Roles of Sea Surface Temperature Warming and Loss of Arctic Sea Ice in the Enhanced Summer Wetting Trend Over Northeastern Siberia During Recent Decades

Abstract

AbstractThe water cycle over middle‐ to high‐latitude regions has experienced rapid changes in recent decades. The sea surface temperature (SST) and Arctic sea ice influence the water cycle over these regions, but the relative roles of SST warming and the loss of Arctic sea ice remain unclear. We identify an enhanced change in the summer (June–August) water cycle over northeastern Siberia (55–70°N, 100–170°E) during the last three decades. The driving force of this enhanced wetting trend is investigated using both observations and model simulations. An increasing trend of low‐level southerly winds and a decrease in sea‐level pressure are observed over northeastern Siberia during summer, leading to stronger lower tropospheric moisture convergence and ascending motion, which favor an increase in precipitation. The wetting trend and the associated atmospheric features are successfully reproduced by an atmospheric model driven by the observed Arctic sea ice concentrations and SSTs, whereas the model driven solely by the Arctic sea ice concentrations simulates a negligible increase in precipitation. This is primarily due to the absence of the stronger southerly winds that transport moisture from the Pacific Ocean. The modeling evidence suggests that SST changes in recent decades have a stronger influence on the intensified precipitation than does sea ice. An atmospheric bridge mechanism links the strengthened southerly winds to an upper‐level Rossby wave train originating from the North Atlantic. Another atmospheric simulation forced only by Atlantic SST warming recreates the observed enhanced wetting trend in northeastern Siberia and supports the hypothesized atmospheric bridge mechanism.