Derivatives. Instantaneous size doesn't matter. You have to measure how they are changing. Furthermore the physical (not climate) models based on these rates of

Derivatives. Instantaneous size doesn't matter. You have to measure how they are changing. Furthermore the physical (not climate) models based on these rates of change suggest that right now at this moment the rate of addition of new material to the ice sheet will not matter because the rate of melting to this point has made it unstable and the process of adding additional material will not be able to counter the processes of melting.