The Role of Sea Ice Dynamics in Modeling CO2 Increases
- James E. Hansen and
- Taro Takahashi
Published Online: 19 MAR 2013
Copyright 1984 by the American Geophysical Union.
Climate Processes and Climate Sensitivity
How to Cite
Hibler, W.D. (1984) The Role of Sea Ice Dynamics in Modeling CO2 Increases, in Climate Processes and Climate Sensitivity (eds J. E. Hansen and T. Takahashi), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM029p0238
- Published Online: 19 MAR 2013
- Published Print: 1 JAN 1984
Print ISBN: 9780875904047
Online ISBN: 9781118666036
- Ocean-atmosphere interaction—Congresses
Sensitivity simulations of a hierarchy of Antarctic sea ice models to atmospheric warming are carried out and analyzed. The study includes models with only a thermodynamic ice cover, models with in-situ leads but no ice transport, and a fully coupled dynamic/thermodynamic model that includes transport, leads and strength-thickness coupling. All models employ a 60-m-thick oceanic mixed layer, together with a spatially and temporally varying heat flux into the mixed layer from the deep ocean. The heat flux was generated interactively by using a fixed fraction of the ice growth and cooling rates from the full dynamic/thermodynamic model. The same spatially and temporally varying heat flux fields (with an average of about 13 W m−2) were used in all sensitivity simulations.
Models including full ice dynamics effects are found to be less sensitive to atmospheric warming than thermodynamics-only models, while models with specified lead fractions are more sensitive than thermodynamics-only models. The decreased sensitivity in a fully coupled model is found to depend on the ice velocity field also being modified by the atmospheric warming. In all cases the fully coupled model has a greater seasonal swing of ice extent than the thermodynamics-only model and fixed lead fraction model. All models show an enhanced sensitivity in the summer ice extent as compared to winter.
With regard to air-sea heat exchanges, models including leads and full dynamics show a reduced sea-to-air heat exchange over ice-covered regions under warming conditions, while the thermodynamics-only model shows an increase. In the control simulations the sea-to-air exchanges through the ice cover are about five times larger in the full model than in the thermodynamics-only model.
Sensitivity of the fully coupled model to oceanic forcing and variable thickness parameterization was also investigated. In the standard control run temporally and spatially varying heat fluxes were found to reduce the seasonal swing of ice extent as compared to constant heat flux values. Similarly, in comparison to a 30-m mixed layer, the 60-m mixed layer, reduced the seasonal ice extent variation.