Atmospheric energy transport in spring of years with low September sea-ice extent
(English)Manuscript (preprint) (Other academic)
A significant change in Arctic climate is the declining trend of September sea ice. However, large year-to-year variations are superimposed on this trend. Understanding this variability is important for understanding processes contributing to the long-term decline and for seasonal sea-ice predictions, which become increasingly important for a range of activities in an emerging ice-free Arctic summer. Previous studies suggested that the atmosphere plays a key role: transport of heat and moisture into the Arctic during spring enhances the incoming surface longwave radiation, thereby controling the initiation of the annual ice melt and setting the stage for the September ice minimum. Here we explore the atmospheric dynamics promoting advection of heat and moisture into the Arctic. We find that years with a low September sea-ice concentration (SIC) are characterized by periods of increased net surface longwave radiation (LWN) in spring, triggering an early melt onset. A set of atmospheric circulation patterns related to these episodes is identified that support transport of heat and moisture into the Arctic. The most dominant circulation patterns promote transport either from northern Russia and the Kara Sea or from the North Pacific; the latter resembles the so-called Arctic dipole anomaly. However, episodes of enhanced LWN also occur in years with high September SICs and are associated with similar atmospheric circulation patterns. Differences between years with low and high September SICs are not due to different spring processes resulting from different circulation patterns. Instead it is the duration and strength of these patterns that makes the difference. Years with low September SICs feature episodes that are consistently stronger and more persistent than years with high SICs.
Sea ice, Arctic, climate variability, atmospheric dynamics
Earth and Related Environmental Sciences
Research subject Atmospheric Sciences and Oceanography
IdentifiersURN: urn:nbn:se:su:diva-119826OAI: oai:DiVA.org:su-119826DiVA: diva2:848597