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An extremely strong Arctic cyclone (AC) developed in August 2016. The AC exhibited a minimum sea level pressure (SLP) of 967.2 hPa and covered the entire Pacific sector of the Arctic Ocean on 16 August. At this time, the AC was comparable to the strong AC observed in August 2012, in terms of horizontal extent, position, and intensity as measured by SLP. Two processes contributed to the explosive development of the AC: growth due to baroclinic instability, similar to extratropical cyclones, during the early phase of the development stage, and later nonlinear development via the merging of upper warm cores. The AC was maintained for more than 1 month through multiple mergings with cyclones both generated in the Arctic and migrating northward from lower latitudes, as a result of the high cyclone activity in summer 2016. [ABSTRACT FROM AUTHOR]

Abstract: Issues relevant to the water mass transformation and circulation in the Nordic Seas are explored using a series of idealized numerical model calculations. The essential aspects of the model configuration are: a marginal sea with two sub-basins separated by a ridge; a sill separating the marginal sea from the open ocean; a region of sloping topography surrounding the marginal sea; surface heat loss; and eddy-resolving physics. A calculation with enhanced topographic slope along the eastern boundary, as is found in the Lofoten Basin, produces a hydrography and circulation that are similar to that observed in the Nordic Seas, including two poleward warm currents, a mid-depth thermocline in the eastern basin (the model’s Lofoten Basin), and deep convection in the western basin (the model’s Greenland Sea). It is shown that the key elements to the mid-ocean poleward warm current and the mid-depth thermocline in the eastern basin are: an asymmetry in the eddy heat flux from the boundary into the basin interior, here related to a region of steep bottom topography that makes the eastern boundary current more unstable than the western boundary current, and a mid-ocean ridge that partially, but not completely, inhibits exchange between eastern and western basins. This exchange can take place by baroclinic eddy fluxes or by flow through deep gaps in the ridge. The basin-scale hydrography and circulation in this idealized Nordic Seas are controlled to a large degree by eddy fluxes, which are themselves strongly influenced by regional features of the bottom topography that are located far from the convection sites. [Copyright &y& Elsevier]