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  • 151.
    Håkansson, Bertil
    et al.
    SMHI, Research Department, Oceanography.
    Moberg, Mats
    SMHI.
    Thompson, Thomas
    SMHI.
    REAL-TIME USE OF ERS-1 SAR IMAGERY FOR ICE SERVICE AND ICEBREAKING OPERATIONS IN THE BALTIC SEA1995In: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 16, no 17, p. 3441-3458Article in journal (Refereed)
    Abstract [en]

    Sea ice forms every winter in the Baltic Sea and several icebreakers in Sweden and Finland keep the major ports in the area open for sea-trade all the year around. Information and forecasts of the sea ice formation, drift and deformation are vital for safe and efficient winter navigation. In this respect, Synthetic Aperture Radar (SAR) imagery is of great interest, since this technique is almost cloud independent and has potential for real-time ice mapping. The usefulness of SAR imagery for sea ice operations has been evaluated in the Baltic Sea. The imagery was used both for ice mapping, for icebreaker operations and ship routeing. Images presented onboard the icebreakers were highly appreciated and easily interpreted by the crew. The data were frequently used for ship routeing (33 per cent) of merchant vessels and for direct icebreaker assistance (53 per cent). It was concluded by several icebreaker masters that an image resolution of about 100 m was indeed enough to distinguish ridged areas and in the same time obtain a large enough geographical coverage per image.

  • 152.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Invasive species in the Baltic Sea A model study of plankton transport2016Report (Other academic)
    Abstract [en]

    In this report, an ensemble of releases of passive particles at locations close to some

    selected ports around the Baltic Sea and Kattegat are modelled. The particles are

    transported with the currents. Maps of particle densities at 2, 4, 8, 16, 32 and 52

    weeks after the release are presented.

    The results indicate that many basins are narrow enough for the particles to cross

    from shore to shore within two weeks, e.g., in the Kattegat, Gulf of Finland and

    Kvarken. The results also show an asymmetry in the transport between different

    locations, which means that particles released from one location to another require

    substantially more time to reach the other location, if at all, than particles going

    in the opposite direction. Some potential barriers to transport are identified and

    discussed.

  • 153.
    Höglund, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Environmentally safe areas and routes in the Baltic proper using Eulerian tracers2012In: Marine Pollution Bulletin, ISSN 0025-326X, E-ISSN 1879-3363, Vol. 64, no 7, p. 1375-1385Article in journal (Refereed)
    Abstract [en]

    In recent years, the shipping of environmentally hazardous cargo has increased considerably in the Baltic proper. In this study, a large number of hypothetical oil spills with an idealized, passive tracer are simulated. From the tracer distributions, statistical measures are calculated to optimize the quantity of tracer from a spill that would stay at sea as long as possible. Increased time may permit action to be taken against the spill before the oil reaches environmentally vulnerable coastal zones. The statistical measures are used to calculate maritime routes with maximum probability that an oil spill will stay at sea as long as possible. Under these assumptions, ships should follow routes that are located south of Bornholm instead of the northern routes in use currently. Our results suggest that the location of the optimal maritime routes depends on the season, although interannual variability is too large to identify statistically significant changes. (c) 2012 Elsevier Ltd. All rights reserved.

  • 154.
    Höglund, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Broman, Barry
    SMHI, Research Department, Climate research - Rossby Centre.
    Kriezi, Ekaterini
    SMHI.
    Validation and correction of regionalised ERA-40 wind fields over the Baltic Sea using the Rossby Centre Atmosphere model RCA3.02009Report (Other academic)
    Abstract [en]

    Surface wind fields from ERA-40 regionalised with the Rossby Centre Atmosphere model RCA3.0 are underestimated. In this report a method for correcting the wind fields is evaluated. The method is based on the empirical linear relationship between gusty winds and mean wind. For the validation observations from 26 automatic stations along the Swedish coasts have been used. We found that the validation of wind over the open sea is difficult due to the impact of land that cannot be resolved properly by the atmospheric model as the horizontal grid resolution amounts to about 25 km. In addition, long homogeneous wind data sets are not available due to a switch from manual to automatic readings during the 1990s. The results show that the correction method improves the frequency distribution of simulated wind speed at most stations. Thus the corrected wind fields may be used to force Baltic Sea models during 1961-2004. However, the suggested correction method should be regarded only as a temporary solution while waiting for improved boundary layer

  • 155.
    Höglund, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Pemberton, Per
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Ice conditions for maritime traffic in the Baltic Sea in future climate2017In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 22, p. 245-265Article in journal (Refereed)
  • 156. Ikauniece, Anda
    et al.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Kalnina, Laimdota
    Introduction for the SI "Understanding the Baltic Sea"2017In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 195, p. 1-3Article in journal (Refereed)
  • 157. Jahn, A.
    et al.
    Aksenov, Y.
    de Cuevas, B. A.
    de Steur, L.
    Hakkinen, S.
    Hansen, E.
    Herbaut, C.
    Houssais, M. -N
    Karcher, M.
    Kauker, F.
    Lique, C.
    Nguyen, A.
    Pemberton, Per
    SMHI, Research Department, Oceanography.
    Worthen, D.
    Zhang, J.
    Arctic Ocean freshwater: How robust are model simulations?2012In: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, ISSN 2169-9275, Vol. 117, article id C00D16Article in journal (Refereed)
    Abstract [en]

    The Arctic freshwater (FW) has been the focus of many modeling studies, due to the potential impact of Arctic FW on the deep water formation in the North Atlantic. A comparison of the hindcasts from ten ocean-sea ice models shows that the simulation of the Arctic FW budget is quite different in the investigated models. While they agree on the general sink and source terms of the Arctic FW budget, the long-term means as well as the variability of the FW export vary among models. The best model-to-model agreement is found for the interannual and seasonal variability of the solid FW export and the solid FW storage, which also agree well with observations. For the interannual and seasonal variability of the liquid FW export, the agreement among models is better for the Canadian Arctic Archipelago (CAA) than for Fram Strait. The reason for this is that models are more consistent in simulating volume flux anomalies than salinity anomalies and volume-flux anomalies dominate the liquid FW export variability in the CAA but not in Fram Strait. The seasonal cycle of the liquid FW export generally shows a better agreement among models than the interannual variability, and compared to observations the models capture the seasonality of the liquid FW export rather well. In order to improve future simulations of the Arctic FW budget, the simulation of the salinity field needs to be improved, so that model results on the variability of the liquid FW export and storage become more robust. Citation: Jahn, A., et al. (2012), Arctic Ocean freshwater: How robust are model simulations?, J. Geophys. Res., 117, C00D16, doi: 10.1029/2012JC007907.

