Climate change and variability in a single column coupled sea ice/ocean mixed-layer model

In general circulation model experiments, the Arctic region shows an amplified response to global warming scenarios. In the real climate system, the detection of high latitude climate change is likely to be obscured by the natural variability which is present in the system. Both the feedback mechanisms which contribute to the enhanced Arctic response and the natural variability which occurs in the Arctic climate system are poorly understood. Due to large uncertainties in many of the parameters used to model sea ice, models with significantly different physical processes can be tuned to obtain realistic present day simulations. However, in studies of climate change, it is the response of the model to various perturbations which is important. This response can be significantly different in sea ice models which exclude various physical processes. This study addresses the simulation of climate change and variability with the use of a new coupled sea ice/ocean mixed layer model which includes relatively sophisticated thermodynamics and an ice thickness distribution.; The model performance is evaluated and the importance of various processes is assessed. Several climate applications of this model are considered. These include studies of ice/ocean/atmosphere exchange, the simulated Arctic response to high frequency forcing, the strength and interactions of thermodynamic feedback mechanisms, and the natural climate variability of the perennial Arctic ice pack. It is found that the ice thickness distribution is a crucial component for accurately simulating ice/ocean/atmosphere exchange, the ice mass balance, feedback mechanisms, and the general Arctic climate.; The presence of the ice thickness distribution and an interactive ocean mixed layer allows for the relatively accurate representation of ocean feedback processes. These feedback mechanisms provide an enhancement in the model response to heat flux perturbations which is similar in size to that provided by the ice/albedo feedback. The incorporation of both ice/albedo and ice/ocean feedback mechanisms is important for determining the climate change and variability of the Arctic system. Additionally, the natural variability in the ice dynamical forcing causes a majority of the variance in the ice average thickness for specific locations. Based on the results of these studies, it is recommended that future modeling of Arctic and global climate include an interactive ocean mixed layer, sub-gridscale ice thickness distribution, and explicit ice dynamics.