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Late Glacial and Holocene paleoceanography in the Skagerrak from high-resolution grain size records
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
2005 (English)In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 222, no 3-4, 344-369 p.Article in journal (Refereed) Published
Abstract [en]

High-resolution grain size analyses of the AMS 14C-dated, 32 m long core MD99-2286 from the northeastern Skagerrak were performed in order to study late Glacial and Holocene paleoceanographic and sedimentary changes. All ages in this study are given in calibrated thousand years before present (= AD 1950), abbreviated ‘kyr’, unless otherwise noted.

The distinct ending of IRD (ice rafted debris) in core MD99-2286, which was retrieved from a location down current from the final calving ice margin in the region, indicates that iceberg calving in the Skagerrak ended between 10.6 and 10.2 kyr.

A clay-rich sequence in core MD99-2286, deposited between 11.3 and 10.3 kyr, is attributed to outflow from the Baltic basin across south central Sweden. The sequence is correlated to similar units from cores along the Swedish west coast. The onset of this clay-rich deposition occurs progressively later in cores further south along the coast, supporting a previous hypothesis that differential glacio-isostatic uplift caused a southward migration of the Baltic outflow from the Otteid-Stenselva to the Göta Älv outlet.

A distinct coarsening towards younger sediments in core MD99-2286 indicates a hydrographic shift at 8.5 kyr, which is correlated to a shift previously reported in the Skagerrak, Kattegat and the Norwegian Channel. This shift reflects the establishment of the modern circulation system in the eastern North Sea, as a consequence of the opening of the English Channel and the Danish straits and increased Atlantic water inflow, and the subsequent development of the South Jutland Current. A general trend of coarsening, poorer sorting and increasing variability from 8.5 kyr until the present indicates increasing strength and influence of the variable South Jutland Current.

A series of changes from ca. 6.3 to ca. 3.8 kyr in core MD99-2286 reflects strengthening of the Jutland Current towards the present day sedimentation system in the Skagerrak–Kattegat. These changes are correlated to previously reported hydrographic shifts at 5.5 14C years BP in the Skagerrak and at 4.0 14C years BP in the Kattegat. It is suggested that these shifts were separate features of a transitional period related to strengthening of the current system. The resulting changes are differently manifested in different parts of the Skagerrak–Kattegat, due to the complex circulation system.

The last 800 years are characterised by poorly sorted sediments with a relatively high and variable proportion of coarse material, reflecting a circulation system significantly modified by regional climatic conditions, especially the general wind directions and storm frequency over the southern North Sea.

Place, publisher, year, edition, pages
Elsevier B.V. , 2005. Vol. 222, no 3-4, 344-369 p.
Keyword [en]
Skagerrak; Holocene; grain size; sediment; Baltic Sea; hydrographic shift
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:su:diva-23628DOI: 10.1016/j.palaeo.2005.03.025OAI: diva2:193568
Part of urn:nbn:se:su:diva-413Available from: 2005-03-23 Created: 2005-03-23 Last updated: 2011-01-18Bibliographically approved
In thesis
1. Holocene and Latest Glacial Paleoceanography in the North-Eastern Skagerrak
Open this publication in new window or tab >>Holocene and Latest Glacial Paleoceanography in the North-Eastern Skagerrak
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Detailed information on past oceanographic and climatic changes is crucial for our understanding of natural climate variability and for the assessment of future climate variations. Sediments strongly influenced by the North Atlantic Current accumulate at high rates in the northeastern Skagerrak, forming a potential highresolution archive for information on past climatic and oceanographic processes and events. Through a highresolution, multi-proxy study of the 32 meter long core MD99-2286 from the north-eastern Skagerrak, and interpretation of chirp sonar profiles from the coring area, this thesis provides new and detailed insights about the paleoceanographic development of the eastern North Sea region since the deglaciation.

The chronostratigraphic control of core MD99-2286 relies on 27 radiocarbon dates. Ages are presented in calibrated thousand years before present (abbreviated “kyr”). Core MD99-2286 was correlated to chirp sonar profiles using measured physical properties. This correlation demonstrates that a strong regional acoustic reflector, previously assumed to represent the Pleistocene/Holocene boundary, was formed as a result of rapid ice retreat during the latest Pleistocene. Based on the distribution of ice rafted debris in the core, ice berg calving in the Skagerrak ended at 10.7 kyr. Detailed grain-size analyses of the core were interpreted using a novel 3D-visualization technique. Between 11.3 and 10.3 kyr, clay-rich distal glacial marine sediments were deposited in the northeastern Skagerrak, derived from Baltic melt-water outflow across south-central Sweden through the Otteid-Stenselva strait. As a result of differential isostatic uplift, the route of the major outflow and the associated sediment deposition moved southwards along the Swedish west coast. After 10.3 kyr, sediment deposition in the north-eastern Skagerrak gradually adopted to a fully interglacial normal marine sedimentation dominated by Atlantic inflow and the North Jutland Current.

The establishment of the modern circulation system in the eastern North Sea is marked by abrupt coarsening of the sediments in core MD99-2286 at 8.5 kyr. This was a result of increased Atlantic inflow, opening of the English Channel and the Danish straits, and formation of the South Jutland Current. Mineral magnetic properties of the core show a distinct relationship reflecting general sediment source variability. After 8.5 kyr, sediments in the northeastern Skagerrak were derived predominantly from the Atlantic Ocean and the North Sea, with varying contributions from the South Jutland Current, the Baltic Current, and the currents along the coasts of western Sweden and southern Norway. Between 6.3 and 3.8 kyr, the eastern North Sea was further developed towards the modern situation by an increase of the South Jutland Current flow. The Skagerrak bottom currents were probably forced by strong Atlantic water inflow between 0.9 and 0.5 kyr, and after that by increased wind stress. The influence of regional climate on the eastern North Sea circulation has increased since the middle of the Holocene.

Place, publisher, year, edition, pages
Stockholm: Institutionen för geologi och geokemi, 2005. 30 p.
Meddelanden från Stockholms universitets institution för geologi och geokemi, ISSN 1101-1599 ; 322
Skagerrak, Holocene, sediment, chirp sonar, grain size, mineral magnetic properties
National Category
Earth and Related Environmental Sciences
urn:nbn:se:su:diva-413 (URN)91-7155-038-0 (ISBN)
Public defence
2005-04-15, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 8 C, Stockholm, 10:00
Available from: 2005-03-23 Created: 2005-03-23Bibliographically approved

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