E. nigrum shoots that was considered responsible for the regional 26% NDVI decline. Plot and leaf level NDVI provided useful additional information that could not be obtained from vegetation surveys and regional remote sensing (MODIS) alone. The major damage of an extreme winter warming event appears to be relatively transitory. However, potential knock-on effects on higher trophic levels (e.g., rodents, reindeer, and bear) could be unpredictable and large. Repeated warming events year after year, which can be expected under winter climate warming, could result in damage that may take much longer to recover.

Pollen record with radiocarbon datings from Faddeyevskiy Island, Laptev Sea

Pollen, plant macrofossil, loss-on-ignition and radiocarbon analyses of a 1.4-m section in thermokarst topography from Faddeyevskiy Island (75°20'N, 143°50'E, 30 m elevation) provides new information on Late Pleistocene interstadial environmental history of this high Arctic region. Conventional radiocarbon dates (25,700 ± 1000, 32,780 ± 500, 35,200 ± 650 yr BP) and two AMS dates (29,950 ± 660 and 42,990 ± 1280 yr BP) indicate that the deposits accumulated during the Kargian (Boutellier) interval. Numerous mammoth (Mammuthus primigenius) remains that have been collected in vicinity of the site in this study were radio-carbon dated to 36,700-18,500 yr BP. Rare bison (Bison priscus) bones were dated to 32,200 ± 600 and 33,100 ± 320 yr BP. Poaceae, Cyperaceae, and Artemisia pollen dominate the spectra with some Ranunculaceae, Caryophyllaceae, Rosaceae, and Asteraceae. The pollen spectra reflect steppe-like (tundra-steppe) vegetation, which was dominant on the exposed shelf of the Arctic Ocean. Numerous Carex macrofossils suggest that the summer climate was at least 2°C warmer than today. The productivity of the local vegetation during the Kargian interstadial was high enough to feed the population of grazing mammals.