Deep-water aeration and the Barents Sea ecosystem renewal: Natural regulation of the Northeast Arctic cod recruitment

Abstract

For the bottom water of the Kola Section (70° 30′ − 72° 30′ N, 33° 30′ E, 215–280 m), located in the central Barents Sea, we studied the continuous series of oxygen saturation for 1957–2017. Changes in the oxygen saturation are directly related to the volume of the Atlantic Water flow to the western Barents Sea. The oxygen saturation of the bottom waters has fallen by 1–3% over the past 60 years, mainly during the period of climate warming. The lowest (71–83% saturation) oxygen content in the bottom waters of the eastern Barents Sea troughs corresponds to their approximate age of 12–16 years as estimated by tritium water dating. The study identified a strong correlation between the oxygen saturation and the recruitment of the North-East Arctic cod used by ICES Arctic Fisheries Working Group to produce long-term stock forecasts. Optimal environmental conditions for NEA cod recruitment emerge during periods of increasing oxygen saturation (aeration) of bottom waters, which is associated with the outflow of dense Barents Sea Waters into the Arctic basin and their replacement with Atlantic Waters. The impact of oxygen saturation on cod recruitment is compared for the Baltic and Barents Seas.