Kjell Arne Mork

Institute of Marine Research in Norway | IMR · Research Group of Oceanography

Biogeochemical (BGC) Argo floats were used in this study to investigate phytoplankton blooms. We assessed the seasonal and annual rates of net primary and community production, along with respiration in the Norwegian Sea. The years 2020 and 2021 were contrasted to illuminate similarities and differences. In both years the onset of the bloom occurre...

As a part of regular monitoring of the marine environment, IMR conducts 10 fixed transects on a multiannual basis during which hydrographical, chemical and plankton data are collected at the same positions several times a year. The transect data sets, which in some cases span up to seven decades, have been vital to the understanding of long-term va...

CES Report on Ocean Climate (IROC) combines decades of ocean observations across the North Atlantic ICES regions to describe the current status of sea temperature, salinity, and atmospheric conditions, as well as observed trends and recent variability. Regional analyses are prepared by the local experts who are directly involved in the monitoring p...

This study investigates the large-scale distribution patterns of the acoustic scattering layers and micronekton density across the Northeast Atlantic Ocean during daylight hours. A research cruise on board R/V “Kronprins Haakon” was conducted during May 2019 from Cape Verde to Bay of Biscay. Hydrological data were obtained at 20 conductivity-temper...

The ICES Report on Ocean Climate (IROC) combines decades of ocean observations across the North Atlantic ICES regions to describe the current status of sea temperature, salinity, and atmospheric conditions, as well as observed trends and recent variability. The IROC production focuses the main efforts from ICES Working Group on Oceanic Hydrograph

The ocean climate of the southern Norwegian Sea - the Norwegian Basin - is largely set by the relative amount of Atlantic Water in the eastern and Arctic Water in the western region. Here we utilized hydrographic data from repeated sections, together with annually gridded survey data of the upper 1000 m, to resolve the main hydrographic changes ove...

The deep-pelagic ocean (waters deeper than 200 m) is the largest habitat by volume on Earth. It is necessary to increase our knowledge in the deep-pelagic ocean given its value in the provision of ecosystem services. Thus, meso- and bathypelagic fish were investigated (with reference to their diversity, density and biomass) in order to determine th...

Micronekton are an assemblage of small and diverse organisms (1–20 cm in size), which form a key trophic link between primary production and top predators. Many micronekton aggregate in the mesopelagic zone and can be observed as deep scattering layers (DSLs). Many of the organisms in these deep scattering layers conduct diel vertical migrations, a...

The presence of invasive species in the Mediterranean Sea is much higher than in other European seas, and understanding the reasons behind the range expansion of this invasive species is important for minimising any possible impacts to the already highly pressurised Mediterranean marine ecosystem. In this work, a brief description of sightings of t...

Summary: https://marine.copernicus.eu/news/ocean-state-report-5-summary-now-available Full report: https://www.tandfonline.com/doi/full/10.1080/1755876X.2021.1946240

The survival of Atlantic salmon (Salmo salar), an increasingly rare anadromous species, has declined dramatically during its marine phase, with disproportionate impacts on the poorly understood early post‐smolt period. Logistical constraints on collecting oceanic data to inform this issue pose a formidable obstacle. To advance understanding of post...

The report is a hearing document sent to the Ministry of Petroleum and Energy regarding a proposed program for environmental assessment connected to extraction of minerals on the Norwegian continental shelf areas. In the hearing document, Institute of Marine Research emphasize the extensive lack of knowledge, both with respect to biodiversity and e...

The influence of oceanographic variables on assemblages of meso- and bathypelagic fish was investigated along a Northeastern Atlantic Ocean transect (Cape Verde to the Bay of Biscay) during May 2019. Fish were collected using a mrozooplankton trawl during daylight hours at ten stations. Along the transect, 17 hydrographic stations were also perform...

ICES Report on Ocean Climate (IROC) provides summary information on climatic conditions in the North Atlantic. The full-text of IROC is available at http://doi.org/10.17895/ices.pub.7537.

