Deglacial nitrogen isotope changes in the Gulf of Mexico: evidence from bulk sedimentary and foraminifera-bound nitrogen in Orca Basin sediments
Constraining variations in marine N 2 -fixation over glacial-interglacial timescales is crucial for determining the role of the marine nitrogen cycle in modifying ocean productivity and climate, yet paleo-records from N 2 -fixation regions are sparse. Here we present new nitrogen isotope ( δ 15 N) r...
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fteawag:oai:dora:eawag_6808 2023-05-15T17:54:02+02:00 Deglacial nitrogen isotope changes in the Gulf of Mexico: evidence from bulk sedimentary and foraminifera-bound nitrogen in Orca Basin sediments Meckler, A. Nele Ren, Haojia Sigman, Daniel M. Gruber, Nicolas Plessen, Birgit Schubert, Carsten J. Haug, Gerald H. 2011 https://doi.org/10.1029/2011PA002156 eng eng Wiley Paleoceanography--Paleoceanography--journals:2295--0883-8305 eawag:6808 journal id: journals:2295 issn: 0883-8305 ut: 000297675400002 local: 15193 scopus: 2-s2.0-82255170815 doi:10.1029/2011PA002156 Text Journal Article 2011 fteawag https://doi.org/10.1029/2011PA002156 2023-04-09T04:47:20Z Constraining variations in marine N 2 -fixation over glacial-interglacial timescales is crucial for determining the role of the marine nitrogen cycle in modifying ocean productivity and climate, yet paleo-records from N 2 -fixation regions are sparse. Here we present new nitrogen isotope ( δ 15 N) records of bulk sediment and foraminifera test-bound (FB) nitrogen extending back to the last ice age from the oligotrophic Gulf of Mexico (GOM). Previous studies indicate a substantial terrestrial input during the last ice age and early deglacial, for which we attempt to correct the bulk sediment δ 15 N using its observed relationship with the C/N ratio. Both corrected bulk and FB- δ 15 N reveal a substantial glacial-to-Holocene decrease of δ 15 N toward Holocene values of around 2.5 ‰, similar to observations from the Caribbean. This δ 15 N change is most likely due to a glacial-to-Holocene increase in regional N 2 -fixation. A deglacial peak in the FB- δ 15 N of thermocline dwelling foraminifera Orbulina universa probably reflects a whole ocean increase in the δ 15 N of nitrate during deglaciation. The δ 15 N of the surface dwelling foraminifera Globigerinoides ruber and the corrected bulk δ 15 N show little sign of this deglacial peak, both decreasing from last glacial values much earlier than does the δ 15 N of O. universa this may indicate that G. ruber and bulk N reflect the euphotic zone signal of an early local increase in N 2 -fixation. Our results add to the evidence that, during the last ice age, the larger iron input from dust did not lead to enhanced N 2 -fixation in this region. Rather, the glacial-to-Holocene decrease in δ 15 N is best explained by a response of N 2 -fixation within the Atlantic to the deglacial increase in global ocean denitrification. Article in Journal/Newspaper Orca DORA Eawag Paleoceanography 26 4 |
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Open Polar |
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DORA Eawag |
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fteawag |
language |
English |
description |
Constraining variations in marine N 2 -fixation over glacial-interglacial timescales is crucial for determining the role of the marine nitrogen cycle in modifying ocean productivity and climate, yet paleo-records from N 2 -fixation regions are sparse. Here we present new nitrogen isotope ( δ 15 N) records of bulk sediment and foraminifera test-bound (FB) nitrogen extending back to the last ice age from the oligotrophic Gulf of Mexico (GOM). Previous studies indicate a substantial terrestrial input during the last ice age and early deglacial, for which we attempt to correct the bulk sediment δ 15 N using its observed relationship with the C/N ratio. Both corrected bulk and FB- δ 15 N reveal a substantial glacial-to-Holocene decrease of δ 15 N toward Holocene values of around 2.5 ‰, similar to observations from the Caribbean. This δ 15 N change is most likely due to a glacial-to-Holocene increase in regional N 2 -fixation. A deglacial peak in the FB- δ 15 N of thermocline dwelling foraminifera Orbulina universa probably reflects a whole ocean increase in the δ 15 N of nitrate during deglaciation. The δ 15 N of the surface dwelling foraminifera Globigerinoides ruber and the corrected bulk δ 15 N show little sign of this deglacial peak, both decreasing from last glacial values much earlier than does the δ 15 N of O. universa this may indicate that G. ruber and bulk N reflect the euphotic zone signal of an early local increase in N 2 -fixation. Our results add to the evidence that, during the last ice age, the larger iron input from dust did not lead to enhanced N 2 -fixation in this region. Rather, the glacial-to-Holocene decrease in δ 15 N is best explained by a response of N 2 -fixation within the Atlantic to the deglacial increase in global ocean denitrification. |
format |
Article in Journal/Newspaper |
author |
Meckler, A. Nele Ren, Haojia Sigman, Daniel M. Gruber, Nicolas Plessen, Birgit Schubert, Carsten J. Haug, Gerald H. |
spellingShingle |
Meckler, A. Nele Ren, Haojia Sigman, Daniel M. Gruber, Nicolas Plessen, Birgit Schubert, Carsten J. Haug, Gerald H. Deglacial nitrogen isotope changes in the Gulf of Mexico: evidence from bulk sedimentary and foraminifera-bound nitrogen in Orca Basin sediments |
author_facet |
Meckler, A. Nele Ren, Haojia Sigman, Daniel M. Gruber, Nicolas Plessen, Birgit Schubert, Carsten J. Haug, Gerald H. |
author_sort |
Meckler, A. Nele |
title |
Deglacial nitrogen isotope changes in the Gulf of Mexico: evidence from bulk sedimentary and foraminifera-bound nitrogen in Orca Basin sediments |
title_short |
Deglacial nitrogen isotope changes in the Gulf of Mexico: evidence from bulk sedimentary and foraminifera-bound nitrogen in Orca Basin sediments |
title_full |
Deglacial nitrogen isotope changes in the Gulf of Mexico: evidence from bulk sedimentary and foraminifera-bound nitrogen in Orca Basin sediments |
title_fullStr |
Deglacial nitrogen isotope changes in the Gulf of Mexico: evidence from bulk sedimentary and foraminifera-bound nitrogen in Orca Basin sediments |
title_full_unstemmed |
Deglacial nitrogen isotope changes in the Gulf of Mexico: evidence from bulk sedimentary and foraminifera-bound nitrogen in Orca Basin sediments |
title_sort |
deglacial nitrogen isotope changes in the gulf of mexico: evidence from bulk sedimentary and foraminifera-bound nitrogen in orca basin sediments |
publisher |
Wiley |
publishDate |
2011 |
url |
https://doi.org/10.1029/2011PA002156 |
genre |
Orca |
genre_facet |
Orca |
op_relation |
Paleoceanography--Paleoceanography--journals:2295--0883-8305 eawag:6808 journal id: journals:2295 issn: 0883-8305 ut: 000297675400002 local: 15193 scopus: 2-s2.0-82255170815 doi:10.1029/2011PA002156 |
op_doi |
https://doi.org/10.1029/2011PA002156 |
container_title |
Paleoceanography |
container_volume |
26 |
container_issue |
4 |
_version_ |
1766161743864659968 |