Research papersSalinity and streamflow variability in the Mid-Atlantic region of the United States and its relationship with large-scale atmospheric circulation patterns

- A new ENA pattern was identified.
- The ENA pattern is closely linked to historical and salinity variability.
- The ENA pattern explains more streamflow variability than the NAO and PNA patterns.
- The ENA pattern is associated with tropical wave activity and ENSO.

The historical variability of streamflow and salinity was examined for three large estuaries of the Mid-Atlantic region of the United States (US) in order to determine how they are influenced by large-scale circulation patterns. New wavelet methods identified 2- and 4-year periodicities from the streamflow time series. A composite analysis of meteorological data revealed that the anomalously high daily streamflow events coincided with Rossby waves emanating from the tropical Pacific and an eastern mean sea-level pressure (MSLP) dipole pattern in which negative MSLP anomalies were situated over the southeast US and positive MSLP anomalies were situated over the northwestern North Atlantic Ocean. Based on this pattern, a new Eastern North American (ENA) index was constructed that could explain more daily streamflow variance than existing climate indices. A wavelet coherence analysis identified ENA index relationships with streamflow and salinity at periods of 2-4 years, suggesting that the ENA index may offer predictability beyond the weather forecasting timescale. The ENA index was also found to be phase-locked to the Gulf Stream index at a period of 74 months. Because the MSLP dipole pattern is linked to the upstream Rossby wave train, salinity variability at that timescale may have resulted from MSLP dipole-related changes in precipitation.