A review of postglacial emergence on Svalbard, Franz Josef Land and Novaya Zemlya, northern Eurasia

Abstract

The pattern of postglacial emergence in the Barents Sea is pivotal to constraining the timing of deglaciation and extent and thickness of the last ice sheet in northern Eurasia. This review unites records of Holocene relative sea level from Svalbard, Franz Josef Land, and Novaya Zemlya to better understand the geometries of past ice sheet loads. Emergence data from northern Eurasia confine the maximum area of glacier loading to the northwestern Barents Sea, where >100 m of emergence is measured on Kongsøya. Deglacial unloading commenced on western and northern Spitsbergen c. 13–12 14C ka ago, and by c. 10.5 14C ka on eastern Svalbard and more distal sites on Franz Josef Land and Novaya Zemlya. The marine limit phase (c. 13–12 14C ka) on western and northern Spitsbergen is characterized by the construction of spits indicating a dominance of long-shore drift over storm-generated fetch, reflecting extensive sea-ice coverage of coastal areas. At sites in proximity to the ice sheet margin on western and northern Spitsbergen there is evidence for a transgressive–regressive cycle c. 6–4 14C ka, possibly reflecting back migration of displaced mantle material. A modern transgression is inferred from the marine erosion of 17th century cultural features and 14C ages of whalebone and terrestrial peat buried by modern storm gravels that place sea level at its present position by c. 2 to 1 ka ago. The greatest observed emergence on Franz Josef Land occurs on Bell Island, with a marine limit at 49 m aht, formed c. >10 14C ka. Available emergence data since 9 ka show rising strandlines toward the southwest at ∼0.3 m/km. The northern limit of emergence on Franz Josef Land is poorly constrained because relative sea-level data is sparse north of 80°30′N. In contrast to Svalbard and Franz Josef Land, the marine limit on northern Novaya Zemlya is only 10–15 m above high tide and formed between 6.5 and 5.0 14C ka when global sea level was stabilizing. All sites show little apparent emergence during the past 2 ka, with the youngest raised landforms at identical heights to storm beaches. This minimal glacio-isostatic signature on Novaya Zemlya and on Vaygach Island, where deglaciation commenced >10 ka ago, indicates ice sheet thicknesses of <1.5 km. The spatial variation in emergence for the Barents Sea indicates that western and northern Spitsbergen and Novaya Zemlya were near the reactive margin of the ice sheet and these areas sustained the briefest ice coverage (2–6 ka) and were probably not in isostatic equilibrium. In contrast, central and eastern Svalbard and southern Franz Josef Land were beneath a substantial ice load and probably sustained this load for c. 10 14C ka and achieved isostatic equilibrium. Isostasy residual from an ice sheet model portrays well the general pattern of uplift and load response at the centre of ice sheets, but deviates substantial at the ice sheet margin or areas covered by thin ice, like Novaya Zemlya.