ICES Report on Ocean Climate (IROC) provides summary information on climatic conditions in the North Atlantic. The full-text of IROC is available at https://doi.org/10.17895/ices.pub.5461.

The Argo Program has been implemented and sustained for almost two decades, as a global array of about 4000 profiling floats. Argo provides continuous observations of ocean temperature and salinity versus pressure, from the sea surface to 2000 dbar. The successful installation of the Argo array and its innovative data management system arose opport...

The Argo Program has been implemented and sustained for almost two decades, as a global array of about 4000 profiling floats. Argo provides continuous observations of ocean temperature and salinity versus pressure, from the sea surface to 2000 dbar. The successful installation of the Argo array and its innovative data management system arose opport...

Climate variability in the Norwegian Sea, comprising the Norwegian and Lofoten Basins, was investigated based upon monthly estimates of ocean heat and freshwater contents using data from Argo floats during 2002–18. Both local air–sea exchange and advective processes were examined and quantified for monthly to interannual time scales. In the recent...

The ICES (International Council for the Exploration of the Sea) Working Group on Oceanic Hydrography (WGOH) was established in the late 1970's with the aim of gathering experts in physical oceanography to provide regular science-based assessments of the North Atlantic hydrographical condition (basically termohaline fields). From the beginning, the...

ICES Report on Ocean Climate (IROC) provides summary information on climatic conditions in the North Atlantic. The full-text of IROC is available at http://doi.org/10.17895/ices.pub.4625.

This study investigates the distribution and abundance of mesopelagic organisms in relation to environmental and biological conditions. A multidisciplinary cruise was conducted on board the G.O. Sars during summer 2018 in the North-east Atlantic, east of the Reykjanes Ridge. During the cruise multiple methods were used to measure zooplankton and mi...

The Greenland Sea gyre is one of the few areas where the water column is ventilated through open ocean convection. This process brings both anthropogenic carbon and oxygen from the atmosphere and surface ocean into the deep ocean, and also makes the Greenland Sea gyre interesting in a global perspective. In this study, a combination of ship- and fl...

Wind observations during May–June 2009, 2010, 2011 and 2012 at Slåtterøy Lighthouse, adjacent to the North Sea, showing wind blowing from each direction divided in sectors of 30° and frequency distribution of wind speed in %. Data by the Norwegian Meteorological Institute.

Isopleth diagrams chlorophyll a (μg L− 1) (a, b), nitrite (μM) (c, d), nitrate (μM) (e, f), phosphate (μM) (g, h), and silicate (μM) (i, j) along the Fedje – Shetland section during 13–14 February 2010 (upper panels; a, c, e, g, i) and during 4–5 May 2010 (lower panel; b, d, f, h, j).

Examples of particles encountered in the Raunefjord at 5 m during 2010 and 2011. The images are obtained by scanning electron microscopy (SEM): (a) the diatom Arcocellulus cornucervis, (b) the diatom Chaetoceros sp., (c) lorica of tintinnid consisting mainly of coccoliths from Emiliania huxleyi and resting spores of Chaetoceros sp., (d) the diatom...

Different types of iron-Fe-sequestering bacteria from the Raunefjord at 5 m during 2010 and 2011. The images are obtained by scanning electron microscopy (SEM): (a) the iron encrusted appendages form wire-like twisted loops. The total lengths of the appendages were in the range of 100 to 400 μm, (b) cells were surrounded by 8 to 10 arms, forming a...

Protist composition at 5 m and 50 m in the Raunefjord during spring-early summer 2010. A relative quantification on a scale from 1 to 5 is also given, where 1 indicates lowest concentration and 5 the highest concentration.

The aim of this study was to reveal the relative content of C, N, Ca, Si, P, Mg, K, S and Fe in seston particles in Norwegian coastal water (NCW), and how it relates to biological and hydrographic processes during seasonal cycles from October 2009–March 2012. The following over all stoichiometric relationship for the time series was obtained: C66N1...

