33 results on '"Simon, Margit H."'
Search Results
2. Atlantic inflow and low sea-ice cover in the Nordic Seas promoted Fennoscandian Ice Sheet growth during the Last Glacial Maximum
- Author
-
Simon, Margit H., Rutledal, Sunniva, Menviel, Laurie, Zolles, Tobias, Haflidason, Haflidi, Born, Andreas, Berben, Sarah M. P., and Dokken, Trond M.
- Published
- 2023
- Full Text
- View/download PDF
No additional results were found in
Catalog
3. Rapid reductions and millennial-scale variability in Nordic Seas sea ice cover during abrupt glacial climate changes
- Author
-
Sadatzki, Henrik, Maffezzoli, Niccolò, Dokken, Trond M., Simon, Margit H., Berben, Sarah M. P., Fahl, Kirsten, Kjær, Helle A., Spolaor, Andrea, Stein, Ruediger, Vallelonga, Paul, Vinther, Bo M., and Jansen, Eystein more...
- Published
- 2020
4. Independent tephrochronological evidence for rapid and synchronous oceanic and atmospheric temperature rises over the Greenland stadial-interstadial transitions between ca. 32 and 40 ka b2k
- Author
-
Berben, Sarah M.P., Dokken, Trond M., Abbott, Peter M., Cook, Eliza, Sadatzki, Henrik, Simon, Margit H., and Jansen, Eystein
- Published
- 2020
- Full Text
- View/download PDF
5. Development of a protocol to obtain the composition of terrigenous detritus in marine sediments -a pilot study from International Ocean Discovery Program Expedition 361
- Author
-
Simon, Margit H., Babin, Daniel P., Goldstein, Steven L., Cai, Merry Yue, Liu, Tanzhuo, Han, Xibin, Haws, Anne A., Johns, Matthew, Lear, Caroline, and Hemming, Sidney R.
- Published
- 2020
- Full Text
- View/download PDF
6. A late Pleistocene dataset of Agulhas Current variability
- Author
-
Simon, Margit H., Ziegler, Martin, Barker, Stephen, van der Meer, Marcel T. J., Schouten, Stefan, and Hall, Ian R.
- Published
- 2020
- Full Text
- View/download PDF
7. Behaviourally modern humans in coastal southern Africa experienced an increasingly continental climate during the transition from Marine Isotope Stage 5 to 4
- Author
-
Göktürk, Ozan Mert, primary, Simon, Margit H., additional, Sobolowski, Stefan Pieter, additional, Zhang, Zhongshi, additional, Van Der Bilt, Willem, additional, Mørkved, Pål Tore, additional, D’Andrea, William J., additional, van Niekerk, Karen L., additional, Henshilwood, Christopher S., additional, Armitage, Simon J., additional, and Jansen, Eystein, additional more...
- Published
- 2023
- Full Text
- View/download PDF
8. Deep-water circulation changes lead North Atlantic climate during deglaciation
- Author
-
Muschitiello, Francesco, D’Andrea, William J., Schmittner, Andreas, Heaton, Timothy J., Balascio, Nicholas L., deRoberts, Nicole, Caffee, Marc W., Woodruff, Thomas E., Welten, Kees C., Skinner, Luke C., Simon, Margit H., and Dokken, Trond M. more...
- Published
- 2019
- Full Text
- View/download PDF
9. Sensitivity of coastal southern African climate to changes in coastline position and associated land extent over the last glacial
- Author
-
Göktürk, Ozan Mert, primary, Sobolowski, Stefan Pieter, additional, Simon, Margit H., additional, Zhang, Zhongshi, additional, and Jansen, Eystein, additional
- Published
- 2023
- Full Text
- View/download PDF
10. Eastern South African hydroclimate over the past 270,000 years
- Author
-
Simon, Margit H., Ziegler, Martin, Bosmans, Joyce, Barker, Stephen, Reason, Chris J.C., and Hall, Ian R.
