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Book ; Online: Monsoon-driven changes in aeolian and fluvial sediment input to the central Red Sea recorded throughout the last 200 000 years

Ehrmann, Werner / Wilson, Paul A. / Arz, Helge W. / Schulz, Hartmut / Schmiedl, Gerhard

eISSN: 1814-9332

2024

Abstract: Climatic and associated hydrological changes controlled the transport processes and composition of the sediments in the central Red Sea during the last ca. 200 kyr. Three different source areas for mineral dust are identified. The dominant source is ... ...

Abstract	Climatic and associated hydrological changes controlled the transport processes and composition of the sediments in the central Red Sea during the last ca. 200 kyr. Three different source areas for mineral dust are identified. The dominant source is located in the eastern Sahara (Sudan and southernmost Egypt). We identify its imprint on Red Sea sediments by high smectite and Ti contents, low 87 Sr / <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="527256ea34e0af356380afd605ccefc0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cp-20-37-2024-ie00001.svg" width="8pt" height="14pt" src="cp-20-37-2024-ie00001.png"/></svg:svg> 86 Sr, and high ε Nd . The availability of deflatable sediments was controlled by the intensity of tropical rainfall and vegetation cover over North Africa linked to the African monsoon. Intense dust input to the Red Sea occurred during arid phases, and low input occurred during humid phases. A second, less significant source indicated by palygorskite input is probably located on the eastern Arabian Peninsula and/or Mesopotamia, while the presence of kaolinite suggests an additional minor dust source in northern Egypt. Our grain size data reflect episodes of fluvial sediment discharge to the central Red Sea and document the variable strength in response to all of the precession-paced insolation maxima during our study interval including both those that were strong enough to trigger sapropel formation in the eastern Mediterranean Sea and those that were not. The African humid period most strongly expressed in our Red Sea record was the one during the Eemian last interglacial at ca. 125 ka (when the Baraka River was far more active than today), followed by those at 198, 108, 84, and 6 ka.
Subject code	333 ; 550
Language	English
Publishing date	2024-01-03
Publishing country	de
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book ; Online: Monsoon-driven changes in aeolian and fluvial sediment input to the central Red Sea recorded throughout the last 200,000 years

Ehrmann, Werner / Wilson, Paul A. / Arz, Helge W. / Schulz, Hartmut / Schmiedl, Gerhard

eISSN: 1814-9332

2023

Abstract	Climatic and associated hydrological changes controlled the transport processes and composition of the sediments in the central Red Sea during the last ca. 200 kyr. Three different source areas for mineral dust are identified. The dominant source is located in the eastern Sahara (Sudan and southernmost Egypt). We identify its imprint on Red Sea sediments by high smectite and Ti contents, high 87 Sr/ 86 Sr and low ε Nd . The availability of deflatable sediments was controlled by the intensity of tropical rainfall and vegetation cover over northern Africa linked to the African monsoon. Intense dust input to the Red Sea occurred during arid phases, low input during humid phases. A second, less significant source indicated by palygorskite input is probably located on the eastern Arabian Peninsula and/or Mesopotamia, while the presence of kaolinite suggests an additional minor dust source in northern Egypt. Our grain size data reflect episodes of fluvial sediment discharge to the central Red Sea and document the variable strength in response to all of the precession-paced insolation maxima during our study interval including both those that were strong enough to trigger sapropel formation in the eastern Mediterranean Sea and those that were not. The African Humid Period most strongly expressed in our Red Sea record was the one during the Eemian last interglacial at ca. 125 ka, followed by those at 198 ka, 108 ka, 84 ka and 6 ka.
Subject code	550 ; 333
Language	English
Publishing date	2023-06-06
Publishing country	de
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Intensity of African Humid Periods Estimated from Saharan Dust Fluxes.

Ehrmann, Werner / Schmiedl, Gerhard / Beuscher, Sarah / Krüger, Stefan

PloS one

2017 Volume 12, Issue 1, Page(s) e0170989

Abstract: North Africa experienced dramatic changes in hydrology and vegetation during the late Quaternary driven by insolation-induced shifts of the tropical rain belt and further modulated by millennial-scale droughts and vegetation-climate feedbacks. While most ...

