Seafloor terraces and semi-circular depressions related to fluid discharge in Stockholm Archipelago, Baltic Sea

2016 ◽  
Vol 46 (1) ◽  
pp. 305-306 ◽  
Author(s):  
M. Jakobsson ◽  
M. O'Regan ◽  
R. Gyllencreutz ◽  
T. Flodén
Keyword(s):  
Baltic Sea ◽  
Stockholm Archipelago

scholarly journals Potential links between Baltic Sea submarine terraces and groundwater seeping

2020 ◽  
Vol 8 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Martin Jakobsson ◽  
Matt O'Regan ◽  
Carl-Magnus Mörth ◽  
Christian Stranne ◽  
Elizabeth Weidner ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Geological Mapping ◽  
The Baltic Sea ◽  
Remotely Operated Vehicle ◽  
Sea Floor ◽  
Groundwater Levels ◽  
Starting Point ◽  
Glacial Clay ◽  
Stockholm Archipelago ◽  
The Baltic

Abstract. Submarine groundwater discharge (SGD) influences ocean chemistry, circulation, and the spreading of nutrients and pollutants; it also shapes sea floor morphology. In the Baltic Sea, SGD was linked to the development of terraces and semicircular depressions mapped in an area of the southern Stockholm archipelago, Sweden, in the 1990s. We mapped additional parts of the Stockholm archipelago, areas in Blekinge, southern Sweden, and southern Finland using high-resolution multibeam sonars and sub-bottom profilers to investigate if the sea floor morphological features discovered in the 1990s are widespread and to further address the hypothesis linking their formation to SGD. Sediment coring and sea floor photography conducted with a remotely operated vehicle (ROV) and divers add additional information to the geophysical mapping results. We find that terraces, with general bathymetric expressions of about 1 m and lateral extents of sometimes >100 m, are widespread in the surveyed areas of the Baltic Sea and are consistently formed in glacial clay. Semicircular depressions, however, are only found in a limited part of a surveyed area east of the island of Askö, southern Stockholm archipelago. While submarine terraces can be produced by several processes, we interpret our results to be in support of the basic hypothesis of terrace formation initially proposed in the 1990s; i.e. groundwater flows through siltier, more permeable layers in glacial clay to discharge at the sea floor, leading to the formation of a sharp terrace when the clay layers above seepage zones are undermined enough to collapse. By linking the terraces to a specific geologic setting, our study further refines the formation hypothesis and thereby forms the foundation for a future assessment of SGD in the Baltic Sea that may use marine geological mapping as a starting point. We propose that SGD through the submarine sea floor terraces is plausible and could be intermittent and linked to periods of higher groundwater levels, implying that to quantify the contribution of freshwater to the Baltic Sea through this potential mechanism, more complex hydrogeological studies are required.

scholarly journals Effects of boating activities on aquatic vegetation in the Stockholm archipelago, Baltic Sea

2004 ◽  
Vol 61 (2) ◽  
pp. 339-349 ◽  
Author(s):  
B.K. Eriksson ◽  
A. Sandström ◽  
M. Isæus ◽  
H. Schreiber ◽  
P. Karås
Keyword(s):  
Baltic Sea ◽  
Aquatic Vegetation ◽  
Stockholm Archipelago

scholarly journals Recovery from multi‐millennial natural coastal hypoxia in the Stockholm Archipelago, Baltic Sea, terminated by modern human activity

2020 ◽  
Vol 65 (12) ◽  
pp. 3085-3097 ◽  
Author(s):  
Niels A. G. M. Helmond ◽  
Bryan C. Lougheed ◽  
Annika Vollebregt ◽  
Francien Peterse ◽  
Guillaume Fontorbe ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Human Activity ◽  
Modern Human ◽  
Stockholm Archipelago

scholarly journals Abundance and composition of near surface microplastics and plastic debris in the Stockholm Archipelago, Baltic Sea

2017 ◽  
Vol 120 (1-2) ◽  
pp. 292-302 ◽  
Author(s):  
Berit Gewert ◽  
Martin Ogonowski ◽  
Andreas Barth ◽  
Matthew MacLeod
Keyword(s):  
Baltic Sea ◽  
Near Surface ◽  
Plastic Debris ◽  
Stockholm Archipelago

Evaluation of the Stockholm Archipelago sediments, northwestern Baltic Sea Proper, as a trap for freshwater runoff organic carbon

2005 ◽  
Vol 56 (1-2) ◽  
pp. 167-178 ◽  
Author(s):  
Anders Jönsson ◽  
Martin Lindström ◽  
Rolf Carman ◽  
Carl-Magnus Mörth ◽  
Markus Meili ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Baltic Sea ◽  
Freshwater Runoff ◽  
Stockholm Archipelago

scholarly journals Links between Baltic Sea submarine terraces and groundwater sapping

2019 ◽  
Author(s):  
Martin Jakobsson ◽  
Matt O'Regan ◽  
Carl-Magnus Mörth ◽  
Christian Stranne ◽  
Elizabeth Weidner ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Geological Mapping ◽  
The Baltic Sea ◽  
Groundwater Levels ◽  
Additional Information ◽  
Future Assessment ◽  
Starting Point ◽  
Glacial Clay ◽  
Stockholm Archipelago ◽  
The Baltic

Abstract. Submarine Groundwater Discharge (SGD) influences ocean chemistry, circulation, spreading of nutrients and pollutants, and shapes seafloor morphology. In the Baltic Sea, SGD was linked to the development of terraces and semi-circular depressions mapped in an area of the southern Stockholm Archipelago, Sweden, in the 1990s. We mapped additional parts of the Stockholm Archipelago, areas in Blekinge, southern Sweden, and southern Finland using high-resolution multibeam sonars and sub-bottom profilers to investigate if the seafloor morphological features discovered in the 1990s are widespread and to further address the hypothesis linking SGD to their formation. Sediment coring and seafloor photography conducted with a Remote Operated Vehicle (ROV) and divers add additional information to the geophysical mapping results. We find that terraces, with general bathymetric expressions of about 1 m and lateral extents of sometimes > 100 m, are widespread in the surveyed areas of the Baltic Sea and are consistently formed in glacial clay. Semi-circular depressions, however, are only found in a limited part of a surveyed area east of the island Askö, southern Stockholm Archipelago. Our study supports the basic hypothesis of terrace formation initially proposed in the 1990s, i.e. groundwater flows through siltier permeable layers in glacial clay to discharge at the seafloor, leading to the formation of a sharp terrace when the clay layers above seepage zones are undermined enough to collapse. By linking the terraces to a specific geologic setting, our study further refines the formation hypothesis and forms the foundation for a future assessment of SGD in the Baltic Sea that may use marine geological mapping as a starting point. We propose that SGD through the sub-marine seafloor terraces is most likely intermittent and linked to periods of higher groundwater levels, implying that to quantify the contribution of freshwater to the Baltic Sea through this mechanism, more complex hydrogeological studies are required.

scholarly journals Supplementary material to "Efficient removal of phosphorus and nitrogen in sediments of the eutrophic Stockholm Archipelago, Baltic Sea"

2019 ◽  
Author(s):  
Niels A. G. M. van Helmond ◽  
Elizabeth K. Robertson ◽  
Daniel J. Conley ◽  
Martijn Hermans ◽  
Christoph Humborg ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Efficient Removal ◽  
Stockholm Archipelago ◽  
Supplementary Material
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