- Published
- 2015
- Full Text
- View/download PDF
11. Antarctic icebergs reorganize ocean circulation during Pleistocene glacials
- Author
-
Starr, Aidan, Hall, Ian R., Barker, Stephen, Rackow, Thomas, Zhang, Xu, Hemming, Sidney R., van der Lubbe, H. J.L., Knorr, Gregor, Berke, Melissa A., Bigg, Grant R., Cartagena-Sierra, Alejandra, Jiménez-Espejo, Francisco J., Gong, Xun, Gruetzner, Jens, Lathika, Nambiyathodi, LeVay, Leah J., Robinson, Rebecca S., Ziegler, Martin, Brentegani, Luna, Caley, Thibaut, Charles, Christopher D., Coenen, Jason J., Crespin, Julien G., Franzese, Allison M., Han, Xibin, Hines, Sophia K.V., Jimenez Espejo, Francisco J., Just, Janna, Koutsodendris, Andreas, Kubota, Kaoru, Norris, Richard D., dos Santos, Thiago Pereira, Rolison, John M., Simon, Margit H., Tangunan, Deborah, Yamane, Masako, Zhang, Hucai, Ministerio de Ciencia e Innovación (España), Natural Environment Research Council (UK), National Key Research and Development Program (China), Helmholtz Association, European Commission, and Geology and Geochemistry more...
- Subjects
Atlantic hurricane ,Oceanic circulation ,Multidisciplinary ,010504 meteorology & atmospheric sciences ,Pleistocene ,Global climate ,North Atlantic Deep Water ,Ocean current ,010502 geochemistry & geophysics ,01 natural sciences ,Iceberg ,Oceanography ,SDG 14 - Life Below Water ,Glacial period ,General ,Atlantic Ocean ,Geology ,0105 earth and related environmental sciences ,Teleconnection - Abstract
The dominant feature of large-scale mass transfer in the modern ocean is the Atlantic meridional overturning circulation (AMOC). The geometry and vigour of this circulation influences global climate on various timescales. Palaeoceanographic evidence suggests that during glacial periods of the past 1.5 million years the AMOC had markedly different features from today; in the Atlantic basin, deep waters of Southern Ocean origin increased in volume while above them the core of the North Atlantic Deep Water (NADW) shoaled. An absence of evidence on the origin of this phenomenon means that the sequence of events leading to global glacial conditions remains unclear. Here we present multi-proxy evidence showing that northward shifts in Antarctic iceberg melt in the Indian–Atlantic Southern Ocean (0–50° E) systematically preceded deep-water mass reorganizations by one to two thousand years during Pleistocene-era glaciations. With the aid of iceberg-trajectory model experiments, we demonstrate that such a shift in iceberg trajectories during glacial periods can result in a considerable redistribution of freshwater in the Southern Ocean. We suggest that this, in concert with increased sea-ice cover, enabled positive buoyancy anomalies to ‘escape’ into the upper limb of the AMOC, providing a teleconnection between surface Southern Ocean conditions and the formation of NADW. The magnitude and pacing of this mechanism evolved substantially across the mid-Pleistocene transition, and the coeval increase in magnitude of the ‘southern escape’ and deep circulation perturbations implicate this mechanism as a key feedback in the transition to the ‘100-kyr world’, in which glacial–interglacial cycles occur at roughly 100,000-year periods., Acknowledgements This research used samples and/or data provided by the International Ocean Discovery Program (IODP). Funding for this research was provided by The Natural Environmental Research Council GW4+ Doctoral Training Partnership (A.S.) and NERC grant NE/P000037/1 (I.R.H.). A.S. acknowledges further funding through the Antarctic Science International Bursary. X.Z. acknowledges funding from Lanzhou University (number 225000-830006) and National Key R&D programme of China (number 2018YFA0606403). F.J.J.-E. acknowledges funding through Spanish Ministry of Science and Innovation (grant CTM2017-89711-C2-1-P), co-funded by the European Union through FEDER funds. G.K. acknowledges funding by the German Helmholtz national REKLIM initiative and the BMBF project PalMod. L. Owen, S. Slater, A. Nedebragt and D. Muir are thanked for laboratory assistance. more...
