Sea ice melt water has no alkalinity.

[maltrud]

When sea ice BGC is active along with ocean BGC, there is an exchange of DIC when ice melts. However, there is no corresponding flux of alkalinity, resulting in an unrealistic dilution of alkalinity in surface waters. Since the current implementation of sea ice BGC doesn’t explicitly calculate alkalinity, this flux needs to be approximated. We propose to simply set the alkalinity flux equal to the DIC flux, exactly as is done for river inputs of alkalinity.