Decadal prediction of Colorado River streamflow anomalies using ocean-atmosphere teleconnections

The Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO) time series are used to forecast a decade ahead streamflow anomalies in the upper Colorado River at Lee's Ferry. In the instrumental record, we obtain unusually high decadal forecast skill that is statistically significant at the 95% confidence level, suggesting strong ocean-atmosphere-land teleconnection. In order to test whether such teleconnection existed in the past, we compare the retrospective forecast skill to the skills obtained using the available ocean-atmosphere teleconnection and streamflow reconstructions derived from tree rings. We find much lower skill in the reconstructed record. Using frequency analysis, we show that the streamflow and sea surface temperature oscillations in the instrumental records all have dominant low frequency periodicities (>35years) that explain much of the total variance. However, such dominant periodicities do not appear in the power spectra of the reconstructed records of AMO, PDO and streamflow. Given that these dominant low periodicities are likely responsible for the high prediction skill in the instrumental record, it remains uncertain whether reliable decadal streamflow predictions in the upper Colorado River basin will be possible in the years ahead.