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Abstract: Oceanographic and ice‐mass‐balance records are presented from two moorings deployed on landfast multiyear ice in the Wandel Sea (North Greenland) during June–August 2015. Here we show that the melting and drainage of >1 m of snow from June 14 to July 14 created a double‐diffusive vertical stratification which resulted in supercooling of water and enabled the formation of platelet crystals below the sea ice. Although the effect of supercooling, with temperatures up to 0.5°C below the freezing point, might be overestimated considerably in our records, this process led to the formation of ∼1.1–1.2 m‐thick subice platelet layer. While warm water temperatures lead to the complete loss of this layer at one mooring site, the layer persisted through summer and became incorporated into the congelation ice at the second site. The warm water that melted out the platelet layer can be ascribed to two different sources: (1) in situ heating from solar radiation resulting in a temperature increase up to 0.8°C in late July and (2) advection of warm surface water (with temperatures up to 3–4°C) from the ice‐free coastal regions in mid‐August. The combination of processes causing the seasonal growth of a platelet layer and either its subsequent ablation or incorporation into congelation ice is discussed with respect to the ice‐mass balance and stability of the landfast ice cover in the Wandel Sea. Furthermore, this study provides evidence for the formation of a platelet layer in the Arctic, a phenomenon that historically has only been observed in the Antarctic. [ABSTRACT FROM AUTHOR]

Abstract: Late Cenozoic opening of the Fram Strait led to formation of the NW–SE striking, eastern North Greenland oblique-shear margin at transition from the Norwegian–Greenland Sea to the SW Eurasia Basin. Onshore geology exposed on large peninsulas in front of the major Greenland Inland Ice reveals a highly complex, Paleozoic–early Cenozoic pre-opening setting. However, due to extreme ice conditions, very little is known about the offshore areas seawards of – and between – the peninsulas. Consequently, prevailing structural-tectonic models of the margin tend to be significantly oversimplified and inadequate. We present the first, combined onshore–offshore, model of the margin integrating onshore outcrops with potential field data, new offshore seismic reflection data and receiver-function analysis of seismic broad band data. The results reveal a margin which is far more complex than previously anticipated. In particular, we interpret strong margin segmentation along N/NE-striking fault structures. The structures are likely to have formed by Late Mesozoic–early Cenozoic strike-slip tectonics and have continued to be active during the late Cenozoic. A more than 8km deep sedimentary basin is interpreted to underlie the central Wandel Sea, confined by these N/NE-striking structures. We suggest that similar margin segmentation affected the conjugate Yermak Plateau–North Svalbard margin as well as parts of the NE Greenland margin to the SE. Hence, the results have important implications for the general understanding of the Mesozoic–early Cenozoic development of the intra-continental De Geer Mega-shear Region between North Greenland and Eurasia. [Copyright &y& Elsevier]