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Snow and Ice Feedback and Climate Sensitivity (Abstract)

Published online by Cambridge University Press:  20 January 2017

Alan Robock
Alan Robock*
Affiliation:
Department of Meteorology, University of Maryland College Park, Maryland 20742, U.S.A.
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Abstract

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Abstract
Information
Annals of Glaciology , Volume 5 , 1984 , pp. 225
Copyright
Copyright © International Glaciological Society 1984

A new parameterization of snow and ice area and albedo is presented, based on recent satellite observations of snow and ice extent (Reference RobockRobock 1980, Reference Robock1983). This parameterization is incorporated into a seasonal energy-balance climate model. Experiments are conducted with the model to determine the effects of this parameterization on the latitudinal and seasonal distribution of model sensitivity to external forcings of climate change (solar constant variations and volcanic dust) and to internally forced climate change.

The snow/ice area and snow/ice meltwater feedbacks are found to determine the sensitivity pattern to external forcing, producing enhanced sensitivity in the polar regions in the winter and decreased sensitivity in the polar regions in the summer. This result holds for both equilibrium experiments, where a step function forcing is applied at the beginning of the simulation and the model is run to equilibrium (Reference RobockRobock 1983), and for transient experiments where the forcing is time-dependent (Reference RobockRobock 1981). This pattern is produced by the sea-ice thermal inertial feedback. Snow and ice albedo feedbacks are relatively weak.

This response pattern is the same as that found by Reference Manabe and StoufferManabe and Stouffer (1980) with a general circulation model. The enhanced sensitivity in the summer found by Reference Ramanathan, Lian and CessRamanathan and others (1979) is shown to be due to a surface albedo feedback parameterization which does not allow the thermal inertia to change.

The sensitivity to internal forcing is amplified by the snow/ice feedback, producing a higher variance of the resulting temperature time series. The spectra of the series are shifted to more variance in the lower frequencies. The latitudinal and seasonal pattern of variance shows higher variance at higher latitudes due to the lower mean thermal inertia, but the pattern is relatively unaffected by the presence or absence of snow/ice feedbacks because the mean thermal inertia does not change.

This work has been supported by US National Science Foundation grants ATM-7918215 and ATM- 8213194.

References

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Ramanathan, V, Lian, M S, Cess, R D 1979 Increased atmospheric CO2: zonal and seasonal estimates of the effect on the radiation energy balance and surface temperature. Journal of Geophysical Research 84(C8) 4949–4958 CrossRefGoogle Scholar
Robock, A 1980 The seasonal cycle of snow cover, sea ice and surface albedo. Monthly Weather Review 108(3): 267–285 Google Scholar
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Robock, A 1983 Ice and snow feedbacks and the latitudinal and seasonal distribution of climate sensitivity. Journal of the Atmospheric Sciences 40: 986–997 2.0.CO;2>CrossRefGoogle Scholar