the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Paleogeographic numerical modelling of marginal seas for the Holocene – an exemplary study of the Baltic Sea
Abstract. Sustainable management of marginal seas is based on a thorough understanding of their evolutionary trends in the past. Paleogeographic evolution of marginal seas is controlled by not only global and regional driving forces (eustatic sea level change and isostatic/tectonic movements) but also sediment erosion, transport, and deposition at smaller scales. Consistent paleogeographic reconstructions at a marginal sea scale considering the global, regional and local processes is yet to be derived, and this study presents an effort towards this goal. We present a high-resolution (0.01°×0.01°) paleogeographic reconstruction of the entire Baltic Sea and its coast for the Holocene period by combining eustatic sea-level change, glacio-isostatic movement, and sediment deposition. Our results are validated by comparison with field-based reconstructions of RSL and successfully reproduce the connection/disconnection between the Baltic Sea and the North Sea during the transitions between lake and sea phases. A consistent map of Holocene sediment thickness in the Baltic Sea has been generated, which shows that relatively thick Holocene sediment deposits (up to 36 m) are located in the southern and central parts of the Baltic Sea, corresponding to depressions of sub-basins including the Arkona Basin, the Bornholm Basin as well as the Eastern and Western Gotland Basins. In addition, some shallower coastal areas in the southern Baltic Sea also host locally confined deposits with thickness larger than 20 m and are mostly associated with alongshore sediment transport and formation of barrier islands. In contrast to the southern Baltic Sea, the Holocene sediment thickness in the northern Baltic Sea is relatively thin and mostly less than 6 m. Morphological evolution of the Baltic Sea and its coastline is featured by two distinct patterns. In the north-eastern part, change of the coastline and offshore morphology is dominated by regression caused by post-glacial rebound that outpaces the eustatic sea level rise, and the influence of sediment transport is very minor, whereas a transgression together with active sediment erosion, transport and deposition have constantly shaped the coastline and the offshore morphology in the south-eastern part, leading to formation of a wide variety of landscapes and seascapes such as barrier islands, spits and lagoons.
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Status: final response (author comments only)
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RC1: 'Comment on egusphere-2024-1931', Anonymous Referee #1, 05 Aug 2024
This manuscript presents a marginal sea basin-scale reconstruction of palaeogeography based on the combination of a big dataset including the eustatic sea levels, the GIA and the Holocene sediment accumulation for the Baltic Basin. A comparison between the modelled results and proxy-data-based reconstruction can improve the GIA model parameters, which is important for the study on Holocene sea-level history. I only have minor comments as below:
1. line 130, please explain why ΔSED should be included in the equation of relative sea level.
2. line 305, constant sediment accumulation rate was assumed in the estimation of sedimentation thickness at each time slice. However, sedimentation rate varies largely because of the changes in relative sea level, sediment supply, etc. particularly in coastal zone. Authors made a discussion in the last section of 5.3 for effect of the sediment dynamics. I feel this is not enough and expect an evaluation of the spatial distribution of areas characterized by changing sedimentation rate.
3. line 401, "whereas the Vistula Spit curves shows continuous sea-level fall" should be "whereas the Vistula Spit curves show continuous sea-level rise".
Citation: https://doi.org/10.5194/egusphere-2024-1931-RC1 -
AC3: 'Reply on RC1', Wenyan Zhang, 04 Nov 2024
Dear Reviewer,
we greatly appreciate your comments and suggestions for improving our study. Please find attached our point-to-point response to your comments.
Best regards,
Jakub Miluch, Wenyan Zhang, Jan Harff, Andreas Groh, Peter Arlinghaus and Celine Denker
Citation: https://doi.org/10.5194/egusphere-2024-1931-AC3 -
AC4: 'Reply on RC1', Wenyan Zhang, 04 Nov 2024
Dear Reviewer,
apparently we made mistake again by pressing the wrong button before uploading the response letter. We sincerely appologize for this.
Please find attached the response letter to each of your comments/questions/suggestions.
Best regards,
Jakub Miluch, Wenyan Zhang, Jan Harff, Andreas Groh, Peter Arlinghaus, and Celine Denker
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AC3: 'Reply on RC1', Wenyan Zhang, 04 Nov 2024
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RC2: 'Comment on egusphere-2024-1931', Anonymous Referee #2, 26 Sep 2024
General comments to the submitted manuscript: ‘Paleogeographic numerical modelling of marginal seas for the Holocene – an exemplary study of the Baltic Sea’ by Miluch et al.
The paper describes the paleogeographic distribution of the Baltic Sea during the Holocene. They base their observations on different data sets gathered from different countries along the Baltic Sea. For the reconstruction, they mainly use three parameters: vertical changes of the water level, vertical changes of the landmasses (tectonics and isostasy), and the thickness of the sediment deposits.
The novelty is that they include the latter one. The paper is well structured, and the Figures are certainly relevant for the message.
After reading the manuscript I have some general discussion points left:
- The spatial resolution of the grid size in the Baltic is not always clear. I have no idea how accurate and variable for instance the input data of the isostacy is, nor of those of the sediment thickness data. In qualitative sense, they indicate for instance at the data in the northern Baltic Sea is sparse, but I have no idea how sparse (in a quantitative sense, how many data points per km2).
- The spatial interpolation and extrapolation techniques are not always explicitly mentioned. A Table for all parameters including it’s resolution and spatial interpolation technique would be nice.
- The discussion about the different phases is much based on the glacial history of the area. While reading the paper, I wondered how large the influx from major rivers in central Europe was, and how this differed during the Holocene. These rivers will certainly transport sediments towards the southern shores of the Baltic.
- The interpretation around the Danish straits is based on very view data and probably also modeled in a very course sense. The authors discuss their results with those over earlier studies and conclude that not all studies for instance have two straits. How comparable are these studies if both studies are based on not a lot of observations, nor have a detailed modeling grid.
- The novelty is concentrated on the inclusion of sediment thickness data for the Baltic Sea. In the manuscript, the authors talk about ‘sediment dynamics’, ‘sediment budget’, ‘sediment mass’, and ‘sediment thickness’. The paper becomes much more precise when a clear terminology is chosen.
Really like your terms 'thickness' or 'mass'. Perhaps even better 'thickness' and 'vertical changes in thickness'.
'Budget' is perhaps more than you present (with a budget, you normally also mention lateral fluxes in the system).
'Dynamics' is closely related to sediment transport resulting in areas with erosion or deposition and you are not showing that.
More specific comments are included in the pdf-file of the manuscript.
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AC1: 'Reply on RC2', Wenyan Zhang, 04 Nov 2024
Dear Reviewer,
we greatly appreciate your comments and suggestions for improving our study. Please find attached our point-to-point response to your comments.
Best regards,
Jakub Miluch, Wenyan Zhang, Jan Harff, Andreas Groh, Peter Arlinghaus and Celine Denker
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AC2: 'Reply on RC2', Wenyan Zhang, 04 Nov 2024
Dear Reviewer,
please ignore the previous attachment since it was the reponse to RC1. We appologize for the mistake.
Please find attached our point-to-point response to your comments, questions and suggestions.
Best regards,
Jakub Miluch, Wenyan Zhang, Jan Harff, Andreas Groh, Peter Arlinghaus, and Celine Denker
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EC1: 'Comment on egusphere-2024-1931', Ira Didenkulova, 03 Oct 2024
This is the late review from Reviewer 3. Please, take it into account in the paper revision.
- AC5: 'Reply on EC1', Wenyan Zhang, 04 Nov 2024
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