Form and flow of the Academy of Sciences Ice Cap, Severnaya Zemlya, Russian High Arctic

Abstract

[ 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.

Seasonal speed-up of two outlet glaciers of Austfonna, Svalbard, inferred from continuous GPS measurements

“…This velocity pattern appears to be typical for many Arctic ice caps, e.g. the Devon Island Ice Cap in Arctic Canada or the Academy of Sciences Ice Cap in the Russian Arctic (Dowdeswell et al, 2002). Model results suggest that the large ice thickness within these valleys allows for temperate basal conditions, and hence, basal motion as the dominant mechanism of ice flow (Dunse et al, 2011).…”

Two-dimensional prognostic experiments for fast-flowing ice streams from the Academy of Sciences Ice Cap

“…2; Dowdeswell et al, 2002). The four ice streams were 17-37 km long and 4-8 km wide (Dowdeswell et al, 2002). Bedrock elevations of these areas were below sea level, and the ice flow velocities attained a value of 70-140 m a −1 (Fig.…”

“…2; Dowdeswell et al, 2002). The four ice streams were 17-37 km long and 4-8 km wide (Dowdeswell et al, 2002).…”

“…Such fast flow-line features are typical for outlet glaciers and ice streams in both the Arctic and the Antarctic. These ice streams are the major locations of iceberg calving from the Academy of Sciences Ice Cap (Dowdeswell et al, 2002).…”

“…These experiments can be performed by mathematical modeling, and in this study a two-dimensional ice flow model was applied to predict future conditions of fastflowing ice streams on the southern side of the Academy of Sciences Ice Cap on Komsomolets Island, Severnaya Zemlya archipelago ( Fig. 1; Dowdeswell et al, 2002).…”