Oceanologia No. 48 (3) / 06





A model-measurements comparison of atmospheric forcing and surface fluxes of the Baltic Sea
Oceanologia 2006, 48(3), 333-360

Claudia Rudolph, Andreas Lehmann
Leibniz Institute of Marine Science at the University of Kiel,
Duestembrooker Weg 20, D-24105 Kiel, Germany;
e-mail: alehmann@ifm-geomar.de

Keywords: Baltic Sea, coupled sea-ice-ocean model, air-sea interaction, surface fluxes, model-measurements comparison

Received 9 February 2006, revised 31 August 2006, accepted 11 September 2006.
Observed basic meteorological quantities, heat and radiation fluxes from three different measurement stations in the Baltic Sea are compared with model data of the coupled sea-ice-ocean model BSIOM in order to evaluate the atmospheric forcing, corresponding surface fluxes and the sea surface response. Observational data were made available from the BASIS winter campaigns in 1998 and 2001 as well as from the r/v "Alkor" cruise in June 2001. Simulated fluxes were calculated from prescribed atmospheric forcing provided from the SMHI meteorological database and modelled sea surface temperatures. The comparison of these fluxes with observations demonstrates a strong correlation, even though mean differences in sensible heat fluxes range from 4 to 12 W m-2 in winter and -25 W m-2 in the June experiment. Differences in latent heat fluxes range from -10 to 23 W m-2. The short-wave radiation flux used as model forcing is on average 15 W m-2 less than the corresponding observations for the winter experiments and 40 W m-2 for the June experiment. Differences in net long-wave radiation fluxes range from -5 to 12 W m-2 in winter and -62 W m-2 for the June experiment. The correspondence between measured and calculated momentum fluxes is very high, which confirms the usability of our model component for calculating surface winds and wind stresses from the atmospheric surface pressure.
full, complete article (PDF - compatibile with Acrobat 4.0), 4495 KB

Influence of wind climate changes on the mean sea level and current regime in the coastal waters of west Estonia, Baltic Sea
Oceanologia 2006, 48(3), 361-383

Ülo Suursaar, Tiit Kullas
Estonian Marine Institute, University of Tartu,
Mäealuse 10a, EE-12618 Tallinn, Estonia;
e-mail: ulo.suursaar@ut.ee

Keywords: sea level, wind driven circulation, climate change, hydrodynamic models, Baltic Sea

Received 29 March 2006, revised 2 August 2006, accepted 7 August 2006.

This work was supported by the Estonian Science Foundation through grants Nos 5929 and 5763.
The response of semi-realistic wind speed increase scenarios to the mean sea level and current regime of semi-enclosed sub-basins in the Baltic Sea is studied with a 2D hydrodynamic model. According to the model output of spatial mean sea levels, an increase in the westerly wind component by 2 m s-1 leads, for example, to a mean sea level rise of up to 3 cm in windward locations in the study area. The sea level change patterns depend on the wind scenario and coastline configuration. The increases in wind speed considered here also lead to enhanced water exchange through the straits, strengthening of the basin-scale circulation, enhancement of up- and downwelling, and increased bottom stresses near coasts.
full, complete article (PDF - compatibile with Acrobat 4.0), 4599 KB

Production of transparent exopolymer particles (TEP) in the nitrogen fixing cyanobacterium Anabaena flos-aquae OL-K10
Oceanologia 2006, 48(3), 385-394

Waldemar Surosz1*, Katarzyna A. Palińska2, Agnieszka Rutkowska1
1Institute of Oceanography, University of Gdańsk,
al. Marszałka Piłsudskiego 46, PL-81-378 Gdynia, Poland;
e-mail: ocews@univ.gda.pl
*corresponding author
2Carl von Ossietzky University, ICBM, Geomicrobiology,
PO Box 2503, D-26111 Oldenburg, Germany

Keywords: transparent exopolymer particles (TEP), Anabaena flos-aquae, chlorophyll a concentration

Received 13 January 2006, revised 8 August 2006, accepted 28 August 2006.
The aim of the study was to measure the transparent exopolymer particles (TEP) concentration in cultures of Anabaena flos-aquae OL-K10 and to determine the relationship between the quantity of particles produced and the light intensity, the age of the culture and the presence of nitrogen in the culture medium. This is the first time TEP production has been investigated in the Nostocales, an order of nitrogen-fixing phytoplankton species. The results showed that TEP production depends on the presence of nitrogen in the culture medium. The longer the culture is grown, the higher the correlation between its TEP content and its chlorophyll a concentration.
full, complete article (PDF - compatibile with Acrobat 4.0), 527 KB

Modelling longshore sediment transport under asymmetric waves
Oceanologia 2006, 48(3), 395-412

Rafał Ostrowski, Marek Szmytkiewicz
Institute of Hydroengineering,
Polish Academy of Sciences, (IBW PAN)
Kościerska 7, PL-80-328 Gdańsk, Poland;
e-mail: rafi@ibwpan.gda.pl

