资源环境科技发展态势分析平台

Climate models often parameterize isopycnal mixing by mesoscale eddies using a diffusion operator that acts in the isopycnal direction, multiplied by an isopycnal-mixing coefficient. The magnitude of this coefficient is uncertain, with observational estimates ranging from 10 to 10,000 m(2)/s. In an idealized-geometry ocean model, the isopycnal-mixing coefficient is varied across a similar range without allowing the circulation to change: This leads to large changes in the ventilation of the deep ocean. Passive tracers are used to assess the impact of varying the isopycnal-mixing coefficient on water mass distributions. Increasing the isopycnal-mixing coefficient from 50 to 5,000 m(2)/s leads to a 63% reduction in the amount of North Atlantic Deep Water and a doubling in the amount of Antarctic Bottom Water in the deep Pacific ocean. This change is associated with a 700-yr reduction in the ideal age of water in the deep Pacific ocean.