Discussion/comments regarding “Trends in<Emphasis Type="Italic"> p</Emphasis>CO<Subscript>2</Subscript> and sea–air CO<Subscript>2</Subscript> flux over the global open oceans for the last two decades” by Y. Iida,A. Kojima,Y. Takatani,T. Nakano,H. Sugimoto,T. Midorikawa,M. Ishii

A paper by Iida et al. that was recently published in this journal (J Oceanogr 17:637–661, 2015) presented trends in the partial pressure of carbon dioxide in surface seawater and the estimated sea–air carbon dioxide flux over the global open oceans for the last two decades. The purpose of the present discussion is to demonstrate that the formula used by Iida et al. in their assessments can also be employed to estimate the sea–air carbon dioxide flux based on long-term wind statistics, i.e., based on data showing how the mean wind speed 10 m above the sea surface has varied over a long period. Examples of the application of this approach are given here, based on long-term wind statistics for the northern North Sea and the North West Shelf of Australia.     

A coupled ice–ocean model for the Greenland,Iceland and Norwegian Seas

Simulations from a coupled ice–ocean model that highlight the importance of synoptic forcing on sea-ice dynamics are described. The ocean model is a non-hydrostatic primitive equation model coupled to a dynamic thermodynamic sea ice model. The ice modelling sensitivity study presented here is part of an ongoing research programme to define the role played by sea ice in the energy balance of the Greenland Sea. The different categories of sea ice found in the subpolar regions are simulated through the use of equations for thin ice, thick ice and the Marginal Ice Zone. A basin scale numerical model of the Greenland, Iceland and Norwegian Seas has a horizontal resolution of 20 km and a vertical grid spacing of 50 m. This resolution is adequate for resolving the mesoscale topographic structures known to control the circulation in this region. The spin-up reproduces the main features of the circulation, including the cyclonic gyres in the Norwegian and Greenland Basins and Iceland Plateau. Topographic steering of the flow is evident. The baroclinic Rossby radius of deformation is between 5 and 10 km so that the model is not eddy-resolving. The coupled ice–ocean model was run for a period of two weeks. The influence of horizontal resolution of the atmospheric model was tested by comparing simulations using six hourly wind fields from the ECMWF with those generated using six hourly fields from a HIRLAM, with horizontal resolutions of 1° and 0.18° respectively. The simulations show reasonable agreement with satellite ice compactness data and data of ice transports across sections at 79°N, 75°N and Denmark Strait.     

Biooptical characteristics of the surface layer of the Baltic,Norwegian, and Barents seas in summer 2014–2016 from shipboard and satellite data

The article presents the results of shipboard and satellite measurements in the surface layer of the Baltic, Norwegian, and Barents seas during legs from the Baltic to the White Sea in June–August 2014–2016. Special attention is paid to marine phytoplankton blooms of cyanobacteria in the Baltic Sea and coccolithophores in the Barents Sea. No blooms were found in the Norwegian Sea. The efficiency of combined application of in situ and satellite optical methods for studying the parameters of phytoplankton blooms is shown.     

Seep carbonate formation controlled by hydrothermal vent complexes: a case study from the Vøring Basin, the Norwegian Sea

Several hundred hydrothermal vent complexes were formed in the Vøring Basin as a consequence of magmatic sill emplacement in the late Palaeocene. The 6607/12-1 exploration well was drilled through a 220-m-thick sequence of Eocene–Miocene diatomites with carbonate nodules above the apex of one of these vent complexes. Analysed calcites and dolomites from this interval have isotopic signatures typical for methane seep carbonates, with low ¹³C signatures of –28 to –54 PDB. The data suggest that the vent complex acted as a fluid migration pathway for about 50×10⁶ years after its formation, leading to near-surface microbial activity and seep carbonate formation.