Abstract	North Africa experienced dramatic changes in hydrology and vegetation during the late Quaternary driven by insolation-induced shifts of the tropical rain belt and further modulated by millennial-scale droughts and vegetation-climate feedbacks. While most past proxy and modelling studies concentrated on the temporal and spatial dynamics of the last African humid period, little is known about the intensities and characteristics of pre-Holocene humid periods. Here we present a high-resolution record of fine-grained eastern Saharan dust from the Eastern Mediterranean Sea spanning the last 180 kyr, which is based on the clay mineral composition of the marine sediments, especially the kaolinite/chlorite ratio. Minimum aeolian kaolinite transport occurred during the African Humid Periods because kaolinite deflation was hampered by increased humidity and vegetation cover. Instead, kaolinite weathering from kaolinite-bearing Cenozoic rocks was stored in lake basins, river beds and soils during these periods. During the subsequent dry phases, fine-grained dust was mobilised from the desiccated lakes, rivers and soils resulting in maximum aeolian uptake and transport of kaolinite. The kaolinite transport decreased again when these sediment sources exhausted. We conclude that the amount of clay-sized dust blown out of the Sahara into the Eastern Mediterranean Sea is proportional to the intensity of the kaolinite weathering and accumulation in soils and lake sediments, and thus to the strength of the preceding humid period. These humid periods provided the windows for the migration of modern humans out of Africa, as postulated previously. The strongest humid period occurred during the Eemian and was followed by two weaker phases centred at ca. 100 ka and ca. 80 ka.
MeSH term(s)	Africa, Northern ; Aluminum Silicates/chemistry ; Droughts ; Dust/analysis ; Geologic Sediments/analysis ; Geologic Sediments/chemistry ; Humans ; Humidity ; Lakes ; Rain ; Rivers ; Tropical Climate
Chemical Substances	Aluminum Silicates ; Dust ; clay (1302-87-0)
Language	English
Publishing date	2017
Publishing country	United States
Document type	Journal Article
ISSN	1932-6203
ISSN (online)	1932-6203
DOI	10.1371/journal.pone.0170989
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Synchronous retreat of Thwaites and Pine Island glaciers in response to external forcings in the presatellite era.

Clark, Rachel W / Wellner, Julia S / Hillenbrand, Claus-Dieter / Totten, Rebecca L / Smith, James A / Miller, Lauren E / Larter, Robert D / Hogan, Kelly A / Graham, Alastair G C / Nitsche, Frank O / Lehrmann, Asmara A / Lepp, Allison P / Kirkham, James D / Fitzgerald, Victoria T / Garcia-Barrera, Georgina / Ehrmann, Werner / Wacker, Lukas

Proceedings of the National Academy of Sciences of the United States of America

2024 Volume 121, Issue 11, Page(s) e2211711120

Abstract: Today, relatively warm Circumpolar Deep Water is melting Thwaites Glacier at the base of its ice shelf and at the grounding zone, contributing to significant ice retreat. Accelerating ice loss has been observed since the 1970s; however, it is unclear ... ...

Abstract	Today, relatively warm Circumpolar Deep Water is melting Thwaites Glacier at the base of its ice shelf and at the grounding zone, contributing to significant ice retreat. Accelerating ice loss has been observed since the 1970s; however, it is unclear when this phase of significant melting initiated. We analyzed the marine sedimentary record to reconstruct Thwaites Glacier's history from the early Holocene to present. Marine geophysical surveys were carried out along the floating ice-shelf margin to identify core locations from various geomorphic settings. We use sedimentological data and physical properties to define sedimentary facies at seven core sites. Glaciomarine sediment deposits reveal that the grounded ice in the Amundsen Sea Embayment had already retreated to within ~45 km of the modern grounding zone prior to ca. 9,400 y ago. Sediments deposited within the past 100+ y record abrupt changes in environmental conditions. On seafloor highs, these shifts document ice-shelf thinning initiating at least as early as the 1940s. Sediments recovered from deep basins reflect a transition from ice proximal to slightly more distal conditions, suggesting ongoing grounding-zone retreat since the 1950s. The timing of ice-shelf unpinning from the seafloor for Thwaites Glacier coincides with similar records from neighboring Pine Island Glacier. Our work provides robust new evidence that glacier retreat in the Amundsen Sea was initiated in the mid-twentieth century, likely associated with climate variability.
Language	English
Publishing date	2024-02-26
Publishing country	United States
Document type	Journal Article
ZDB-ID	209104-5
ISSN	1091-6490 ; 0027-8424
ISSN (online)	1091-6490
ISSN	0027-8424
DOI	10.1073/pnas.2211711120
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Book: Geophysics and Meteorology at the University of Leipzig

