mass balance

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mass balance
1. Generally, a term used in comparisons of the inputs and outputs of processes.

2. The balance of elements in ocean water, which is assumed to be constant, i.e. influx and removal of elements occurs at the same rate. Influxes include river water, elements released from sediment pore fluid, and melting ice. Reaction between sea water and rocks is probably insignificant. The removal of elements from sea water occurs by precipitation of chemical sediments, ion exchange, and the burial of pore fluids.

3. The relation between the input and output of a glacier. Input (accumulation) is dominated by snow precipitation and output (ablation) by surface melting. The difference between accumulation and ablation for a glacier over a year is the net (mass) balance. A positive net balance implies that a glacier is growing; a negative net balance that it is shrinking; and a zero net balance that it is stable.