  • 158. Jeworrek, Julia
    et al.
    Wu, Lichuan
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Rutgersson, Anna
    SMHI, Research Department, Climate research - Rossby Centre.
    Characteristics of convective snow bands along the Swedish east coast2017In: Earth System Dynamics, ISSN 2190-4979, E-ISSN 2190-4987, Vol. 8, p. 163-175Article in journal (Refereed)
  • 159. Jonsson, Per R.
    et al.
    Kotta, Jonne
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Herkul, Kristjan
    Virtanen, Elina
    Sandman, Antonia Nystrom
    Johannesson, Kerstin
    High climate velocity and population fragmentation may constrain climate-driven range shift of the key habitat former Fucus vesiculosus2018In: Diversity & distributions: A journal of biological invasions and biodiversity, ISSN 1366-9516, E-ISSN 1472-4642, Vol. 24, no 7, p. 892-905Article in journal (Refereed)
  • 160. Jutterstrom, S.
    et al.
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Omstedt, A.
    Malmaeus, J. M.
    Multiple stressors threatening the future of the Baltic Sea-Kattegat marine ecosystem: Implications for policy and management actions2014In: Marine Pollution Bulletin, ISSN 0025-326X, E-ISSN 1879-3363, Vol. 86, no 1-2, p. 468-480Article in journal (Refereed)
    Abstract [en]

    The paper discusses the combined effects of ocean acidification, eutrophication and climate change on the Baltic Sea and the implications for current management strategies. The scientific basis is built on results gathered in the BONUS+ projects Baltic-C and ECOSUPPORT. Model results indicate that the Baltic Sea is likely to be warmer, more hypoxic and more acidic in the future. At present management strategies are not taking into account temporal trends and potential ecosystem change due to warming and/or acidification, and therefore fulfilling the obligations specified within the Marine Strategy Framework Directive, OSPAR and HELCOM conventions and national environmental objectives may become significantly more difficult. The paper aims to provide a basis for a discussion on the effectiveness of current policy instruments and possible strategies for setting practical environmental objectives in a changing climate and with multiple stressors. (C) 2014 The Authors. Published by Elsevier Ltd.

  • 161.
    Jönsson, Anette
    et al.
    SMHI, Core Services.
    Broman, Barry
    SMHI, Research Department, Climate research - Rossby Centre.
    Rahm, Lars
    SMHI, Research Department, Oceanography.
    Variations in the Baltic Sea wave fields2003In: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258, Vol. 30, no 1, p. 107-126Article in journal (Refereed)
    Abstract [en]

    The surface waves in the Baltic Sea are hindcast with the spectral wave model HYPAS during a 12-month period. The model results show a strong temporal and spatial variation in the wave field due to the physical dimensions of the different basins and the predominant wind field. The highest waves in the area are found in the outer part of Skagerrak, as well as in the central and southern parts of the Baltic Proper. To get significant waves above 6 m high, strong winds (15-20 m/s) must have been blowing for 6 to 24 h from a favourable direction over a deep area. (C) 2002 Elsevier Science Ltd. All rights reserved.

  • 162. KAHRU, M
    et al.
    Håkansson, Bertil
    SMHI, Research Department, Oceanography.
    RUD, O
    DISTRIBUTIONS OF THE SEA-SURFACE TEMPERATURE FRONTS IN THE BALTIC SEA AS DERIVED FROM SATELLITE IMAGERY1995In: Continental Shelf Research, ISSN 0278-4343, E-ISSN 1873-6955, Vol. 15, no 6, p. 663-679Article in journal (Refereed)
    Abstract [en]

    A 9-month time series of satellite infrared imagery was used to examine the sea surface temperature (SST) variability in the northern and central Baltic Sea. Objective multi-level edge detection techniques were applied to find sharp SST gradient areas known as fronts. The spatial distribution of frontal frequency was calculated over time periods from a few days to 9 months covering different thermal and wind conditions. The 9-month average frequency that a front is detected in a pixel of 1.1 x 1.1 km is up to 10% in certain areas whereas the median is around 2%. Large scale fronts are aligned to the coast and isobaths, and occur predominantly in areas of straight and uniformly sloping bottom topography. The major frontal areas are along the eastern coast of the Bothnian Sea and along the north-western coast of the Gulf of Finland. Low large-scale frontal frequency is characteristic to areas with highly structured bottom topography. The major mechanism of front generation is coastal upwelling, being complemented by coastal jets, eddies, differential heating and cooling, and water exchange between basins with different water characteristics. Filaments (''squirts'') originating from upwelling areas are shown to be an important mechanism for transporting water and substances over long distances.

  • 163.
    Karlson, Bengt
    SMHI, Research Department, Oceanography.
    Algblomningar skapar rubriker2017In: Havet 1988 / [ed] Svedäng H, Svärd M, Johansen Lilja T, Lundberg F, Göteborg: Havsmiljöinstitutet , 2017, p. 80-83Chapter in book (Refereed)
  • 164.
    Karlson, Bengt
    SMHI, Research Department, Oceanography.
    Förödande algblomning drabbar hela Västerhavets ekosystem2017In: Havet 1988 / [ed] Svedäng H, Svärd M, Johansen Lilja T, Lundberg F, Göteborg: Havsmiljöinstitutet , 2017, p. 77-79Chapter in book (Refereed)
  • 165.
    Karlson, Bengt
    SMHI, Research Department, Oceanography.
    Kraftfulla alggifter bromsar musselodlingens framväxt2017In: Havet 1988 / [ed] Svedäng H, Svärd M, Johansen Lilja T, Lundberg F, Göteborg: Havsmiljöinstitutet , 2017, p. 86-88Chapter in book (Refereed)
  • 166.
    Karlson, Bengt
    et al.
    SMHI, Research Department, Oceanography.
    Andersson, C.R
    Coyne, K.J.
    Kudela, R.
    Sellner, K.G.
    Anderson, D.M.
    Designing an observing system for early detection of harmful algal blooms2017In: Harmful Algal Blooms (HABs) and Desalination: A Guide to Impacts, Monitoring and Management / [ed] Anderson D. M., S. F. E. Boerlage, M. B. Dixon, Paris: IOC, UNESCO , 2017, p. 89-117Chapter in book (Refereed)
  • 167.
    Karlson, Bengt
    et al.
    SMHI, Research Department, Oceanography.
    Andersson, Lars
    SMHI, Core Services.
    The Chattonella-bloom in year 2001 and effects of high freshwater input from river Göta Älv to the Kattegat-Skagerrak area2003Report (Other academic)
    Abstract [en]

    In autumn year 2000 and winter-spring 2001 the precipitation in the catchment area of Lake Vänern was higher than normal. During spring 2001, the flow in river Göta älv was around 1200 m3/s, nearly three times higher than the average indicating extreme conditions. The flow in the smaller rivers entering the Bohus coast is minor compared to river Göta Älv. To investigate possible effects on the marine environment in the area close to the river mouth an investigation with weekly sampling at four locations was initated by SMHI. Physical and chemical variables in the water was measured as well as phytoplankton composition and abundance. The Swedish Environmental Protection Agency and the Water Quality Association of the Bohus Coast co-funded the investigation together with SMHI. Effects on the water quality such as low surface salinities, high concentrations of dissolved inorganic nitrogen and dissolved phosphate and silicate compared to monthly averages 1990-99 was observed close to the river mouth but not off shore. Effects on the Secchi depth were not observed. On a few occassion high phytoplankton biomass, measured as chlorophyll a, was observed. At other locations along the Bohus coast effects where absent or small. Primary productivity measurements at the mouth of the Gullmar Fjord, showed no effects from the river outflow. During the investigation a bloom of the harmful alga Chattonella sp. occurred in the Kattetat and the Skagerrak.. The bloom of this small flagellate, which is described in the report, is probably not connected to the river input. A unique or unusual feature of the Chattonella-bloom is that it occured in cold water right after the diatom spring bloom in early March. In conclusion the effects of the extreme flooding were less than expected, the fresh water from the river were quickly mixed with the water in the sea and only small effects were seen. No connection between the flooding and the Chattonella bloom was detected.