Börngen, Michael / Ehrmann, Werner / Wendisch, Manfred

on the Occasion of the 100th Anniversary of the Foundation of the Geophysical Institute in 1913

(Leipziger Geowissenschaften : Special issue ; 2 ; Wissenschaftliche Mitteilungen aus dem Institut für Meteorologie der Universität Leipzig : Special issue ; 2)

2013

Institution	Institut für Geophysik und Geologie
Author's details	Werner Ehrmann ... (eds.). With contrib. by Michael Börngen
Series title	Leipziger Geowissenschaften : Special issue ; 2 Wissenschaftliche Mitteilungen aus dem Institut für Meteorologie der Universität Leipzig : Special issue ; 2
Language	English
Size	111 S, zahlr. Ill., graph. Darst.
Edition	[1. Aufl.]
Publisher	Leipziger Univ.-Verl
Publishing place	Leipzig
Document type	Book
ISBN	9783865837424 ; 3865837425
Database	Former special subject collection: coastal and deep sea fishing

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Book: The West Antarctic Ice Sheet retreat in Pine Island Bay, Amndsen Sea, Antarctica, as documented by clay mineral assemblages

Ehrmann, Werner

Abstract: The study aims in improving our understanding of the deglaciation history of the West Antarctic Ice Sheet after the last glacial maximum. It builds on ongoing self-financed investigations in Bellingshausen Sea and concentrates on the continental shelf of ...

Institution	Universitaet Leipzig, Institut fuer Geophysik und Geologie, Talstr. 35, 04103, Leipzig, DE
Abstract	The study aims in improving our understanding of the deglaciation history of the West Antarctic Ice Sheet after the last glacial maximum. It builds on ongoing self-financed investigations in Bellingshausen Sea and concentrates on the continental shelf of Pine Island Bay in Amundsen Sea. This region is extremely important, because it is located offshore from Pine Island Glacier and Thwaites Glacier, which exhibit the most rapid ice thinning and grounding line retreat in present-day Antarctica. Mainly sediments from the continental shelf, but also from a few sites at the continental slope will be investigated for their clay mineral assemblages. Surface samples will be investigated to map the distribution of the individual clay minerals in order to identify different clay mineral provinces, source areas and present transport pathways and processes. Core samples will be investigated to decipher temporal and spatial changes in the clay mineralogical signature in order to reconstruct the maximum glacial extent of the ice sheet and glaciers, the ice flow directions, the subglacial and gravitational depositional processes and the retreat history of the ice sheet. The proposed investigation is linked to comprehensive research activities at British Antarctic Survey in Cambridge and at Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, which comprise the full range of geophysical, sedimentological, geochemical, stratigraphical and palaeontological studies.
Keywords	Studie ; Ansammlung ; Finanzierung ; Meer ; Konzentrat ; Kontinentalschelf ; Kiefer (Baum) ; Lehm ; Insel ; Region ; Offshore ; Gletscher ; Verduennung ; Sediment ; Hang ; Tonmineral ; Fluss (Bewegung) ; Karte ; Kartographie ; Erlass (Recht) ; Gebiet ; Verkehr ; Erdmessung ; Meereskunde ; Forschung ; Geochemie ; Antarktis ; Bremerhaven ; Island
Language	English
Document type	Book
Remark	project start: 01/01/2007 project end: 06/01/2010 grant ID: EH 89/10
Database	Environmental research database (UFORDAT) of the German Federal Environment Agency (UBA)

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Article ; Online: End-member modelling as a tool for climate reconstruction-An Eastern Mediterranean case study.

