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Many marine organisms have a permanent presence both inshore and offshore and spawn in multiple areas, yet their status as separate populations or stocks remain unclear. This is the situation for the northern shrimp (Pandalus borealis) around the Arctic Ocean, which in northern Norway represents an important income for a small-scale coastal fishery and a large-vessel offshore fleet. In Norwegian waters, we uncovered two distinct genetic clusters, viz. a Norwegian coastal and a Barents Sea cluster. Shrimps with a mixed heritage from the Norwegian coastal and the Barents Sea clusters, and genetically different from both, inhabit the fjords at the northernmost coast (Finnmark). Genetic structure between fjords did not display any general trend, and only the Varangerfjord in eastern Finnmark displayed significant genetic structure within the fjord. Shrimps in the Finnmark fjords differed in some degree from shrimps both in the adjacent Barents Sea and along the rest of the coast and should probably be considered a separate management unit. [ABSTRACT FROM AUTHOR]

Spawning of polar cod (Boreogadus saida) in the vicinity of the Svalbard archipelago has not been directly observed. From the distribution pattern of polar cod 0-group observed during annual monitoring of the Barents Sea, it has, however, been inferred that spawning occurs in Svalbard waters most years. We wanted to investigate the possibility of back-tracking the larvae from these observed distribution areas to the spawning areas from which they originated and applied a coupled ocean–sea ice and particle tracking model to simulate the drift of particles released at suggested spawning sites. The model was run for 1 year (December 2006–September 2007), and the results were compared to observations of polar cod larvae in the autumns of 2007 and 2004–2010. The particles released in the western fjords were mostly retained in the fjords. For the rest of the suggested spawning grounds, the released particles drifted mostly clockwise around the archipelago. Model runs mainly indicated a drift pattern with end points that qualitatively match the main features of the August–September distribution of the polar cod 0-group observed. We conclude that the suggested spawning sites on the southern, northern and eastern sides of Svalbard could have caused a distribution of 0-group polar cod similar to that observed during August–September 2007. From the environmental factors experienced during drift of eggs and larvae and assumptions about habitat suitability for survival and growth, we conclude that spawning in the Svalbard area probably occurs on the southern and eastern sides and later than the area in the southeastern Barents Sea. [ABSTRACT FROM AUTHOR]

Abstract Tidewater glaciers in Kongsfjorden, Svalbard, are retreating, and it is expected that they will terminate on land at some time in the future. Plumes, the submerged runoff emerging at the bases of tidewater glacier fronts, contribute to large-scale circulation within the inner fjord. A transition to a fjord with only land-terminating glaciers will affect the fjord circulation, with further implications for the biogeochemistry and ecosystem in Kongsfjorden. In this paper we compare the present and predicted future circulation using the ocean model system ROMS, and identify and quantify changes resulting from the altered forcing. Removal of subglacial discharge due to retreating tidewater glaciers causes substantial reduction of subsurface volume fluxes, and hence exchange rates, in the inner part of the fjord, and results in enhanced stratification during summer months. The increase in fjord extent due to tidewater glacier retreat results in a slight increase in tidal velocities, in particular overtide components, but this effect is not strong enough to compensate for the reduction in current velocities due to removal of freshwater plumes at glacier fronts. The freshwater content (practical salinity < 34.8) in the fjord during the melting season is predicted to increase in the future, primarily due to enhanced retention of freshwater in the inner parts of the fjord. However, freshwater in the future will mostly be confined to a relatively thin surface layer whereas at present freshwater is found in a thicker layer, in particular in the proximity of the tidewater glacier fronts. [ABSTRACT FROM AUTHOR]

The abundance of salmon lice in the Hardangerfjord is potentially large enough to be a threat to the wild fish stocks of the fjord. The salmon louse spends a period of 2–4 weeks in its planktonic stages drifting in the current of the upper water masses of the fjord looking for suitable hosts on which to settle. It is important to assess the abundance and distribution of the lice in their planktonic phases in order to evaluate the infection pressure they represent to the wild fish. The current system of the upper water masses in the Hardangerfjord is highly variable and consists of a multitude of components. This implicates a similar variability of the salmon lice dispersion. We find the most efficient transport mechanism for planktonic salmon lice to be from internal pressure due to lateral variations of the water mass density. From current observations we find large water exchanges of the upper water masses in the fjord lasting for several days, approximately monthly. Numerical model results indicate that these exchange episodes extend for the whole length of the fjord. Hence, the salmon lice will be regularly transported several tens of kilometres. We find the influence area of salmon lice from a source to be potentially large as a small number of lice can cover large areas. However, the majority of the lice will stay relatively close to the source but not necessarily with the highest abundance in the source area. We also find aggregations of lice in certain areas, typically close to land and in bays. [ABSTRACT FROM PUBLISHER]

