Emergence of the North Pacific heat storage pattern delayed by decadal wind-driven redistribution

Abstract

Storage of anthropogenic heat in the oceans is spatially inhomogeneous, impacting regional climates and human societies. Climate models project enhanced heat storage in the mid-latitude North Pacific (MNP) and much weaker storage in the tropical Pacific. However, the observed heat storage during the past half-century shows a more complex pattern, with limited warming in the central MNP and enhanced warming in the northwest tropical Pacific. Based on observational datasets, ocean model experiments, and climate models, we show that emergence of human-induced heat storage is likely postponed in the North Pacific by natural variability to the late-21st century. Specifically, phase shifts of the Pacific Decadal Oscillation (PDO) have vitally contributed to trends in the North Pacific winds during recent decades. Changes in surface winds drove meridional heat redistribution via Rossby wave dynamics, leading to regional warming and cooling structures and a more complex historical heat storage than models project. Despite this, enhanced anthropogenic warming has already been emerging in marginal seas along the North Pacific basin rim, for which we shall prepare for the pressing consequences such as increasing marine heatwaves.