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Long-term coastal openness variation and its impact on sediment grain-size distribution : A case study from the Baltic Sea

Ning, Wenxin LU ; Tang, Jing and Filipsson, Helena L. LU (2016) In Earth Surface Dynamics 4(4). p.773-780
Abstract

We analysed the long-term variations in grain-size distribution in sediments from Gåsfjärden, a fjordlike inlet in the southwestern Baltic Sea, and explored potential drivers of the recorded changes in the sediment grain-size data. Over the last 5.4 thousand years (ky) in the study region, the relative sea level decreased 17 m, which was caused by isostatic land uplift. As a consequence, Gåsfjärden was transformed from an open coastal setting to a semi-closed inlet surrounded by numerous small islands on the seaward side. To quantitatively estimate the morphological changes in Gåsfjärden over the investigated time period and to further link the changes to the grain-size distribution data, a digital elevation model (DEM)-based openness... (More)

We analysed the long-term variations in grain-size distribution in sediments from Gåsfjärden, a fjordlike inlet in the southwestern Baltic Sea, and explored potential drivers of the recorded changes in the sediment grain-size data. Over the last 5.4 thousand years (ky) in the study region, the relative sea level decreased 17 m, which was caused by isostatic land uplift. As a consequence, Gåsfjärden was transformed from an open coastal setting to a semi-closed inlet surrounded by numerous small islands on the seaward side. To quantitatively estimate the morphological changes in Gåsfjärden over the investigated time period and to further link the changes to the grain-size distribution data, a digital elevation model (DEM)-based openness index was calculated. The largest values of the openness indices were found between 5.4 and 4.4 cal ka BP, which indicates relatively high bottom water energy. During the same period, the highest sand content (∼0.4 %) and silt / clay ratio (∼0.3) in the sediment sequence were also recorded. After 4.4 cal ka BP, the average sand content was halved to ∼0.2% and the silt / clay ratio showed a significant decreasing trend over the last 4 ky. These changes were found to be associated with the gradual embayment of Gåsfjärden, as represented by the openness indices. The silt / clay ratios exhibited a delayed and relatively slower change compared with the sand content, which indicates different grain-size sediment responses to the changes in hydrodynamic energy. Our DEM-based coastal openness indices have proved to be a useful tool for interpreting the temporal dynamics of sedimentary grain size.

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author
organization
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Contribution to journal
publication status
published
subject
in
Earth Surface Dynamics
volume
4
issue
4
pages
8 pages
publisher
Copernicus Gesellschaft Mbh
external identifiers
  • scopus:84991660601
  • wos:000386591900001
ISSN
2196-6311
DOI
10.5194/esurf-4-773-2016
language
English
LU publication?
yes
id
d23920df-a8a8-4b01-ad40-05d54b0f921d
date added to LUP
2016-11-15 14:45:17
date last changed
2017-01-01 08:39:40
@article{d23920df-a8a8-4b01-ad40-05d54b0f921d,
  abstract     = {<p>We analysed the long-term variations in grain-size distribution in sediments from Gåsfjärden, a fjordlike inlet in the southwestern Baltic Sea, and explored potential drivers of the recorded changes in the sediment grain-size data. Over the last 5.4 thousand years (ky) in the study region, the relative sea level decreased 17 m, which was caused by isostatic land uplift. As a consequence, Gåsfjärden was transformed from an open coastal setting to a semi-closed inlet surrounded by numerous small islands on the seaward side. To quantitatively estimate the morphological changes in Gåsfjärden over the investigated time period and to further link the changes to the grain-size distribution data, a digital elevation model (DEM)-based openness index was calculated. The largest values of the openness indices were found between 5.4 and 4.4 cal ka BP, which indicates relatively high bottom water energy. During the same period, the highest sand content (∼0.4 %) and silt / clay ratio (∼0.3) in the sediment sequence were also recorded. After 4.4 cal ka BP, the average sand content was halved to ∼0.2% and the silt / clay ratio showed a significant decreasing trend over the last 4 ky. These changes were found to be associated with the gradual embayment of Gåsfjärden, as represented by the openness indices. The silt / clay ratios exhibited a delayed and relatively slower change compared with the sand content, which indicates different grain-size sediment responses to the changes in hydrodynamic energy. Our DEM-based coastal openness indices have proved to be a useful tool for interpreting the temporal dynamics of sedimentary grain size.</p>},
  author       = {Ning, Wenxin and Tang, Jing and Filipsson, Helena L.},
  issn         = {2196-6311},
  language     = {eng},
  month        = {10},
  number       = {4},
  pages        = {773--780},
  publisher    = {Copernicus Gesellschaft Mbh},
  series       = {Earth Surface Dynamics},
  title        = {Long-term coastal openness variation and its impact on sediment grain-size distribution : A case study from the Baltic Sea},
  url          = {http://dx.doi.org/10.5194/esurf-4-773-2016},
  volume       = {4},
  year         = {2016},
}