Mixed-layer entrainment damps Intertropical-Convergence-Zone shift under projected Arctic sea-ice loss: A hierarchical modeling study

Abstract:

It is known that ocean dynamic is important in modulating the response to Arctic sea-ice loss. Momentum coupling of oceanic Ekman flow is widely accepted as the main factor damping the Intertropical Convergence Zone (ITCZ) shift. Stratification difference (vertical temperature gradient in the tropics) between the Ekman flow and return flow largely determines the effectiveness of damping. From this point of view, the seasonal variation of mixed-layer thickness may play an important modulator because it may change the stratification through bottom entrainment. In order to study their contribution, we develop a hierarchy of ocean models which include Ekman flow and variable mixed-layer. It is found that ITCZ shift can be further damped when mixed-layer entrainment is present compared to Ekman-flow-only model.