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We evaluate changes in dissolved inorganic carbon (DIC) in the Greenland Sea between 2002 and 2016, a period characterized by increasing convection depths. We find a mid‐depth maximum in anthropogenic carbon (Cant) accumulation that occurred as waters at these depths were rejuvenated by deeper reaching convection; broadly, these waters have caught up with the atmospheric CO2 rise that had happened between the last time they were ventilated and 2002 and also tracked the atmospheric CO2 rise 2002–2016. The overlying waters only tracked the atmospheric CO2 rise 2002–2016. The mid‐depth maximum in Cant accumulation was not evident in estimates generated with commonly used multiple linear regression (MLR) methods. We analyze the reasons why and show that the eMLR(C*) method may not fully capture nonsteady state changes in Cant when applied along a single hydrographic section as done here. This nonsteady component equates to redistribution of C*, whose spatial gradients in the Greenland Sea are dominated by Cant. We also show that the regular extended multiple linear regression method is sensitive to loss of spatial DIC gradients, which now happens as more and more Cant enters the ocean. Our findings demonstrate that MLR‐based estimates of the Cant accumulation rate should not be taken at face value in highly dynamical ocean regions, such as the Greenland Sea, and the need for also considering the total change in DIC and how this is affected by natural processes. Further investigations into the ability of MLR methods to reproduce nonsteady state changes in Cant are encouraged. Plain Language Summary: The ocean holds vast quantities of carbon. Each year this inventory increases as the ocean absorbs a quarter of our CO2 emissions. Keeping track of ocean carbon is a key climate change research priority. Observations from the Greenland Sea indicate at first glance a steady rise in DIC concentrations in the upper approximately 1,500–2,000 m of the water column, roughly equal to what one would expect from the atmospheric CO2 rise. This is unusually deep compared to the rest of the global ocean but reflects the deep‐water formation that occurs in this region. A closer inspection of the data, however, reveals that the seemingly uneventful rise in carbon in this region is the net result of several counteracting processes. In response to deeper convection, mid‐depth waters have lost inorganic carbon generated by the remineralization of organic matter, natural carbon. This has been counteracted by an unusually large rise in their content of man‐made, or anthropogenic carbon. Widely adopted methods for estimating decadal rises in anthropogenic carbon struggle to quantify these changes, such that our ability to detect the nature of effects of climate variability and change on the efficiency of the ocean carbon sink can be questioned. Key Points: Deeper convection caused a mid‐depth maximum in the rate of anthropogenic carbon increase in the Greenland Sea from 2002 to 2016The mid‐depth maximum in anthropogenic carbon accumulation was not evident in estimates generated with multiple linear regression methodsNonsteady state anthropogenic carbon accumulation may bias the eMLR(C*) method when applied along a single hydrographic section [ABSTRACT FROM AUTHOR]

The North Sea is one of the busiest and most exploited marine areas on Earth and is home to many highly migratory and economically important species. At the northern boundary, a 300‐km corridor between Norway and Shetland forms a major egress point from the North Sea to the Norwegian Sea and broader Atlantic Ocean, which is known to be used by many focal species including Atlantic salmon, European eel, European sturgeon, Atlantic bluefin tuna, basking shark, Atlantic mackerel, spiny dogfish, among others. We argue that this relatively shallow 300‐km corridor is a critical area for ecological and oceanographic research in the North Sea to understand species distribution, migratory patterns, responses to climate, fisheries, and more. Instrumentation of the Bergen‐Shetland Corridor with a line of oceanographic and biological tracking infrastructure would help capture the spatiotemporal dynamics of the ocean and its major fauna between the North Sea and Norwegian Sea, a boundary between management areas from ICES and OSPAR. [ABSTRACT FROM AUTHOR]

The effect of submarine carbon dioxide (CO2) vents on seawater carbonate chemistry have been determined using hydrographical and marine carbonate data obtained from two submarine hydrothermal vent fields, as well as a reference station, all near the Jan Mayen Island in the Norwegian-Greenland Sea. We have shown that one can successfully determine the excess carbon that enters the seawater from the vents by applying a modified version of a back-calculation technique, which is traditionally used to study the invasion of excess atmospheric CO2 in the surface ocean. As a result of this excess carbon, total dissolved inorganic carbon ( CT) in the seawater surrounding the vents was on average 12 μmol kg−1 (1-30 μmol kg−1) higher compared to samples obtained from a reference station outside the venting areas. The observed excess CT was most significant between 100 m and 200 m but was noticeable in all depths with the exception of the upper 10-20 m. The absence of a venting CO2 signal in the surface water and the realism of the results are discussed. We believe the present method is promising for monitoring (detection and quantification) of CO2 leakage into the water column due to its high sensitivity and readiness for automation. [ABSTRACT FROM AUTHOR]

A carbon budget for the Nordic Seas is derived by combining recent inorganic carbon data from the CARINA database with relevant volume transports. Values of organic carbon in the Nordic Seas' water masses, the amount of carbon input from river runoff, and the removal through sediment burial are taken from the literature. The largest source of carbon to the Nordic Seas is the Atlantic Water that enters the area across the Greenland-Scotland Ridge; this is in particular true for the anthropogenic CO2 . The dense overflows into the deep North Atlantic are the main sinks of carbon from the Nordic Seas. The budget show that presently 12.3 ± 1.4 Gt C yr-1 is transported into the Nordic Seas and that 12.5 ± 0.9 Gt C yr-1 is transported out, resulting in a net advective carbon transport Out of the Nordic Seas of 0.17 ± 0.06 Gt C yr-1 . Taking storage into account, this implies a net air-to-sea CO2 transfer of 0.19 ± 0.06 Gt C yr-1 into the Nordic Seas. The horizontal transport of carbon through the Nordic Seas is thus approximately two orders of magnitude larger than the CO2 uptake from the atmosphere. No difference in CO2 uptake was found between 2002 and the preindustrial period, but the net advective export of carbon from the Nordic Seas is smaller at present due to the accumulation of anthropogenic CO2. [ABSTRACT FROM AUTHOR]

This study evaluates the anthropogenic changes of CO2 (ΔCant) and δ13C (Δδ13Cant) in the Nordic seas, the northern limb of the Atlantic Meridional Overturning Circulation, that took place between 1981 and 2002/2003. The changes have been determined by comparing data obtained during the Transient Tracers in the Ocean, North Atlantic Study (TTO-NAS) with data obtained during the Nordic seas surveys of R/V Knorr in 2002 and R/V G.O. Sars in 2003 using an extended multilinear regression approach. The estimated Δδ13Cant and ΔCant and their relationship to each other and to water mass distribution suggest that the Polar Water entering the Nordic seas from the north is undersaturated with respect to the present atmospheric anthropogenic CO2 levels and promotes a local uptake of Cant within the Nordic seas. In contrast, the Atlantic Water entering from the south appears equilibrated. It carries with it anthropogenic carbon which will be sequestered at depth as the water overturns. This preequilibration leaves no room for further uptake of Cant in the parts of the Nordic seas dominated by Atlantic Water. The upper ocean pCO2 in these regions appears to have increased at a greater rate than the atmospheric pCO2 over the last 2 decades; this is reconcilable with a large lateral advective supply of Cant. [ABSTRACT FROM AUTHOR]

Reports on the design and construction of an optical instrumentation system by which fine-scale vertical displacements of microalgae can be studied in artificial water column without influencing fine physical, chemical and biological structures of the water column; Examination of the fine-behavioral responses of microalgae to vertical gradients in environmental parameters.