  • 168.
    Karlson, Bengt
    et al.
    SMHI, Research Department, Oceanography.
    Andersson, Lars
    SMHI, Core Services.
    Kaitala, S.
    Kronsell, Johan
    SMHI, Core Services.
    Mohlin, M.
    Seppala, J.
    Wranne, A. Willstrand
    A comparison of FerryBox data vs. monitoring data from research vessels for near surface waters of the Baltic Sea and the Kattegat2016In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 162, p. 98-111Article in journal (Refereed)
  • 169.
    Karlson, Bengt
    et al.
    SMHI, Research Department, Oceanography.
    Axe, Philip
    SMHI, Research Department, Oceanography.
    Funquist, Lennart
    SMHI, Research Department, Oceanography.
    Kaitala, Seppo
    FIMR, Finnish Institute for Marine Research/SYKE Marine Centre.
    Sørensen, Kai
    NIVA, Norwegian Institute for Water Research.
    Infrastructure for marine monitoring and operational oceanography2009Report (Other academic)
    Abstract [en]

    Automated systems for observing physical, chemical and biological conditions in the sea are being implemented worldwide as part of the Global Ocean Observing System. This report describes their use in the Baltic and the Skagerrak-Kattegat areas. An evaluation of the use of FerryBox systems in the waters around Sweden shows that the quality of data from near surface waters is high, and that the frequent sampling makes possible observations of short term phenomena such as algal blooms. These events are often overlooked by infrequent sampling using research vessels, which leads to erroneous estimates of phytoplankton biomass, ecosystem carrying capacity etc. Data come from the Helsinki Lübeck route, operated by the Finnish Institute for Marine Research and from routes in the Skagerrak- Kattegat operated by the Norwegian Institute for Water Research. FerryBox data were compared with data from traditional sampling, principally from RV Argos operated by SMHI, but also from the HELCOM databank at ICES.Observations using automated systems such as satellites, stationary platforms (buoys and piles) and FerryBox systems may contribute substantially to improving the quality of results from models describing the physical and biogeochemical conditions in Scandinavian waters. Boundary conditions for models can be obtained using measurements in the eastern North Sea and in the Skagerrak, while data assimilation from a network of buoys, FerryBoxsystems and research vessels improves the quality of model results. Today, between four and six automated oceanographic observation systems are in operation in Swedish waters, which can be compared to more than 700 for meteorological purposes. A dramatic increase in the number of observations is necessary for effective data assimilation. To make the observations useful for biogeochemical models, parameters such as inorganic nutrients, phytoplankton biomass and oxygen must be added to the basic parameters salinity and temperature.A detailed proposal for a new infrastructure for marine monitoring and operational oceanography in Sweden is put forward. FerryBox systems should be operated in collaboration with institutes in Finland, Estonia, Poland, Germany, Denmark and Norway. Coastal buoys contribute to the monitoring needs of the EU Water Framework Directive while offshore buoys are for long term climate and ecological research and for fulfilment of the EU Marine Strategy Directive . Products combining satellite data with in-situ observations should be developed. These automated systems augment monitoring using research vessels but do not replace it. SMHI, the Swedish Institute for the Marine Environment, the Swedish Water Authorities, the Swedish Environmental Protection Agency, Swedish Navy, Coast guard, Maritime Administration and Board of Fisheries are proposed to govern and operate the system, with SMHI as the lead partner. The function -National data host for operational oceanographic data- is proposed, to be established at the National Oceanographic Data Centre at SMHI.A number of indicators for describing the status of the pelagic environment around Sweden are proposed. Some already exist while some are new. New ones include indicators for acidification, changes in plankton community structure and physical climate indicators. Basin wide indicators are based on measurements using a combination of sampling platforms. Other indicators are more specific, e.g. for transport between basins and inflow of water to the deep basins of the Baltic Proper.This report was commissioned by the Swedish National Environment Protection Agency

  • 170.
    Karlson, Bengt
    et al.
    SMHI, Research Department, Oceanography.
    Edler, Lars
    SMHI, Research Department, Oceanography.
    Graneli, W
    Sahlsten, Elisabeth
    SMHI, Research Department, Oceanography.
    Kuylenstierna, M
    Subsurface chlorophyll maxima in the Skagerrak - Processes and plankton community structure1996In: Journal of Sea Research, ISSN 1385-1101, E-ISSN 1873-1414, Vol. 35, no 1-3, p. 139-158Article in journal (Refereed)
    Abstract [en]

    Subsurface chlorophyll maxima are common phenomena in both the coastal and open ocean. The main objective of this study was to clarify possible differences in the structure and function of the plankton community in subsurface chlorophyll maxima and at the surface. Sampling was performed at seven stations in the Skagerrak, northeast Atlantic, during five cruises in May and August 1992 and April, May and August 1993. Subsurface chlorophyll fluorescence maxima (FM) occurred on 25 out of 32 sampling occasions. The FMs were usually situated below the pycnocline and associated with the nutricline. The ratio of chlorophyll a to particulate carbon and the light-saturated primary production were higher for plankton at the FM than at the surface, although assimilation numbers (primary production rate:chlorophyll a) were not different from surface plankton. The light protective pigment diadinoxanthin occurred in higher concentrations relative to chlorophyll a in surface plankton than in FM plankton. Respiration was higher in the FM than at the surface. This was not related to abundance of bacteria or bacterial production since no differences between surface and FM values were detected for these parameters. FM plankton was characterized by high nutrient uptake rates, but in this study there were no significant differences compared to surface plankton. 'New' production was on average 25%, but up to about 50% in the western Skagerrak in spring. The average nitrogen uptake rates were dominated by the regenerated nutrients ammonium and urea, accounting for about 50 and 25%, respectively. The <3 mu m size fraction contributed significantly to concentrations of total chlorophyll a, particulate carbon, and nitrogen as well as to nitrogen uptake. Its contribution was highest when total values were low. Microscopical investigations and analysis of pigments specific to algal groups showed that diatoms dominated in the FMs in spring and that peridinin-containing dinoflagellates dominated in FMs in August. Autotrophic nanoplankton was dominated by the Prymnesiophyceae contributing about 50% of total cell numbers. Colonies of Phaeocystis sp. were abundant along the NW Danish coast in April and May 1993, Autotrophic eukaryotic picoplankton occurred in cell numbers up to about 30 x 10(6) cells . dm(-3) along the Swedish coast. The highest cell numbers of cyanobacteria of the Synechococcus-type, about 100 x 10(6) cells . dm(-3), were found in the central Skagerrak in August and the abundance of Synechococcus was correlated with nitrogen uptake in the <3 mu m size fraction.

