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The northeastern part of the North Atlantic subpolar gyre is a key passage for the Atlantic Meridional Overturning Circulation upper cell. To this day, the precise pathway and intensity of bottom currents in this area is not clear. In this study, we make use of regional high resolution numerical modeling to suggest that the main bottom current flowing south of Iceland originates from both the Faroe‐Banks Channel and the Iceland‐Faroe Ridge and then flows along the topographic slope. When flowing over the rough topography, this bottom current generates a 200 m large bottom mixed layer. We further demonstrate that many submesoscale structures are generated at the southernmost tip of the Icelandic shelf, which subsequently spread water masses in the Iceland Basin. These findings have major implication for the understanding of the water masses transport in the North Atlantic, and also for the distribution of benthic species along the Icelandic shelf. Plain Language Summary: Water masses formed in the Arctic Ocean overflow into the North Atlantic at the bottom of the ocean, forming the so‐called upper cell of the Atlantic Meridional Overturning Circulation (AMOC). The pathway of the currents carrying these water masses is still under debate due to a lack of observations. In this study, we discuss in details the pathway of these bottom currents in the specific area south of Iceland. We show that a steady current flows along the Icelandic continental shelf, and then divide in smaller structures when reaching the southernmost tip of Iceland. We also show that on its way, the current mixes the bottom layer of the ocean. These findings have major implication in the understanding of heat and carbon transport at depth in this area, which constitute an important response of the climate to anthropogenic forcing. Key Points: An intense bottom boundary current originating from the Iceland‐Faroe Ridge and the Faroe Bank Channel flows along the Icelandic ShelfThe rough topography and the intensity of the current lead to bottom mixing and sustain a large bottom mixed layerSubsmesoscale structures generated locally participate in the spreading of deep water masses in the Iceland Basin [ABSTRACT FROM AUTHOR]

Geological understanding of the NE Atlantic and Arctic regions has increased greatly over the last two decades, revealing remarkable similarities. Continental extension in both regions onset during pausing or cessation of adjacent orogenies – the Verkhoyansk-Chukotka and Alpine orogenies – which relaxed compressional stresses and permitted extension. Severe extension accompanied by high-volume magmatism did not onset abruptly but was the culmination of long-term, regional tectonic and magmatic unrest. It was complex and piecemeal, with extension and volcanism occurring along multiple axes simultaneously, a process still ongoing in Iceland today. Large Igneous Province emplacement did not drive breakup but occurred as a consequence of continental extension. The High Arctic Large Igneous Province did not progress to breakup. As a result, much of the Arctic Ocean is floored by hyper-extended continental crust overlain by seaward-dipping reflectors. This crust resembles the passive margins of the NE Atlantic. The Alpha-Mendeleev Rise in the Arctic Ocean is a double-sided passive margin underlain by hyper-extended continental crust draped with seaward-dipping reflectors. A similar structure has been proposed for the Greenland-Iceland-Faroe Ridge. If correct, present-day volcanism in Iceland is building SDRs today. Up to ∼50% of the NE Atlantic Ocean oceanward of the continental shelves is likely underlain by at least some continental crust. For the Arctic Ocean this figure is ∼80%. Similar structures are found elsewhere, including the Madagascar Channel, the NW Indian Ocean, and the South Atlantic. These new ideas suggest promising directions of future study including assessing the true extent of continental crust in the oceans globally. • Orogenic stress relaxation allowed the NE Atlantic and Arctic Oceans to open. • LIP magmatism did not drive breakup but was a consequence of extension. • ∼80% the Arctic Ocean and ∼ 50% of the NE Atlantic Ocean contains hybrid crust. • The Arctic Alpha-Mendeleev Rise is a continental, double-sided passive margin. • The Greenland-Iceland-Faroe Ridge is underlain by hybrid crust. [ABSTRACT FROM AUTHOR]