Convection of North Pacific deep water during the early Cenozoic

The history of deep water formation and abyssal flow is poorly known but important to establish in order to develop a better understanding of changes in oceanic mass, heat, salt, and nutrient transport. North Atlantic high-latitude regions currently are the dominant deep water producers, but paleogeographic constraints, proxy interpretations, and physical models have suggested other modes for the past, such as those characterized by high-latitude Pacific sources, subtropical sources, or widespread, nonlocalized sources. Here we present new North Pacific Late Cretaceous-Paleogene Nd isotope data from fossil fish debris and detrital silicates, combined with results of coupled climate model simulations to test these hypothesized circulation modes. The data and model simulations support a circulation mode characterized by high-latitude, bipolar Pacific convection. Deep convection in the North Pacific, and likely the South Pacific, was most intense during the relatively "cool" portion of the Late Cretaceous-Paleocene and waned prior to the peak global warmth of the Early Eocene (ca. 52 Ma).