  • 171.
    Karlson, Bengt
    et al.
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Johansson, Johannes
    SMHI, Core Services.
    Linders, Johanna
    SMHI, Core Services.
    Mohlin, Malin
    SMHI.
    Willstrand Wranne, Anna
    SMHI, Core Services.
    Wåhlstrom, Irene
    SMHI, Research Department, Oceanography.
    Distribution of cyanobacteria blooms in the Baltic Sea2017In: Marine and Fresh-Water Harmful Algae. / [ed] Proenca, L. A. O. and Hallegraeff, G., International Society for the Study of Harmful Algae Intergovernmental Oceanographic Commission of UNESCO , 2017, p. 100-103Conference paper (Refereed)
  • 172.
    Karlson, Bengt
    et al.
    SMHI, Research Department, Oceanography.
    Mohlin, Malin
    Hu, Ye O.O.
    Andersson, Anders F.
    Miljöövervakning av växtplankton i Kattegatt och Östersjön med rDNA-barcoding och mikroskopi: En jämförelse av molekylärbiologisk metodik och mikroskopi.2018Report (Other academic)
  • 173.
    Karlson, Bengt
    et al.
    SMHI, Research Department, Oceanography.
    Rehnstam-Holm, Ann-Sofi
    Göteborg University, Clinical Bacteriology, Institution of Laboratory Medicine, SE-413 46 Gothenburg, Sweden & Kristianstad University, Institution of Mathematics and Natural Sciences, SE-29188 Kristianstad, Sweden..
    Loo, Lars-Ove
    Department of Marine Ecology, Göteborg University, Tjärnö Marine Biological Laboratory, SE-452 96 Strömstad, Sweden..
    Temporal and spatial distribution of diarrhetic shellfish toxins in blue mussels, Mytilus edulis (L.), at the Swedish West Coast, NE Atlantic, years 1988-20052007Report (Other academic)
    Abstract [en]

    The main goal of this report is to compile and present available data on algal toxins in blue mussels from the west coast of Sweden. The hazards associated with the consumption of mussels are mostly dependent on the occurrence and composition of toxic algae in the areas where shellfish are grown. Diarrhetic shellfish toxins (DST), i.e. okadaic acid (OA) and dinophysistoxin-1 (DTX-1) have occurred regularly in blue mussels (Mytilus edulis) at the Swedish west coast (i.e. Skagerrak) during the past years. A maximum residue limit of 160 µg.kg-1 mussel meat has been set by National Food Administration. The toxic incidences in the region has been linked to the occurrence of Dinophysis acuminata and D. acuta. In general there is seasonal variation of DST in mussels with low concentrations from March to August (160 µg.kg-1 mussel meat). Peaks above the maximum residue limit have in some years also occurred in late June to late July. Rapid intoxication vs. slow detoxification of mussels is a common phenomenon, especially in autumn-winter. Temporal and regional differences are large. There is also a considerable variation in toxin levels between years. In 1994 almost 5000 µg DST.kg-1 mussel meat was detected. In 1997 mussel farmers experienced very low levels, i.e. only three samples above the restriction limit of DST. In autumn 1989 to spring 1990 and in early autumn 2000 to early 2001, high levels (about 200 to 2000 µg DTX.kg-1 mussel meat) were recorded during 26 weeks. The Koljö Fjord region had low levels of toxins until 1998, despite regular recordings of potentially DST producing algae in the area. Today mussels grown and harvested in this area have similar toxin levels to mussels from other fjords in the Skagerrak region. Measurements of other toxins than DST are few and are not included in the report. Målet med denna rapport är att sammanställa och presentera tillgängliga data med algtoxiner i blåmusslor från svenska västkusten. Risken att bli förgiftad av algtoxiner via musslor hänger samman med förekomst och sammansättning av toxiska alger i det vatten där musslorna växer. Diarréframkallande ämnen (diarrheic shellfish toxins), t.ex. okadasyra (OA) och dinophysistoxin-1 (DTX-1) har förkommit regelbundet i blåmusslor (Mytilus edulis) längs svenska västkusten (Skagerack) de senaste tjugofyra åren. Ett gränsvärde på 160 µg.kg-1 musselkött är fastställt av livmedelsverket. Toxinförekomsten i regionen associeras till förekomsten av Dinophysis acuminata och D. acuta. "Normalt" är det en säsongsvariation av DST i musslor med låga koncentrationer från mars till augusti (<160 µg.kg-1 musselkött) och höga från oktober till december (>160 µg.kg-1 musselkött). Toppar över gränsvärdet för konsumtion har vissa år förekommit från slutet av juni till slutet av juli. En snabb ökning i toxinhalt respektive långsam minskning är också ett vanligt förekommande fenomen, speciellt under höst-vinter. Tidsmässiga och regionala skillnader är stora. Det är också en stor skillnad i toxinhalt mellan åren. 1994 uppmättes den högsta toxinhalten till nästan 5000 µg DST.kg-1 musselkött. Under 1997 var halterna låga under hela säsongen, endast vid tre tillfällen var halterna över gränsvärdet. Från hösten 1989 till våren 1990 och från tidig höst 2000 till tidig vår 2001 uppmättes höga halter (ca 200 to 2000 µg DTX.kg-1 musselkött) under 26 veckor i en följd. I Koljöfjorden var det låga halter av toxiner fram till år 1998, trots förekomst av potentiellt DST producerande alger i området. I dag har musslor som växer och skördas i detta område ungefär samma nivåer av toxin som från andra områden. Mätningar av andra algtoxiner än DST är fåtaliga och tas inte upp i rapporten.

  • 174.
    Karlson, Bengt
    et al.
    SMHI, Research Department, Oceanography.
    Skjevik, Ann-Turi
    SMHI, Core Services.
    Algblomningar - en utmaning för miljöövervakning och forskning2017In: Västerhavet, ISSN 1104-3458, p. 4-5Article in journal (Other (popular science, discussion, etc.))
  • 175. Karlsson, Therese M.
    et al.
    Arneborg, Lars
    SMHI, Research Department, Oceanography.
    Brostrom, Goran
    Almroth, Bethanie Carney
    Gipperth, Lena
    Hassellov, Martin
    The unaccountability case of plastic pellet pollution2018In: Marine Pollution Bulletin, ISSN 0025-326X, E-ISSN 1879-3363, Vol. 129, no 1, p. 52-60Article in journal (Refereed)
  • 176. Kauker, F
    et al.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Modeling decadal variability of the Baltic Sea: 1. Reconstructing atmospheric surface data for the period 1902-19982003In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 108, no C8, article id 3267Article in journal (Refereed)
    Abstract [en]

