Summertime M2 Internal Tides in the Northern Yellow Sea

The summertime M2 internal tide in the northern Yellow Sea is investigated with moored current meter observations and numerical current model results. The hydrodynamic model, which is implemented from the Regional Ocean Model System (ROMS) with 1 km horizontal resolution, is capable of resolving the internal tidal dynamics and the results are validated in a comparison with observations. The vertical pattern of a mode-1, semi-diurnal internal tide is clearly captured by the moored ADCP as well as in the simulation results. Spectral analysis of the current results shows that the M2 internal tide is dominant in the northern Yellow Sea. Analysis of the major M2 internal tide energetics demonstrated a complex spatial pattern. The tidal mixing front along the Korean coast and on the northern shelf provided proper conditions for the generation and propagation of the internal tides. Near the Changshan islands, the M2 internal tide is mainly generated near the local topography anomalies with relatively strong current magnitude, equal to about 30% of the barotropic component, thus modifying the local current field. These local internal tides are short-lived phenomena rapidly being dissipated along the propagation pathway, restricting their influence within a few kilometers around the islands.publishedVersio

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

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

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

Rapid water temperature variations at the northern shelf of the Yellow Sea

During summer, there is great spatial variability in bottom water temperature on the northern shelf of the Yellow Sea. This variability is associated with a thermal front along the shelf. Oscillatory currents from semidiurnal and fortnightly period tides transport water masses laterally, resulting in oscillations of bottom water temperature at fixed positions, sometimes with large amplitudes. Temperature variations, as demonstrated in the present work, can cause damage to bottom-cultured scallops. In particular, in the scallop sea ranching area near Zhangzidao Island, such oscillations are evident in late summer. We constructed a spatial index of aggregated temperature variability from current model results identifying how temporal variability during the summer period varies in space. This information can be useful both in selecting favorable ranching areas and designing laboratory stress experiments on aquaculture candidate species.publishedVersio

Description and validation of a three-dimensional numerical model of the nordic and Barents Seas

As a part of the VEINS project, IMR carries out both a numerical model study of the seasonal and interannual variability of the flow through the Barents Sea and an observational programme at the Bear Island-Fugløya section. A numerical simulation with realistic wind forcing covering the period November 1996 to April 1998 has been performed, and the results of this simulation are compared to observations. The numerical ocean model results are generally in reasonable agreement with the observations, and the simulated transports across the Bear Island-Fugløya section are in accordance with previous knowledge. A weakness of the present version of the model is the lack of ice modelling, and the model performance in areas of ice formation and strong thermodynarnical forcing is unsatisfying. However, after a scheduled inclusion of an ice model, the model performance is expected to improve significantly in the Barents Sea

Transport of Atlantic Water in the western Barents Sea

Measurements from an array of current meter moorings along a section between Norway and Bear Island indicate that the seasonal mean of inflowing Atlantic Water extends further to the north during the summer than during the winter. To further investigate this seasonal divergence and the transport routes of Atlantic Water in the western Barents Sea, numerical experiments of tracer advection have been performed. The numerical results agree with the observations by showing a more northerly transport route of tracer water masses in the western Barents Sea during summer. The tracer water masses originate in the core of the Atlantic Water inflow at the Norway-Bear Island section, thus represents an indication of the transport routes of the Atlantic Water. The main reason for this change from summer to winter is probably the seasonal changes in the atmospheric fields

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

Fysisk oseanografiske forhold i produksjonsområdene for akvakultur

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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