Role of Mixed Layer Depth in the Location and Development of the Northeast Pacific Warm Blobs

Abstract

AbstractWarm blobs are persistent warm anomalies in the Northeast Pacific (NEP) upper ocean. Here, we assess the role of mixed layer depth (MLD) in their location and development based on ocean‐atmosphere reanalysis data. We find that warm blobs occur more frequently over 165°–130°W and 35°–50°N with shallow MLD. They are largely confined to the mixed layer, although substantial portions exist beneath it in summer when the MLD shoals. Based on a mixed‐layer heat budget analysis, we reveal that anomalous MLD and heat flux contribute dominantly to the surface heat flux term over the study area from May to July and from September to March, respectively, and have a large effect on warm blob development. Therefore, the MLD has important implications for the location and seasonal evolution of warm blobs and temperature diagnosis over the NEP.