Millennial-scale variability of Atlantic water inflow in the northern Nordic Seas and the northwestern Barents Sea - Relationship to abrupt climate oscillations, cryosphere and methane seepage from the seafloor
Climate change affects the Arctic to a greater extent than the global average, causing rapid sea-ice loss and changes in the inflow of warm Atlantic water in the Arctic. Arctic sediments host vast amounts of greenhouse gases in the form of gas hydrates (ice-like cages that trap gas within), that can...
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Format: | Doctoral or Postdoctoral Thesis |
Language: | English |
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UiT Norges arktiske universitet
2021
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Online Access: | https://hdl.handle.net/10037/22253 |
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ftunivtroemsoe:oai:munin.uit.no:10037/22253 |
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record_format |
openpolar |
institution |
Open Polar |
collection |
University of Tromsø: Munin Open Research Archive |
op_collection_id |
ftunivtroemsoe |
language |
English |
topic |
VDP::Mathematics and natural science: 400::Geosciences: 450::Marine geology: 466 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Marin geologi: 466 DOKTOR-004 |
spellingShingle |
VDP::Mathematics and natural science: 400::Geosciences: 450::Marine geology: 466 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Marin geologi: 466 DOKTOR-004 El Bani Altuna, Naima Millennial-scale variability of Atlantic water inflow in the northern Nordic Seas and the northwestern Barents Sea - Relationship to abrupt climate oscillations, cryosphere and methane seepage from the seafloor |
topic_facet |
VDP::Mathematics and natural science: 400::Geosciences: 450::Marine geology: 466 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Marin geologi: 466 DOKTOR-004 |
description |
Climate change affects the Arctic to a greater extent than the global average, causing rapid sea-ice loss and changes in the inflow of warm Atlantic water in the Arctic. Arctic sediments host vast amounts of greenhouse gases in the form of gas hydrates (ice-like cages that trap gas within), that can be released to the seafloor if temperature increases and/or pressure decreases. Climate projections anticipate a further warming in the Arctic, but to improve such projections and better understand future changes interactions between climate, the ocean and the carbon cycle, it is necessary to improve long-term past climate and oceanic records. The main goal of this thesis is to reconstruct bottom water temperatures in the northern Nordic Seas and the NW Barents Sea to understand the evolution of Atlantic water inflow in the last deglaciation, and in last glacial period at times of millennial-scale climate oscillations, when the climate fluctuated between glacial-like stadials to abrupt (i.e., a few decades) warm interstadials (Dansgaard-Oeschger events; DO-events). We have also reconstructed (1) sea-ice variability and studied its linkage to the inflow of Atlantic water in the northern Nordic Seas, and (2) the gas hydrate stability zone (zone in the sediments where gas hydrates are stable) in the ‘Pingo area’ (NW Barents Sea) to investigate the effect of Atlantic water inflow in such a shallow gas hydrate system. To reconstruct bottom water temperatures, we used benthic foraminiferal Mg/Ca, that we complemented with an array of other proxies (sea-ice biomarkers, foraminiferal stable isotopes, benthic foraminiferal assemblages and ice-rafted debris) to reconstruct the overall paleoceanographic conditions in the study sites. The bottom water temperatures in both sites show considerable warming of up to 5°C during Heinrich Stadials, indicating that the inflow of Atlantic water reached the seafloor beneath a persistent sea-ice and meltwater layer. Instead, modern-like oceanographic conditions with colder bottom water temperatures occurred during interstadials. Our work demonstrates a strong coupling between sea ice and Atlantic water inflow during the last glacial period and potentially the important role of these two parameters shaping DO-events. Furthermore, the results in the ‘Pingo area’ reveal the key role of bottom water temperature shaping the dynamics of the gas hydrate stability zone and dissociation of gas hydrates. The promising results presented in this thesis highlight the importance of generating bottom water temperature records and studying its impacts on the carbon cycle and its paleoceanographic and paleoclimatic implications in the Arctic region. |
format |
Doctoral or Postdoctoral Thesis |
