EVIDENCE FOR FLOATING ICE SHELVES IN FRANZ-JOSEF-LAND, RUSSIAN HIGH ARCTIC

Examination of digital Landsat TM and MSS imagery of Franz Josef Land, Russian High Arctic, reveals a number of ice caps with apparently ver y low surface gradients at their seaward margins. The largest of these low gradient areas is 45 kM2. The areas are dynamically a part of the parent ice mass, and have a marked break of slope at their inner marg ins. They generally occur in protected embayments and often have relat ively deep water offshore. The presence of deep inter-island channels (up to 600 m) in the archipelago also suggests that deglaciation after the last glaciation may have proceeded rapidly due to enhanced iceber g calving. Tabular icebergs (maximum observed length 2.3 km) are produ ced from several of the low gradient ice cap margins today. Ice surfac e profiles, derived from analysis of vertical aerial photographs, show slopes of 0.5-degrees on these features, as compared with 3.5 to 50 o n other ice caps. At least some are likely to be floating ice shelves. They have similar ice surface gradients to a known ice shelf on Sever naya Zemlya. There is no requirement for deep water to occur beneath t hese features, but simply that they become buoyant over a significant part of their base. Glacier thinning, due to reduced mass balance sinc e the termination of the Little Ice Age, may have contributed to the p resence of these features. An origin for some of these low gradient ma rgins by deformation of an unlithified substrate cannot be ruled out. Field radio-echo experiments could be used to test the interpretation of these features as ice shelves.