SEAICE_AGE_VOL: adding option to use volume instead of area for integrating SEAICE_AGE
SEAICE_AGE_VOL: adding option to use volume instead of area for integrating SEAICE_AGE

altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h