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Glacial Meltwater Impacts Marine Carbonate Chemistry on Iceland's Continental Shelf.

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Title: Glacial Meltwater Impacts Marine Carbonate Chemistry on Iceland's Continental Shelf.
Authors: Ljungberg, Wilma1 (AUTHOR) wilma.ljungberg@gu.se, Ulfsbo, Adam1 (AUTHOR), Majtényi‐Hill, Claudia1 (AUTHOR), Ruiz‐Angulo, Angel2 (AUTHOR), Yan Yau, Yvonne Yu1,3 (AUTHOR), McKenzie, Tristan1 (AUTHOR), Henriksson, Linnea1 (AUTHOR), Böttcher, Michael Ernst4,5,6 (AUTHOR), Santos, Isaac R.1 (AUTHOR)
Source: Journal of Geophysical Research. Oceans. Feb2026, Vol. 131 Issue 2, p1-16. 16p.
Subject Terms: *Glacial melting, *Acid neutralizing capacity, *Carbon sequestration, *Ocean acidification, Continental shelf
Geographic Terms: Iceland
Abstract: Increased meltwater runoff from glaciers may drive localized ocean acidification and impact carbon dioxide (CO2) uptake in the coastal ocean. However, the paucity of carbonate system observations from continental shelves receiving inputs from glaciers limits our understanding of cryosphere‐ocean connectivity. Here, we contrast meltwater impacts on seawater carbonate chemistry and stable isotopes (δ13C‐DIC) off marine‐ and land‐terminating glacier outflows off Iceland. On the shelf outside a marine‐terminating glacier, glacial meltwater reduced the seawater buffer capacity of receiving surface waters through dilution of total alkalinity, and increased CO2 uptake through salinity‐driven drawdown of pCO2. Primary production acted as a counterbalance to the lowered [TA‐DIC]. On the shelf area receiving meltwater from large glacial river deltas, CO2 uptake was almost halved and the saturation state of aragonite was 0.2 units lower than on the marine‐terminating glacier shelf. Reduced net autotrophy due to higher turbidity and upwelling of low‐pH deep waters off the delta‐dominated shelf likely explain those differences. The diverging carbonate dynamics on the two shelves build on previous observations that land‐terminating glaciers can reduce the buffer capacity as well as CO2 uptake potential of nearshore surface waters in comparison to marine‐terminating glaciers. The future retreat of many marine‐terminating glaciers onto land is likely to modify how meltwater will impact coastal seawater carbonate chemistry. Plain Language Summary: Glaciers are rapidly retreating, increasing meltwater release to the coastal ocean and altering meltwater pathways. Understanding the impacts of changing glacial systems on carbon budgets becomes increasingly important. We investigated how meltwater from an ocean‐terminating glacier (via a glacial lagoon) and from land‐terminating glaciers (via large river deltas) affects the capacity for absorption of atmospheric CO2 and ocean acidification resilience on the Icelandic continental shelf. Outside the ocean‐terminating glacier, surface seawater could absorb more CO2. In contrast, on the river delta area, CO2 uptake was nearly halved and the ability of the seawater to withstand ocean acidification was lower than outside the marine‐terminating glacier due to turbid waters limiting photosynthesis and mixing with low‐pH deep water. The large impact of meltwater on coastal carbon dynamics emphasizes the need for observations across diverse systems as glaciers rapidly retreat. Key Points: CO2 air‐sea gas exchange was negative across the whole shelf, with a net area weighted uptake of −8.4 ± 1.4 mmol CO2 m−2 day−1Glacial meltwater reduced the buffer capacity and enhanced CO2 uptake on the continental shelf outside a marine‐terminating glacierHigh turbidity and inflow of low‐pH bottom waters explained lower CO2‐uptake and buffer capacity outside land‐terminating glaciers [ABSTRACT FROM AUTHOR]
Copyright of Journal of Geophysical Research. Oceans 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: Glacial Meltwater Impacts Marine Carbonate Chemistry on Iceland's Continental Shelf.
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  Data: <searchLink fieldCode="AR" term="%22Ljungberg%2C+Wilma%22">Ljungberg, Wilma</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> wilma.ljungberg@gu.se</i><br /><searchLink fieldCode="AR" term="%22Ulfsbo%2C+Adam%22">Ulfsbo, Adam</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Majtényi‐Hill%2C+Claudia%22">Majtényi‐Hill, Claudia</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Ruiz‐Angulo%2C+Angel%22">Ruiz‐Angulo, Angel</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Yan+Yau%2C+Yvonne+Yu%22">Yan Yau, Yvonne Yu</searchLink><relatesTo>1,3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22McKenzie%2C+Tristan%22">McKenzie, Tristan</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Henriksson%2C+Linnea%22">Henriksson, Linnea</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Böttcher%2C+Michael+Ernst%22">Böttcher, Michael Ernst</searchLink><relatesTo>4,5,6</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Santos%2C+Isaac+R%2E%22">Santos, Isaac R.</searchLink><relatesTo>1</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Journal+of+Geophysical+Research%2E+Oceans%22">Journal of Geophysical Research. Oceans</searchLink>. Feb2026, Vol. 131 Issue 2, p1-16. 16p.
