Rock magnetic and geochemical signals of late Quaternary climate variability over northwest Africa
This thesis investigates the paleo- climatic and environmental changes over northwest Africa by focusing on the Senegal region and the Gulf of Guinea. Emphasis was placed on the timing of past climate changes, the frequency of occurrence, and regional impact. Possible shifts in the position of the i...
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Universität Bremen
2008
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Online Access: | https://media.suub.uni-bremen.de/handle/elib/2557 https://nbn-resolving.org/urn:nbn:de:gbv:46-diss000111701 |
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ftsubbremen:oai:media.suub.uni-bremen.de:Publications/elib/2557 2023-05-15T17:32:00+02:00 Rock magnetic and geochemical signals of late Quaternary climate variability over northwest Africa Gesteinsmagnetische und geochemische Signale der spätquartärenKlimavariabilität Nordwestafrikas Itambi Cletus, Achakie von Dobeneck, Tilo Dekkers, Mark 2008-10-10 application/pdf https://media.suub.uni-bremen.de/handle/elib/2557 https://nbn-resolving.org/urn:nbn:de:gbv:46-diss000111701 eng eng Universität Bremen FB5 Geowissenschaften https://media.suub.uni-bremen.de/handle/elib/2557 urn:nbn:de:gbv:46-diss000111701 info:eu-repo/semantics/openAccess Northwest Africa Senegal Heinrich Events D-O signals Magnetic minerals ITCZ West African monsoon Millennial-scale hematie goethite droughts 550 550 Earth sciences and geology ddc:550 Dissertation doctoralThesis 2008 ftsubbremen 2022-11-09T07:09:50Z This thesis investigates the paleo- climatic and environmental changes over northwest Africa by focusing on the Senegal region and the Gulf of Guinea. Emphasis was placed on the timing of past climate changes, the frequency of occurrence, and regional impact. Possible shifts in the position of the intertropical conversion zone (ITCZ) were also investigated. A multi proxy approach integrating rock and environmental magnetic parameters diffuse reflectance spectrophotometry, scanning electron microscopy, color reflectance and climate modeling experiments was employed. The results show that a climatic boundary which certainly reflects the southward shift of the northern limit of summer position of the ITCZ existed between 13 and 12à �à °N during the last glacial. The West African monsoon varied at D O times-scales at 12à �à °N, demonstrating that drier conditions occurred further south of the Sahel than previously reported. A fresh water hosing experiment using coupled climate model experiment suggested that the North Atlantic sea surface temperature and West African climate are linked by shifts in the position of the monsoon trough and the mid tropospheric African Easterly jet. The cooling of the North Atlantic sea surface is directly linked to the weakening of the Atlantic Meridional Overturing Circulation. Further more, climate change regulated the influx of magnetic minerals and post depositional alteration in the Senegalese sediments. Interglacial showed lower concentrations of magnetic particles, with high concentration of euhedral and framboidal pyrite. Wind derived sediments dominated the glacial with hematite and goethite prominent at these intervals as a result of increase input of Saharan dust. This studies shows that climate over this region varies at different times scales and is interconnected with global climatic signals. Doctoral or Postdoctoral Thesis North Atlantic Media SuUB Bremen (Staats- und Universitätsbibliothek Bremen) |
institution |
Open Polar |
collection |
Media SuUB Bremen (Staats- und Universitätsbibliothek Bremen) |
op_collection_id |
ftsubbremen |
language |
English |
topic |
Northwest Africa Senegal Heinrich Events D-O signals Magnetic minerals ITCZ West African monsoon Millennial-scale hematie goethite droughts 550 550 Earth sciences and geology ddc:550 |
spellingShingle |
Northwest Africa Senegal Heinrich Events D-O signals Magnetic minerals ITCZ West African monsoon Millennial-scale hematie goethite droughts 550 550 Earth sciences and geology ddc:550 Itambi Cletus, Achakie Rock magnetic and geochemical signals of late Quaternary climate variability over northwest Africa |
topic_facet |
Northwest Africa Senegal Heinrich Events D-O signals Magnetic minerals ITCZ West African monsoon Millennial-scale hematie goethite droughts 550 550 Earth sciences and geology ddc:550 |
description |
This thesis investigates the paleo- climatic and environmental changes over northwest Africa by focusing on the Senegal region and the Gulf of Guinea. Emphasis was placed on the timing of past climate changes, the frequency of occurrence, and regional impact. Possible shifts in the position of the intertropical conversion zone (ITCZ) were also investigated. A multi proxy approach integrating rock and environmental magnetic parameters diffuse reflectance spectrophotometry, scanning electron microscopy, color reflectance and climate modeling experiments was employed. The results show that a climatic boundary which certainly reflects the southward shift of the northern limit of summer position of the ITCZ existed between 13 and 12à �à °N during the last glacial. The West African monsoon varied at D O times-scales at 12à �à °N, demonstrating that drier conditions occurred further south of the Sahel than previously reported. A fresh water hosing experiment using coupled climate model experiment suggested that the North Atlantic sea surface temperature and West African climate are linked by shifts in the position of the monsoon trough and the mid tropospheric African Easterly jet. The cooling of the North Atlantic sea surface is directly linked to the weakening of the Atlantic Meridional Overturing Circulation. Further more, climate change regulated the influx of magnetic minerals and post depositional alteration in the Senegalese sediments. Interglacial showed lower concentrations of magnetic particles, with high concentration of euhedral and framboidal pyrite. Wind derived sediments dominated the glacial with hematite and goethite prominent at these intervals as a result of increase input of Saharan dust. This studies shows that climate over this region varies at different times scales and is interconnected with global climatic signals. |
author2 |
von Dobeneck, Tilo Dekkers, Mark |
format |
Doctoral or Postdoctoral Thesis |
author |
Itambi Cletus, Achakie |
author_facet |
Itambi Cletus, Achakie |
author_sort |
Itambi Cletus, Achakie |
title |
Rock magnetic and geochemical signals of late Quaternary climate variability over northwest Africa |
title_short |
Rock magnetic and geochemical signals of late Quaternary climate variability over northwest Africa |
title_full |
Rock magnetic and geochemical signals of late Quaternary climate variability over northwest Africa |
title_fullStr |
Rock magnetic and geochemical signals of late Quaternary climate variability over northwest Africa |
title_full_unstemmed |
Rock magnetic and geochemical signals of late Quaternary climate variability over northwest Africa |
title_sort |
rock magnetic and geochemical signals of late quaternary climate variability over northwest africa |
publisher |
Universität Bremen |
publishDate |
2008 |
url |
https://media.suub.uni-bremen.de/handle/elib/2557 https://nbn-resolving.org/urn:nbn:de:gbv:46-diss000111701 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
https://media.suub.uni-bremen.de/handle/elib/2557 urn:nbn:de:gbv:46-diss000111701 |
op_rights |
info:eu-repo/semantics/openAccess |
_version_ |
1766129904645046272 |