Projected mixed layer depth change in the North Pacific Ocean and its impacts on primary production

Abstract

This study examines changes in the mixed layer depth (MLD) in the North Pacific Ocean (NP) in response to global warming and their impacts on primary production by comparing outputs from eleven models of the coupled model intercomparison projects phase 3 (CMIP3). We find consistent MLD changes in future in the NP from most of the eleven CMIP3 models: a shoaling in the KE region and a deepening north of the Kuroshio front. The shoaling is attributable to the weakening in the windstress and the associated decrease in the ocean cooling in the KE, whereas the deepening is mainly driven by the northward shift in the KE. In the 21st century, the entrainment production, estimated by MLD changes, in the KE will decrease by 10.7–40.3% and spring blooms will occur 0–13 d earlier in response to the changes in MLD in the KE region. Despite the consistent changes, the magnitude of changes in primary production and the timing of the spring blooms are quite different depending on models and latitudes.n projects phase 3 (CMIP3).