On Dense Bottom Currents in the Baltic Deep Water

1977 ◽  
Vol 8 (5) ◽  
pp. 297-316 ◽  
Author(s):  
Flemming Bo Pedersen
Keyword(s):  
Deep Water ◽  
Oxygen Supply ◽  
Bottom Current ◽  
Bornholm Basin ◽  
Bottom Currents ◽  
Water Currents ◽  
Baltic Proper ◽  
The Baltic

A rational entrainment function for a subcritical dense bottom current is outlined. As an example the formula has been used to some orders of magnitude calculations of the deep water currents from the Darss Sill to the Stolpe Channel. It is shown that the salt and oxygen supply to the deep water of the Baltic Proper during a »normal« year stems from this bottom current and its entrained water. The renewal of the deep water in the Baltic Proper can be traced in the Bornholm Basin, and hence it is strongly recommended, that continous measurements of salinity, temperature, oxygen, phosphate etc. are performed in the Bornholm Basin, especially in the highly entraining area just north of Bornholm.

Deep water exchange in the Baltic Proper

1993 ◽  
Vol 45 (4) ◽  
pp. 311-324 ◽  
Author(s):  
Tarmo KóUts ◽  
Anders Omstedt
Keyword(s):  
Deep Water ◽  
Water Exchange ◽  
Baltic Proper ◽  
The Baltic

scholarly journals Holocene Spatiotemporal Redox Variations in the Southern Baltic Sea

2021 ◽  
Vol 9 ◽  
Author(s):  
Dalton S. Hardisty ◽  
Natascha Riedinger ◽  
Noah J. Planavsky ◽  
Dan Asael ◽  
Steven M. Bates ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Solid Phase ◽  
Bornholm Basin ◽  
The Holocene ◽  
Isotope Data ◽  
Fe Speciation ◽  
Baltic Proper ◽  
Southern Baltic ◽  
The Baltic ◽  
Ancylus Lake

Low oxygen conditions in the modern Baltic Sea are exacerbated by human activities; however, anoxic conditions also prevailed naturally over the Holocene. Few studies have characterized the specific paleoredox conditions (manganous, ferruginous, euxinic) and their frequency in southern Baltic sub-basins during these ancient events. Here, we apply a suite of isotope systems (Fe, Mo, S) and associated elemental proxies (e.g., Fe speciation, Mn) to specifically define water column redox regimes through the Baltic Holocene in a sill-proximal to sill-distal transect (Lille Belt, Bornholm Basin, Landsort Deep) using samples collected during the Integrated Ocean Drilling Program Expedition 347. At the sill-proximal Lille Belt, there is evidence for anoxic manganous/ferruginous conditions for most of the cored interval following the transition from the Ancylus Lake to Littorina Sea but with no clear excursion to more reducing or euxinic conditions associated with the Holocene Thermal Maximum (HTM) or Medieval Climate Anomaly (MCA) events. At the sill-distal southern sub-basin, Bornholm Basin, a combination of Fe speciation, pore water Fe, and solid phase Mo concentration and isotope data point to manganous/ferruginous conditions during the Ancylus Lake-to-Littorina Sea transition and HTM but with only brief excursions to intermittently or weakly euxinic conditions during this interval. At the western Baltic Proper sub-basin, Landsort Deep, new Fe and S isotope data bolster previous Mo isotope records and Fe speciation evidence for two distinct anoxic periods but also suggest that sulfide accumulation beyond transient levels was largely restricted to the sediment-water interface. Ultimately, the combined data from all three locations indicate that Fe enrichments typically indicative of euxinia may be best explained by Fe deposition as oxides following events likely analogous to the periodic incursions of oxygenated North Sea waters observed today, with subsequent pyrite formation in sulfidic pore waters. Additionally, the Mo isotope data from multiple Baltic Sea southern basins argue against restricted and widespread euxinic conditions, as has been demonstrated in the Baltic Proper and Bothnian Sea during the HTM or MCA. Instead, similar to today, each past Baltic anoxic event is characterized by redox conditions that become progressively more reducing with increasing distance from the sill.

