| Summary: | Despite the undisputed role of the Arctic Ocean in the modern and Pliocene climate system, the Arctic has only recently attracted public awareness that ongoing, fundamental change in the Arctic cryosphere could be a response to global warming. Clarification of the Arctic's role in global climate during the Pliocene is, however, largely hampered by equivocal stratigraphic constraints. From a well-dated Pliocene sequence from the Yermak Plateau, off NW Spitsbergen, we present sedimentological and geochemical data indicating that 4 million years ago terrigenous sediment supply and sources changed abruptly in response to a regional tectonic uplift event. We argue that this event together with contemporary uplift and tilting along the northwestern European continental margin preconditioned the landmasses for glacial ice build-up during intensification of the Northern Hemisphere Glaciation (INHG). Our data further suggest that the final deepening/widening of the Arctic-Atlantic gateway, the Fram Strait, between 6.5 and 5 Ma gradually caused increased deep-water mass exchange which, in turn, likely contributed to the intensification of the North Atlantic thermohaline circulation. Coupled to the North Atlantic warm pool as a regional moisture source, declining atmospheric CO 2 levels and other feedback mechanisms during the Pliocene, the regional tectonic activities in the high northern latitudes caused decreased summer ablation and thus allowed the initial build-up of glacial ice both in Scandinavia, and the sub-aerially exposed Svalbard/Barents Sea, culminating in the first large-scale coastline-shelf edge glaciations at ~2.75 Ma ago.
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