Radio Echo-Sounding of Svalbard Glaciers

Abstract

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.

Ice Volume Estimates from Ground-Penetrating Radar Surveys, Wedel Jarlsberg Land Glaciers, Svalbard

“…The underestimate of Wedel Jarlsberg Land glacier volumes by most of the V-A relationships is likely due to the fact that these glaciers are generally thicker than those in western Nordenskiöld Land, and the share of tidewater glaciers in the Wedel Jarlsberg Land sample is far larger than in the western Nordenskiöld Land study, so the real volume/area ratio is expected to be higher. The best overall result is provided by the relationship derived by Hagen et al (1993), which underestimates by 4% the measured volume of the ensemble, whereas the worst performance is shown by the relationship of Macheret and Zhuravlev (1982), which underestimates the volume of the ensemble by 34%. Dowdeswell et al (1984a) pointed out that the results from airborne Soviet radio-echo soundings in the early 1980s using 440 and 620 MHz radar systems (Macheret, 1981;Macheret and Zhuravlev, 1982) had underestimated the ice thickness by 33-50%, and consequently their empirical relationship based on the measured volumes is biased in a similar way.…”

“…The best overall result is provided by the relationship derived by Hagen et al (1993), which underestimates by 4% the measured volume of the ensemble, whereas the worst performance is shown by the relationship of Macheret and Zhuravlev (1982), which underestimates the volume of the ensemble by 34%. Dowdeswell et al (1984a) pointed out that the results from airborne Soviet radio-echo soundings in the early 1980s using 440 and 620 MHz radar systems (Macheret, 1981;Macheret and Zhuravlev, 1982) had underestimated the ice thickness by 33-50%, and consequently their empirical relationship based on the measured volumes is biased in a similar way. The other scaling approaches that underestimate the volume of the ensemble are those of Chen and Ohmura (1990), by 19%; Bahr et al (1997), by 21%;and Grinsted (2013), by 26% when using the relationship derived from the GLIMS Inventory, and by 10% when using the relationship derived from the Randolph Glacier Inventory.…”

“…At a regional scale, these new volume estimates add to the available set of GPR-based volume estimates of individual glaciers on Svalbard (Dowdeswell et al, 2008;Pettersson et al, 2011;Lapazaran et al, 2013;Saintenoy et al, 2013;Martín-Español et al, 2013). These estimates have allowed a new V-A relationship specific for Svalbard glaciers (Martín-Español, 2013) to be derived that is more reliable than those currently available (Macheret and Zhuravlev, 1982;Hagen et al, 1993), which were based on the limited and low-accuracy icethickness estimates from airborne radio-echo soundings in the late 1970s and early 1980s (Macheret, 1981;Macheret and Zhuravlev, 1982;Dowdeswell et al, 1984aDowdeswell et al, , 1984b. The interest of V-A scaling relations characterizing individual glacier shapes, slopes, and sizes, as well as plausible glaciological conditions (such as steady-state, or sustained retreat or advance), has recently been pointed out by Adhikari and Marshall (2012), and thus regional V-A relations have become a matter of particular interest.…”

Cold surface layer thinning on Storglaciären, Sweden, observed by repeated ground penetrating radar surveys

“…[5] The use of GPR to detect internal reflections attributed to the thermal regime on polythermal glaciers was introduced by Macheret and Zhuravlev [1982], Dowdeswell et al [1984] and Kotlyakov and Macheret [1987]. GPR surveys combined with temperature measurements in bore holes have indicated a close relation between internal reflections and the thermal structure [Bamber, 1987;Jania et al, 1996].…”

“…[2] Polythermal glaciers are common in the Canadian Arctic [Blatter, 1987;Blatter and Kappenberger, 1988] and Svalbard [Macheret and Zhuravlev, 1982;Dowdeswell et al, 1984;Ødegård et al, 1992;Björnsson et al, 1996], but also on the drier side of the Scandinavian mountains [Schytt, 1968;Hooke et al, 1983;Holmlund and Eriksson, 1989]. Such glaciers are characterized by a cold surface layer covering a temperate core and are frozen to the bed along their margins and terminus.…”