scholarly journals Bathymetric Properties of the Baltic Sea

2019 ◽  
Author(s):  
Martin Jakobsson ◽  
Christian Stranne ◽  
Matt O'Regan ◽  
Sarah L. Greenwood ◽  
Bo Gustafsson ◽  
...  
Keyword(s):  
High Resolution ◽  
Baltic Sea ◽  
Ocean Circulation ◽  
Deep Water ◽  
Water Exchange ◽  
The Baltic Sea ◽  
Resolution Mapping ◽  
Baltic Proper ◽  
Southern Side ◽  
The Baltic

Abstract. Marine science and engineering commonly require reliable information about seafloor depth (bathymetry), e.g. for studies of ocean circulation, bottom habitats, fishing resources, sediment transport, geohazards and site selection for platforms and cables. Baltic Sea bathymetric properties are analysed here using the using the newly released Digital Bathymetric Model (DBM) by the European Marine Observation and Data Network (EMODnet). The analyses include hypsometry, volume, descriptive depth statistics, and km-scale seafloor ruggedness, i.e. terrain heterogeneity, for the Baltic Sea as a whole as well as for 17 sub-basins defined by the Baltic Marine Environment Protection Commission (HELCOM). We compare the new EMODnet DBM with IOWTOPO, the previously most widely used DBM of the Baltic Sea which has served as the primary gridded bathymetric resource in physical and environmental studies for nearly two decades. The area of deep water exchange between the Bothnian Sea and the Northern Baltic Proper across the Åland Sea is specifically analysed in terms of depths and locations of critical bathymetric sills. The EMODnet DBM provides a bathymetric sill depth of 88 m at the northern side of the Åland Sea and 60 m at the southern side, differing from previously identified sill depths of 100 and 70 m respectively. High-resolution multibeam bathymetry acquired from this deep water exchange path, where vigorous bottom currents interacted with the seafloor, allows us to assess what we are missing in presently available DBMs in terms of physical characterisation and our ability to then interpret seafloor processes and highlights the need for continued work towards complete high-resolution mapping of the Baltic Sea seafloor.

scholarly journals The turbidite-contourite-tidalite-baroclinite-hybridite problem: orthodoxy vs. empirical evidence behind the “Bouma Sequence”

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
G. Shanmugam
Keyword(s):  
Deep Water ◽  
General Term ◽  
Bottom Current ◽  
Turbidity Currents ◽  
Facies Model ◽  
Bottom Currents ◽  
Gravity Flows ◽  
Slope Flow ◽  
Baroclinic Currents ◽  
Facies Models

AbstractThe underpinning problems of deep-water facies still remain unresolved. (1) The Tb, Tc, and Td divisions of the turbidite facies model, with traction structures, are an integral part of the “Bouma Sequence” (Ta, Tb, Tc, Td, Te). However, deposits of thermohaline contour currents, wind-driven bottom currents, deep-marine tidal currents, and baroclinic currents (internal waves and tides) also develop discrete rippled units, mimicking Tc. (2) The application of “cut-out” logic of sequences, which was originally introduced for the “Bouma Sequence”, with sharp basal contacts and sandy divisions containing well-developed traction structures, to muddy contorts with gradational basal contacts and an absence of well-developed traction structures is incongruent. (3) The presence of five internal divisions and hiatus in the muddy contoured facies model is in dispute. (4) Intersection of along slope contour currents with down slope sediment-gravity flows, triggering hybrid flows, also develops traction structures. (5) The comparison of genuine hybrid flows with down slope flow transformation of gravity flows is inconsistent with etymology of the term “hybrid”. (6) A reexamination of the Annot Sandstone at the Peira Cava type locality in SE France fails to validate either the orthodoxy of five internal divisions of the “Bouma Sequence” or their origin by turbidity currents. For example, the “Ta” division is composed of amalgamated units with inverse grading and floating mudstone clasts, suggesting a mass-transport deposit (MTD). The “Tb” and “Tc” divisions are composed of double mud layers and sigmoidal cross bedding, respectively, which suggest a tidalite origin. (7) Although it was reasonable to introduce a simplistic “Bouma Sequence” in 1962, at a time of limited knowledge on deep-water processes, it is obsolete now in 2021 to apply this model to the rock record amid a wealth of new knowledge. (8) The disconnect between 12 observed, but questionable, modern turbidity currents and over 10,000 interpreted ancient turbidites defies the doctrine of uniformitarianism. This disconnect is attributed to routine application of genetic facies models, without a pragmatic interpretation of empirical data. (9) A suggested solution to these problems is to interpret traction structures in the sedimentary record pragmatically on the basis of empirical field and experimental evidence, without any built-in bias using facies models, such as the “Bouma Sequence”. (10) Until reliable criteria are developed to distinguish traction structures of each type of bottom currents based on uniformitarianism, a general term “BCRS” (i.e., bottom-current reworked sands) is appropriate for deposits of all four kinds of bottom currents.

