Articles | Volume 7-osr10
https://doi.org/10.5194/sp-7-osr10-11-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/sp-7-osr10-11-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
30 Sep 2026
| OSR10 | Chapter 2.8
| 30 Sep 2026 | OSR10 | Chapter 2.8
Long term trends and variability of the mixed layer depth in the Baltic Sea
Urmas Raudsepp
Tallinn University of Technology, Ehitajate tee 5, 19086, Tallinn, Estonia
Ulvi Ahmadov
Tallinn University of Technology, Ehitajate tee 5, 19086, Tallinn, Estonia
Ilja Maljutenko
CORRESPONDING AUTHOR
Tallinn University of Technology, Ehitajate tee 5, 19086, Tallinn, Estonia
Amirhossein Barzandeh
Tallinn University of Technology, Ehitajate tee 5, 19086, Tallinn, Estonia
Mariliis Kõuts
Tallinn University of Technology, Ehitajate tee 5, 19086, Tallinn, Estonia
Priidik Lagemaa
Tallinn University of Technology, Ehitajate tee 5, 19086, Tallinn, Estonia
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Urmas Raudsepp, Ilja Maljutenko, Jan-Victor Björkqvist, Amirhossein Barzandeh, Sander Rikka, Aarne Männik, Siim Pärt, Priidik Lagemaa, Victor Alari, Kaimo Vahter, and Rivo Uiboupin
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Over the past 3 decades, the Baltic Sea has warmed and become saltier, reflecting broader atmospheric trends. Heat content changes are mainly driven by subsurface temperature variations in the upper 100 m, influenced by air temperature, evaporation, and wind stress. Freshwater content changes are largely controlled by salinity shifts in the halocline (40–120 m), with key drivers being saline inflows, precipitation, and zonal wind stress.
Amirhossein Barzandeh, Matjaž Ličer, Marko Rus, Matej Kristan, Ilja Maljutenko, Jüri Elken, Priidik Lagemaa, and Rivo Uiboupin
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We evaluated a deep-learning model, HIDRA2, for predicting sea levels along the Estonian coast and compared it to traditional numerical models. HIDRA2 performed better overall, offering faster forecasts and valuable uncertainty estimates using ensemble predictions.
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Baltic deep water is generally warmer than surface water during winter when district heating is required. Depending on the location, depth, and oceanographic situation, bottom water of Tallinn Bay can be used as an energy source for seawater heat pumps until the end of February, covering the major time interval when heating is needed. Episodically, there are colder-water events when seawater heat extraction has to be complemented by other sources of heating energy.
Anja Lindenthal, Claudia Hinrichs, Simon Jandt-Scheelke, Tim Kruschke, Priidik Lagemaa, Eefke M. van der Lee, Ilja Maljutenko, Helen E. Morrison, Tabea R. Panteleit, and Urmas Raudsepp
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In 2022, large parts of the Baltic Sea experienced the third-warmest to warmest summer and autumn temperatures since 1997 and several marine heatwaves (MHWs). Using remote sensing, reanalysis, and in situ data, this study characterizes regional differences in MHW properties in the Baltic Sea in 2022. Furthermore, it presents an analysis of long-term trends and the relationship between atmospheric warming and MHW occurrences, including their propagation into deeper layers.
Karina von Schuckmann, Lorena Moreira, Mathilde Cancet, Flora Gues, Emmanuelle Autret, Ali Aydogdu, Lluis Castrillo, Daniele Ciani, Andrea Cipollone, Emanuela Clementi, Gianpiero Cossarini, Alvaro de Pascual-Collar, Vincenzo De Toma, Marion Gehlen, Rianne Giesen, Marie Drevillon, Claudia Fanelli, Kevin Hodges, Simon Jandt-Scheelke, Eric Jansen, Melanie Juza, Ioanna Karagali, Priidik Lagemaa, Vidar Lien, Leonardo Lima, Vladyslav Lyubartsev, Ilja Maljutenko, Simona Masina, Ronan McAdam, Pietro Miraglio, Helen Morrison, Tabea Rebekka Panteleit, Andrea Pisano, Marie-Isabelle Pujol, Urmas Raudsepp, Roshin Raj, Ad Stoffelen, Simon Van Gennip, Pierre Veillard, and Chunxue Yang
State Planet, 4-osr8, 2, https://doi.org/10.5194/sp-4-osr8-2-2024, https://doi.org/10.5194/sp-4-osr8-2-2024, 2024
Jan Åström, Fredrik Robertsen, Jari Haapala, Arttu Polojärvi, Rivo Uiboupin, and Ilja Maljutenko
The Cryosphere, 18, 2429–2442, https://doi.org/10.5194/tc-18-2429-2024, https://doi.org/10.5194/tc-18-2429-2024, 2024
Short summary
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The HiDEM code has been developed for analyzing the fracture and fragmentation of brittle materials and has been extensively applied to glacier calving. Here, we report on the adaptation of the code to sea-ice dynamics and breakup. The code demonstrates the capability to simulate sea-ice dynamics on a 100 km scale with an unprecedented resolution. We argue that codes of this type may become useful for improving forecasts of sea-ice dynamics.
Urmas Raudsepp, Ilja Maljutenko, Amirhossein Barzandeh, Rivo Uiboupin, and Priidik Lagemaa
State Planet, 1-osr7, 7, https://doi.org/10.5194/sp-1-osr7-7-2023, https://doi.org/10.5194/sp-1-osr7-7-2023, 2023
Short summary
Short summary
The freshwater content in the Baltic Sea has wide sub-regional variability characterized by the local climate dynamics. The total freshwater content trend is negative due to the recent increased inflows of saltwater, but there are also regions where the increase in runoff and decrease in ice content have led to an increase in the freshwater content.
Urmas Raudsepp and Ilja Maljutenko
Geosci. Model Dev., 15, 535–551, https://doi.org/10.5194/gmd-15-535-2022, https://doi.org/10.5194/gmd-15-535-2022, 2022
Short summary
Short summary
A model's ability to reproduce the state of a simulated object is always a subject of discussion. A new method for the multivariate assessment of numerical model skills uses the K-means algorithm for clustering model errors. All available data that fall into the model domain and simulation period are incorporated into the skill assessment. The clustered errors are used for spatial and temporal analysis of the model accuracy. The method can be applied to different types of geoscientific models.
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Short summary
Over the past 30 years, the Baltic Sea's surface mixed layer has changed unevenly: it is shoaling in the southwest due to warming and increased stratification, while deepening in the northeast as ice loss allows more winter mixing. These shifts may affect ecosystems by reducing deep-water ventilation and worsening hypoxia in the south, while enhancing nutrient redistribution and spring bloom potential in the north. The Baltic Sea's climate response is strongly regional.
Over the past 30 years, the Baltic Sea's surface mixed layer has changed unevenly: it is...
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