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Permafrost and Active Layer Temperature and Freeze/Thaw Timing Reflect Climatic Trends at Bayelva, Svalbard.

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Title: Permafrost and Active Layer Temperature and Freeze/Thaw Timing Reflect Climatic Trends at Bayelva, Svalbard.
Authors: Grünberg, Inge1 (AUTHOR) inge.gruenberg@awi.de, Groenke, Brian1,2 (AUTHOR), Westermann, Sebastian3 (AUTHOR), Boike, Julia1,4 (AUTHOR)
Source: Journal of Geophysical Research. Earth Surface. Jul2024, Vol. 129 Issue 7, p1-25. 25p.
Subject Terms: *Atmospheric temperature, *Soil moisture measurement, *Snow cover, *Climate change, Snow accumulation
Abstract: Permafrost warming has been observed all around the Arctic, however, variations in temperature trends and their drivers remain poorly understood. We present a comprehensive analysis of climatic changes spanning 25 years (1998–2023) at Bayelva (78.92094°N, 11.83333°E) on Spitzbergen, Svalbard. The quality controlled hourly data set includes air temperature, radiation fluxes, snow depth, rainfall, active layer temperature and moisture, and, since 2009, permafrost temperature. Our Bayesian trend analysis reveals an annual air temperature increase of 0.9 ± 0.5°C/decade and strongest warming in September and October. We observed a significant shortening of the snow cover by −14 ± 8 days/decade, coupled with reduced winter snow depth. The active layer simultaneously warmed by 0.6 ± 0.7°C/decade at the top and 0.8 ± 0.5°C/decade at the bottom. While the soil surface got drier, in particular during summer, soil moisture below increased in accordance with the longer unfrozen period and higher winter temperatures. The thawed period prolonged by 10–15 days/decade at different depths. In contrast to earlier top‐soil warming, we observed stable temperatures since 2010 and only little permafrost warming (0.14 ± 0.13°C/decade). This is likely due to recently stable winter air temperature and continuously decreasing winter snow depth. This recent development highlights a complex interplay among climate and soil variables. Our distinctive long‐term data set underscores (a) the changes in seasonal warming patterns, (b) the influential role of snow cover decline, and (c) that air temperature alone is not a sufficient indicator of change in permafrost environments, thereby highlighting the importance of investigating a wider range of parameters, such as soil moisture and snow characteristics. Plain Language Summary: Permafrost is warming across the Arctic, but it is not yet well understood why temperature trends vary and what affects them the most. Our detailed study investigates 25 years (1998–2023) of data at the Bayelva permafrost observatory on Svalbard. We analyzed a quality‐controlled data set, including hourly measurements of air temperature, radiation, snow depth, rainfall, permafrost temperature, and active layer conditions. We looked beyond annual averages, examining changes in each month. The air warmed strongly by 0.9°C/decade and even stronger in September and October. Continuous snow cover shortened by −14 days/decade and winter snow depth decreased. Simultaneously, the active layer warmed by 0.6°C/decade at the top and 0.8°C/decade at the bottom. While the surface dried in summer, deeper soil layers became moister due to a longer unfrozen period and higher temperatures in winter. The thawed period extended by 10–15 days/decade, with slightly stronger changes toward later freezing in autumn. We found that soil warming stopped in recent years and attributed this effect to the lower winter snow depth since 2010. Therefore, if we want to know how permafrost warms or cools in the future, we need to consider additional measurements such as soil moisture and snow properties. Key Points: Snow cover thinning and winter air temperature variability are the most important drivers of trends in permafrost temperatureWhile mean annual air temperature continues to increase, the top soil at Bayelva, Svalbard, stopped warming since 2010The fully snow‐covered season shortened by −14 days per decade since 1998, which led to longer unfrozen conditions in the active layer [ABSTRACT FROM AUTHOR]
Copyright of Journal of Geophysical Research. Earth Surface is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Permafrost and Active Layer Temperature and Freeze/Thaw Timing Reflect Climatic Trends at Bayelva, Svalbard.
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  Data: <searchLink fieldCode="AR" term="%22Grünberg%2C+Inge%22">Grünberg, Inge</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> inge.gruenberg@awi.de</i><br /><searchLink fieldCode="AR" term="%22Groenke%2C+Brian%22">Groenke, Brian</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Westermann%2C+Sebastian%22">Westermann, Sebastian</searchLink><relatesTo>3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Boike%2C+Julia%22">Boike, Julia</searchLink><relatesTo>1,4</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Journal+of+Geophysical+Research%2E+Earth+Surface%22">Journal of Geophysical Research. Earth Surface</searchLink>. Jul2024, Vol. 129 Issue 7, p1-25. 25p.