- Published
- 2021
- Full Text
- View/download PDF
12. Data report: evaluation of shipboard magnetostratigraphy by alternating field demagnetization of discrete samples, Expedition 361, Site U1475
- Author
-
Just, J., Hall, Ian R., Hemming, Sidney R., LeVay, Leah J., Barker, Stephen R., Berke, Melissa A., Brentegani, Luna, Caley, Thibaut, Catagena-Sierra, Alejandra, Charles, Christopher D., Coenen, Jason J., Crespin, Julien G., Franzese, Allison M., Gruetzner, Jens, Han, Xibin, Hines, Sophia K. V., Jimenez Espejo, Francisco J., Just, Janna, Koutsodendris, Andreas, Kubota, Kaoru, Lathika, Nambiyathodi, Norris, Richard D., dos Santos, Thiago Pereira, Robinson, Rebecca, Rolison, John M., Simon, Margit H., Tangunan, Deborah, van der Lubbe, Jeroen J. L., Yamane, Masako, Zhang, Hucai, and Rooks-Cast, Nina more...
- Abstract
The paleomagnetic shipboard data of International Ocean Discovery Program Site U1475, with a record reaching back to approximately 7 Ma, allowed for the identification of major magnetic polarity chrons and subchrons back to ~3.5 Ma. However, the natural remanent magnetization (NRM) was very weak, and transitional intervals with unclear polarity were as thick as several meters. The midpoints of these transitional intervals were reported in the shipboard results without decimal places because of the poor data quality. To evaluate and possibly refine the shipboard magnetostratigraphy, subsampling was performed across the polarity transitions. Detailed alternating field (AF) demagnetization experiments were conducted on these discrete samples and were complemented by anhysteretic remanent magnetization acquisition measurements and subsequent demagnetization. AF demagnetization data of NRM were analyzed using anchored principal component analysis (PCA) to obtain the characteristic remanent magnetization. These PCA results generally confirm the smoothed signal across polarity transitions at Site U1475. However, the midpoint depths of the top of the Keana Subchron, the Gauss-Matuyama and Matuyama-Brunhes boundaries, and the base of the Olduvai Subchron were adjusted. more...
- Published
- 2020
13. Data report: X-ray fluorescence core scanning of IODP Site U1474 sediments, Natal Valley, southwest Indian Ocean, Expedition 361
- Author
-
Babin, Daniel P., Franzese, Allison M., Hemming, Sidney R., Hall, Ian R., LeVay, Leah J., Barker, Stephen, Tejeda, Luis, and Simon, Margit H.
- Abstract
X-ray fluorescence (XRF) core scanning was conducted on core sections from International Ocean Discovery Program Site U1474, located in the Natal Valley off the coast of South Africa. The data were collected at 2 mm resolution along the 255 m length of the splice, but this setting resulted in noisy data. This problem was addressed by applying a 10 point running sum on the XRF data prior to converting peak area to element intensities. This effectively integrates 10 measurements into 1, representing an average over 2 cm resolution, and significantly improves noise in the data. With 25 calibration samples, whose element concentrations were derived using inductively coupled plasma–optical emission spectrometry, the XRF measurements were converted to concentrations using a univariate log-ratio calibration method. The resulting concentrations of terrigenously derived major elements (Al, Si, K, Ti, and Fe) are anticorrelated with Ca concentrations, indicating the main control on sediment chemistry is the variable proportion of terrigenous to in situ produced carbonate material. more...
