Nearshore Wave Modelling in a Norwegian Fjord

Phase averaged wave models is a good supplement of in situ measurements for the study of wave climate in a specific location. In spite of having been tested in smoothly varying coastal areas, they haven’t previously been systematically validated in complex topography (coastline and bathymetry) such as Norwegian fjords, due to lack of measurements. However, in planning for large fjord crossings, the Norwegian Public Roads Administration have launched a number of buoys which allow for validation of model setup. In the present work, nearshore wave conditions in the area of Sulafjord, central Norway, are investigated as derived from numerical modelling with several different setups, and are compared against in situ buoy measurements with good accordance. The analysis is carried out by transferring offshore wave conditions to the nearshore area by successive applications of the well-known third-generation wave model SWAN. As input has been used a very detailed bathymetry of the area, and time series of wind and wave parameters derived from ERA5 and NORA10 datasets. Various scenarios reconstructing the wave input spectra have been considered.

Sediment budget in a recently glaciated western Norwegian fjord

<p>Western Norwegian fjord-valley systems represent archives of changes in sedimentary processes, and typically exhibit a pronounced change in depositional environment related to the transition from glacial to interglacial conditions. During a glacial situation, the fjord-valley system is emptied of its sediments, indicating that most sediments present in the fjord today, was deposited during and after the retreat of the last deglaciation. The purpose of our investigations is to gain a better understanding of the volumes and frequencies of mass transport deposits (subaquatic mass movements such as mass flows, debris flows, slides, slumps, and turbidites) in a recently glaciated fjord-valley system since the deglaciation (approx. 11 700 years BP) by looking at Fjærlandsfjorden, a tributary fjord of Sognefjorden in western Norway. The fjord-valley system consists of steep hillslopes and deep fjord basins with reliefs of up to 1600 meters. Jostedalsbreen, the largest glacier on mainland Europe (ca. 473 km<sup>2</sup>), currently feeds into the catchment of the fjord basin.</p><p>Here we present results from a cruise with R/V G.O. Sars in 2018, where sediment cores, TOPAS seismic profiles and bathymetric data were collected from Fjærlandsfjorden. The integration of high-resolution seismic (<30 cm vertical resolution) and bathymetry (3-5 m resolution) allows us to estimate the total volume of sediments within a fjord setting. By revealing when and how the sediments are deposited, we can establish sedimentation rates with a high spatial and temporal resolution within the fjord basin. X-ray Computed Tomography (CT-scanning) has been particularly useful to characterize sedimentary deposits as it allows for 3D visualization and analysis with ultra-high-resolution (50 μm voxel size) allowing us to see individual silt-sized grains in the sediment cores.</p><p>Seismic data reveal that the Fjærlandsfjorden basin infill consists of basal till, overlain by a thick, acoustically well-laminated glacimarine unit (up to a maximum thickness of ~105 meters thickness), occasionally disrupted by acoustically transparent lenses interpreted to be mass transport deposits (rock avalanches and debris flows). A 2-3 m thick hemipelagic unit drapes the glacimarine unit. Results reveal that ~90 % of the total sediment volume within the fjord basins was deposited as meltwater plumes during the retreat (mainly calving along the fjord) of the margin of the last glacial ice sheet. The retreat began at the mouth of Sognefjorden at the termination of the Younger Dryas Chronozone around 11 700 cal. yrs BP, to a frontal position at the head of Fjærlandsfjorden around 10 700 cal. yrs BP. The remaining volume of sediments are divided into mass transport deposits (MTDs) such as avalanches, debris flows, and flood-related turbidites as well as hemipelagic sedimentation. The largest MTD is a massive rock avalanche measuring up to 5 million m<sup>3</sup> that most likely caused a large tsunami when it occurred.</p>

Prediction of the salmon lice infestation pressure in a Norwegian fjord

A further growth in the Norwegian aquaculture industry might potentially be hampered by the conclusion that it is not environmentally sustainable. As direct measurements of the lice induced mortality on wild salmonids are impossible, the management is based on a set of high-quality and well-documented sustainability indicators. These indicators combine observations from the national Norwegian salmon lice monitoring programme with salmon lice models. Here, we have documented the quality of one of these models used to identify areas where the impact from farmed to wild salmonids is over the prescribed limit. The Hardangerfjord area has been used as a test area, but the model is general and, therefore, suitable for the rest of the coast. It is shown that the model system is robust and also can be used to test whether new knowledge gained from laboratory experiments improves the model. New findings on salmon lice behaviour at low salinities have been incorporated and the new model, consisting of a high-resolution hydrodynamic model coupled with an individual-based salmon lice model and forced with realistic input of salmon lice larvae from aquaculture farms, represents the best realization of the local potential infestation pressure on wild fish.

Investigating microsized anthropogenic particles in Norwegian fjords using opportunistic nondisruptive sampling

Norwegian fjord systems provide a host of ecosystem services and are important for recreational and industrial use. The biodiversity of Norwegian fjords has been—and still is—extensively studied since they are important for fishing and aquaculture industries. However, threats from plastic and microplastic pollution within the fjord systems are largely undocumented. Monitoring efforts of microplastic in Norway are limited to coastal biota monitoring, offshore sediments, and some investigations within Oslofjord. Here, we quantify anthropogenic microparticles in Norwegian fjord subsurface waters, including an analysis of distribution effects. Fifty-two samples were collected during repeated transits from Bergen to Masfjorden covering 250 km. Anthropogenic particles were identified in 89% of samples, with an average abundance within the fjord estimated to be 1.9 particles m−3. This report shows the ubiquitous nature of anthropogenic particles in the subsurface waters of a Norwegian Fjord system. Additionally, methods were validated for opportunistic nondisruptive sampling on-board vessels where microplastics are seldom monitored, including research vessels, commercial freight and transport, and recreational vessels. Further development and implementation of these methods in terms of sampling, chemical characterisation, and long-term monitoring will allow for microplastic quantification and can be easily adapted for worldwide implementation.

Fecundity and early life of the deep-water jellyfish Periphylla periphylla

Comparisons over 6 years of three Norwegian fjord populations of the deep-water scyphomedusa Periphylla periphylla are presented. A minor part of the population in Lurefjord is migrating to the surface during night, which benefits mating encounters by increasing abundance per unit volume and decreasing the distance between individuals. Simulations using a typical water-column density profile and Stoke’s law show that fertilized eggs released in the surface quickly reach a depth where light is insufficient for visual predators. Consequently, the distribution of the smallest juveniles was strongly skewed towards higher depths in all three fjords studied. Mature females in Sognefjord were 4–5 times less abundant than in Lurefjord and Halsafjord, but due to a larger size and strong exponential relationship between size and number of mature oocytes, the potential recruitment rate as recruits m−2 year−1 was not much different from the other two fjords. Nevertheless, the observed number of small (<1 cm) juveniles was 18–31 times higher in Sognefjord than in the other two fjords, and it is assumed that the deeper habitat (up to 1300 m) compared to the other fjords (up to 440 and 530 m) is a superior habitat for the early development of P. periphylla.