Area scaling A method of relating glacier volume or volume changes to glacier area or area changes, based on a tendency for glacier thickness to be well correlated (to 'scale') with glacier area. Glac
ier volume V is the product of area S and mean thickness H. Measured mean thicknesses are well described by a relation of the form H c S1, which is the basis for the volume-area relation V c S . Here c and are parameters estimated from samples of glaciers with measured thicknesses. There is good evidence, as shown by Bahr et al. (1997), that estimates of from observations are nearly consistent with theoretical expectation. Mean thickness is also sometimes estimated as a function of average surface slope and basal shear stress. Volumearea scaling is both a way of estimating regional and global glacier volumes from abundant data on glacier area, and a possible way of estimating (with large random uncertainty) the volume balance of single glaciers from successive measurements of area S1 and S2, for example as2 1 ()2(2V c S S . It can also be used, as a practical alternative to ice-flow modelling, to estimate glacier area changes in attempts to model the response of glaciers to climatic change. Glacier volume is also expected, and found, to scale with glacier length, particularly when the length is that of a flowline.
The change in the volume of a glacier, or part of a glacier, over a stated span of time. A volume balance contains no information about the density of the matter within the volume gained or lost. It i
s meaningful in itself, but is often an intermediate product in the determination of mass balance by geodetic methods. Balances expressed in ice-equivalent or water-equivalent units, such as m3 w. E. A-1, are not volume balances but mass balances.
The volume emission rate, e(r, t, l), is thenumber of photons emitted per unit source volume per second, i.e.photons/(m3 s), as measured along the line of sight between the source pointand the observe
r. The Volume Emission Rate is in general a function of theline-ofsight distance, r, time, t, and wavelength, l. The Volume EmissionRate is actually not a directly measurable quantity. However, the term hasbeen commonly used in both data product descriptions and researchpublications.
The ratio of the volume of the water and ice in a sample to the volume of the whole sample, expressed as a fraction (or, less commonly, as a percentage)