Massive Ice Outcrops and Thermokarst Along the Arctic Shelf Edge: By‐Products of Ongoing Groundwater Freezing and Thawing in the Sub‐Surface.
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| Title: | Massive Ice Outcrops and Thermokarst Along the Arctic Shelf Edge: By‐Products of Ongoing Groundwater Freezing and Thawing in the Sub‐Surface. |
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| Authors: | Paull, Charles K.1 (AUTHOR) paull@MBARI.org, Hong, Jong Kuk2 (AUTHOR), Caress, David W.1 (AUTHOR), Gwiazda, Roberto1 (AUTHOR), Kim, Ji‐Hoon3 (AUTHOR), Lundsten, Eve1 (AUTHOR), Paduan, Jennifer B.1 (AUTHOR), Jin, Young Keun2 (AUTHOR), Duchesne, Mathieu J.4 (AUTHOR), Rhee, Tae Siek2 (AUTHOR), Brake, Virginia4 (AUTHOR), Obelcz, Jeffrey5 (AUTHOR), Walton, Maureen A. L.5 (AUTHOR) |
| Source: | Journal of Geophysical Research. Earth Surface. Oct2024, Vol. 129 Issue 10, p1-22. 22p. |
| Subject Terms: | *Ice, *Seawater salinity, *Groundwater temperature, Oceanographic maps, Bathymetric maps |
| Abstract: | Substantial seafloor morphological changes are rapidly occurring along the Canadian Arctic shelf edge. Five multibeam bathymetric mapping surveys, each partially covering a 15 km2 study area between 120‐ and 200‐m water depth, were conducted over a 12‐year time period. These surveys reveal that 65 new craters have developed between 2010 and 2022, averaging 6.5 m and reaching up to 30 m deep. Remotely operated vehicle investigations revealed massive ice outcrops exposed on two newly formed crater flanks. This ice is not relict subaerially formed Pleistocene permafrost because it is hosted in sediments which were deposited in a submarine setting post‐deglaciation. Low salinity porewater and sediment core ice samples with depleted oxygen isotopic compositions indicate waters with a meteoric signature are discharging and freezing in this area. These ascending brackish groundwaters are likely derived in part from thawed relict permafrost hundreds of meters under the continental shelf. They refreeze as they approach the −1.4°C seafloor, leading to the development of widespread, near seafloor, sub‐bottom ice layers. Conditions appropriate for ice melting also exist nearby where ice is exposed to seawater or warmed by ascending groundwater. Small variations in temperature and salinity lead to shifts between freezing of ascending brackish groundwater or melting of near seafloor ice layers. These conditions have produced a dramatic submarine thermokarst morphology riddled with multi‐aged depressions. Thermokarst geohazards may exist, unmapped, on other Arctic margins with groundwater channeled toward the shelf edge by a relict permafrost cap, and sufficiently cold shelf edge bottom water temperatures. Plain Language Summary: Significant seafloor changes are rapidly happening along the Canadian Arctic shelf edge, where numerous craters and mounds occur. Five seafloor mapping surveys collected over 12 years covering the same area reveal 65 new craters, reaching up to 30 m but averaging 6.5 m deep, were formed between 2010 and 2022. Observations from a remotely operated vehicle showed massive ice outcrops along the flanks of two newly formed craters. Chemical analyses of the ice show that the source of the frozen water is ascending brackish groundwaters that refreeze near the −1.4°C seafloor, forming widespread sub‐bottom ice layers that blister the seafloor producing ice‐cored mounds. The source of the groundwaters is likely melted relict permafrost from beneath the continental shelf. Where ice is exposed to seawater salinity or warmer groundwater, ice melting causes seafloor collapses. Minor temperature and salinity variations cause shifts between freezing of ascending brackish groundwater and melting of near‐seafloor ice layers. These ongoing processes create a dramatic submarine landscape composed of numerous depression and ice‐filled mounds of varying ages. This discovery of sub‐seafloor ice with a groundwater origin significantly expands our understanding of submarine permafrost within the Arctic continental shelves. Key Points: Massive outcrops of submarine ice layers were found within recently formed seafloor craters along the edge of the Arctic continental shelfOn‐going ice growth and decomposition is occurring around seafloor seepages to produce a distinctive submarine thermokarst topographyThermokarst geohazards may exist on other Arctic margins where sub‐zero water temperatures and submarine groundwater seepage occur [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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| Header | DbId: 8gh DbLabel: GreenFILE An: 180560313 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Massive Ice Outcrops and Thermokarst Along the Arctic Shelf Edge: By‐Products of Ongoing Groundwater Freezing and Thawing in the Sub‐Surface. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Paull%2C+Charles+K%2E%22">Paull, Charles K.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> paull@MBARI.org</i><br /><searchLink fieldCode="AR" term="%22Hong%2C+Jong+Kuk%22">Hong, Jong Kuk</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Caress%2C+David+W%2E%22">Caress, David W.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Gwiazda%2C+Roberto%22">Gwiazda, Roberto</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Kim%2C+Ji‐Hoon%22">Kim, Ji‐Hoon</searchLink><relatesTo>3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Lundsten%2C+Eve%22">Lundsten, Eve</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Paduan%2C+Jennifer+B%2E%22">Paduan, Jennifer B.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Jin%2C+Young Keun%22">Jin, Young Keun</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Duchesne%2C+Mathieu+J%2E%22">Duchesne, Mathieu J.</searchLink><relatesTo>4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Rhee%2C+Tae+Siek%22">Rhee, Tae Siek</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Brake%2C+Virginia%22">Brake, Virginia</searchLink><relatesTo>4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Obelcz%2C+Jeffrey%22">Obelcz, Jeffrey</searchLink><relatesTo>5</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Walton%2C+Maureen+A%2E+L%2E%22">Walton, Maureen A. L.