The Role of Pacific Climate on Low-Frequency Hydroclimatic Variability and Predictability in Southern Alberta, Canada

Wavelet and rank correlation analysis were used to identify the links between primary Pacific climate variability modes and low-frequency hydroclimatic variability in the South Saskatchewan River basin (SSRB) of southern Alberta. The April-September average streamflow shows strong interdecadal oscillations with dominant scales of 19-22, 41-42, and 62 yr whereas statistically significant wavelet power in the interannual scale was organized on a background scale of approximately 20-25 yr. At interannual scales, strong coherency is observed between streamflow and the Nino-3 index prior to the 1940s, and in the 1950s, 1970s, and 1980s. However, a change in the phase difference from near 0 degrees in the 1950s to near 180 degrees in the 1980s indicates that the relationship between streamflow and the El Nino-Southern Oscillation (ENSO) is not consistent. Streamflow-Pacific-North America pattern (PNA) and streamflow-Pacific decadal oscillation (PDO) relationships at interannual scales also exhibit similar inconsistencies in phase difference. At interdecadal scales, PDO and streamflow exhibited consistently strong coherence with a stable phase difference of 180 degrees for scales >20 yr. From the period of 1913-2001, the median partial correlation between streamflow and PDO vertical bar Nino-3 (read as PDO given Nino-3) was -0.36, whereas it was zero between streamflow and Nino-3 vertical bar PDO, suggesting that PDO is the primary mode of importance in streamflow variability and predictability in the SSRB. Precipitation variability was also dominated by interdecadal oscillations; however, there is less spatial coherence for dominant scales. Correlations between the basin's winter precipitation and climate indices are also weaker than with streamflow.