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Large differences in surface mass balance between CCSM3 and CCSM4

Dear land model working group,

I'm trying to figure out the reason for the large differences in surface mass balance (Precipitation-Evaporation-Runoff) between CCSM3 and CCSM4.

Attached are two maps of surface mass balance calculations based on the annual mean land model output from control runs for CCSM3 (T85, b30.009) and CCSM4 (1degree, b40.1850.track1.1deg.006).

It's puzzling that the surface mass balance in CCSM4 around Antarctic and Greenland is a factor of 3 to 5 larger than that in CCSM3.

It appears that the surface mass balance in CCSM4 is more realistic. I'm wondering what happens to the CCSM3 simulation, and whether there is any fix to derive the correct surface mass balance from the model output in CCSM3. Thanks!
 
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