Relative sea-level trends in southern Norway during the last millennium

Max HOLTHUIS; F. Chantel NIXON; Malin E. KYLANDER; Willem G. M. VAN DER BILT; Isabel HONG; Kristen M. JOYSE; Thomas R. LAKEMAN; Jake MARTIN; Maria PETER; Simon Solheim HOLME; Benjamin P. HORTON

doi:10.1111/bor.70006

Relative sea-level trends in southern Norway during the last millennium

Max HOLTHUIS^*, F. Chantel NIXON, Malin E. KYLANDER, Willem G. M. VAN DER BILT, Isabel HONG, Kristen M. JOYSE, Thomas R. LAKEMAN, Jake MARTIN, Maria PETER, Simon Solheim HOLME, Benjamin P. HORTON

^*Corresponding author for this work

School of Energy and Environment

Research output: Journal Publications and Reviews › RGC 21 - Publication in refereed journal › peer-review

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Abstract

Geological reconstructions of relative sea level (RSL) from southern Norway show falling RSL during the last 7000 cal. a BP, but tide gauge measurements document a slow RSL rise since at least 1960 CE. With an age gap of c. 1400 years between the youngest geologically reconstructed sea-level index point (SLIP) and the installation of the Tregde tide gauge in southernmost Norway, the exact nature and timing of the onset of RSL rise in southern Norway remain unknown. To fill this gap, we collected peat cores from a salt marsh to reconstruct RSL trends over the past 1000 years using a multiproxy approach, including ²¹⁰Pb and ¹⁴C dating, grain-size analysis, loss-on-ignition (LOI), geochemistry (stable carbon isotopes, carbon to nitrogen ratios and XRF) and diatoms. Our data suggest decreasing tidal current strength and salinity over most of the last millennium, suggesting falling RSL. Sediment geochemistry also appears to vary with wetter and drier climatic periods. An increase in marine-brackish diatoms in combination with an acceleration in sedimentation rates after 1930 CE (1899–1954 CE) suggest that the onset of RSL rise began around this time in southernmost Norway. While most of the proxy data appear to have delayed sensitivity to RSL changes and may be linked to other causal processes, they, nonetheless, provide valuable insight into the environmental response of high-latitude temperate salt marshes to slow rates of RSL change. © 2025 The Author(s). Boreas published by John Wiley & Sons Ltd on behalf of The Boreas Collegium.

Original language	English
Journal	Boreas
Online published	25 Mar 2025
DOIs	https://doi.org/10.1111/bor.70006
Publication status	Online published - 25 Mar 2025

Funding

This research was conducted as part of the \u2018Quantifying past and future sea level changes in Norway\u2019 (QUANTSEA) project, funded by the Geological Survey of Norway (NGU) and the Norwegian Research Council (Norges forskningsr\u00E5d; NFR) (grant number 303594). NGU and NFR supported the contributions of Max Holthuis, Chantel Nixon, Thomas Lakeman, Jake Martin, Maria Peter and Simon Solheim Holme. Willem van der Bilt's contribution was supported by a Starting Grant (TMS2021STG01) from the Trond Mohn Stiftelse (TMS). We thank Mari\u2010Ann \u00D8stensen & Siv Anina Etter from the Trondhjem Biological Station (TBS) for providing access to their lab and for their input on the stable isotope analysis process. We thank Antonio Mart\u00EDnez\u2010Cortizas for his contributions to fruitful discussions on the XRF data and the PCA analysis. We thank Jenny Sj\u00F6strom for her input on the grain\u2010size analysis. We thank Jan Magne Cederstr\u00F8m and Ali Bolkar K\u0131l\u0131\u00E7 for their time and help with the analyses at EARTHLAB, University of Bergen, Bergen, Norway. We thank P\u00E5l Tore M\u00F8rkved for his work on the stable isotopes with the Elemental Analyser at FARLAB, University of Bergen, Bergen, Norway. We thank Mei Ting Law, J\u0119drzej Marcin Majewski, Jennifer Walker and Wenshu Yap for their company in the field and the following discussions. We additionally thank Wesley Farnsworth for his input on how to improve the age\u2010depth model. Lastly, we would like to express our sincere thanks to PalaeoArc for allowing us to contribute to this special issue of Boreas, as well as guest editors Nicolaj Krog Larsen and Juliane M\u00FCller, Harm Jan Pierik, and an anonymous reviewer for their helpful suggestions and valuable comments, which have greatly improved the manuscript.

