Glacier Mass Balance and Regime: Data of Measurements and ...

measurements carried out in the field, annually, by the glaciological method (with only a few exceptionsexplained in Chapter 3). Definitions of these terms are given in Mayo et al (1972).2.1.2. Definition of seasonal mass-balance components.Several components of glacier mass balance are in use in glaciological measurements anddata presentation (FoG, v. 1-7). The original data of mass-balance components, mass gain and loss,have been preserved in Appendix 3 as they were published in FoG volumes and other sources ofinformation used here. One of the important tasks in the future is to use a common method to getcomparable results and to recalculate all previously measured data in one single format for allglaciers (say b wand b s). To accomplish this task, comparable measurements by several methodssimultaneously are needed. Such comparable measurements have been made on a very restrictednumber of glaciers (Dyurgerov and Meier, 1999). The differences between seasonal mass balancecomponents are substantial and are shown in Figures 2.1, 2.2, 2.3. The seasonal mass balancecomponents are the specific winter mass balance (b w) and the specific summer mass balance (b s). Wehave also considered annual snow-ice accumulation (c t) and annual ablation (a t). c tis the trueestimation of annual amount of precipitation as snow/ice (b wminus winter ablation plus summeraccumulation) deposited on the upper surface of a glacier; a tis the true estimation of yearly waterproduction and glacier runoff (excluding melt water refreezing and ice evaporation). However, b w+b s= c t+ a t= b n, which is the annual or net mass balance (b sand a tare considered here as negativevalues). The difference between c tand b w, and between a tand b smay be substantial in somegeographical locations (Figs. 2.1, 2.2). It tends to be greater in regions with continental climateconditions, where snow accumulation and ablation may occur simultaneously (e.g., ShumskiyGlacier, Figs. 2.1, 2.2). In extremely continental climate conditions with very low total precipitationand/or monsoon climates, as in the mountain ranges of Central Asia, more than 75% of theprecipitation may occur on a glacier in summer, mostly as snow (Ageta and Higuchi, 1984). Thismakes the difference between b wand c tlarge compared to maritime climate conditions (Zichu Xie, etal., 1999).22