Tracing the origins of Arctic vapor and clouds

Abstract:

Arctic surface temperatures are strongly linked to variations in Arctic water vapor content and clouds via downwelling longwave radiation. However, the contributions of different geographic sources to this Arctic moisture are not well known, limiting our understanding of the relative influences of local sea ice feedbacks and remote teleconnections on Arctic climate. Here we use a version of the Community Earth System Model (CESM1.3) with online water tracers to directly quantify the contribution of different source regions to Arctic water vapor, cloud liquid content, and cloud ice content. The water tracers indicate that spring - fall season water vapor and cloud water and ice content are dominated by mid and high latitude land sources (> 50% of total vapor and cloud content during summer) as opposed to local Arctic or remote oceanic sources. The amount of land-based Arctic moisture also varies considerably from year to year, with normalized interannual variability comparable to that from oceanic regions. Given the importance of land-based moisture, we examine the relative influences of mid to high latitude terrestrial ET anomalies (e.g. from drought) and terrestrial circulation anomalies on variability in Arctic vapor, cloud cover, surface energy fluxes, and temperature. The results point to a key role for mid latitude evapotranspiration and synoptic variability in shaping Arctic temperature and Arctic amplification.