Glacial–interglacial changes and Holocene variations in Arabian Sea denitrification
At present, the Arabian Sea has a permanent oxygen minimum zone (OMZ) at water depths between about 100 and 1200 m. Active denitrification in the upper part of the OMZ is recorded by enhanced δ15N values in the sediments. Sediment cores show a δ15N increase during the middle and late Holocene, which...
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ftleibnizopen:oai:oai.leibnizopen.de:wnXbXIkBdbrxVwz6P3aX 2023-07-30T03:58:46+02:00 Glacial–interglacial changes and Holocene variations in Arabian Sea denitrification Gaye, Birgit Böll, Anna Segschneider, Joachim Burdanowitz, Nicole Emeis, Kay-Christian Ramaswamy, Venkitasubramani Lahajnar, Niko Lückge, Andreas Rixen, Tim 2018 https://repository.publisso.de/resource/frl:6417919 https://doi.org/10.5194/bg-15-507-2018 https://www.biogeosciences.net/15/507/2018/#section7 eng eng https://creativecommons.org/licenses/by/4.0/ Biogeosciences, 15:507–527 Denitrification Glacial-interglacial variation 2018 ftleibnizopen https://doi.org/10.5194/bg-15-507-2018 2023-07-16T23:24:00Z At present, the Arabian Sea has a permanent oxygen minimum zone (OMZ) at water depths between about 100 and 1200 m. Active denitrification in the upper part of the OMZ is recorded by enhanced δ15N values in the sediments. Sediment cores show a δ15N increase during the middle and late Holocene, which is contrary to the trend in the other two regions of water column denitrification in the eastern tropical North and South Pacific. We calculated composite sea surface temperature (SST) and δ15N ratios in time slices of 1000 years of the last 25 kyr to better understand the reasons for the establishment of the Arabian Sea OMZ and its response to changes in the Asian monsoon system. Low δ15N values of 4–7 ‰ during the last glacial maximum (LGM) and stadials (Younger Dryas and Heinrich events) suggest that denitrification was inactive or weak during Pleistocene cold phases, while warm interstadials (ISs) had elevated δ15N. Fast changes in upwelling intensities and OMZ ventilation from the Antarctic were responsible for these strong millennial-scale variations during the glacial. During the entire Holocene δ15N values > 6 ‰ indicate a relatively stable OMZ with enhanced denitrification. The OMZ develops parallel to the strengthening of the SW monsoon and monsoonal upwelling after the LGM. Despite the relatively stable climatic conditions of the Holocene, the δ15N records show regionally different trends in the Arabian Sea. In the upwelling areas in the western part of the basin, δ15N values are lower during the mid-Holocene (4.2–8.2 ka BP) compared to the late Holocene (< 4.2 ka BP) due to stronger ventilation of the OMZ during the period of the most intense southwest monsoonal upwelling. In contrast, δ15N values in the northern and eastern Arabian Sea rose during the last 8 kyr. The displacement of the core of the OMZ from the region of maximum productivity in the western Arabian Sea to its present position in the northeast was established during the middle and late Holocene. This was probably caused by (i) ... Other/Unknown Material Antarc* Antarctic LeibnizOpen (The Leibniz Association) Antarctic Pacific The Antarctic Biogeosciences 15 2 507 527 |
institution |
Open Polar |
collection |
LeibnizOpen (The Leibniz Association) |
op_collection_id |
ftleibnizopen |
language |
English |
topic |
Denitrification Glacial-interglacial variation |
spellingShingle |
Denitrification Glacial-interglacial variation Gaye, Birgit Böll, Anna Segschneider, Joachim Burdanowitz, Nicole Emeis, Kay-Christian Ramaswamy, Venkitasubramani Lahajnar, Niko Lückge, Andreas Rixen, Tim Glacial–interglacial changes and Holocene variations in Arabian Sea denitrification |
topic_facet |
Denitrification Glacial-interglacial variation |
description |
At present, the Arabian Sea has a permanent oxygen minimum zone (OMZ) at water depths between about 100 and 1200 m. Active denitrification in the upper part of the OMZ is recorded by enhanced δ15N values in the sediments. Sediment cores show a δ15N increase during the middle and late Holocene, which is contrary to the trend in the other two regions of water column denitrification in the eastern tropical North and South Pacific. We calculated composite sea surface temperature (SST) and δ15N ratios in time slices of 1000 years of the last 25 kyr to better understand the reasons for the establishment of the Arabian Sea OMZ and its response to changes in the Asian monsoon system. Low δ15N values of 4–7 ‰ during the last glacial maximum (LGM) and stadials (Younger Dryas and Heinrich events) suggest that denitrification was inactive or weak during Pleistocene cold phases, while warm interstadials (ISs) had elevated δ15N. Fast changes in upwelling intensities and OMZ ventilation from the Antarctic were responsible for these strong millennial-scale variations during the glacial. During the entire Holocene δ15N values > 6 ‰ indicate a relatively stable OMZ with enhanced denitrification. The OMZ develops parallel to the strengthening of the SW monsoon and monsoonal upwelling after the LGM. Despite the relatively stable climatic conditions of the Holocene, the δ15N records show regionally different trends in the Arabian Sea. In the upwelling areas in the western part of the basin, δ15N values are lower during the mid-Holocene (4.2–8.2 ka BP) compared to the late Holocene (< 4.2 ka BP) due to stronger ventilation of the OMZ during the period of the most intense southwest monsoonal upwelling. In contrast, δ15N values in the northern and eastern Arabian Sea rose during the last 8 kyr. The displacement of the core of the OMZ from the region of maximum productivity in the western Arabian Sea to its present position in the northeast was established during the middle and late Holocene. This was probably caused by (i) ... |
author |
Gaye, Birgit Böll, Anna Segschneider, Joachim Burdanowitz, Nicole Emeis, Kay-Christian Ramaswamy, Venkitasubramani Lahajnar, Niko Lückge, Andreas Rixen, Tim |
author_facet |
Gaye, Birgit Böll, Anna Segschneider, Joachim Burdanowitz, Nicole Emeis, Kay-Christian Ramaswamy, Venkitasubramani Lahajnar, Niko Lückge, Andreas Rixen, Tim |
author_sort |
Gaye, Birgit |
title |
Glacial–interglacial changes and Holocene variations in Arabian Sea denitrification |
title_short |
Glacial–interglacial changes and Holocene variations in Arabian Sea denitrification |
title_full |
Glacial–interglacial changes and Holocene variations in Arabian Sea denitrification |
title_fullStr |
Glacial–interglacial changes and Holocene variations in Arabian Sea denitrification |
title_full_unstemmed |
Glacial–interglacial changes and Holocene variations in Arabian Sea denitrification |
title_sort |
glacial–interglacial changes and holocene variations in arabian sea denitrification |
publishDate |
2018 |
url |
https://repository.publisso.de/resource/frl:6417919 https://doi.org/10.5194/bg-15-507-2018 https://www.biogeosciences.net/15/507/2018/#section7 |
geographic |
Antarctic Pacific The Antarctic |
geographic_facet |
Antarctic Pacific The Antarctic |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_source |
Biogeosciences, 15:507–527 |
op_rights |
https://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.5194/bg-15-507-2018 |
container_title |
Biogeosciences |
container_volume |
15 |
container_issue |
2 |
container_start_page |
507 |
op_container_end_page |
527 |
_version_ |
1772809509479120896 |