- Published
- 2020
14. Strong glacial-interglacial variability in upper ocean hydrodynamics, biogeochemistry, and productivity in the southern Indian Ocean
- Author
-
Tangunan, Deborah, Berke, Melissa A., Cartagena-Sierra, Alejandra, Flores, José Abel, Gruetzner, Jens, Jiménez-Espejo, Francisco, LeVay, Leah J., Baumann, Karl Heinz, Romero, Oscar, Saavedra-Pellitero, Mariem, Coenen, Jason J., Starr, Aidan, Hemming, Sidney R., Hall, Ian R., Barker, Stephen, Brentegani, Luna, Caley, Thibaut, Charles, Christopher D., Crespin, Julien G., Franzese, Allison M., Han, Xibin, Hines, Sophia K.V., Jimenez Espejo, Francisco J., Just, Janna, Koutsodendris, Andreas, Kubota, Kaoru, Lathika, Nambiyathodi, Norris, Richard D., dos Santos, Thiago Pereira, Robinson, Rebecca S., Rolison, John M., Simon, Margit H., van der Lubbe, Jeroen J.L., Yamane, Masako, Zhang, Hucai, Tangunan, Deborah, Berke, Melissa A., Cartagena-Sierra, Alejandra, Flores, José Abel, Gruetzner, Jens, Jiménez-Espejo, Francisco, LeVay, Leah J., Baumann, Karl Heinz, Romero, Oscar, Saavedra-Pellitero, Mariem, Coenen, Jason J., Starr, Aidan, Hemming, Sidney R., Hall, Ian R., Barker, Stephen, Brentegani, Luna, Caley, Thibaut, Charles, Christopher D., Crespin, Julien G., Franzese, Allison M., Han, Xibin, Hines, Sophia K.V., Jimenez Espejo, Francisco J., Just, Janna, Koutsodendris, Andreas, Kubota, Kaoru, Lathika, Nambiyathodi, Norris, Richard D., dos Santos, Thiago Pereira, Robinson, Rebecca S., Rolison, John M., Simon, Margit H., van der Lubbe, Jeroen J.L., Yamane, Masako, and Zhang, Hucai more...
- Abstract
In the southern Indian Ocean, the position of the subtropical front – the boundary between colder, fresher waters to the south and warmer, saltier waters to the north – has a strong influence on the upper ocean hydrodynamics and biogeochemistry. Here we analyse a sedimentary record from the Agulhas Plateau, located close to the modern position of the subtropical front and use alkenones and coccolith assemblages to reconstruct oceanographic conditions over the past 300,000 years. We identify a strong glacial-interglacial variability in sea surface temperature and productivity associated with subtropical front migration over the Agulhas Plateau, as well as shorter-term high frequency variability aligned with variations in high latitude insolation. Alkenone and coccolith abundances, in combination with diatom and organic carbon records indicate high glacial export productivity. We conclude that the biological pump was more efficient and strengthened during glacial periods, which could partly account for the reported reduction in atmospheric carbon dioxide concentrations. more...
- Published
- 2021
15. A multi-decadal record of oceanographic changes of the past ~165 years (1850-2015 AD) from Northwest of Iceland
- Author
-
Simon, Margit H., primary, Muschitiello, Francesco, additional, Tisserand, Amandine A., additional, Olsen, Are, additional, Moros, Matthias, additional, Perner, Kerstin, additional, Bårdsnes, Siv Tone, additional, Dokken, Trond M., additional, and Jansen, Eystein, additional more...
- Published
- 2020
- Full Text
- View/download PDF
16. A late Pleistocene dataset of Agulhas Current variability
- Author
-
Stratigraphy and paleontology, Organic geochemistry, Stratigraphy & paleontology, Simon, Margit H., Ziegler, Martin, Barker, Stephen, van der Meer, Marcel T.J., Schouten, Stefan, Hall, Ian R., Stratigraphy and paleontology, Organic geochemistry, Stratigraphy & paleontology, Simon, Margit H., Ziegler, Martin, Barker, Stephen, van der Meer, Marcel T.J., Schouten, Stefan, and Hall, Ian R. more...
