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

Abstract

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 Niño-3 index prior to the 1940s, and in the 1950s, 1970s, and 1980s. However, a change in the phase difference from near 0° in the 1950s to near 180° in the 1980s indicates that the relationship between streamflow and the El Niño?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° for scales >20 yr. From the period of 1913?2001, the median partial correlation between streamflow and PDO|Niño-3 (read as PDO given Niño-3) was ?0.36, whereas it was zero between streamflow and Niño-3|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.