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title = "Relative sea-level trends in southern Norway during the last millennium",

abstract = "Geological reconstructions of relative sea level (RSL) from southern Norway show falling RSL during the last 7000 cal. a BP, but tide gauge measurements document a slow RSL rise since at least 1960 CE. With an age gap of c. 1400 years between the youngest geologically reconstructed sea-level index point (SLIP) and the installation of the Tregde tide gauge in southernmost Norway, the exact nature and timing of the onset of RSL rise in southern Norway remain unknown. To fill this gap, we collected peat cores from a salt marsh to reconstruct RSL trends over the past 1000 years using a multiproxy approach, including 210Pb and 14C dating, grain-size analysis, loss-on-ignition (LOI), geochemistry (stable carbon isotopes, carbon to nitrogen ratios and XRF) and diatoms. Our data suggest decreasing tidal current strength and salinity over most of the last millennium, suggesting falling RSL. Sediment geochemistry also appears to vary with wetter and drier climatic periods. An increase in marine-brackish diatoms in combination with an acceleration in sedimentation rates after 1930 CE (1899–1954 CE) suggest that the onset of RSL rise began around this time in southernmost Norway. While most of the proxy data appear to have delayed sensitivity to RSL changes and may be linked to other causal processes, they, nonetheless, provide valuable insight into the environmental response of high-latitude temperate salt marshes to slow rates of RSL change. {\textcopyright} 2025 The Author(s). Boreas published by John Wiley & Sons Ltd on behalf of The Boreas Collegium.",

author = "Max HOLTHUIS and NIXON, {F. Chantel} and KYLANDER, {Malin E.} and {VAN DER BILT}, {Willem G. M.} and Isabel HONG and JOYSE, {Kristen M.} and LAKEMAN, {Thomas R.} and Jake MARTIN and Maria PETER and HOLME, {Simon Solheim} and HORTON, {Benjamin P.}",

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language = "English",

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T1 - Relative sea-level trends in southern Norway during the last millennium

AU - HOLTHUIS, Max

AU - NIXON, F. Chantel

AU - KYLANDER, Malin E.

AU - VAN DER BILT, Willem G. M.

AU - HONG, Isabel

AU - JOYSE, Kristen M.

AU - LAKEMAN, Thomas R.

AU - MARTIN, Jake

AU - PETER, Maria

AU - HOLME, Simon Solheim

AU - HORTON, Benjamin P.

PY - 2025/3/25

Y1 - 2025/3/25

N2 - Geological reconstructions of relative sea level (RSL) from southern Norway show falling RSL during the last 7000 cal. a BP, but tide gauge measurements document a slow RSL rise since at least 1960 CE. With an age gap of c. 1400 years between the youngest geologically reconstructed sea-level index point (SLIP) and the installation of the Tregde tide gauge in southernmost Norway, the exact nature and timing of the onset of RSL rise in southern Norway remain unknown. To fill this gap, we collected peat cores from a salt marsh to reconstruct RSL trends over the past 1000 years using a multiproxy approach, including 210Pb and 14C dating, grain-size analysis, loss-on-ignition (LOI), geochemistry (stable carbon isotopes, carbon to nitrogen ratios and XRF) and diatoms. Our data suggest decreasing tidal current strength and salinity over most of the last millennium, suggesting falling RSL. Sediment geochemistry also appears to vary with wetter and drier climatic periods. An increase in marine-brackish diatoms in combination with an acceleration in sedimentation rates after 1930 CE (1899–1954 CE) suggest that the onset of RSL rise began around this time in southernmost Norway. While most of the proxy data appear to have delayed sensitivity to RSL changes and may be linked to other causal processes, they, nonetheless, provide valuable insight into the environmental response of high-latitude temperate salt marshes to slow rates of RSL change. © 2025 The Author(s). Boreas published by John Wiley & Sons Ltd on behalf of The Boreas Collegium.

AB - Geological reconstructions of relative sea level (RSL) from southern Norway show falling RSL during the last 7000 cal. a BP, but tide gauge measurements document a slow RSL rise since at least 1960 CE. With an age gap of c. 1400 years between the youngest geologically reconstructed sea-level index point (SLIP) and the installation of the Tregde tide gauge in southernmost Norway, the exact nature and timing of the onset of RSL rise in southern Norway remain unknown. To fill this gap, we collected peat cores from a salt marsh to reconstruct RSL trends over the past 1000 years using a multiproxy approach, including 210Pb and 14C dating, grain-size analysis, loss-on-ignition (LOI), geochemistry (stable carbon isotopes, carbon to nitrogen ratios and XRF) and diatoms. Our data suggest decreasing tidal current strength and salinity over most of the last millennium, suggesting falling RSL. Sediment geochemistry also appears to vary with wetter and drier climatic periods. An increase in marine-brackish diatoms in combination with an acceleration in sedimentation rates after 1930 CE (1899–1954 CE) suggest that the onset of RSL rise began around this time in southernmost Norway. While most of the proxy data appear to have delayed sensitivity to RSL changes and may be linked to other causal processes, they, nonetheless, provide valuable insight into the environmental response of high-latitude temperate salt marshes to slow rates of RSL change. © 2025 The Author(s). Boreas published by John Wiley & Sons Ltd on behalf of The Boreas Collegium.

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DO - 10.1111/bor.70006

M3 - RGC 21 - Publication in refereed journal

SN - 0300-9483

JO - Boreas

JF - Boreas

ER -

Relative sea-level trends in southern Norway during the last millennium

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