– Name: Subject
  Label: Subject Terms
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  Data: *<searchLink fieldCode="DE" term="%22Glacial+melting%22">Glacial melting</searchLink><br />*<searchLink fieldCode="DE" term="%22Acid+neutralizing+capacity%22">Acid neutralizing capacity</searchLink><br />*<searchLink fieldCode="DE" term="%22Carbon+sequestration%22">Carbon sequestration</searchLink><br />*<searchLink fieldCode="DE" term="%22Ocean+acidification%22">Ocean acidification</searchLink><br /><searchLink fieldCode="DE" term="%22Continental+shelf%22">Continental shelf</searchLink>
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  Data: <searchLink fieldCode="DE" term="%22Iceland%22">Iceland</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Increased meltwater runoff from glaciers may drive localized ocean acidification and impact carbon dioxide (CO2) uptake in the coastal ocean. However, the paucity of carbonate system observations from continental shelves receiving inputs from glaciers limits our understanding of cryosphere‐ocean connectivity. Here, we contrast meltwater impacts on seawater carbonate chemistry and stable isotopes (δ13C‐DIC) off marine‐ and land‐terminating glacier outflows off Iceland. On the shelf outside a marine‐terminating glacier, glacial meltwater reduced the seawater buffer capacity of receiving surface waters through dilution of total alkalinity, and increased CO2 uptake through salinity‐driven drawdown of pCO2. Primary production acted as a counterbalance to the lowered [TA‐DIC]. On the shelf area receiving meltwater from large glacial river deltas, CO2 uptake was almost halved and the saturation state of aragonite was 0.2 units lower than on the marine‐terminating glacier shelf. Reduced net autotrophy due to higher turbidity and upwelling of low‐pH deep waters off the delta‐dominated shelf likely explain those differences. The diverging carbonate dynamics on the two shelves build on previous observations that land‐terminating glaciers can reduce the buffer capacity as well as CO2 uptake potential of nearshore surface waters in comparison to marine‐terminating glaciers. The future retreat of many marine‐terminating glaciers onto land is likely to modify how meltwater will impact coastal seawater carbonate chemistry. Plain Language Summary: Glaciers are rapidly retreating, increasing meltwater release to the coastal ocean and altering meltwater pathways. Understanding the impacts of changing glacial systems on carbon budgets becomes increasingly important. We investigated how meltwater from an ocean‐terminating glacier (via a glacial lagoon) and from land‐terminating glaciers (via large river deltas) affects the capacity for absorption of atmospheric CO2 and ocean acidification resilience on the Icelandic continental shelf. Outside the ocean‐terminating glacier, surface seawater could absorb more CO2. In contrast, on the river delta area, CO2 uptake was nearly halved and the ability of the seawater to withstand ocean acidification was lower than outside the marine‐terminating glacier due to turbid waters limiting photosynthesis and mixing with low‐pH deep water. The large impact of meltwater on coastal carbon dynamics emphasizes the need for observations across diverse systems as glaciers rapidly retreat. Key Points: CO2 air‐sea gas exchange was negative across the whole shelf, with a net area weighted uptake of −8.4 ± 1.4 mmol CO2 m−2 day−1Glacial meltwater reduced the buffer capacity and enhanced CO2 uptake on the continental shelf outside a marine‐terminating glacierHigh turbidity and inflow of low‐pH bottom waters explained lower CO2‐uptake and buffer capacity outside land‐terminating glaciers [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
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  Data: <i>Copyright of Journal of Geophysical Research. Oceans 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: 10.1029/2025JC023671
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 16
        StartPage: 1
    Subjects:
      – SubjectFull: Glacial melting
        Type: general
      – SubjectFull: Acid neutralizing capacity
        Type: general
      – SubjectFull: Carbon sequestration
        Type: general
      – SubjectFull: Ocean acidification
        Type: general
      – SubjectFull: Continental shelf
        Type: general
      – SubjectFull: Iceland
        Type: general
    Titles:
      – TitleFull: Glacial Meltwater Impacts Marine Carbonate Chemistry on Iceland's Continental Shelf.
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            NameFull: Ulfsbo, Adam
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            NameFull: Majtényi‐Hill, Claudia
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            NameFull: Ruiz‐Angulo, Angel
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            NameFull: Yan Yau, Yvonne Yu
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            NameFull: McKenzie, Tristan
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              M: 02
              Text: Feb2026
              Type: published
              Y: 2026
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