Desarrollo de la Antártica

Tahesi Nagata I THE ADVANCEMENT OF SCIENTIFIC RESEARCH ••• ice lO'ss amO'unt of this categO'ry estimated by different investigatO'rs rauges frO'm 1 x 10 10 tO'ns/year tO' 2 x lQill tO'ns/year. The tO'tal ice 10'85 of Antarctic ice sheet estimated in the above table is abO'ut1.66 x ,10 12 tO'ns/year, which appears considó'rably smaller than the tO'tal amO'unt O'í snO'w accumulatiO'n O'n tJhe ice sheet, i.e. i2. O xl 0 12 tO'ns/year. In other wO'rds, it appears that lhe Antarctic ice sheet is gradually grO'wing up at presento HO'wever, the estimates O'f snO'w accumulatiO'n and particularly ice lO'5s in Antarctica are nO't fully accurate yet at presento It may be prO'vi– sionally cO'ncluded tlhat the ice balance of the Antarctic ice sheet is O'f a positive excess O'r in an apprO'ximate equilibrium. iii. Shape O'f the profile and ice flO'w The surface shape O'f Antarctic ice sheet and the bed rO'ck tO'pO'graphy are well summarized in Atlas Antarktiki 1 (1966) a,nd JI (1969) edited by the Academy O'f Sciences, USSR. íThe prO'file shape thrO'ugh the crest pO'int O'f Antarctic ice sheet can be apprO'ximately repre– sented by an elliptic curve as !/hO'wn in Fig. 3, where the maximum thickness O'f ice-sheet excede~ 3.0'00 m. The snO'w and ice accumu– lating O'n the ice sheet surface flO'w outwards thrO'ugh the ice-sheet and they gO' O'ut intO" rhe O'cea,n O'r the atmO'sphere by variO'us dif– ferent lO's5 mechanisms in the neighbO'urhO'O'd O'f the ice sheet O'uter edge lineo Generally, thé outwarrl :horizontal velO'city O'f ice flow within the ice sheet increases from almO'st zerO' at the crest paint tO' abO'ut 100 m/year at the O'uter edge. However, tlhe hO'rizO'ntal velO'cities O'f valley glaciers and ice shelves amO'unt tO' 500 '-' 1,000 m/year. The O'utgO'ing velocity O'f rhe outer edge O'f Shirase glacier amO'unts even tO' 2,500 m/year. c. lee Shelf There are 10 large ice shelves (!arger than 3 x 10 4 km 2 in area) alO'ng the Antarctic coast, the tO'tal ice shelf area amO'unting tO' about 1.6 x 10 6 km 2 • On these ice shelves, the average annual rate O'f snO'w accumulatiO'n is in a range O'f 18 __ 70 gfcm 2 /year, which is considerably larger than the average snO'w accumulatiO'n O'n the Antarctic ice sheet (abO'ut 15 g/cm 2 /year). HO'wever, the inflO'w O'f ice ilirO'ugh ice streams intO' the ice shelf frO'm the inland ice plateau amO'unts tO' a cO'nsiderably larger value than tlhe snO'w accumulatiO'n as shO'wn in the fO'llO'wing table (Table 4) f.or example. Since the A'ntarctic ice shelves seem tO' be stable, the ice mass 87