    A statistical model is developed to reconstruct atmospheric surface data for the period 1902-1998 to force a coupled sea ice-ocean model of the Baltic Sea. As the response timescale of the Baltic Sea on freshwater inflow is of the order of 30-40 years, climate relevant model studies should cover at least century-long simulations. Such an observational atmospheric data set is not available yet. We devised a statistical model using a "redundancy analysis'' to reconstruct daily sea level pressure (SLP) and monthly surface air temperature (SAT), dew-point temperature, precipitation, and cloud cover of the Baltic. The predictor fields are daily SLP at 19 stations and monthly coarse gridded SAT and precipitation available for the period 1902 to 1998. The second input is a gridded atmospheric data set, with high resolution in space and time, based on synoptic stations, which is available for the period 1970-2001. Spatial patterns are selected by maximizing predictand variance during the "learning'' period 1980-1998. The remainder period 1970-1979 is used for validation. We found the highest skill of the statistical model for SLP and the lowest skill for cloud cover. For wintertime the dominant modes of variability on the interannual to interdecadal timescales of the reconstruction are discussed. It is shown that the wintertime variability of SLP, SAT, and precipitation is related to well-known atmospheric patterns of the Northern Hemisphere: the North Atlantic Oscillation, the Scandinavia pattern, the East Atlantic/West Russia pattern, and the Barents Sea Oscillation.

  • 177. Kauker, Frank
    et al.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Reconstructing atmospheric surface data for the period 1902-1998 to force a coupled ocean-sea ice model of the Baltic Sea2002Report (Other academic)
  • 178. Kirkwood, D S
    et al.
    Aminot, A
    Carlberg, Stig
    SMHI, Research Department, Oceanography.
    The 1994 QUASIMEME laboratory performance study: Nutrients in seawater and standard solutions1996In: Marine Pollution Bulletin, ISSN 0025-326X, E-ISSN 1879-3363, Vol. 32, no 8-9, p. 640-645Article in journal (Refereed)
    Abstract [en]

    The 1994 QUASIMEME (nutrients) Laboratory-Performance Study (LPS) is presented, The year's programme consisted of two periods, December-May and June-November, (These are referred to as Round 2 and Round 3, respectively, the previous 1993 LPS being Round 1.) In each period, participating laboratories were sent two types of sample material, that is seawater samples and a standard solution containing a mixture of nutrient salts, The standard solution required dilution (by participants) and multiple analyses over several weeks in order to assess long-term repeatability, In Round 2, a few laboratories, identified as poor performers in Round 1 (1993), undertook a 'learning programme' in which they received, unknowingly, samples identical to those analysed in Round 1, The other laboratories received samples different from those used in Round 1, In Round 3, all laboratories received the same package of samples, different from those used in Round 1 and Round 2, The results clearly indicate that general all-round improvements in data quality have been achieved. Crown copyright (C) 1996 Published by Elsevier Science Ltd

  • 179.
    Kjellström, Erik
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Atmospheric response to different sea surface temperatures in the Baltic Sea: coupled versus uncoupled regional climate model experiments2005In: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 36, no 4-5, p. 397-409Article in journal (Refereed)
    Abstract [en]

    A climate change experiment with a fully coupled high resolution regional atmosphere-ocean model for the Baltic Sea is compared to an experiment with a stand-alone regional atmospheric model. Both experiments simulate 30-yr periods with boundary data from the same global climate model system. This particular global model system simulates very high sea surface temperatures during summer for the Baltic Sea at the end of this century under the investigated emission scenario. We show that the sea surface temperatures are less warm in the coupled regional model compared to the global model system and that this difference is dependent on the atmospheric circulation. In summers with a high NAO index and thereby relatively strong westerly flow over the North Atlantic the differences between the two models are small, while in summers with a weaker, more northerly flow over the Baltic Sea the differences are very large. The higher sea surface temperatures in the uncoupled experiment lead to an intensified hydrological cycle over the Baltic Sea, with more than 30% additional precipitation in summer taken as an average over the full 30-yr period and over the entire Baltic Sea. The differences are mostly local, over the sea, but there are differences in surrounding land areas.

  • 180. Kniebusch, Madline
    et al.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Neumann, Thomas
    Borgel, Florian
    Temperature Variability of the Baltic Sea Since 1850 and Attribution to Atmospheric Forcing Variables2019In: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 124, no 6, p. 4168-4187Article in journal (Refereed)
  • 181.
    Koenigk, Torben
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Caian, Mihaela
    SMHI, Research Department, Climate research - Rossby Centre.
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Regional Arctic sea ice variations as predictor for winter climate conditions2016In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 46, no 1-2, p. 317-337Article in journal (Refereed)
    Abstract [en]

    Seasonal prediction skill of winter mid and high northern latitudes climate from sea ice variations in eight different Arctic regions is analyzed using detrended ERA-interim data and satellite sea ice data for the period 1980-2013. We find significant correlations between ice areas in both September and November and winter sea level pressure, air temperature and precipitation. The prediction skill is improved when using November sea ice conditions as predictor compared to September. This is particularly true for predicting winter NAO-like patterns and blocking situations in the Euro-Atlantic area. We find that sea ice variations in Barents Sea seem to be most important for the sign of the following winter NAO-negative after low ice-but amplitude and extension of the patterns are modulated by Greenland and Labrador Seas ice areas. November ice variability in the Greenland Sea provides the best prediction skill for central and western European temperature and ice variations in the Laptev/East Siberian Seas have the largest impact on the blocking number in the Euro-Atlantic region. Over North America, prediction skill is largest using September ice areas from the Pacific Arctic sector as predictor. Composite analyses of high and low regional autumn ice conditions reveal that the atmospheric response is not entirely linear suggesting changing predictive skill dependent on sign and amplitude of the anomaly. The results confirm the importance of realistic sea ice initial conditions for seasonal forecasts. However, correlations do seldom exceed 0.6 indicating that Arctic sea ice variations can only explain a part of winter climate variations in northern mid and high latitudes.

  • 182. Kotilainen, Aarno T.
    et al.
    Arppe, Laura
    Dobosz, Slawomir
    Jansen, Eystein
    Kabel, Karoline
    Karhu, Juha
    Kotilainen, Mia M.
    Kuijpers, Antoon
    Lougheed, Bryan C.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Moros, Matthias
    Neumann, Thomas
    Porsche, Christian
    Poulsen, Niels
    Rasmussen, Peter
    Ribeiro, Sofia
    Risebrobakken, Bjorg
    Ryabchuk, Daria
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Snowball, Ian
    Spiridonov, Mikhail
    Virtasalo, Joonas J.
    Weckstrom, Kaarina
    Witkowski, Andrzej
    Zhamoida, Vladimir
    Echoes from the Past: A Healthy Baltic Sea Requires More Effort2014In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 43, no 1, p. 60-68Article in journal (Refereed)
    Abstract [en]

    Integrated sediment multiproxy studies and modeling were used to reconstruct past changes in the Baltic Sea ecosystem. Results of natural changes over the past 6000 years in the Baltic Sea ecosystem suggest that forecasted climate warming might enhance environmental problems of the Baltic Sea. Integrated modeling and sediment proxy studies reveal increased sea surface temperatures and expanded seafloor anoxia (in deep basins) during earlier natural warm climate phases, such as the Medieval Climate Anomaly. Under future IPCC scenarios of global warming, there is likely no improvement of bottom water conditions in the Baltic Sea. Thus, the measures already designed to produce a healthier Baltic Sea are insufficient in the long term. The interactions between climate change and anthropogenic impacts on the Baltic Sea should be considered in management, implementation of policy strategies in the Baltic Sea environmental issues, and adaptation to future climate change.

