Dynamics of medium-intensity dense water plumes in the Arkona Basin, Western Baltic Sea
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In this study, the dynamics of medium-intensity inflow events over Drogden Sill into the Arkona Sea are investigated. Idealised model simulations carried out with the General Estuarine Transport Model suggest that most of the salt transport during such inflow events occur north of Kriegers Flak, a shoal with less than 20 m water depth surrounded by water depths of more than 40 m. This assumption about the pathway is supported by recent ship-based observations in the Arkona Sea during a medium-intensity inflow event. The propagation of a saline bottom plume could be observed during several days after having passed Drogden Sill. In the area north of Kriegers Flak the plume was about 10 m thick, and propagated with more than 0.5 m s−1 and a salinity of up to 20 psu (with ambient water salinity being 8 psu) eastwards. Although the model simulations were idealised, the structural agreement between the observation and model result was good. The structure and pathways of these medium-intensity inflow events are of specific interest due to the plans for erecting extensive offshore wind farms in the Arkona Sea which may under certain circumstances lead to increased entrainment of ambient water into the bottom plumes.
KeywordsBottom plumes Entrainment Turbulent mixing Baltic Sea
The work for this study was carried out in the framework of the international QuantAS Consortium (Quantification of water mass transformation processes in the Arkona Sea), which is partially funded by the QuantAS-Off project (QuantAS—Impact of Offshore Wind Farms) by the German Federal Ministry of Environment, Nature Conservation and Nuclear Safety (BMU). We are further grateful for the support and flexibility of the crew on board of the R/V Helmsand without which the observations presented here could not have been obtained. The Royal Danish Administration of Navigation and Hydrography made the current velocity observations on Drogden Sill available. The sea level data were obtained from the Swedish Meteorological and Hydrological Institute. All two-dimensional graphics in this paper have been generated with the Generic Mapping Tool (GMT), and we are grateful to the specific support given by Paul Wessel, Hawaii. We are further grateful for the constructive comments by two anonymous reviewers.
- Bo Pedersen F (1980) A monograph on turbulent entrainment and friction in two-layer stratified flow. Ph.D. thesis, Danish Technical University, Lyngby, Denmark, published as Series paper 25, IHHE, DTU, Lyngby, Denmark, 397 ppGoogle Scholar
- Burchard H, Bolding K (2002) GETM—a general estuarine transport model. Scientific documentation. Tech Rep EUR 20253 EN, European CommissionGoogle Scholar
- Feistel R, Nausch G, Matthäus W, Hagen E (2003a) Temporal and spatial evolution of the Baltic deep water renewal in spring 2003. Oceanologia 45:623–642Google Scholar
- Feistel R, Nausch G, Mohrholz V, Lysiak-Pastuszak E, Seifert T, Matthäus W, Krüger S, Hansen IS (2003b) Warm waters of summer 2002 in the deep Baltic Proper. Oceanologia 45:571–592Google Scholar
- Feistel R, Nausch G, Heene T, Piechura J, Hagen E (2004) Evidence for a warm water inflow into the Baltic Proper in summer 2003. Oceanologia 46:581–598Google Scholar
- Hansen N-EO, Møller JS (1989) Zero blocking solution for the Great Belt Link. In: Pratt L (ed) Physical Oceanography of Sea Straits. NATO ASI series C, vol 318, pp 153–170Google Scholar
- Jakobsen F, Lintrup MJ, Møller JS (1997) Observations of the specific resistance in Öresund. Nordic Hydrol 28:217–232Google Scholar
- Lass HU, Mohrholz V (2003) On the dynamics and mixing of inflowing salt-water in the Arkona Sea. J Geophys Res 108:3042, doi: 10.1029/2002JC001,465Google Scholar
- Stigebrandt A (1992) Bridge-induced flow reduction in sea straits with reference to effects of a planned bridge across Öresund. Ambio 21:130–134Google Scholar
- Umlauf L, Lemmin U (2005) Inter-basin exchange and mixing in the hypolimnion of a large lake: the role of long internal waves. Limnol Oceanogr 2005, in pressGoogle Scholar