AbstractWe used changing relationships between primary climate variables and the Pacific Decadal Oscillation (PDO) index to quantify novel climate conditions during rapid warming of the Gulf of Alaska in 2014–2019. Using Bayesian regression, we show that the PDO had a weaker relationship with North Pacific sea‐level pressure than in previous decades and was associated with warmer regional temperatures, reduced wind mixing, and weaker alongshore transport. Climate conditions mapping onto the PDO during 2014–2019 appear to be unique in the historical record. The potential for surprising ecological responses to novel climates is highlighted by a switch to unique, negative correlations between the PDO and salmon production, contrasting with positive or neutral correlations during previous decades. Novel climates are emerging globally, and tracking changing associations between primary variables and climate indices may be a useful approach for quantifying both the degree of climate novelty and the potential for surprising ecological responses.