unpack: summer surface

[brandonnodnarb]

def from Glossary of Geology

summer surface An observable horizon (e.g. dirt band) in a glacier, marking the end of melting in one balance year and the beginning of snow accumulation in the next. Cf: net balance.

(for reference)
net balance The change in mass of a glacier from the time of minimum mass in one year to the time of minimum mass in the succeeding year (balance year); the mass change between one summer surface and the next. It can be determined at a point, in which case it is referred to as a "specific net balance", or as a total-mass change for the glacier. Units of millimeters, meters, or cubic meters, of water equivalent are generally used. Synonym: net budget. Cf: annual balance.