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  Data: *<searchLink fieldCode="DE" term="%22Atmospheric+temperature%22">Atmospheric temperature</searchLink><br />*<searchLink fieldCode="DE" term="%22Soil+moisture+measurement%22">Soil moisture measurement</searchLink><br />*<searchLink fieldCode="DE" term="%22Snow+cover%22">Snow cover</searchLink><br />*<searchLink fieldCode="DE" term="%22Climate+change%22">Climate change</searchLink><br /><searchLink fieldCode="DE" term="%22Snow+accumulation%22">Snow accumulation</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Permafrost warming has been observed all around the Arctic, however, variations in temperature trends and their drivers remain poorly understood. We present a comprehensive analysis of climatic changes spanning 25 years (1998–2023) at Bayelva (78.92094°N, 11.83333°E) on Spitzbergen, Svalbard. The quality controlled hourly data set includes air temperature, radiation fluxes, snow depth, rainfall, active layer temperature and moisture, and, since 2009, permafrost temperature. Our Bayesian trend analysis reveals an annual air temperature increase of 0.9 ± 0.5°C/decade and strongest warming in September and October. We observed a significant shortening of the snow cover by −14 ± 8 days/decade, coupled with reduced winter snow depth. The active layer simultaneously warmed by 0.6 ± 0.7°C/decade at the top and 0.8 ± 0.5°C/decade at the bottom. While the soil surface got drier, in particular during summer, soil moisture below increased in accordance with the longer unfrozen period and higher winter temperatures. The thawed period prolonged by 10–15 days/decade at different depths. In contrast to earlier top‐soil warming, we observed stable temperatures since 2010 and only little permafrost warming (0.14 ± 0.13°C/decade). This is likely due to recently stable winter air temperature and continuously decreasing winter snow depth. This recent development highlights a complex interplay among climate and soil variables. Our distinctive long‐term data set underscores (a) the changes in seasonal warming patterns, (b) the influential role of snow cover decline, and (c) that air temperature alone is not a sufficient indicator of change in permafrost environments, thereby highlighting the importance of investigating a wider range of parameters, such as soil moisture and snow characteristics. Plain Language Summary: Permafrost is warming across the Arctic, but it is not yet well understood why temperature trends vary and what affects them the most. Our detailed study investigates 25 years (1998–2023) of data at the Bayelva permafrost observatory on Svalbard. We analyzed a quality‐controlled data set, including hourly measurements of air temperature, radiation, snow depth, rainfall, permafrost temperature, and active layer conditions. We looked beyond annual averages, examining changes in each month. The air warmed strongly by 0.9°C/decade and even stronger in September and October. Continuous snow cover shortened by −14 days/decade and winter snow depth decreased. Simultaneously, the active layer warmed by 0.6°C/decade at the top and 0.8°C/decade at the bottom. While the surface dried in summer, deeper soil layers became moister due to a longer unfrozen period and higher temperatures in winter. The thawed period extended by 10–15 days/decade, with slightly stronger changes toward later freezing in autumn. We found that soil warming stopped in recent years and attributed this effect to the lower winter snow depth since 2010. Therefore, if we want to know how permafrost warms or cools in the future, we need to consider additional measurements such as soil moisture and snow properties. Key Points: Snow cover thinning and winter air temperature variability are the most important drivers of trends in permafrost temperatureWhile mean annual air temperature continues to increase, the top soil at Bayelva, Svalbard, stopped warming since 2010The fully snow‐covered season shortened by −14 days per decade since 1998, which led to longer unfrozen conditions in the active layer [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Journal of Geophysical Research. Earth Surface is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1029/2024JF007648
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 25
        StartPage: 1
    Subjects:
      – SubjectFull: Atmospheric temperature
        Type: general
      – SubjectFull: Soil moisture measurement
        Type: general
      – SubjectFull: Snow cover
        Type: general
      – SubjectFull: Climate change
        Type: general
      – SubjectFull: Snow accumulation
        Type: general
    Titles:
      – TitleFull: Permafrost and Active Layer Temperature and Freeze/Thaw Timing Reflect Climatic Trends at Bayelva, Svalbard.
        Type: main
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            NameFull: Grünberg, Inge
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            NameFull: Groenke, Brian
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            NameFull: Westermann, Sebastian
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            NameFull: Boike, Julia
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          Dates:
            – D: 01
              M: 07
              Text: Jul2024
              Type: published
              Y: 2024
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              Value: 129
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              Value: 7
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            – TitleFull: Journal of Geophysical Research. Earth Surface
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