Seasonal mass-balance gradients in Norway

Previously discovered regularity in vertical profiles of net balance, b(n)(z), on ten glaciers in Norway also exists in profiles of both winter, b(w)(z), and summer, b(s)(z), seasonal balances. All three profiles, unlike those of many glaciers elsewhere in the world, are remarkably linear. Variations of gradients, db(w)/dz and db(s)/dz, from year to year are small and correlate poorly with glacier-total balances b(w) and b(s). Glacier-to-glacier correlation is weak for both gradients but is strongly positive for b(w) and b(s). There are two direct consequences of these properties of the gradients that apply to both seasonal balances b(w) and b(s). First, because db/dz varies so little from year to year, the difference in balance, Delta b, from year to year is nearly the same over the entire glacier, except near the top and bottom of its altitude range. Therefore, balance at a site near the middle of the altitude range of the glacier correlates very well with glacier-total balance. Second, this correlation, combined with the strong positive correlation of balance from glacier to glacier, is the reason balance at one altitude on one glacier correlates well with glacier-total balance at other nearby glaciers.