Pacific Decadal Oscillation Climate Variability and Temporal Pattern of Winter Flows in Northwestern North America

Abstract

There is growing concern about the effects of large-scale oceanic atmospheric climate variability, such as the Pacific decadal oscillation (PDO), on regional hydrology and water resources. In this paper, the effects of PDO on temporal patterns of winter (January-March) flow in northwestern North America (NWNA), which is believed to be a PDO-sensitive region, is studied for the period 1943-2007 using daily streamflow data from a much larger set of 179 stations, compared to previous studies in which only smaller subsets of these stations were analyzed. Time series of winter flows were divided into two nonoverlapping blocks corresponding to change points detected in time series of December-March mean monthly PDO indices. Both parametric and nonparametric measures of correlation and average percentage differences and average standardized differences from the period-of-record mean were explored. Like some of the previous studies, it is found that, on average, winter flows tend to be higher (lower) during the warm (cold) phase of the PDO and that establishes the physical link between large-scale climate variability and basin response. It is shown that the serial structure of time series of PDO indices conforms to that of a stochastic process with long-term persistence (LTP). Based on this finding and the climate-streamflow physical link, it is plausible to investigate temporal variations in winter flows with the LTP hypothesis, in addition to assuming merely independence (IND) or short-term persistence (STP). The results of the analysis demonstrate that the LTP mechanism, in combination with the STP, is able to explain more than half of the significant trends noted, with the IND assumption suggesting that the significance of trends reported in previous studies in NWNA may have been overstated. This result has important implications for future planning of regional water resources.

Concurrent Hydroclimatic Hazards from Catchment to Global Scales

“…For example, Hamlet and Lettenmaier (2007) North America and Europe, and found that the statistically significant trends detected were almost the same as the ones expected by chance, with changes in major floods dominated instead by climate patterns such as the PDO and AMO. In north-western North America the PDO is found to have an effect on winter river flows, with flows being higher during the warm PDO phase (and vice versa) (Khaliq and Gachon, 2010). The PDO is also known to influence flows in Alaska (Hodgkins, 2009;Neal et al, 2002), where its signal does not change significantly on annual river flows, but it does on monthly and seasonal time scales, with warm PDO winter river flows being higher than the cold PDO ones (Neal et al, 2002).…”

“…America, Europe and central Asia (Lee et al, 2018). Moreover, when PDO is positive, the central and south-western USA tends to experience flooding during all the seasons, except during winter (Mallakpour and Villarini, 2016;Tootle et al, 2005), when increased streamflow are observed in north-western North America (Hodgkins, 2009;Khaliq and Gachon, 2010;Neal et al, 2002).…”

“…As mentioned above, some studies that looked at the interactions between ENSO and river flows, peak flows and flooding, also included signatures from the PDO (Hamlet and Lettenmaier, 2007;Lee et al, 2018;Mallakpour and Villarini, 2016;Ouyang et al, 2014;Tootle et al, 2005). However, other works considered the PDO on its own or along with other indices (Cai and Rensch, 2012;Hodgkins, 2009;Hodgkins et al, 2017;Khaliq and Gachon, 2010;Neal et al, 2002), with North America being the favoured study area. For example, Hamlet and Lettenmaier (2007) North America and Europe, and found that the statistically significant trends detected were almost the same as the ones expected by chance, with changes in major floods dominated instead by climate patterns such as the PDO and AMO.…”

Non-stationary hydrologic frequency analysis using B-spline quantile regression

“…In fact, several recent studies in North America have modelled the non-stationarity of precipitation and streamflow using climate indices. The most used climate indices in this context are El Nino Southern Oscillation (ENSO) (e.g., Regonda et al, 2005;Cannon, 2010;Nasri et al, 2013), Pacific Decadal Oscillation (PDO) (e.g., Brabets and Walvoord, 2009;Khaliq and Gachon, 2010;Cannon, 2010;Nasri et al, 2013), Atlantic Multi-decadal Oscillation (AMO) (Teegavarapu et al, 1969) and North Atlantic Oscillation (NAO) (Hurrell and Van Loon, 1997). To our knowledge, no studies have previously studied streamflow extremes using nonparametric quantile regression incorporating B-Spline functions.…”

Forms and drivers of annual streamflow variability in the headwaters of Canadian Prairies during the 20th century

“…In western North America, large interannual and interdecadal variability is a common climate feature (see Bonsal & Shabbar, ) and is associated with extreme shifts in low‐ and high‐flow events of many river systems in this region (e.g., Burn, ; Déry, Hernández‐Henríquez, Owens, Parkes, & Petticrew, ; Doney & Sailley, ; Gobena, Weber, & Fleming, ; Mauget, ; Sauchyn, Vanstone, & Perez‐Valdivia, ), including the SSR (e.g., Axelson, Sauchyn, & Barichivich, ; Marchildon et al, ). Such climate variability is mainly attributed to various large‐scale climate circulation patterns (see Bonsal & Shabbar, ; Shabbar & Bonsal, , ; Shabbar, Bonsal, & Khandekar, ; Shabbar & Khandekar, ) with the dominant streamflow mode in the SSR being the Pacific Decadal Oscillation (PDO; see, e.g., Bonsal et al, ; Fleming & Whitfield, ; Khaliq & Gachon, ; St. Jacques et al, ; Whitfield, Moore, Fleming, & Zawadzki, ). The PDO is a large‐scale interdecadal climate variability index, with negative and positive phases, which is linked to North Pacific sea surface temperature anomalies (Bonsal, Shabbar, & Higuchi, ; Mantua & Hare, ; Minobe, ).…”