  • 183. Kotovirta, Ville
    et al.
    Jalonen, Risto
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Riska, Kaj
    Berglund, Robin
    A system for route optimization in ice-covered waters2009In: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 55, no 1, p. 52-62Article in journal (Refereed)
    Abstract [en]

    Information about ice is indispensable to navigation in ice-covered sea areas. For vessels traveling long distances in ice, it is worth planning routes that will reduce fuel consumption and travel time, as well as the risk of ending up in hazardous areas or getting stuck in the ice. In addition to observations on board. there is a multitude of data sources available for seafarers like satellite images, ice model data, weather observations and forecasts. However, it is difficult for a human to take into consideration all the time-varying data parameters when planning a route. In this paper, a prototype system for optimizing routes through the ice field is presented. The system integrates state-of-the-art ice modeling, ship transit modeling, and an enduser system as a route optimization tool for vessels navigating in ice-covered waters. The system has recently been validated on board merchant vessels in the Baltic Sea, and the system's performance has been analyzed statistically using AIS data. Based on the AIS data analysis the mean relative error of the estimated transit time was 0.144 [s/s] with a standard deviation of 0.147 [s/s] for long routes (90-650 km), and 0.018 [s/s] with standard deviation of 0.193 [s/s] for 50 km route segments. (C) 2008 Elsevier B.V. All rights reserved.

  • 184. Kratzer, S
    et al.
    Håkansson, Bertil
    SMHI, Research Department, Oceanography.
    Sahlin, C
    Assessing Secchi and photic zone depth in the Baltic Sea from satellite data2003In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 32, no 8, p. 577-585Article in journal (Refereed)
    Abstract [en]

    Long-term trends in the Secchi depth of the Baltic Sea have been interpreted in terms of eutrophication (1, 2). The spectral attenuation coefficient K-d (490) can be estimated from remote sensing data (3). Given the empirical and theoretical relationships between diffuse attenuation and Secchi depth, it is therefore possible to estimate the trophic state from remote sensing data. This paper considers relationships among remotely sensed and in-water measured K-d (490), and Secchi depth data obtained during dedicated sea-truthing campaigns in the eastern Baltic Proper in 1999 (4) and in the western Baltic Proper/Himmerfjarden area during 2001 and 2002. In-water measurements are used to establish the relationship between the PAR and the spectral attenuation coefficient in the Baltic Sea via regression analysis. The analysis showed that in the area of investigation K-d(490) is about 1.48 times higher than K-d(PAR). This relationship is then used to define the link between the photic zone depth and the remote sensing optical depth, K-d (490)(-1). The results show that the depth of the euphotic zone is about 6.8 times K-d (490)(-1). The regression analysis between K-d (PAR) and Secchi depth confirmed previous work that K-d (PAR) is about 1.7 of the inverse Secchi depth. Furthermore, an in-water algorithm between Secchi depth and K-d (490) is used to simulate a Secchi depth map of the Bartic sea from seaWiFS K-d (490) data. This map is verified against sea-truthing data. K-d (490) data derived from satellite is compared to in situ Kd (490), and the sources of error are discussed.

  • 185.
    Kuznetsov, Ivan
    et al.
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Model study on the variability of ecosystem parameters in the Skagerrak-Kattegat area, effect of load reduction in the North Sea and possible effect of BSAP on Skagerrak-Kattegat area2016Report (Other academic)
    Abstract [en]

    Newly developed ecosystem model NEMO-Nordic-SCOBI was applied to Skagerrak - Kattegat area to investigate the variability of some indicators of the ecosystem. Also, two sensitivity runs were performed to investigate possible effect of the Baltic Sea Action Plan (BSAP) and a river loads reduction scenario on the Skagerrak - Kattegat area. The performed investigation could be used “to provide a basis to assist with the interpretation of measurement data before the Intermediate Assessments Eutrophication status assessment”. Comparison of simulation results with observations indicates acceptable model performance. Modeled sea surface salinity, temperature and dissolved inorganic phosphate (DIP) are in good agreement with observations. At the same time, the model has a bias in certain areas of the investigated region for dissolved inorganic nitrogen (DIN) and dissolved silicate during the winter season. However, the model in its current state shows good enough results for the performed investigation. Results of the two sensitivity studies show a decrease of sea surface nutrients concentrations during winter period in both regions. In the Skagerrak area the decrease is due to reduction in river nutrient loads in North Sea. In the Kattegat area there is a decrease of dissolved phosphate due to the implementation of BSAP. At the same time, in both scenarios, no significant changes were obtained for near bottom oxygen or surface layer Chl-a.

  • 186.
    Kuznetsov, Ivan
    et al.
    SMHI, Research Department, Oceanography.
    Neumann, Thomas
    Simulation of carbon dynamics in the Baltic Sea with a 3D model2013In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 111, p. 167-174Article in journal (Refereed)
    Abstract [en]

    A full resolved three-dimensional physical-biogeochemical model ERGOM (Ecological ReGional Ocean model) was used to simulate the carbon dynamics in the Baltic Sea. Here, a simple carbon cycle has been included in the model. This was accomplished by the addition of dissolved inorganic carbon and total alkalinity to the model. Model results of the hindcast simulation (1961-2007) are in a good agreement with observations. Lateral gradients of the alkalinity are well reproduced by the model. A net inorganic carbon transport from the Baltic Sea to the Kattegat is in the range of the results of previous studies. Further, two climate projections with different nutrient load scenarios reflecting the possible development of the carbon system dynamics in the Baltic Sea were conducted. Climate scenario simulations (1961-2100) showed a continuous "acidification effect" of the Baltic Sea that mainly is controlled by changing of the atmospheric pCO(2). However, changes in pH due to other factors (such as changing temperature, primary production) are different for different regions of the sea. Simulated mean total alkalinity and dissolved inorganic carbon decrease in scenarios of climate change despite the increase of total alkalinity and dissolved inorganic carbon loads. The performed climate simulations show that mean total alkalinity decreases by about 150 mmol m(-3) and dissolved inorganic carbon by about 80-120 mmol m(-3). At the same time total alkalinity to salinity relations change in future climate due to that salinity decreases "faster" than alkalinity. Simultaneously, export of the total alkalinity and the dissolved inorganic carbon from the Baltic Sea to the North Sea has the trend to increase from 11% to 18% depending on the climate scenario. C) 2012 Elsevier B.V. All rights reserved.

