[ 1 ] The 5,575-km 2 Acad emy of Sciences Ice Cap is the largest in the Russia n Arctic. A 100-M Hz airbo rne radar, digital Landsat imagery, and satelli te syntheti c apertu re radar (SAR) interfero metry are used to investig ate its form and flow, incl uding the propor tion of mass lost throu gh iceberg calvi ng. The ice cap was covered by a 10-km -space d grid of radar fli ght paths , and the centr al porti on was covered by a grid at 5-km inte rvals: a total of 1,657 km of radar data. Digit al elevation model s (DEM s) of ice surfa ce elevation, ice thickness, and bed elevat ion data sets wer e produce d (cell size 500 m). The DEMs wer e used in the selec tion o f a deep ice core dril l site. To tal ice cap volum e is 2,1 84 km 3 ( $ 5.5 mm sea level equiva lent). The ice cap has a single dome reachi ng 749 m. Maxi mum ice thic kness is 819 m. About 200 km, or 42%, of the ice margin is mari ne. About 50% of the ice cap bed is below sea level. The central divide of the ice cap and severa l maj or drain age basins, in the south an d east of the ice cap and of up to 975 km 2 , are delimited from satel lite ima gery. The re is no eviden ce of past surge ac tivity on the ice cap. SAR interfero metric frin ges and phase-unwrapped velociti es for the whole ice cap indicate slow flow in the interior and much of the margin, punctu ated by four fast flowin g featu res with late ral shear zones and maxi mum veloci ty of 140 m y r À 1 . These ice streams extend back into the slower moving ice to wi thin 5 -10 km of the ice cap crest. They have lengths of 17 -37 km a nd widths of 4 -8 km. Mass flux from these ice streams is $ 0.54 km 3 yr À 1 . Tabular icebergs up to $ 1.7 km long are produce d. Total iceberg flux from the ice cap is $ 0.65 km 3 yr À 1 and probably represe nts $ 40% of the overal l mass loss , with the rema inder coming from surfa ce mel ting. Drivin g stre sses are general ly low est (<40 kP a) close to the ice cap divides and in severa l of the ice stre ams. Ice stream motion is likely to incl ude a signifi cant basal compo nent and may involve deformabl e marine sedim ents.

The results of measurements of radio-wave velocities (RWV) by wide-angle reflection (WAR) methods in the temperate Abramov Glacier in the Alai Mountain Ridge and the “two-layered” sub-polar Fridtjovbreen and Hansbreen on Svalbard using a low-frequency (2–13 MHz) radar are considered and discussed. The experimental data obtained and the data from the literature show that the values of RWV could be a good indicator of the hydrothermal state of glaciers. As such, these data enable the identification of cold, temperate and transitional (two-layered) glaciers, and can be used for estimation of the water content in glaciers and changes in the hydrothermal state.

ABSTRACT. Peculiarities of radio echo-sounding of mountain glaciers and ice fields between nunataks from terrestrial vehicles and from helicopters are considered in this paper. The possibility of using comparatively high frequencies (of up to 865 MHz) for sounding such glaciers is demonstrated on the basis of experimental data. Results of airborne radio echo-sounding of Svalbard glaciers of various types, dimensions, and regime obtained with the help of the 620 M Hz airborne equipment of high resolution are shown. Returns from the glacier bed have been obtained on the majority of glaciers under investigation. The firn regions of ice fields with temperate regimes flowing between nunataks are, mostly, an exception. Depression in the glacier bed with the ice thickness up to 540 m, as well as internal reflecting boundaries have been detected in some glaciers. Ice volumes of glaciers have been determined from the airborne radio echo-sounding data with the use of a parabolic approximation to the cross-section glacier profiles. Good correlational dependence between ice volume and surface area of glaciers has been established and is used to estimate the ice and water resources in Svalbard glaciers. RESUME. Sondages par echo-radio des glaciers du Sualbard. Dans cet article on examine les particularites des sondages par echo-radio de glaciers de type de montagne ou de piedmont depuis des vehicules terrestres ou par helicoptere. Sur la base des donnees experimentales on montre une possibilite d'utiliser a titre de comparaison des hautes frequences (jusqu 'a 865 MHz) pour sonder de tels glaciers. On donne et on discute les resultats de sondages aeriens par echo-radio des glaciers du Svalbard de type montagne, piedmont et calotte, avec des appareils de 620 MHz a gran de capacite de resolution spatiale. Des signaux rI:flechis sur le lit du glacier ont ete recueillis sur la majorite des glaciers sondes. Les zones de neves des glaciers de type piedmont avec des regimes thermiques " chauds" (glaciers temperes) sont, la plupart du temps , une exception. On a decouvert sur une serie de glaciers des depressions du fond du lit avec des valeurs de l'epaisseur de glace allant jusqu' a 540 m, ainsi que des pi ages de reflexion interne. A partir de sondages par echo-radio en utilisant une approximation parabolique pour les profils des sections transversales d'un glacier on a pu determiner les volumes des glaciers et etablir une bonne correlation avec la surface englacee. On en a tire une estimation des ressources en glace et en eau des glaciers du Svalbard.

The results of measurements of radio-wave velocities (RWV) by wide-angle reflection (WAR) methods in the temperate Abramov Glacier in the Alai Mountain Ridge and the “two-layered” sub-polar Fridtjovbreen and Hansbreen on Svalbard using a low-frequency (2–13 MHz) radar are considered and discussed. The experimental data obtained and the data from the literature show that the values of RWV could be a good indicator of the hydrothermal state of glaciers. As such, these data enable the identification of cold, temperate and transitional (two-layered) glaciers, and can be used for estimation of the water content in glaciers and changes in the hydrothermal state.

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