Two Lateral Stirring Regimes in the Northeast Pacific

Abstract Lateral stirring is a key process shaping the physical and biogeochemical state of the ocean, yet it remains under‐sampled and poorly understood, particularly at submesoscales (1–80 km). Along Line P, a long‐term transect in the Northeast Pacific, lateral stirring was characterized using 15 glider lines with an effective horizontal resolution of 3 km, collected between September 2019 and December 2024. Temperature anomalies along an isopycnal reveal distinct offshore and nearshore lateral stirring regimes and significant inter‐annual variability, particularly in the offshore regime. Nearshore, tracer gradient spectra follow a power‐law of , and thus have a weighting toward more high wavenumber variance than many previous studies, but less than predicted by Surface Quasi‐Geostrophy or Interior‐Quasi Geostrophy. Offshore, tracer gradient spectra vary with eddy activity: slopes follow in the submesoscale during active periods and , consistent with Kolmogorov scaling, during quieter phases. Large‐scale temporal changes in the temperature field are also seen, marked by shifts in water mass circulation and temperature range, though the driving mechanisms remain uncertain. To contextualize these observations, a regional ocean model is analyzed. Simulated temperature variability was consistent with glider observations in the mesoscale but underestimated at the submesoscale and did not have the distinct regime change between the nearshore and offshore waters. These discrepancies suggest that the model parameterizations of lateral stirring should be investigated and possibly improved.