온난화 환경에서 북태평양 혼합층깊이 및 일차생산 변화

Abstract

Projected changes in the ocean mixed layer depth (MLD) over the North Pacific under global warming are examined using climate models from the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4). The MLDs consistently decrease up to 50 % by the end of 21st century in the Kuroshio Extension (KE) in all the models examined. The MLD change in the western subploar region, on the other hand, varies significantly depending on models. Stratification measured by the buoyancy frequency intensifies especially within the main thermocline, supporting the idea that MLD under global warming will be decreased mainly due to intensified stratification. The KE front shifts northward in response to the wind stress curl shift, which provides an additional factor in understanding the spatial pattern of the MLD changes. These results suggest that changes in the wind stress and ocean circulation, in addition to the intensified surface stratification due to direct radiative warming, contribute significantly to MLD changes in a warming world. Given these changes in the upper mixed layer, we also make projections on their impacts on primary production. We estimate the change in primary production based on the change in the entrainment of nutrients by winter mixing at selected locations in the North Pacific.