Beuscher, Sarah / Krüger, Stefan / Ehrmann, Werner / Schmiedl, Gerhard / Milker, Yvonne / Arz, Helge / Schulz, Hartmut

PloS one

2017 Volume 12, Issue 9, Page(s) e0185136

Abstract: The Eastern Mediterranean Sea is a sink for terrigenous sediments from North Africa, Europe and Asia Minor. Its sediments therefore provide valuable information on the climate dynamics in the source areas and the associated transport processes. We ... ...

Abstract	The Eastern Mediterranean Sea is a sink for terrigenous sediments from North Africa, Europe and Asia Minor. Its sediments therefore provide valuable information on the climate dynamics in the source areas and the associated transport processes. We present a high-resolution dataset of sediment core M40/4_SL71, which was collected SW of Crete and spans the last ca. 180 kyr. We analysed the clay mineral composition, the grain size distribution within the silt fraction, and the abundance of major and trace elements. We tested the potential of end-member modelling on these sedimentological datasets as a tool for reconstructing the climate variability in the source regions and the associated detrital input. For each dataset, we modelled three end members. All end members were assigned to a specific provenance and sedimentary process. In total, three end members were related to the Saharan dust input, and five were related to the fluvial sediment input. One end member was strongly associated with the sapropel layers. The Saharan dust end members of the grain size and clay mineral datasets generally suggest enhanced dust export into the Eastern Mediterranean Sea during the dry phases with short-term increases during Heinrich events. During the African Humid Periods, dust export was reduced but may not have completely ceased. The loading patterns of two fluvial end members show a strong relationship with the Northern Hemisphere insolation, and all fluvial end members document enhanced input during the African Humid Periods. The sapropel end member most likely reflects the fixation of redox-sensitive elements within the anoxic sapropel layers. Our results exemplify that end-member modelling is a valuable tool for interpreting extensive and multidisciplinary datasets.
MeSH term(s)	Aluminum Silicates/chemistry ; Climate ; Geologic Sediments/chemistry ; Mediterranean Sea ; Models, Statistical ; Time Factors
Chemical Substances	Aluminum Silicates ; clay (1302-87-0)
Language	English
Publishing date	2017
Publishing country	United States
Document type	Journal Article
ISSN	1932-6203
ISSN (online)	1932-6203
DOI	10.1371/journal.pone.0185136
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Drivers of river reactivation in North Africa during the last glacial cycle

Blanchet, Cécile L. / Osborne, Anne Helen / Tjallingii, Rik / Ehrmann, Werner / Friedrich, Tobias / Timmermann, Axel / Brückmann, Warner / Frank, Martin

2021

Abstract: North African greening phases, during which large rivers ran through the Sahara Desert, occurred repeatedly during the Quaternary and are regarded as key periods for the development of past human populations. However, the timing and mechanisms ... ...

Abstract	North African greening phases, during which large rivers ran through the Sahara Desert, occurred repeatedly during the Quaternary and are regarded as key periods for the development of past human populations. However, the timing and mechanisms responsible for the reactivation of the presently dormant fluvial systems remain highly uncertain. Here we present hydroclimate changes over the past 160,000 years, reconstructed from analyses of the provenance of terrestrial sediments in a marine sediment record from the Gulf of Sirte (offshore Libya). By combining high-resolution proxy data with transient Earth system model simulations, we are able to identify the various drivers that led to the observed shifts in hydroclimate and landscapes. We show that river runoff occurred during warm interglacial phases of Marine Isotope Stages 1 and 5 due to precession-forced enhancements in the summer and autumn rainfall over the entire watershed, which fed presently dry river systems and intermittent coastal streams. In contrast, shorter-lasting and less-intense humid events during glacial Marine Isotope Stages 3 and 4 were related to autumn and winter precipitation over the Libyan coastal regions driven by Mediterranean storms. Our results reveal large shifts in hydroclimate environments during the last glacial cycle, which probably exerted a strong evolutionary and structural control on past human populations, potentially pacing their dispersal across northern Africa.
Subject code	550
Language	English
Publishing date	2021-01-28
Publisher	Nature Research
Publishing country	de
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book: Quartaerer Tiefen- und Bodenwasseraustausch zwischen Suedozean und Indischem Ozean

Ehrmann, Werner

Abstract: Aufbauend auf sedimentologischen, geochemischen, isotopengeochemischen und mikropalaeontologischen Untersuchungen entlang eines Transekts vom suedafrikanischen Kontinentalrand nach SE zur Conradkuppe (Sedimentkerne der Polarsternreise ANT XI/4) soll der ... ...