- Published
- 2020
17. Independent tephrochronological evidence for rapid and synchronous oceanic and atmospheric temperature rises over the Greenland stadial-interstadial transitions between ca. 32 and 40 ka b2k
- Author
-
Berben, Sarah M. P., Dokken, Trond M., Abbott, Peter M., Cook, Eliza, Sadatzki, Henrik, Simon, Margit H., Jansen, Eystein, Berben, Sarah M. P., Dokken, Trond M., Abbott, Peter M., Cook, Eliza, Sadatzki, Henrik, Simon, Margit H., and Jansen, Eystein more...
- Published
- 2020
18. Sequential extraction procedure to obtain the composition of terrigenous detritus in marine sediments
- Author
-
Simon, Margit H., primary, Babin, Daniel P., additional, Goldstein, Steven L., additional, Cai, Merry Yue, additional, Liu, Tanzhuo, additional, Han, Xibin, additional, Haws, Anne A., additional, Johns, Matthew, additional, Lear, Caroline, additional, and Hemming, Sidney R., additional more...
- Published
- 2020
- Full Text
- View/download PDF
19. Rapid reductions and millennial-scale variability in Nordic Seas sea ice cover during abrupt glacial climate changes.
- Author
-
Henrik Sadatzki, Maffezzoli, Niccolò, Dokken, Trond M., Simon, Margit H., Berben, Sarah M. P., Fahl, Kirsten, Kjær, Helle A., Spolaor, Andrea, Stein, Ruediger, Vallelonga, Paul, Vinther, M., and Jansen, Eystein more...
- Subjects
SEA ice ,GLACIAL climates ,GREENLAND ice ,ICE cores ,CLIMATE change - Abstract
Constraining the past sea ice variability in the Nordic Seas is critical for a comprehensive understanding of the abrupt Dansgaard- Oeschger (D-O) climate changes during the last glacial. Here we present unprecedentedly detailed sea ice proxy evidence from two Norwegian Sea sediment cores and an East Greenland ice core to resolve and constrain sea ice variations during four D-O events between 32 and 41 ka. Our independent sea ice records consistently reveal a millennial-scale variability and threshold response between an extensive seasonal sea ice cover in the Nordic Seas during cold stadials and reduced seasonal sea ice conditions during warmer interstadials. They document substantial and rapid sea ice reductions that may have happened within 250 y or less, concomitant with reinvigoration of deep convection in the Nordic Seas and the abrupt warming transitions in Greenland. Our empirical evidence thus underpins the cardinal role of rapid sea ice decline and related feedbacks to trigger abrupt and large-amplitude climate change of the glacial D-O events. [ABSTRACT FROM AUTHOR] more...
- Published
- 2020
- Full Text
- View/download PDF
20. Proceedings of the International Ocean Discovery Program; South African climates (Agulhas LGM density profile); Expedition 361 of the riserless drilling platform, Port Louis, Mauritius, to Cape Town, South Africa; Sites U1474-U1479, 30 January-31 March 2016
- Author
-
Hall, Ian R., Hemming, Sidney R., Levay, Leah J., Barker, Stephen R., Berke, Melissa A., Luna Brentegani, Thibaut Caley, Alejandra Cartagena-Sierra, Charles, Christopher D., Coenen, Jason J., Crespin, Julien G., Franzese, Allison M., Jens Gruetzner, Han Xibin, Hines, Sophia K. V., Jimenez Espejo, Francisco J., Janna Just, Andreas Koutsodendris, Kaoru Kubota, Nambiyathodi Lathika, Norris, Richard D., Thiago Pereira dos Santos, Rebecca Robinson, Rolison, John M., Simon, Margit H., Deborah Tangunan, Jeroen van der Lubbe, Masako Yamane, Zhang Hucai, and Geology and Geochemistry more...
