Density driven currents in the Barents Sea calculated by a numerical model

A baroclinic, 3-D model is described. It is adapted to a Barents Sea situation in order to simulate the currents in this area. The model is of a so-called level type which contains fixed, but permeable levels. It also includes thermodynamics which allow freezing and melting of ice. Using density data obtained during the autumn 1988, a current pattern, driven by density and bottom topography is simulated. No wind is applied. The simulated current pattern gives an overall picture which is similar to what is observed through the few measurements that are available. Good agreements with the observations is found on the Svalbard bank, Tromsøflaket and along the Nowaya Zemlya Coast. In the Bear Island/Hopen depth the model predicts a large eddy which has not been observed. Several smaller, topographical steared eddies are seen in the eastern part of the model area

Physical constrains and productivity in the future Arctic Ocean

Published version. Also available at http://dx.doi.org/10.3389/fmars.2015.00085Today's physical oceanography and primary and secondary production was investigated for the entire Arctic Ocean (AO) with the physical-biologically coupled SINMOD model. To obtain indications on the effect of climate change in the twenty-first century the magnitude of change, and where and when these may take place SINMOD was forced with down-scaled climate trajectories of the International Panel of Climate Change with the A1B climate scenario which appears to predict an average global atmospheric temperature increase of 3.5–4°C at the end of this century. It is projected that some surface water features of the physical oceanography in the AO and adjacent regions will change considerably. The largest changes will occur along the continuous domains of Pacific and in particular regarding Atlantic Water (AW) advection and the inflow shelves. Withdrawal of ice will increase primary production, but stratification will persist or, for the most, get stronger as a function of ice-melt and thermal warming along the inflow shelves. Thus, the nutrient dependent new and harvestable production will not increase proportionally with increasing photosynthetic active radiation (PAR). The greatest increases in primary production are found along the Eurasian perimeter of the AO (up to 40 g C m−2 y−1) and in particular in the northern Barents and Kara Seas (40–80 g C m−2 y−1) where less ice-cover implies less Arctic Water (ArW) and thus less stratification. Along the shelf break engirdling the AO upwelling and vertical mixing supplies nutrients to the euphotic zone when ice-cover withdraws northwards. The production of Arctic copepods along the Eurasian perimeter of the AO will increase significantly by the end of this century (2–4 g C m−2 y−1). Primary and secondary production will decrease along the southern sections of the continuous advection domains of Pacific and AW due to increasing thermal stratification. In the central AO primary production will not increase much due to stratification-induced nutrient limitation

Ecological investigations in the marginal ice zone in the Barents Sea the summers 1979 and 1980

During the summers of l979 and 1980, ecological investigations were carried out in the marginal ice zone in the Barents Sea. In the investigation an attempt is made to follow the development of the production processes, from nutrients via phytoplankton and zooplankton to capelin, in order to map the feeding conditions for the capelin and its variations. The methods used in the field work and most of the results obtained during the two summer seasons are presented by ELLERTSEN -et -al. (1981). In the present report we discuss and summarize the field results so far and compare them with the results from a model. The results show a close relationship between ice melting and recession and a phytoplankton bloom occurring at the ice edge. It seems that the decrease in salinity in the upper few meters due to ice melting produce a sharp increase in water stability. Thereby favourable conditions are created for an intense phytoplankton bloom. This bloom seems to occur somewhat earlier than the spring bloom in the areas of the Barents Sea not covered by ice, where water stability is mainly influenced by the warming of the upper layers. Zooplankton development follows very close that of the phytoplankton, with a bloom starting near the ice edge. The biomass was found to increase with the distance from the edge. This tendency is most clear in the upper layers, where the zooplankton spawning and the development of the zooplankton larvae occur. The main bulk of the zooplankton consisted of the copepod Calanus finmarchicus. The most numerous species was the small copepod Oithona similis. There was a change in age composition of -C. finmarchicus with the distance from the ice, the nauplii and the younger copepodite stages predominating in the north. The younger stages (I-III) were most abundant in the surface layer where they had hatched earlier in the year, while the older stages (IV-V and adult females) had overwintered and predominated in the deeper layer. The stomach contents of 12-18 cm capelin from several stations were investigated. The stomach filling seemed to be related to the plankton density in the sea, with highest filling in areas with much plankton. The species composition in the stomachs roughly corresponded with the plankton composition, with a tendency to a higher numeric percentage of euphausiids and chaetognaths in the stomachs than in the plankton. Near half of the contents, as weight, consisted of calanoid copepods, while the euphausiids, chaetognaths and amphipods made up 30, 10 and 6 per cent of the weight respectively. A model describing the growth of phytoplankton and zooplankton along a north-south section in the Barents Sea is also briefly described. Using ice map data obtained via satellite, several simulation runs have been performed. The dynamics of the phytoplankton growth seems to agree with what we believe it should according to the available data. However, some discrepancies indicate areas that should be further investigated in order to increase our knowledge and improve the model. The zooplankton part of the model produces results that are more questionable. Variations in zooplankton biomass are reasonably calculated whereas the stage distribution does not fit our data. Reasons for this are discussed

