Theoretical Archetypes for Understanding Interactions Between Sea-Ice and Large-Scale Atmospheric Dynamics

University Of Chicago, Chicago IL

Investigators

Abstract

The development of sea-ice parameterizations for use in general circulation models (GCMs) has historically been characterized by a focus on increasing the complexity of the parameterization. Currently, ice model development has involved adding previously un-represented or under-represented physics, such as melt ponds, ice ridging, etc. Increased physical complexity, however, is not the core issue in the GCM parameterization. In the case of parameterizing moist convection, parameterization is the link between that which provides a "control" upon the physical process being parameterized and the "feedback" the physical process provides. With sea-ice parameterizations, there does not currently appear to be an adequate understanding of how the large and small-scales interact. What the large-scale ultimately cares about, both a control and as a recipient of feedback, is not the microscale physical behavior per se, but rather what the parameterized process dynamically accomplishes. Preliminary work in adding a stochastic parameterization for winter leads to the ARCSyM Arctic regional climate model suggests that climate sensitivity to ice processes lies fundamentally in how the ice couples with large-scale atmosphere dynamics, and not so much in the ice model itself. In this project, very small perturbations to ice concentration can result in melting of nearly half of the January ice pack, and also appear to affect the development and evolution of synoptic cyclones. Since the sea-ice model reasonably emulates mean ice extent, the coupled model 's sensitivity appears due to ice-atmosphere interactions and feedbacks.