NorKyst-800: A high-resolution coastal ocean circulation model for Norway

ECM12, Twelth International Conference on Estuarine and Coastal Modeling, St Augustine, Florida, 7-9 November 201

New validation method for hydrodynamic fjord models applied in the Hardangerfjord, Norway

We introduce a new intuitive evaluation method for comparison of fjord model results and current measurements. The approach is tested using high resolution model simulations and measurements in the Hardangerfjord, a large fjord system in Norway with huge aquaculture production. The method is easy to interpret, clearly distinguishes periods with good and poor model performance, and relate them to physical driving forces. This makes it possible to identify potential shortcomings in the models’ representation of physical processes. The applied model mostly performs well in the Hardangerfjord. Good performance often coincides with strong local fjord forcing (i.e. strong winds in the fjord). In periods with poor model performance, internal waves induced by pressure perturbations on the coastal shelf tend to propagate erroneously into the fjord. Stratification biases in coastal waters, connected to the applied model boundary conditions, seems to be an important cause. Demonstrated flexibility of time frame and performance criteria suggests applicability of the validation method for a wide set of geophysical variables in various physical environments.publishedVersio

Fysisk oseanografiske forhold i produksjonsområdene for akvakultur - Oppdatering september 2020

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The coastal model NorKyst-800 – a model of the currents along the whole Norwegian coast

Kystmodellen NorKyst-800 er en beregningsmodell som simulerer bl.a. strøm, saltholdighet og temperatur med 800 meters romlig oppløsning og med høy oppløsning i tid for hele norskekysten. NorKyst-800 er utviklet på Havforskningsinstituttet i samarbeid med Meteorologisk institutt og Niva. :: The coastal model NorKyst-800 is a computer model that simulates variables such as currents, salinity and temperature along the whole Norwegian coast, at an 800 metre spatial resolution and at high temporal resolution. NorKyst-800 has been developed by the Institute of Marine Research, in collaboration with the Norwegian Meteorological Institute and NIVA

Hvilken betydning har oppløsning for kyst- og fjordmodeller? - Validering og representasjonsberegninger av strømmodeller med eksempler fra Sulafjorden, Møre og Romsdal

Strømmodeller er nyttige verktøy som kan brukes til å beskrive det fysiske miljøet i havet og i kystsonen. Havforskningsinstituttet (HI) bruker resultater fra slike modeller i svært mye av den forskningen og rådgivningen som foregår. For kyst- og fjordområdene er det NorKyst800 (NK800) som er arbeidshesten, og dette modellsystemet er hovedsakelig utviklet av Havforskningsinstituttet og Meteorologisk institutt. Denne modellen har en gitteroppløsning på 800 m. HI har dessuten utviklet et modellsystem parallelt med NK800 som kalles NorFjords160, og dette består av fjordmodeller med fem ganger bedre oppløsning. NorFjords160 er ment for applikasjoner som skal beskrive det fysiske miljøet i fjordområder der farvannene er for smale og trange til at NorKyst800 er egnet.publishedVersio

Cod at drift in the North Sea

There has been a large-scale geographical re-distribution of the North Sea cod stock over the past century, and recent surveys indicate a north-eastern modal distribution. Here we assess the consequences of the contemporary distribution of North Sea cod (Gadus morhua) spawning biomass to inter-ocean recruitment potential. By simulations of drifting cod eggs and larvae spawned in the northern North Sea over 16 spawning seasons (in the period 1995–2016), we show that a large portion of the North Sea produced pelagic juveniles most likely settle along the Norwegian Sea shelf. For example during the early 2000s when the North Sea cod spawning biomass was at its lowest, 20% to 27% of larvae produced in the northern North Sea most likely settled along the Norwegian Sea shelf, while as few as 8% and 10% were retained within the North Sea in some years. We hypothesise the spillover of North Sea cod into nursery habitat along the Norwegian north-western coast to be beneficial to the stock, as larvae would encounter far higher abundances of their favoured prey, the copepod Calanus finmarchicus. Looking back at a century of overfishing, warming, and variable nursery conditions for cod in the North Sea, getting entrained in the Norwegian coastal current seems like a viable “back-door exit” strategy, allowing the north-eastern spawning cod to thrive even in seemingly adverse climatic periods.publishedVersio

Fysisk oseanografiske forhold i produksjonsområdene for akvakultur

publishedVersio

Fysisk oseanografiske forhold i produksjonsområdene for akvakultur - oppdatering september 2019

Rapporten beskriver det fysiske miljøet med fokus på vanntemperatur og saltholdighet, sistnevnte gjennom tidsserier av modellert overflatesaltholdighet og ferskvannsavrenning for perioden 2012-2019. Sjøtemperatur påvirker lakselusas vekst og utviklingshastighet, mens ferskvannspåvirkning indikerer i hvilken grad villfisk beskyttes gjennom et utviklet brakkvannslag. Rapporten er Appendiks III til hovedrapporten om "Vurdering av lakseindusert dødelighet per produksjonsområde i 2019".publishedVersio

Modeling the Distribution of Habitat-Forming, Deep-Sea Sponges in the Barents Sea: The Value of Data

The use of species occurrence as a proxy for habitat type is widespread, probably because it allows the use of species distribution modeling (SDM) to cost-effectively map the distribution of e.g., vulnerable marine ecosystems. We have modeled the distribution of epibenthic megafaunal taxa typical of soft-bottom, Deep-Sea Sponge Aggregations (DSSAs), i.e., “indicators,” to discover where in the Barents Sea region this habitat is likely to occur. The following taxa were collectively modeled: Hexadella cf. dedritifera, Geodia spp., Steletta sp., Stryphnus sp. The data were extracted from MarVid, the video database for the Marine AREAl database for NOrwegian waters (MAREANO). We ask whether modeling density data may be more beneficial than presence/absence data, and whether using this list of indicator species is enough to locate the target habitat. We use conditional inference forests to make predictions of probability of presence of any of the target sponges, and total density of all target sponges, for an area covering a large portion of the Norwegian Barents Sea and well beyond the data’s spatial range. The density models explain 0.88), depending on the variables/samples used to train the model. The predicted surfaces were then classified on the basis of a probability threshold (0.75) and a density threshold (13 n/100 m2) to obtain polygons of “core area” and “hotspots” respectively (zones). The DSSA core area comprises two main regions: the Egga shelf break/Tromsøflaket area, and the shelf break southwest of Røst bank in the Træna trench. Four hotspots are detected within this core area. Zones are evaluated in the light of whole-community data which have been summarized as taxon richness and density of all megafauna. Total megafaunal density was significantly higher inside the hotspots relative to the background. Richness was not different between zones. Hotspots appeared different to one another in their richness and species composition although no tests were possible. We make the case that the effectiveness of the indicator species approach for conservation planning rests on the availability of density data on the target species, and data on co-occurring species.publishedVersio