Plio-Pleistocene ocean circulation changes in the GOA and its impacts on the carbon and nitrogen cycles and the CIS development
The modern Gulf of Alaska (GOA) is a high nutrient low chlorophyll (HNLC) region, estimated to be important for nutrient cycling and CO2 exchange. Little is known of the GOA evolution over the Pliocene and Pleistocene as well as its impact on the Cordilleran Ice Sheet (CIS) development, when other e...
Published in: | Paleoceanography and Paleoclimatology |
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American Geophysical Union
2022
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Online Access: | http://dro.dur.ac.uk/36335/ http://dro.dur.ac.uk/36335/1/36335.pdf http://dro.dur.ac.uk/36335/2/36335VoR.pdf https://doi.org/10.1029/2021PA004341 |
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ftunivdurham:oai:dro.dur.ac.uk.OAI2:36335 2023-05-15T16:41:14+02:00 Plio-Pleistocene ocean circulation changes in the GOA and its impacts on the carbon and nitrogen cycles and the CIS development Sánchez Montes, M.L. Romero, O.E. Cowan, A.E. Müller, J. Moy, C.M. LLoyd, J.M. McClymont, E.L. 2022-07 application/pdf http://dro.dur.ac.uk/36335/ http://dro.dur.ac.uk/36335/1/36335.pdf http://dro.dur.ac.uk/36335/2/36335VoR.pdf https://doi.org/10.1029/2021PA004341 unknown American Geophysical Union dro:36335 issn:2572-4525 doi:10.1029/2021PA004341 http://dro.dur.ac.uk/36335/ https://doi.org/10.1029/2021PA004341 http://dro.dur.ac.uk/36335/1/36335.pdf http://dro.dur.ac.uk/36335/2/36335VoR.pdf An edited version of this paper was published by AGU. Copyright (2022) American Geophysical Union. Paleoceanography and Paleoclimatology, 2022, Vol.37(7), pp.e2021PA004341 [Peer Reviewed Journal] Article PeerReviewed 2022 ftunivdurham https://doi.org/10.1029/2021PA004341 2022-08-04T22:25:26Z The modern Gulf of Alaska (GOA) is a high nutrient low chlorophyll (HNLC) region, estimated to be important for nutrient cycling and CO2 exchange. Little is known of the GOA evolution over the Pliocene and Pleistocene as well as its impact on the Cordilleran Ice Sheet (CIS) development, when other evidence for changing North Pacific circulation has emerged. We analysed IODP Expedition 341 Site U1417 sediments, which extend through the Plio-Pleistocene transition (4-1.7 Ma), focussing on productivity-related biomarkers (alkenones, brassicasterol), siliceous microfossils and bulk carbon and nitrogen stable isotopes. Our results show two dominant water column regimes: one characterised by high silica and low organic matter preservation, containing microorganism remains from a mix of habitats (4-3.7 Ma) and a second characterised by low biogenic silica and increased organic matter preservation of microorganisms from dominantly open ocean habitats (3.33-3.32 Ma and 2.8-1.66 Ma). An increase of phytoplankton diversity (3.7-3.35 Ma, 3.19-2.82 Ma) characterises the two transitions of water column conditions, from oxygenated to reductive, that we attribute to a change from ocean mixing to strong stratified conditions with some occasional mixing. The biogeochemical changes in the GOA follow 400 and 100 kyr eccentricity cycles which are also reflected in changes in the CIS. We conclude that the CIS expansion created HNLC conditions in the GOA during the Mid Piacenzian Warm Period (MPWP) and the early Pleistocene. In turn, positive feedbacks increased marine productivity export, atmospheric CO2 drawdown and further CIS expansion. Article in Journal/Newspaper Ice Sheet Alaska Durham University: Durham Research Online Gulf of Alaska Pacific Paleoceanography and Paleoclimatology 37 7 |
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Open Polar |
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Durham University: Durham Research Online |
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ftunivdurham |
language |
unknown |
description |