- Subjects
Agulhas Current ,Algae ,Atlantic Ocean ,Biostratigraphy ,Cenozoic ,Cores ,Correlation ,Diatoms ,Expedition 361 ,Foraminifera ,Geochemistry ,Hydrochemistry ,Indian Ocean ,International Ocean Discovery Program ,Invertebrata ,Lithostratigraphy ,Magnetostratigraphy ,Marine sediments ,Microfossils ,Mozambique Channel ,Nannofossils ,Neogene ,Paleo-oceanography ,Paleoclimatology ,Physical properties ,Plantae ,Pore water ,Protista ,Quaternary ,Sediments ,South Atlantic ,Southeast Atlantic ,Tertiary ,West Indian Ocean ,12 Stratigraphy, Historical Geology and Paleoecology - Published
- 2017
21. Salt exchange in the Indian-Atlantic Ocean Gateway since the Last Glacial Maximum: A compensating effect between Agulhas Current changes and salinity variations?
- Author
-
Simon, Margit H., Gong, Xun, Hall, Ian R., Ziegler, Martin, Barker, Stephen, Knorr, Gregor, van der Meer, Marcel T J, Kasper, Sebastian, Schouten, Stefan, Stratigraphy and paleontology, Organic geochemistry, Stratigraphy & paleontology, Organic geochemistry & molecular biogeology, Stratigraphy and paleontology, Organic geochemistry, Stratigraphy & paleontology, and Organic geochemistry & molecular biogeology more...
- Subjects
Water mass ,Salinity ,010504 meteorology & atmospheric sciences ,Palaeontology ,Paleontology ,Last Glacial Maximum ,Agulhas leakage ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,13. Climate action ,Climatology ,Interglacial ,Agulhas Current ,Paleosalinity ,Last glacial termination ,Glacial period ,Stadial ,Hydrography ,Geology ,0105 earth and related environmental sciences - Abstract
The import of relatively salty water masses from the Indian Ocean to the Atlantic is considered to be important for the operational mode of the Atlantic Meridional Overturning Circulation (AMOC). However, the occurrence and the origin of changes in this import behavior on millennial and glacial/interglacial timescales remains equivocal. Here we reconstruct multiproxy paleosalinity changes in the Agulhas Current since the Last Glacial Maximum and compare the salinity pattern with records from the Indian-Atlantic Ocean Gateway (I-AOG) and model simulations using a fully coupled atmosphere-ocean general circulation model. The reconstructed paleosalinity pattern in the Agulhas Current displays coherent variability with changes recorded in the wider I-AOG region over the last glacial termination. We infer that salinities simultaneously increased in both areas consistent with a quasi interhemispheric salt-seesaw response, analogous to the thermal bipolar seesaw in response to a reduced cross-hemispheric heat and salt exchange during times of weakened AMOC. Interestingly, these hydrographic shifts can also be recognized in the wider Southern Hemisphere, which indicates that salinity anomalies are not purely restricted to the Agulhas Current System itself. More saline upstream Agulhas waters were propagated to the I-AOG during Heinrich Stadial 1 (HS1). However, the salt flux into the South Atlantic might have been reduced due to a decreased volume transport through the I-AOG during the AMOC slowdown associated with HS1. Hence, our combined data-model interpretation suggests that intervals with higher salinity in the Agulhas Current source region are not necessarily an indicator for an increased salt import via the I-AOG into the South Atlantic. more...
- Published
- 2015
22. Salt exchange in the Indian-Atlantic Ocean Gateway since the LGM: A compensating effect between Agulhas Current changes and salinity variations?
