As Arctic sea ice steadily disappears and temperatures rise across the region, the tundra has generally been greening, with shrubs and small trees growing more robustly. But a new study of growth rings in Arctic shrubs reveals a countervailing trend — the withering of plants in some areas because summer conditions have grown too hot and dry.
Researchers from Poland and the United States examined growth rings in shrubs in various Arctic regions, from Alaska, to Greenland, to the Svalbard archipelago in Norway. Reporting in the Proceedings of the National Academy of Sciences (PNAS), the scientists revealed that while 57 percent of Arctic shrubs grew more rapidly over the past few decades as sea ice retreated and precipitation increased, 37 percent experienced stunted growth as temperatures soared at more than twice the global average.
The study found that the withering of tundra vegetation was most pronounced in drier or rockier soils or on well-drained ridges, where increasing temperatures have led to reduced water availability. The study aligned with findings in the annual Arctic Report Card, released last week by the U.S. National Oceanic and Atmospheric Administration, which said that the browning of sections of the Arctic tundra “has emerged as an increasingly important phenomenon.”
One key aspect of the PNAS study was its examination of growth rings in shrubs, applying the science of dendrochronology — the study of growth rings in trees to reveal past climate trends — to tiny rings found in bushes.