Borealization of the Arctic Ocean in Response to Anomalous Advection From Sub-Arctic Seas

An important yet still not well documented aspect of recent changes in the Arctic Ocean is associated with the advection of anomalous sub-Arctic Atlantic- and Pacific-origin waters and biota into the polar basins, a process which we refer to as borealization. Using a 37-year archive of observations (1981-2017) we demonstrate dramatically contrasting regional responses to atlantification (that part of borealization related to progression of anomalies from the Atlantic sector of sub-Arctic seas into the Arctic Ocean) and pacification (the counterpart of atlantification associated with influx of anomalous Pacific waters). Particularly, we show strong salinification of the upper Eurasian Basin since 2000, with attendant reductions in stratification, and potentially altered nutrient fluxes and primary production. These changes are closely related to upstream conditions. In contrast, pacification is strongly manifested in the Amerasian Basin by the anomalous influx of Pacific waters, creating conditions favorable for increased heat and freshwater content in the Beaufort Gyre halocline and expansion of Pacific species into the Arctic interior. Here, changes in the upper (overlying) layers are driven by local Arctic atmospheric processes resulting in stronger wind/ice/ocean coupling, increased convergence within the Beaufort Gyre, a thickening of the fresh surface layer, and a deepening of the nutricline and deep chlorophyll maximum. Thus, a divergent (Eurasian Basin) gyre responds altogether differently than does a convergent (Amerasian Basin) gyre to climate forcing. Available geochemical data indicate a general decrease in nutrient concentrations Arctic-wide, except in the northern portions of the Makarov and Amundsen Basins and northern Chukchi Sea and Canada Basin. Thus, changes in the circulation pathways of specific water masses, as well as the utilization of nutrients in upstream regions, may control the availability of nutrients in the Arctic Ocean. Model-based evaluation of the trajectory of the Arctic climate system into the future suggests that Arctic borealization will continue under scenarios of global warming. Results from this synthesis further our understanding of the Arctic Ocean\u27s complex and sometimes non-intuitive Arctic response to climate forcing by identifying new feedbacks in the atmosphere-ice-ocean system in which borealization plays a key role

Virtual Proof of Concept - Can large scale bubble curtains lower the surface temperature ocean waters

Computer simulations were used to investigate the potential of large-scale bubble curtains for lowering the sea surface temperature locally and regionally. Large scale simulations of this type have not been reported in the literature to our knowledge nor does large scale validation data exist. It is partly due to the latter and the cost involved in generating such validation data that a "Virtual Proof of Concept" was chosen to build confidence in the science behind the technological concept of using bubble curtains to lower sea surface temperatures over large areas. With the assumptions inherent in the use-case definition we find that the technology has potential to reduce sea surface temperatures (SST) both locally and on a regional basis. The merits and assumptions are discussed in the report.publishedVersio

A Model of Phytoplankton Production in the Marginal Sea Ice Zone of the Barents Sea

The primary production in the Barents Sea must be high since it can sustain large stocks of fish. The factors controlling the primary production is not well understood. This paper takes the physical conditions (as far as we know them) in some of the ice-covered areas of the Barents Sea as an input to a plankton model. Simulations with different combinations of vertical turbulence and ice cover indicate that the ice concentration is important in shallow areas with strong tidal mixing, whereas the date of the start of melting of the ice and the resulting stabilization of the water column are more important in deeper parts of the Arctic waters. Where the Atlantic waters flow towards the ice border, the primary production starts early in the spring. High phytoplankton concentration is always found in this area. Study of the model results shows that the following mechanism could he responsible for the elevated biomass: turbulent Atlantic water, relatively rich in nutrients, stabilizes when meeting the ice or brackish water from the melting process and allows a high growth rate as soon as there is enough light early in the spring. High production may last for 2-3 months in this area