This chapter discusses past and ongoing change in the following physical variables within the North Sea: temperature, salinity and stratification; currents and circulation; mean sea level; and extreme sea levels. Also considered are carbon dioxide; pH and nutrients; oxygen; suspended particulate matter and turbidity; coastal erosion, sedimentation...

The North Atlantic spring bloom is a massive annual growth event of marine phytoplankton, tiny free-floating algae that form the base of the ocean's food web and generates a large fraction of the global primary production of organic matter. The conditions that trigger the onset of the spring bloom in the Nordic Seas, at the northern edge of the Nor...

The North Atlantic spring bloom is a massive annual growth event of marine phytoplankton, tiny free-floating algae that form the base of the ocean's food web and generates a large fraction of the global primary production of organic matter. The conditions that trigger the onset of the spring bloom in the Nordic Seas, at the northern edge of the Nor...

More than 90% of the heat energy accumulation in the climate system between 1971 and the present has been in the ocean. Thus, the ocean plays a crucial role in determining the climate of the planet. Observing the oceans is problematic even under the most favourable of conditions. Historically, shipboard ocean sampling has left vast expanses, partic...

The North Atlantic spring bloom is a massive annual growth event of marine phytoplankton, tiny free-floating algae that form the base of the ocean’s food web and generates a large fraction of the global primary production of organic matter. The conditions that trigger the onset of the spring bloom in the Nordic Seas, at the northern edge of the Nor...

Climate variability in the Norwegian Sea was investigated in terms of ocean heat and fresh water contents of Atlantic water above a reference surface, using hydrographic data during spring 1951–2010. The main processes acting on this variability were examined and then quantified. The area averaged water mass cooled and freshened, but a deepening of...

Despite its fundamental role in controlling the Earth's climate, present estimates of global organic carbon export to the deep sea are affected by relatively large uncertainties. These uncertainties are due to lack of observations as well as disagreement among methods and assumptions used to estimate carbon export. Complementary observations are th...

This manual presents a series of tests for QC procedures. The goal is to provide guidance to the U.S. IOOS and the wave community at large on an agreed-upon, documented, and implemented standard process. U.S. IOOS/QARTOD maintains a code repository (www.ioos.noaa.gov/qartod) where operators may find or post examples of code in use. Although certain...

Reddin, D. G., Hansen, L. P., Bakkestuen, V., Russell, I., White, J., Potter, E. C. E., Dempson, J. B., Sheehan, T. F., Ó Maoiléidigh, N., Smith, G. W., Isaksson, A., Jacobsen, J. A., Fowler, M., Mork, K. A., and Amiro, P. 2013. Distribution and biological characteristics of Atlantic salmon (Salmo salar) at Greenland based on the analysis of histor...

Jacobsen, J. A., Hansen, L. P., Bakkestuen, V., Halvorsen, R., Reddin, D. G., White, J., Ó Maoiléidigh, N., Russell, I.C., Potter, E. C. E., Fowler, M., Smith, G. W., Mork, K. A., Isaksson, A., Oskarsson, S., Karlsson, L., and Pedersen, S. 2012. Distribution by origin and sea age of Atlantic salmon (Salmo salar) in the sea around the Faroe Islands...

Mork, K. A., Gilbey, J., Hansen, L. P., Jensen, A. J., Jacobsen, J. A., Holm, M., Holst, J. C., Ó Maoiléidigh, N., Vikebø, F., McGinnity, P., Melle, W., Thomas, K., Verspoor, E., and Wennevik, V. 2012. Modelling the migration of post-smolt Atlantic salmon (Salmo salar) in the Northeast Atlantic. – ICES Journal of Marine Science, 69: 1616–1624. The...

Skagseth, Ø., and Mork, K. A. 2012. Heat content in the Norwegian Sea, 1995–2010. – ICES Journal of Marine Science, 69: 826–832. Spatio-temporal hydrographic data from the Nordic Seas during spring over the period 1995–2010 were investigated in terms of the relative heat content (RHC) above the density surface σt = 27.9, chosen to capture the chang...