Institution	Universitaet Leipzig, Institut fuer Geophysik und Geologie, Talstr. 35, 04103, Leipzig, DE
Abstract	Aufbauend auf sedimentologischen, geochemischen, isotopengeochemischen und mikropalaeontologischen Untersuchungen entlang eines Transekts vom suedafrikanischen Kontinentalrand nach SE zur Conradkuppe (Sedimentkerne der Polarsternreise ANT XI/4) soll der Austausch von Tiefen- und Bodenwassermassen zwischen dem Suedatlantik/Suedozean und dem Indischen Ozean rekonstruiert werden. Ziel der geplanten Untersuchungen ist es zu klaeren, ueber welche Wassermassen Klimasignale aus der Antarktis bzw. der Nordhemisphaere in den Indischen Ozean uebertragen werden. Neben der Rekonstruktion der langfristigen Aenderungen im Milankovitch-Bandbereich seit dem Pliozaen sollen kurzfristige Aenderungen (tausender Jahre-Bereich) fuer den letzten Glazial-Interglazial-Zyklus untersucht werden.
Keywords	Geochemie ; Bohrkern ; Sedimentkoerper ; Ameise ; Suedatlantik ; Indischer Ozean ; Antarktis ; Hemisphaere (noerdlich)
Language	German
Document type	Book
Remark	Projektbeginn: 01.01.2003 Projektende: 31.12.2008 Foerdernummer:
Database	Environmental research database (UFORDAT) of the German Federal Environment Agency (UBA)

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Book ; Online: Clay mineral distribution in sediment core AND-2A, supplementary data to: Franke, Daniel; Ehrmann, Werner U (2010): Neogene clay mineral assemblages in the AND-2A drill core (McMurdo Sound, Antarctica) and their implications for environmental change. Palaeogeography, Palaeoclimatology, Palaeoecology, 286, 55-65

Franke, Daniel / Ehrmann, Werner U

2009

Abstract: data provision 2009-11-09), abstract will be provided after acceptance ... Clay mineral assemblages in sediments from ANDRILL drill core AND-2A were used to reconstruct the Neogene palaeoenvironment. For the first time a clay mineral data set can be ... ...

Abstract	(data provision 2009-11-09), abstract will be provided after acceptance Clay mineral assemblages in sediments from ANDRILL drill core AND-2A were used to reconstruct the Neogene palaeoenvironment. For the first time a clay mineral data set can be presented for southern McMurdo Sound, Ross Sea, Antarctica, that covers an expanded and fairly continuous Lower and Middle Miocene section. Although the occurrence of some authigenic smectites, zeolites and opal-CT documents diagenetic processes, the clay mineral assemblages allow a subdivision of the core into three intervals that reflect changes in provenance and volcanic activity. Interval I (1000-440 mbsf, 20.0-16.5 Ma) is characterised by a dominant sediment source in the Transantarctic Mountains. Frequent and short-term changes in the illite and smectite concentrations were caused by the influx of volcanic sediment components from southern McMurdo Sound and by diagenesis. Interval II (440-225 mbsf, 16.5-15.0 Ma) has much more uniform illite and smectite contents. The assemblage is derived from the Transantarctic Mountains. Interval III (225-0 mbsf, 15.0-0 Ma, containing major hiatuses) shows a distinctly enhanced volcanic influence and sediment components that come from the south of McMurdo Sound. The AND-2A clay mineral assemblages indicate persistent physical weathering conditions and do not mirror the Mid-Miocene Climatic Optimum. They indicate that the climatic changes were probably not strong enough to cause a modification in the weathering regime on the Antarctic continent.
Language	English
Dates of publication	2009-9999
Size	Online-Ressource
Publisher	PANGAEA - Data Publisher for Earth & Environmental Science
Publishing place	Bremen/Bremerhaven
Document type	Book ; Online
Note	This dataset is supplement to doi:10.1016/j.palaeo.2009.12.003
DOI	10.1594/PANGAEA.729023
Database	Library catalogue of the German National Library of Science and Technology (TIB), Hannover

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