author |
El Bani Altuna, Naima |
author_facet |
El Bani Altuna, Naima |
author_sort |
El Bani Altuna, Naima |
title |
Millennial-scale variability of Atlantic water inflow in the northern Nordic Seas and the northwestern Barents Sea - Relationship to abrupt climate oscillations, cryosphere and methane seepage from the seafloor |
title_short |
Millennial-scale variability of Atlantic water inflow in the northern Nordic Seas and the northwestern Barents Sea - Relationship to abrupt climate oscillations, cryosphere and methane seepage from the seafloor |
title_full |
Millennial-scale variability of Atlantic water inflow in the northern Nordic Seas and the northwestern Barents Sea - Relationship to abrupt climate oscillations, cryosphere and methane seepage from the seafloor |
title_fullStr |
Millennial-scale variability of Atlantic water inflow in the northern Nordic Seas and the northwestern Barents Sea - Relationship to abrupt climate oscillations, cryosphere and methane seepage from the seafloor |
title_full_unstemmed |
Millennial-scale variability of Atlantic water inflow in the northern Nordic Seas and the northwestern Barents Sea - Relationship to abrupt climate oscillations, cryosphere and methane seepage from the seafloor |
title_sort |
millennial-scale variability of atlantic water inflow in the northern nordic seas and the northwestern barents sea - relationship to abrupt climate oscillations, cryosphere and methane seepage from the seafloor |
publisher |
UiT Norges arktiske universitet |
publishDate |
2021 |
url |
https://hdl.handle.net/10037/22253 |
geographic |
Arctic Barents Sea |
geographic_facet |
Arctic Barents Sea |
genre |
Arctic Arctic Barents Sea Climate change Dansgaard-Oeschger events Foraminifera* Nordic Seas Sea ice |
genre_facet |
Arctic Arctic Barents Sea Climate change Dansgaard-Oeschger events Foraminifera* Nordic Seas Sea ice |
op_relation |
Paper I: El bani Altuna, N., Ezat, M.M., Greaves, M. & Rasmussen, T.L. (2021). Millennial-scale changes in bottom water temperature and water mass exchange through the Fram Strait 79°N, 63–13 ka. Paleoceanography and Paleoclimatology, 36 (2), e2020PA004061. Also available in Munin at https://hdl.handle.net/10037/21004 . Paper II: El bani Altuna, N., Rasmussen, T.L., Ezat, M.M., Vadakkepuliyambatta, S., Groeneveld, J. & Greaves, M. Deglacial bottom water warming intensified Arctic methane seepage, Northwestern Barents Sea. (Manuscript in review). Now published in Nature Communications Earth & Environment, 2 , 188, available in Munin at https://hdl.handle.net/10037/22536 . Paper III: El bani Altuna, N., Ezat, M.M., Smik, L., Muschitiello, F., Belt, S.T., Knies, J. & Rasmussen, T.L. Sea ice and Atlantic water coupling during Heinrich Stadials in the northern Nordic Seas during the last glacial period 63-13 ka. (Manuscript). Data related to Paper I: El bani Altuna, N., Ezat, M., Greaves, M. & Rasmussen, T.L. (2020). Benthic and planktic foraminiferal stable isotopes, benthic foraminiferal Mg/Ca data and BWT stack, relative abundance of main benthic foraminiferal species, IRD concentration and magnetic susceptibility of core HH15-1252PC (western Svalbard margin). PANGAEA, https://doi.org/10.1594/PANGAEA.925428 . Data related to Paper II: El bani Altuna, N., Rasmussen, T.L., Ezat, M.M., Vadakkepuliyambatta, S., Groeneveld, J. & Greaves, M. (2021). Benthic and planktic foraminiferal stable isotopes, benthic foraminiferal Mg/Ca data and reconstructed gas hydrate stability zone of core HH18-1059GC (Storfjordrenna, NW Barents Sea). DataverseNO, V1, https://doi.org/10.18710/XFYDFL . info:eu-repo/grantAgreement/RCN/SFF/223259/Norway/Centre for Arctic Gas Hydrate, Environment and Climate/CAGE/ 978-82-8236-447-8 (pdf) https://hdl.handle.net/10037/22253 |
op_rights |
embargoedAccess Copyright 2021 The Author(s) |
_version_ |
1766302255639691264 |
spelling |
ftunivtroemsoe:oai:munin.uit.no:10037/22253 2023-05-15T14:28:07+02:00 Millennial-scale variability of Atlantic water inflow in the northern Nordic Seas and the northwestern Barents Sea - Relationship to abrupt climate oscillations, cryosphere and methane seepage from the seafloor El Bani Altuna, Naima 2021-09-17 https://hdl.handle.net/10037/22253 eng eng UiT Norges arktiske universitet UiT The Arctic University of Norway Paper I: El bani Altuna, N., Ezat, M.M., Greaves, M. & Rasmussen, T.L. (2021). Millennial-scale changes in bottom water temperature and water mass exchange through the Fram Strait 79°N, 63–13 ka. Paleoceanography and Paleoclimatology, 36 (2), e2020PA004061. Also available in Munin at https://hdl.handle.net/10037/21004 . Paper II: El bani