- Author
-
Simon, Margit H., Gong, Xun, Hall, Ian Robert, Ziegler, Martin, Barker, Stephen, Knorr, Gregor, van der Meer, Marcel T. J., Kasper, Sebastian, and Schouten, Stefan
- Abstract
The import of relatively salty water masses from the Indian Ocean to the Atlantic is considered to be important for the operational mode of the Atlantic Meridional Overturning Circulation (AMOC). However, the occurrence and the origin of changes in this import behavior on millennial and glacial/interglacial timescales remains equivocal. Here we reconstruct multiproxy paleosalinity changes in the Agulhas Current since the Last Glacial Maximum and compare the salinity pattern with records from the Indian-Atlantic Ocean Gateway (I-AOG) and model simulations using a fully coupled atmosphere-ocean general circulation model. The reconstructed paleosalinity pattern in the Agulhas Current displays coherent variability with changes recorded in the wider I-AOG region over the last glacial termination. We infer that salinities simultaneously increased in both areas consistent with a quasi interhemispheric salt-seesaw response, analogous to the thermal bipolar seesaw in response to a reduced cross-hemispheric heat and salt exchange during times of weakened AMOC. Interestingly, these hydrographic shifts can also be recognized in the wider Southern Hemisphere, which indicates that salinity anomalies are not purely restricted to the Agulhas Current System itself. More saline upstream Agulhas waters were propagated to the I-AOG during Heinrich Stadial 1 (HS1). However, the salt flux into the South Atlantic might have been reduced due to a decreased volume transport through the I-AOG during the AMOC slowdown associated with HS1. Hence, our combined data-model interpretation suggests that intervals with higher salinity in the Agulhas Current source region are not necessarily an indicator for an increased salt import via the I-AOG into the South Atlantic. more...
- Published
- 2015
23. Millennial-scale Agulhas Current variability and its implications for salt-leakage through the Indian–Atlantic Ocean Gateway
- Author
-
Simon, Margit H., Arthur, Kristina L., Hall, Ian R., Peeters, Frank J.C., Loveday, Benjamin R., Barker, Stephen, Ziegler, Martin, and Zahn, Rainer
- Published
- 2013
- Full Text
- View/download PDF
24. Salt exchange in the Indian-Atlantic Ocean Gateway since the Last Glacial Maximum: A compensating effect between Agulhas Current changes and salinity variations?
- Author
-
Stratigraphy and paleontology, Organic geochemistry, Stratigraphy & paleontology, Organic geochemistry & molecular biogeology, Simon, Margit H., Gong, Xun, Hall, Ian R., Ziegler, Martin, Barker, Stephen, Knorr, Gregor, van der Meer, Marcel T J, Kasper, Sebastian, Schouten, Stefan, Stratigraphy and paleontology, Organic geochemistry, Stratigraphy & paleontology, Organic geochemistry & molecular biogeology, Simon, Margit H., Gong, Xun, Hall, Ian R., Ziegler, Martin, Barker, Stephen, Knorr, Gregor, van der Meer, Marcel T J, Kasper, Sebastian, and Schouten, Stefan more...
- Published
- 2015
25. Development of Middle Stone Age innovation linked to rapid climate change
- Author
-
Ziegler, Martin, primary, Simon, Margit H., additional, Hall, Ian R., additional, Barker, Stephen, additional, Stringer, Chris, additional, and Zahn, Rainer, additional
- Published
- 2013
- Full Text
- View/download PDF
26. A multi-decadal record of oceanographic changes of the past ~165 years (1850-2015 AD) from Northwest of Iceland
- Author
-
Simon, Margit H., Muschitiello, Francesco, Tisserand, Amandine A., Olsen, Are, Moros, Matthias, Perner, Kerstin, Bårdsnes, Siv Tone, Dokken, Trond M., and Jansen, Eystein
- Subjects
Physical sciences ,Earth sciences ,13. Climate action ,Ecology and environmental sciences ,FOS: Physical sciences ,14. Life underwater ,Research Article - Abstract