  • 187.
    Köuts, Tarmo
    et al.
    Estonian Met. And Hyd. Inst. Marine Res..
    Håkansson, Bertil
    SMHI, Research Department, Oceanography.
    Observations of water exchange, currents, sea levels and nutrients in the Gulf of Riga1995Report (Other academic)
  • 188. Lambert, Erwin
    et al.
    Nummelin, Aleksi
    Pemberton, Per
    SMHI, Research Department, Oceanography.
    Ilicak, Mehmet
    Tracing the Imprint of River Runoff Variability on Arctic Water Mass Transformation2019In: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 124, no 1, p. 302-319Article in journal (Refereed)
  • 189.
    Liu, Ye
    et al.
    SMHI, Research Department, Oceanography.
    Fu, Weiwei
    Assimilating high-resolution sea surface temperature data improves the ocean forecast potential in the Baltic Sea2018In: Ocean Science, ISSN 1812-0784, E-ISSN 1812-0792, Vol. 14, no 3, p. 525-541Article in journal (Refereed)
  • 190.
    Liu, Ye
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Reanalyzing temperature and salinity on decadal time scales using the ensemble optimal interpolation data assimilation method and a 3D ocean circulation model of the Baltic Sea2013In: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, ISSN 2169-9275, Vol. 118, no 10, p. 5536-5554Article in journal (Refereed)
    Abstract [en]

    A 30-year (1970-1999) reanalysis of temperature and salinity is conducted by assimilating temperature and salinity profiles into an ocean model of the Baltic Sea with ensemble optimal interpolation approach. Some configurations of the reanalysis are presented. For example, the samples are chosen from the same season as the analysis time to address the strong seasonal variability. The impact of different observation time windows on the analysis results is also discussed. A locally determined alpha is adopted for the long-time-scale simulation. To assess the accuracy of the reanalysis, a set of comparisons between the reanalysis results and the free run results was performed. The root mean square deviations (RMSDs) between the reanalysis results and not-yet-assimilated observations at all levels show that, compared to the free run, temperature and salinity have been improved significantly, that is, by 31.1 and 38.8%, respectively. The vertical structure of the reanalyzed fields is also adjusted. The reanalysis results show that the improvements in both temperature and salinity are smaller at greater water depths. Comparison with independent CTD data, the reanalysis significantly improved temperatures and salinities in all layers relative to the free run. For temperature and salinity during the period of ship voyages, the RMSDs are reduced by 32.9 and 25.5%, respectively. The temporal variations of the deep-water salinity caused by saltwater inflows are better captured by the reanalysis than by the free run. Moreover, the reanalysis improved the estimation of the depth of the halocline and thermocline, which are overestimated in the simulation without data assimilation.

  • 191.
    Liu, Ye
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Improving the multiannual, high-resolution modelling of biogeochemical cycles in the Baltic Sea by using data assimilation2014In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 66, article id 24908Article in journal (Refereed)
    Abstract [en]

    The impact of assimilating temperature, salinity, oxygen, phosphate and nitrate observations on marine ecosystem modelling is assessed. For this purpose, two 10-yr (1970-1979) reanalyses of the Baltic Sea are carried out using the ensemble optimal interpolation (EnOI) method and a coupled physical-biogeochemical model of the Baltic Sea. To evaluate the reanalyses, climatological data and available biogeochemical and physical in situ observations at monitoring stations are compared with results from simulations with and without data assimilation. In the first reanalysis, only observed temperature and salinity profiles are assimilated, whereas biogeochemical observations are unused. Although simulated temperature and salinity improve considerably as expected, the quality of simulated biogeochemical variables does not improve and deep water nitrate concentrations even worsen. This unexpected behaviour is explained by a lowering of the halocline in the Baltic proper due to the assimilation causing increased oxygen concentrations in the deep water and consequently altered nutrient fluxes. In the second reanalysis, both physical and biogeochemical observations are assimilated and good quality in all variables is found. Hence, we conclude that if a data assimilation method like the EnOI is applied, all available observations should be used to perform reanalyses of high quality for the Baltic Sea biogeochemical state estimates.

  • 192.
    Liu, Ye
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Nutrient transports in the Baltic Sea - results from a 30-year physical-biogeochemical reanalysis2017In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 14, no 8, p. 2113-2131Article in journal (Refereed)
  • 193.
    Ljungemyr, Patrik
    et al.
    SMHI, Core Services.
    Gustafsson, Nils
    SMHI, Research Department, Meteorology.
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Parameterization of lake thermodynamics in a high-resolution weather forecasting model1996In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 48, no 5, p. 608-621Article in journal (Refereed)
    Abstract [en]

    A model for the parameterization of lake temperatures and lake ice thicknesses in atmospheric models is presented. The model is verified independently, and it is also tested within the framework of the High Resolution Limited Area Model(HIRLAM), applied operationally for short range weather forecasting at the Swedish Meteorological and Hydrological Institute (SMHI). The lake model is a slab model based upon energy conservation and treats the lakes as well mixed boxes with depths represented by the mean depths. The model is forced by near surface fluxes calculated from total cloudiness, air temperature, air humidity and low-level winds. A data base, describing 92000 Swedish lakes. provides the model with lake mean depths, areal sizes and locations. When the model is used for parameterization of lake effects in the atmospheric model, all the smaller lakes and the fractions of larger lakes within each horizontal grid square of the atmospheric model are parameterized by four model lakes, representing the lake size distribution. The verification of the lake model is done by comparing it with a more advanced, vertically resolved model, including parameterization of turbulent mixing processes, as well as by comparison with observations. A sensitivity test shows great interannual variations of the ice-covered season, which implies that lake models should be used instead of climate data. The results from an experiment with two-way coupling of the lake model to the atmospheric model are verified by comparing forecasted weather parameters with routine meteorological observations. These results show that the impact of lake effects can reach several degrees C in air temperatures close to the surface.

  • 194.
    Ljungman, Olof
    et al.
    SMHI, Research Department, Oceanography.
    Rydberg, Lars
    SMHI, Research Department, Oceanography.
    Goransson, C G
    Modeling and observations of deep water renewal and entrainment in a Swedish sill fjord2001In: Journal of Physical Oceanography, ISSN 0022-3670, E-ISSN 1520-0485, Vol. 31, no 12, p. 3401-3420Article in journal (Refereed)
    Abstract [en]

    A baroclinically forced deep-water renewal event in a small Swedish sill fjord is investigated using a one-dimensional numerical model and a dataset that resolves temporal variations in salinity and oxygen. The observations indicate an almost complete renewal of the basin water within a period of 2-3 weeks. The details of the renewal process are emphasized by modeling the sill flow as well as the resulting dense bottom plume, with various rates of entrainment. It is found that sill mixing is relatively unimportant, but that entrainment increases the deep-water inflow by a factor of 2-4. Different formulas for calculating plume entrainment are compared and the model's sensitivity to variations in sill flow and bottom friction is investigated. It is shown that even weak entrainment, occurring at shallow depths where the density difference between the plume and the resident water is large, has a significant impact. Entrainment prolongs the time it takes for a complete renewal (i.e., to flush out all resident water) and, on the moderate timescales considered here, yields lower post-renewal salinity and oxygen concentrations. This implies that entrainment (and mixing) during renewal may be as important as basin water diffusion in setting the timescale for forthcoming renewal events.