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. Image 1 • New evaluation method for comparison of fjord models and current measurements. • Applied for high resolution simulations and measurements in the Hardangerfjord. • Model performs well >60% of the time for the seasons and depths studied. [ABSTRACT FROM AUTHOR]

Many Arctic glaciers extend into fjords or coastal waters, and their fronts can extend severalhundred meters below the sea surface. Meltwater runoff from such marine terminating or tidewater glaciers often enters the sea near the sea bed, and then rapidly rise towards the surface due to having lower density than the ambient sea water. The discharge of meltwater tends to be concentrated at a few locations along the glacier front, creating distinct plume structures where large volumes of meltwater turbulently mix with sea water, thereby inducing strong vertical and lateral exchanges that plays a prominent role in the overall fjord circulation.Tidewater glaciers in Kongsfjorden, Svalbard, are steadily retreating, in one case (Kronebreen) by 11km over the last 150 years, and will become land terminating at some time in the future if the trend continues. We investigate the impact that this transition will have on the general fjord circulation by comparing the present day circulation and predicted future circulation in the fjord using the ocean model system ROMS. The model setup for the present day Kongsfjorden area is based on a model grid with 160m horizontal resolution and 35 vertical S-coordinates. Atmospheric forcing is provided by 3km WRF data, climatology at lateral open boundaries is provided by a larger domain 800m resolution ROMS model, and fresh water discharges are provided by SnowModel output, where discharge from 3 tidewater glaciers are treated as subglacial sources. A coastline for the future scenario has been constructed based on ice-penetrating radar data. Setup for the future scenario is identical to the present day case, except for the new coastline configuration and associated location of fresh water discharge sources.Our study found that the removal of tidewater glaciers causes a substantial reduction in volume fluxes across transects in the inner part of the fjord, and results in an increased stratification during the summer months. The increase in fjord extent landward due to removal of tidewater glaciers resulted in a slight increase in tidal velocities, in particular for overtide components, but this effect was not strong enough to compensate for the removal of fresh water plumes at tidewater glacier fronts. Fresh water content (salinity < 34.8) in the fjord during the melting season is predicted to increase in the future, primarily due to enhanced retention of fresh water in the inner parts of the fjord. However, fresh water in the future will mostly be confined to a thin surface layer whereas at present fresh water is found in a thicker layer, in particularly near tidewater glacier fronts. [ABSTRACT FROM AUTHOR]

This study investigates the effect of surface currents on wind-generated waves in a complex coastal system with narrow fjords. The simulations are based on a phase-averaged wave model forced with surface currents from a high-resolution coastal ocean and fjord circulation model, and high-resolution winds from a nested atmospheric model. Wave simulations with and without ocean forcing are evaluated by comparing integrated wave parameters and modelled spectra with observations from five wave buoys. The comparison covers three winter seasons (2017–2020) and a case study. The wind sea part of the spectrum is better simulated at all locations when using the current forcing. At the most sheltered location, where wind sea dominated the wave climate, the wave height estimates improved by 12 percentage points when including current forcing. Spectral moments and the shape of the average spectra are also improved at most of the locations when current forcing is applied. The effect of wave–current interactions was found to be more pronounced at inner locations where the relative difference of spectral bandwidth is up 5%, the difference in directional spreading is greater than 5 degrees during strong surface currents, and the relative difference in peak frequency is exceeding 10%. Our results are consequential for narrow, deep and sheltered water bodies, but are not expected to carry over to shallow water areas. • Wave simulations at inner fjords significantly improve by using the ocean forcing. • Ocean forcing improves the simulations of the wind sea at exposed locations. • Ocean forcing changes the spectral bandwidth and directional spreading. [ABSTRACT FROM AUTHOR]