Large-scale climate patterns occurring over multi-annual to multi-decadal time periods strongly influence drought frequency and vegetation productivity. The El Nino Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO) are multi-annual to multi-decadal climate patterns defined by ocean temperature anomalies that can strongly modulate climate variability. Using field-, satellite-, and model-derived data, we evaluate impacts of these climate patterns on drought and vegetation productivity across the Western US. Better understanding of the impacts of large-scale climate patterns on drought and vegetation productivity could help 1) better constrain carbon-climate models, 2) provide critical long-term forecasts to land managers and policy makers, and 3) enhance decision-making and adaptive management for a suite of ecosystem services while reducing the associated environmental impact.
We show that water availability and vegetation productivity are significantly reduced across the Western US during the negative phase of the PDO, especially when coupled with a negative phase of the ENSO (and visa-versa). These findings are consistent across climate data, vegetation productivity estimates, and satellite observations. Regions that are most impacted include the Central Great Plains, the Southern Great Plains, Southern Rocky Mountains, and the Southwest. Our findings suggest that the PDO has likely significantly contributed to the on-going drought across the Western US, although better understanding of the interactive effects of anthropogenic warming is needed. Reliable short-term forecasting of PDO:ENSO dynamics could have major implications for agriculture, water resource, and land management planning across the Western US.