Altuna, N., Rasmussen, T.L., Ezat, M.M., Vadakkepuliyambatta, S., Groeneveld, J. & Greaves, M. Deglacial bottom water warming intensified Arctic methane seepage, Northwestern Barents Sea. (Manuscript in review). Now published in Nature Communications Earth & Environment, 2 , 188, available in Munin at https://hdl.handle.net/10037/22536 . Paper III: El bani Altuna, N., Ezat, M.M., Smik, L., Muschitiello, F., Belt, S.T., Knies, J. & Rasmussen, T.L. Sea ice and Atlantic water coupling during Heinrich Stadials in the northern Nordic Seas during the last glacial period 63-13 ka. (Manuscript). Data related to Paper I: El bani Altuna, N., Ezat, M., Greaves, M. & Rasmussen, T.L. (2020). Benthic and planktic foraminiferal stable isotopes, benthic foraminiferal Mg/Ca data and BWT stack, relative abundance of main benthic foraminiferal species, IRD concentration and magnetic susceptibility of core HH15-1252PC (western Svalbard margin). PANGAEA, https://doi.org/10.1594/PANGAEA.925428 . Data related to Paper II: El bani Altuna, N., Rasmussen, T.L., Ezat, M.M., Vadakkepuliyambatta, S., Groeneveld, J. & Greaves, M. (2021). Benthic and planktic foraminiferal stable isotopes, benthic foraminiferal Mg/Ca data and reconstructed gas hydrate stability zone of core HH18-1059GC (Storfjordrenna, NW Barents Sea). DataverseNO, V1, https://doi.org/10.18710/XFYDFL . info:eu-repo/grantAgreement/RCN/SFF/223259/Norway/Centre for Arctic Gas Hydrate, Environment and Climate/CAGE/ 978-82-8236-447-8 (pdf) https://hdl.handle.net/10037/22253 embargoedAccess Copyright 2021 The Author(s) VDP::Mathematics and natural science: 400::Geosciences: 450::Marine geology: 466 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Marin geologi: 466 DOKTOR-004 Doctoral thesis Doktorgradsavhandling 2021 ftunivtroemsoe 2021-09-15T22:53:54Z Climate change affects the Arctic to a greater extent than the global average, causing rapid sea-ice loss and changes in the inflow of warm Atlantic water in the Arctic. Arctic sediments host vast amounts of greenhouse gases in the form of gas hydrates (ice-like cages that trap gas within), that can be released to the seafloor if temperature increases and/or pressure decreases. Climate projections anticipate a further warming in the Arctic, but to improve such projections and better understand future changes interactions between climate, the ocean and the carbon cycle, it is necessary to improve long-term past climate and oceanic records. The main goal of this thesis is to reconstruct bottom water temperatures in the northern Nordic Seas and the NW Barents Sea to understand the evolution of Atlantic water inflow in the last deglaciation, and in last glacial period at times of millennial-scale climate oscillations, when the climate fluctuated between glacial-like stadials to abrupt (i.e., a few decades) warm interstadials (Dansgaard-Oeschger events; DO-events). We have also reconstructed (1) sea-ice variability and studied its linkage to the inflow of Atlantic water in the northern Nordic Seas, and (2) the gas hydrate stability zone (zone in the sediments where gas hydrates are stable) in the ‘Pingo area’ (NW Barents Sea) to investigate the effect of Atlantic water inflow in such a shallow gas hydrate system. To reconstruct bottom water temperatures, we used benthic foraminiferal Mg/Ca, that we complemented with an array of other proxies (sea-ice biomarkers, foraminiferal stable isotopes, benthic foraminiferal assemblages and ice-rafted debris) to reconstruct the overall paleoceanographic conditions in the study sites. The bottom water temperatures in both sites show considerable warming of up to 5°C during Heinrich Stadials, indicating that the inflow of Atlantic water reached the seafloor beneath a persistent sea-ice and meltwater layer. Instead, modern-like oceanographic conditions with colder bottom water temperatures occurred during interstadials. Our work demonstrates a strong coupling between sea ice and Atlantic water inflow during the last glacial period and potentially the important role of these two parameters shaping DO-events. Furthermore, the results in the ‘Pingo area’ reveal the key role of bottom water temperature shaping the dynamics of the gas hydrate stability zone and dissociation of gas hydrates. The promising results presented in this thesis highlight the importance of generating bottom water temperature records and studying its impacts on the carbon cycle and its paleoceanographic and paleoclimatic implications in the Arctic region. Doctoral or Postdoctoral Thesis Arctic Arctic Barents Sea Climate change Dansgaard-Oeschger events Foraminifera* Nordic Seas Sea ice University of Tromsø: Munin Open Research Archive Arctic Barents Sea |