Jensen, A. J., Ó Maoiléidigh, N., Thomas, K., Einarsson, S. M., Haugland, M., Erkinaro, J., Fiske, P., Friedland, K. D., Gudmundsdottir, A. K., Haantie, J., Holm, M., Holst, J. C., Jacobsen, J. A., Jensås, J. G., Kuusela, J., Melle, W., Mork, K. A., Wennevik, V., and Østborg, G. M. 2012. Age and fine-scale marine growth of Atlantic salmon post-smol...

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More synchronous growth was observed between close, than more distantly separated populations of Atlantic salmon (Salmo salar), during both the first and the second year at sea. The marine growth of seven Norwegian populations, located between 60N and 70N, were correlated with sea surface temperatures (SSTs) in the Barents Sea, the Norwegian Sea, a...

In this study, we quantified the mean flow and the variability in the Norwegian Atlantic Current (NwAC), including the individual branches, with associated error estimates. We accomplished this by combining repeated hydrographic data in the Svinøy section (at 62° N off the coast of Norway toward the northwest) with absolute dynamic sea surface topo...

The trajectories of 61 profiling Argo floats deployed at mid-depth in the Nordic Seas—the Greenland, Lofoten and Norwegian Basins and the Iceland Plateau—between 2001 and 2009 are analysed to determine the pattern, strength and variability of the regional circulation. The mid-depth circulation is strongly coupled with the structure of the bottom to...

The Norwegian Atlantic Current (NwAC) is the main part of Atlantic water (AW) towards the Arctic. Fluxes of volume, heat and freshwater in the NwAC are estimated for the period 1992–2007 by combining data from a repeated hydrographic transect in the Norwegian Sea with a recently available data set of absolute topography. The analysis shows a two-br...

In only 10 years, the Argo Program has grown from an idea into a functioning global observing system for the subsurface ocean. More than 3000 Argo floats now cover the world’s ocean. With these instruments operating on 10-day cycles, the array provides 9000 temperature/salinity/depth profiles every month that are quickly available via the Global Te...

In the Nordic seas, we combine a computation of absolute surface current flow derived from geodetic data with in situ historical hydrographic data to estimate the absolute volume, heat, and salt transports as a function of depth. Our mean dynamic topography (MDT) is calculated from marine, airborne and satellite gravimetry, combined with satellite...

Hydrographic time series in the northeast North Atlantic and Nordic Seas show that the freshening trend of the 1960s-1990s has completely reversed in the upper ocean. Since the 1990s temperature and salinity have rapidly increased in the Atlantic Inflow from the eastern subpolar gyre to the Fram Strait. In 2003-2006 salinity values reached the prev...

Project NISE (Norwegian Iceland Seas Experiment) is a cooperation between the three fisheries (and marine) research institutes in Iceland (MRI), Faroes (IFR), and Norway (IMR), Geophysical Institute (GFI) at the University of Bergen (Norway), and the Nansen Environmental and Remote Sensing Center (NERSC). Project NISE aims at revealing important cl...

The main aim of this paper has been to present a holistic view of the Atlantic water flow along the Norwegian Coast and into the Barents Sea. It has focused on the period starting in the mid-1990s, with simultaneous arrays of moored current meters in the Svinøy section and the Barents Sea Opening. These detailed measurements have provided the bases...

The Nordic Seas (Norwegian, Iceland and Greenland Seas) is one of the regions that have been best covered and continuously monitored with hydrographic observations. The view of the large-scale ocean circulation in the Nordic Seas has traditionally been based on hydrography due to the relatively few direct current measurements. It has been known for...

The first comprehensive description of physical conditions in the Norwegian - and the Barents Seas was provided by Helland-Hansen and Nansen (1909), who described both the two areas individually and the relationships between them. They indicated a 2-year delay in the temperature signal from Sognesjoen (west coast of Norway at about 61° N) to the Ru...

1] The variability of steric height in the Nordic Seas is analyzed on seasonal, interannual, and decadal timescales using a comprehensive data set of temperature and salinity observations for the second half of the twentieth century. Results from a regional Ocean General Circulation Model (OGCM) are used to assess the reliability of the averaging a...