</searchLink><relatesTo>5</relatesTo> (AUTHOR) – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Journal+of+Geophysical+Research%2E+Earth+Surface%22">Journal of Geophysical Research. Earth Surface</searchLink>. Oct2024, Vol. 129 Issue 10, p1-22. 22p. – Name: Subject Label: Subject Terms Group: Su Data: *<searchLink fieldCode="DE" term="%22Ice%22">Ice</searchLink><br />*<searchLink fieldCode="DE" term="%22Seawater+salinity%22">Seawater salinity</searchLink><br />*<searchLink fieldCode="DE" term="%22Groundwater+temperature%22">Groundwater temperature</searchLink><br /><searchLink fieldCode="DE" term="%22Oceanographic+maps%22">Oceanographic maps</searchLink><br /><searchLink fieldCode="DE" term="%22Bathymetric+maps%22">Bathymetric maps</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Substantial seafloor morphological changes are rapidly occurring along the Canadian Arctic shelf edge. Five multibeam bathymetric mapping surveys, each partially covering a 15 km2 study area between 120‐ and 200‐m water depth, were conducted over a 12‐year time period. These surveys reveal that 65 new craters have developed between 2010 and 2022, averaging 6.5 m and reaching up to 30 m deep. Remotely operated vehicle investigations revealed massive ice outcrops exposed on two newly formed crater flanks. This ice is not relict subaerially formed Pleistocene permafrost because it is hosted in sediments which were deposited in a submarine setting post‐deglaciation. Low salinity porewater and sediment core ice samples with depleted oxygen isotopic compositions indicate waters with a meteoric signature are discharging and freezing in this area. These ascending brackish groundwaters are likely derived in part from thawed relict permafrost hundreds of meters under the continental shelf. They refreeze as they approach the −1.4°C seafloor, leading to the development of widespread, near seafloor, sub‐bottom ice layers. Conditions appropriate for ice melting also exist nearby where ice is exposed to seawater or warmed by ascending groundwater. Small variations in temperature and salinity lead to shifts between freezing of ascending brackish groundwater or melting of near seafloor ice layers. These conditions have produced a dramatic submarine thermokarst morphology riddled with multi‐aged depressions. Thermokarst geohazards may exist, unmapped, on other Arctic margins with groundwater channeled toward the shelf edge by a relict permafrost cap, and sufficiently cold shelf edge bottom water temperatures. Plain Language Summary: Significant seafloor changes are rapidly happening along the Canadian Arctic shelf edge, where numerous craters and mounds occur. Five seafloor mapping surveys collected over 12 years covering the same area reveal 65 new craters, reaching up to 30 m but averaging 6.5 m deep, were formed between 2010 and 2022. Observations from a remotely operated vehicle showed massive ice outcrops along the flanks of two newly formed craters. Chemical analyses of the ice show that the source of the frozen water is ascending brackish groundwaters that refreeze near the −1.4°C seafloor, forming widespread sub‐bottom ice layers that blister the seafloor producing ice‐cored mounds. The source of the groundwaters is likely melted relict permafrost from beneath the continental shelf. Where ice is exposed to seawater salinity or warmer groundwater, ice melting causes seafloor collapses. Minor temperature and salinity variations cause shifts between freezing of ascending brackish groundwater and melting of near‐seafloor ice layers. These ongoing processes create a dramatic submarine landscape composed of numerous depression and ice‐filled mounds of varying ages. This discovery of sub‐seafloor ice with a groundwater origin significantly expands our understanding of submarine permafrost within the Arctic continental shelves. Key Points: Massive outcrops of submarine ice layers were found within recently formed seafloor craters along the edge of the Arctic continental shelfOn‐going ice growth and decomposition is occurring around seafloor seepages to produce a distinctive submarine thermokarst topographyThermokarst geohazards may exist on other Arctic margins where sub‐zero water temperatures and submarine groundwater seepage occur [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: 10.1029/2024JF007719 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 22 StartPage: 1 Subjects: – SubjectFull: Ice Type: general – SubjectFull: Seawater salinity Type: general – SubjectFull: Groundwater temperature Type: general – SubjectFull: Oceanographic maps Type: general – SubjectFull: Bathymetric maps Type: general Titles: – TitleFull: Massive Ice Outcrops and Thermokarst Along the Arctic Shelf Edge: By‐Products of Ongoing Groundwater Freezing and Thawing in the Sub‐Surface. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Paull, Charles K. – PersonEntity: Name: NameFull: Hong, Jong Kuk – PersonEntity: Name: NameFull: Caress, David W. – PersonEntity: Name: NameFull: Gwiazda, Roberto – PersonEntity: Name: NameFull: Kim, Ji‐Hoon – PersonEntity: Name: NameFull: Lundsten, Eve – PersonEntity: Name: NameFull: Paduan, Jennifer B. – PersonEntity: Name: NameFull: Jin, Young Keun – PersonEntity: Name: NameFull: Duchesne, Mathieu J. – PersonEntity: Name: NameFull: Rhee, Tae Siek – PersonEntity: Name: NameFull: Brake, Virginia – PersonEntity: Name: NameFull: Obelcz, Jeffrey – PersonEntity: Name: NameFull: Walton, Maureen A. L. IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 10 Text: Oct2024 Type: published Y: 2024 Identifiers: – Type: issn-print Value: 21699003 Numbering: – Type: volume Value: 129 – Type: issue Value: 10 Titles: – TitleFull: Journal of Geophysical Research. Earth Surface Type: main |
| ResultId | 1 |