scholarly journals Bathymetric properties of the Baltic Sea

Ocean Science ◽  
2019 ◽  
Vol 15 (4) ◽  
pp. 905-924 ◽  
Author(s):  
Martin Jakobsson ◽  
Christian Stranne ◽  
Matt O'Regan ◽  
Sarah L. Greenwood ◽  
Bo Gustafsson ◽  
...  
Keyword(s):  
High Resolution ◽  
Baltic Sea ◽  
Deep Water ◽  
Water Exchange ◽  
The Baltic Sea ◽  
Resolution Mapping ◽  
Baltic Proper ◽  
Southern Side ◽  
Northern Side ◽  
The Baltic

Abstract. Baltic Sea bathymetric properties are analysed here using the newly released digital bathymetric model (DBM) by the European Marine Observation and Data Network (EMODnet). The analyses include hypsometry, volume, descriptive depth statistics, and kilometre-scale seafloor ruggedness, i.e. terrain heterogeneity, for the Baltic Sea as a whole as well as for 17 sub-basins defined by the Baltic Marine Environment Protection Commission (HELCOM). We compare the new EMODnet DBM with IOWTOPO the previously most widely used DBM of the Baltic Se aproduced by the Leibniz-Institut für Ostseeforschung Warnemünde (IOW), which has served as the primary gridded bathymetric resource in physical and environmental studies for nearly two decades. The area of deep water exchange between the Bothnian Sea and the Northern Baltic Proper across the Åland Sea is specifically analysed in terms of depths and locations of critical bathymetric sills. The EMODnet DBM provides a bathymetric sill depth of 88 m at the northern side of the Åland Sea and 60 m at the southern side, differing from previously identified sill depths of 100 and 70 m, respectively. High-resolution multibeam bathymetry acquired from this deep water exchange path, where vigorous bottom currents interacted with the seafloor, allows us to assess what presently available DBMs are missing in terms of physical characterization of the seafloor. Our study highlights the need for continued work towards complete high-resolution mapping of the Baltic Sea seafloor.

Changes in apparent oxygen removal in the Baltic proper deep water

2000 ◽  
Vol 25 (3-4) ◽  
pp. 421-429 ◽  
Author(s):  
Charlotta Pers ◽  
Lars Rahm
Keyword(s):  
Deep Water ◽  
Oxygen Removal ◽  
Baltic Proper ◽  
The Baltic

Operational Model and its Validation with Drift Tests in Water Areas Around the Baltic Sea

1994 ◽  
Vol 29 (2-3) ◽  
pp. 293-308
Author(s):  
J. Koponen ◽  
M. Virtanen ◽  
H. Vepsä ◽  
E. Alasaarela
Keyword(s):  
Three Dimensional ◽  
Fast Response ◽  
Velocity Measurements ◽  
Short Term ◽  
Large Lakes ◽  
Operational Model ◽  
Water Currents ◽  
Emergency Situations ◽  
Sensitivity Tests ◽  
The Baltic

Abstract Three-dimensional (3-D) mathematical models of water currents, transport, mixing, reaction kinetic, and interactions with bottom and air have been used in Finland regularly since 1982 and applied to about 40 cases in large lakes, inland seas and their coastal waters. In each case, model validity has been carefully tested with available flow velocity measurements, tracer studies and water quality observations. For operational use, i.e., for spill combatting and sea rescue, the models need fast response, proven validity and illustrative visualization. In 1987-90, validated models were implemented for operational use at five sea areas along the Finnish coast. Further validation was obtained in model applications from nine documented or arranged cases and from seven emergency situations. Sensitivity tests supplement short-term validation. In the Bothnian Sea, it was nescessary to start the calculation of water currents three days prior to the start of the experiment to reduce initial inaccuracies and to make the coastal transport estimates meaningful.

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