  • 195. Lu, Liangliang
    et al.
    Goerlandt, Floris
    Banda, Osiris A. Valdez
    Kujala, Pentti
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Arneborg, Lars
    SMHI, Research Department, Oceanography.
    A Bayesian Network risk model for assessing oil spill recovery effectiveness in the ice-covered Northern Baltic Sea2019In: Marine Pollution Bulletin, ISSN 0025-326X, E-ISSN 1879-3363, Vol. 139, p. 440-458Article in journal (Refereed)
  • 196.
    Lundqvist, Jan-Eric
    et al.
    SMHI.
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Isförhållandena i Sveriges södra och västra farvatten1987Report (Other academic)
  • 197.
    Löptien, Ulrike
    SMHI, Research Department, Oceanography.
    Steady states and sensitivities of commonly used pelagic ecosystem model components2011In: Ecological Modelling, ISSN 0304-3800, E-ISSN 1872-7026, Vol. 222, no 8, p. 1376-1386Article in journal (Refereed)
    Abstract [en]

    Pelagic, coupled ocean circulation-ecosystem models, are widely used in climate research. These tools aim to quantify fluxes of nutrients and carbon in the ocean and are, increasingly, the base of future projections. For this purpose it is crucial to quantify and identify the sources of uncertainties. In contrast to physical models, the underlying equations for ecosystem models are derived from empirical relationships rather than based on first principles. This resulted in the development of a multitude of different ecosystem models - different in respect to both, underlying principles and complexity. Clearly, the question arises, to what extent the sensitivities of these models are comparable. This study focuses on the intrinsic dynamics of some widely used, simple (containing 2-3 prognostic variables) ecosystem models in a 0-D framework (i.e., comprising only the well-mixed oceanic surface layer). A suite of differing model approaches is tuned such that their behavior is similar. The setup resembles the well-mixed oceanic surface layer in the Baltic proper. It is illustrated that strong differences between the model approaches appear due to exemplary, anticipated changes in the external nutrient and light conditions. Herewith, we demonstrate the well-known, but rarely demonstrated fact that, apparent consistency between modeled prognostic variables with today's data bases is not necessarily a good measure of forecast skill. The causes which lead to the different sensitivities are illustrated by considering the steady state solutions. It is pointed out, that apparently small changes in the model formulations can result in very different dynamical behavior and an enormous spread between the model approaches, despite the feasibility to tune a common behavior in a limited range of light and nutrient supply. In our examples, the sensitivity is mainly a function of the formulation of the loss rate of phytoplankton. It is thus, in particular, the formulation of highly unknown heteorotrophic processes that determines the model sensitivity. (C) 2011 Elsevier B.V. All rights reserved.

  • 198. Löptien, Ulrike
    et al.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Ice and AIS: ship speed data and sea ice forecasts in the Baltic Sea2014In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 8, no 6, p. 2409-2418Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea is a seasonally ice-covered marginal sea located in a densely populated area in northern Europe. Severe sea ice conditions have the potential to hinder the intense ship traffic considerably. Thus, sea ice fore-and nowcasts are regularly provided by the national weather services. Typically, the forecast comprises several ice properties that are distributed as prognostic variables, but their actual usefulness is difficult to measure, and the ship captains must determine their relative importance and relevance for optimal ship speed and safety ad hoc. The present study provides a more objective approach by comparing the ship speeds, obtained by the automatic identification system (AIS), with the respective forecasted ice conditions. We find that, despite an unavoidable random component, this information is useful to constrain and rate fore-and nowcasts. More precisely, 62-67% of ship speed variations can be explained by the forecasted ice properties when fitting a mixed-effect model. This statistical fit is based on a test region in the Bothnian Sea during the severe winter 2011 and employs 15 to 25 min averages of ship speed.

  • 199.
    Löptien, Ulrike
    et al.
    SMHI, Research Department, Oceanography.
    Eden, Carsten
    Multidecadal CO2 uptake variability of the North Atlantic2010In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 115, article id D12113Article in journal (Refereed)
    Abstract [en]

    The multidecadal variability of air-sea CO(2)fluxes in the North Atlantic under preindustrial atmospheric CO2 conditions is simulated, using a coupled biogeochemical/circulation model driven by long-term surface forcing reconstructed from the leading modes of sea level pressure observations from 1850 to 2000. Heat fluxes are of great importance for the multidecadal CO2 fluctuations, about equal in magnitude to wind stress, in contrast to their less prominent role for CO2 flux variability on interannual timescales. Another difference, compared to higher frequencies, is the dominance of the North Atlantic Oscillation in driving the variability of the air-sea CO2 fluxes. Two spatially distinct regimes lead to large anomalies in the CO2 fluxes but compensate to a large degree. The first regime is advective and has its clear signature southeast of Greenland while the second one, in the vicinity of the Labrador Sea and off Newfoundland, is convective. In both regimes, the multidecadal CO2 fluctuations are driven mainly by variations in temperature, salinity, and DIC content at the sea surface while the role of the biological pump is of minor importance in this particular model. The magnitude of the simulated multidecadal CO2 uptake changes is on the order of 0.02 Pg C/yr and amounts to 10-15% of the estimated annual anthropogenic CO2 uptake of the North Atlantic.

  • 200.
    Löptien, Ulrike
    et al.
    SMHI, Research Department, Oceanography.
    Martensson, S.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Long-term characteristics of simulated ice deformation in the Baltic Sea (1962-2007)2013In: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, ISSN 2169-9275, Vol. 118, no 2, p. 801-815Article in journal (Refereed)
    Abstract [en]

    The North Atlantic Oscillation (NAO) index is a frequently used measure for the mean winter conditions in Northern Europe. A positive, high index is associated with strong westerlies and anomalous warm temperatures. The effects on sea ice conditions in the Baltic Sea are twofold. Warm temperatures prevent sea ice formation. If ice is present nevertheless, the strong winds can promote the formation of ice ridges which hinders ship traffic. We use an ocean-sea ice model to investigate the NAO impact on the ridged ice area fraction in the Baltic during 1962-2007. Our simulations indicate that in the northern Bothnian Bay, a high NAO index is related to an anomalous accumulation of ridges, while in the rest of the Baltic Sea, the relationship is contrary. The NAO explains locally at most only 20-25% of the ridged ice fraction interannual variability which indicates the systems complexity. However, we find high skill with local correlations around 0.8 for annually averaged ridged ice fraction reconstructed from multilinear regression using winter averaged wind extremes, surface air temperature, and sea surface temperature (SST). This suggests that the amount of ridged ice in late winter can be derived from these routinely measured quantities. In large parts of the basin, it is sufficient to use the atmospheric parameters as a predictor, while in the eastern Bothnian Bay and southern Gulf of Finland, the SST is required to reconstruct the bulk of the ridged ice fraction. Citation: Loptien, U., S. Martensson, H. E. M. Meier, and A. Hoglund (2013), Long-term characteristics of simulated ice deformation in the Baltic Sea (1962-2007), J. Geophys. Res. Oceans, 118, 801-815, doi:10.1002/jgrc.20089.

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