Keywords: wave asymmetry, wave-current interaction, longshore sediment transport

Received 8 March 2006, revised 30 July 2006, accepted 2 August 2006.
Two wave theories are applied in calculations of longshore sediment transport rates: the second Stokes approximation and the cnoidal theory. These approaches are used to model sand motion in nearshore locations beyond and within the surf zone. Wave-current interaction in the nearbed layer and bed shear stresses are solved using a momentum integral method, whereas sediment transport is described by a three-layer model encompassing bedload, contact load and suspended load. Computational results for asymmetric waves are compared with the results obtained using linear wave theory and the conventional sediment transport models of Bailard (1981), Bijker (1971) and Van Rijn (1993).
full, complete article (PDF - compatibile with Acrobat 4.0), 233 KB

Longshore sediment transport at Golden Sands (Bulgaria)
Oceanologia 2006, 48(4), 413-432

Hristo Nikolov1, Ekaterina Trifonova1, Zhivelina Cherneva1, Rafał Ostrowski2,*, Marek Skaja2, Marek Szmytkiewicz2
1Institute of Oceanology, Bulgarian Academy of Sciences,(IO BAS),
PO Box 152, 9000 Varna, Bulgaria
2Institute of Hydroengineering,
Polish Academy of Sciences, (IBW PAN),
Kościerska 7, PL-80-328 Gdańsk, Poland;
e-mail: rafi@ibwpan.gda.pl

*corresponding author

Keywords: Golden Sands, sediment transport, wave refraction and diffraction, offshore wave climate

Received 18 March 2006, revised 6 September 2006, accepted 11 September 2006.

The study was funded by the Ministry of Science and Higher Education, Poland, under programme 2 IBW PAN, and by the IO BAS statutory research programme. The activities relating to this study were also supported within the joint Polish-Bulgarian cooperation project by the Polish Academy of Sciences and the Bulgarian Academy of Sciences, which are hereby gratefully acknowledged.
The paper presents the results of studies on the qualitative and quantitative features of the littoral drift at Golden Sands (Bulgaria), carried out jointly by Polish and Bulgarian researchers. The mathematical modelling of physical coastal processes took wave transformation (wave diffraction and refraction; the effects of shoaling and wave breaking) and longshore sediment transport into account. The computations were carried out for the mean statistical annual wave climate, determined on the basis of IO BAS wave data, simulated using the WAM method from long-term Black Sea wind data. The results of sediment transport computations clearly show that its direction off the Golden Sands shore is from north to south.
full, complete article (PDF - compatibile with Acrobat 4.0), 364 KB

Development and dynamics of a coastal sub-surface phytoplankton bloom in the southwest Kattegat, Baltic Sea
Oceanologia 2006, 48(4), 433-446

Lars Chresten Lund-Hansen
Department of Marine Sciences,
Institute of Biology, Aarhus University,
Finlandsgade 14, 8200 Aarhus N, Denmark;
e-mail: lund-hansen@biology.au.dk

Keywords: sub-surface phytoplankton, bloom dynamics, Kattegat

Received 13 March 2006, revised 29 July 2006, accepted 3 August 2006.

The study was a part of the research programme on Sub-Surface Blooms financially supported by the Danish Natural Science Foundation, contract No SNF 1424-28808.
The study was based on CTD-casts performed on 5 consecutive days at 7 positions along a shallow- to deep-water transect during the spring bloom in the southwest Kattegat. The development, dynamics and fate of the sub-surface chlorophyll maximum (SCM) are described. The SCM developed at a constant rate of 1.4 mg chl a m-3 d-1, which is equal to a carbon fixation rate of 49.0 mg C m-3 d-1. The SCM developed at 6 m depth at low irradiance levels (10-43.0 µE m-2 s-1). Chl a concentrations reached up to 23 mg chl a m-3 in the centre of the SCM. Growth rates in the SCM were estimated at 0.82 d-1. The water column was only weakly stratified, with nutrients in excess in the whole of the water column. The SCM was relocated vertically to depths below the photic zone by wind-induced advection between the bay and the outer Kattegat. There were indications of a horizontal relocation of the SCM by an internal standing wave. Application of high spatial and temporal resolution made it possible to estimate key SCM parameters, such as growth rates [mg chl a m-3 d-1] and carbon fixation rate [mg C m-3 d-1], on the basis of chl a variations in time and space.
full, complete article (PDF - compatibile with Acrobat 4.0), 597 KB


The first observed bloom of the diatom Dactyliosolen fragilissimus (Bergon) Hasle 1996 in the Gulf of Gdańsk
Oceanologia 2006, 48(3), 447-452

Maria Łotocka
Institute of Oceanology, Polish Academy of Sciences,
Powstańców Warszawy 55, PL-81-712 Sopot, Poland;
e-mail: Anna.Olszewska@imgw.pl
present address: lotocka@iopan.gda.pl

Keywords: Dactyliosolen fragilissimus, bloom, Gulf of Gdańsk

Received 24 August 2006, revised 4 September 2006, accepted 12 September 2006.
The diatom Dactyliosolen fragilissimus (Bergon) Hasle 1996 (syn. Rhizosolenia fragilissima Bergon 1903) occurs in the western Baltic Sea predominantly in summer, sometimes forming blooms. In autumn 2005, numerous D. fragilissimus cells were observed for the first time in the coastal waters of the Gulf of Gdańsk. In November 2005 a bloom was formed: at its peak, the diatom count was 1.1 × 106 cells dm-3 and its biomass was 8.9 mg dm-3.
full, complete article (PDF - compatibile with Acrobat 4.0), 265 KB