Eastern U.S. summer streamflow during extreme phases of the North Atlantic oscillation



[1] Numerous studies have suggested streamflow discharge in the conterminous U.S. has been increasing, particularly in the east starting in the latter half of the 20th century. Northern Hemisphere (NH) hydroclimatic variability has been connected to shifts in large-scale atmospheric teleconnection patterns. This study ascertained the spatial and temporal influences of the extreme phases of the North Atlantic Oscillation (NAO) on interannual streamflow variability across the eastern U.S. during the summer season. We also assessed the presence of any delayed streamflow responses to NAO configurations during previous spring (March-April-May) and winter (December-January-February) seasons across the study area. Methods of inquiry included the use of various statistical and compositing analyses applied to records of mean daily summer streamflow obtained from the Hydro-Climatic Data Network between 1950 and 2010. Results of this study suggest that summer streamflow across eastern U.S. may be related to and thus potentially predicted from the NAO up to three seasons in advance, information of significant hydrologic consequences for the area. Depending upon the season and geographic location, the relationships may be both linear and nonlinear in nature and may be masked by the presence of temporal trends in the index. Summer streamflow across the eastern U.S., in general, displays greatest response to the negative phase of the NAO during the previous winter and the concurrent summer seasons. Geographically, the greatest potential for predictability exists across the Northeast where cohesive responses to NAO exist in all three seasons, winter, spring, and summer.