The modern Gulf of Alaska (GOA) is a high nutrient low chlorophyll (HNLC) region, estimated to be important for nutrient cycling and CO2 exchange. Little is known of the GOA evolution over the Pliocene and Pleistocene as well as its impact on the Cordilleran Ice Sheet (CIS) development, when other evidence for changing North Pacific circulation has emerged. We analysed IODP Expedition 341 Site U1417 sediments, which extend through the Plio-Pleistocene transition (4-1.7 Ma), focussing on productivity-related biomarkers (alkenones, brassicasterol), siliceous microfossils and bulk carbon and nitrogen stable isotopes. Our results show two dominant water column regimes: one characterised by high silica and low organic matter preservation, containing microorganism remains from a mix of habitats (4-3.7 Ma) and a second characterised by low biogenic silica and increased organic matter preservation of microorganisms from dominantly open ocean habitats (3.33-3.32 Ma and 2.8-1.66 Ma). An increase of phytoplankton diversity (3.7-3.35 Ma, 3.19-2.82 Ma) characterises the two transitions of water column conditions, from oxygenated to reductive, that we attribute to a change from ocean mixing to strong stratified conditions with some occasional mixing. The biogeochemical changes in the GOA follow 400 and 100 kyr eccentricity cycles which are also reflected in changes in the CIS. We conclude that the CIS expansion created HNLC conditions in the GOA during the Mid Piacenzian Warm Period (MPWP) and the early Pleistocene. In turn, positive feedbacks increased marine productivity export, atmospheric CO2 drawdown and further CIS expansion. |
format |
Article in Journal/Newspaper |
author |
Sánchez Montes, M.L. Romero, O.E. Cowan, A.E. Müller, J. Moy, C.M. LLoyd, J.M. McClymont, E.L. |
spellingShingle |
Sánchez Montes, M.L. Romero, O.E. Cowan, A.E. Müller, J. Moy, C.M. LLoyd, J.M. McClymont, E.L. Plio-Pleistocene ocean circulation changes in the GOA and its impacts on the carbon and nitrogen cycles and the CIS development |
author_facet |
Sánchez Montes, M.L. Romero, O.E. Cowan, A.E. Müller, J. Moy, C.M. LLoyd, J.M. McClymont, E.L. |
author_sort |
Sánchez Montes, M.L. |
title |
Plio-Pleistocene ocean circulation changes in the GOA and its impacts on the carbon and nitrogen cycles and the CIS development |
title_short |
Plio-Pleistocene ocean circulation changes in the GOA and its impacts on the carbon and nitrogen cycles and the CIS development |
title_full |
Plio-Pleistocene ocean circulation changes in the GOA and its impacts on the carbon and nitrogen cycles and the CIS development |
title_fullStr |
Plio-Pleistocene ocean circulation changes in the GOA and its impacts on the carbon and nitrogen cycles and the CIS development |
title_full_unstemmed |
Plio-Pleistocene ocean circulation changes in the GOA and its impacts on the carbon and nitrogen cycles and the CIS development |
title_sort |
plio-pleistocene ocean circulation changes in the goa and its impacts on the carbon and nitrogen cycles and the cis development |
publisher |
American Geophysical Union |
publishDate |
2022 |
url |
http://dro.dur.ac.uk/36335/ http://dro.dur.ac.uk/36335/1/36335.pdf http://dro.dur.ac.uk/36335/2/36335VoR.pdf https://doi.org/10.1029/2021PA004341 |
geographic |
Gulf of Alaska Pacific |
geographic_facet |
Gulf of Alaska Pacific |
genre |
Ice Sheet Alaska |
genre_facet |
Ice Sheet Alaska |
op_source |
Paleoceanography and Paleoclimatology, 2022, Vol.37(7), pp.e2021PA004341 [Peer Reviewed Journal] |
op_relation |
dro:36335 issn:2572-4525 doi:10.1029/2021PA004341 http://dro.dur.ac.uk/36335/ https://doi.org/10.1029/2021PA004341 http://dro.dur.ac.uk/36335/1/36335.pdf http://dro.dur.ac.uk/36335/2/36335VoR.pdf |
op_rights |
An edited version of this paper was published by AGU. Copyright (2022) American Geophysical Union. |
op_doi |
https://doi.org/10.1029/2021PA004341 |
container_title |
Paleoceanography and Paleoclimatology |
container_volume |
37 |
container_issue |
7 |
_version_ |
1766031665601183744 |