Extending oceanographic data beyond the instrumental period is highly needed to better characterize and understand multi-decadal to centennial natural ocean variability. Here, a stable isotope record at unprecedented temporal resolution (1 to 2 years) from a new marine core retrieved off western North Iceland is presented. We aim to better constrain the variability of subsurface, Atlantic-derived Subpolar Mode Water (SPMW), using near surface-dwelling planktic foraminifera and Arctic Intermediate Water (AIW) mass changes using benthic foraminifera over the last ~165 years. The reconstruction overlaps in time with instrumental observations and a direct comparison reveals that the δ18O record of Neogloboquadrina pachyderma is reliably representing temperature fluctuations in the SPMWs. Trends in the N. pachyderma δ13C record match the measured phosphate concentration in the upper 200 m on the North Icelandic Shelf well. Near surface-dwelling foraminifera trace anthropogenic CO2 in the Iceland Sea by ~ 1950 ± 8, however, a reduced amplitude shift in the Marine Suess effect is identified. We argue that this is caused by a contemporary ongoing increase in marine primary productivity in the upper ocean due to enhanced Greenland’s freshwater discharge that has contributed to a nutrient-driven fertilization since the 1940s/50s (Perner et al., 2019). Multi-decadal variability is detected. We find that the 16-year periodicity evident in SPMW and AIWs based on the δ18O of N. pachyderma and M. barleeanum is a signal of SST anomalies propagated into the Nordic Seas via the Atlantic inflow branches around Iceland. Spectral analyses of the planktic foraminiferal δ13C signal indicate intermittent 30-year cycles that are likely reflecting the ocean response to atmospheric variability, presumably the East Atlantic Pattern. A long-term trend in benthic δ18O suggests that Atlantic-derived waters are expanding their core within the water column from the subsurface into deeper intermediate depths towards the present day. This is a result of increased transport by the North Icelandic Irminger Current to the North Iceland Shelf over the historical era. more...
27. A multi-decadal record of oceanographic changes of the past ~165 years (1850-2015 AD) from Northwest of Iceland
- Author
-
Simon, Margit H, Muschitiello, Francesco, Tisserand, Amandine A, Olsen, Are, Moros, Matthias, Perner, Kerstin, Bårdsnes, Siv Tone, Dokken, Trond M, and Jansen, Eystein
- Subjects
Isotopes ,13. Climate action ,Iceland ,Temperature ,Water ,14. Life underwater ,FOS: Earth and related environmental sciences ,Oceanography ,Ecosystem - Abstract
Extending oceanographic data beyond the instrumental period is highly needed to better characterize and understand multi-decadal to centennial natural ocean variability. Here, a stable isotope record at unprecedented temporal resolution (1 to 2 years) from a new marine core retrieved off western North Iceland is presented. We aim to better constrain the variability of subsurface, Atlantic-derived Subpolar Mode Water (SPMW), using near surface-dwelling planktic foraminifera and Arctic Intermediate Water (AIW) mass changes using benthic foraminifera over the last ~165 years. The reconstruction overlaps in time with instrumental observations and a direct comparison reveals that the δ18O record of Neogloboquadrina pachyderma is reliably representing temperature fluctuations in the SPMWs. Trends in the N. pachyderma δ13C record match the measured phosphate concentration in the upper 200 m on the North Icelandic Shelf well. Near surface-dwelling foraminifera trace anthropogenic CO2 in the Iceland Sea by ~ 1950 ± 8, however, a reduced amplitude shift in the Marine Suess effect is identified. We argue that this is caused by a contemporary ongoing increase in marine primary productivity in the upper ocean due to enhanced Greenland's freshwater discharge that has contributed to a nutrient-driven fertilization since the 1940s/50s (Perner et al., 2019). Multi-decadal variability is detected. We find that the 16-year periodicity evident in SPMW and AIWs based on the δ18O of N. pachyderma and M. barleeanum is a signal of SST anomalies propagated into the Nordic Seas via the Atlantic inflow branches around Iceland. Spectral analyses of the planktic foraminiferal δ13C signal indicate intermittent 30-year cycles that are likely reflecting the ocean response to atmospheric variability, presumably the East Atlantic Pattern. A long-term trend in benthic δ18O suggests that Atlantic-derived waters are expanding their core within the water column from the subsurface into deeper intermediate depths towards the present day. This is a result of increased transport by the North Icelandic Irminger Current to the North Iceland Shelf over the historical era. more...
28. International Ocean Discovery Program; Expedition 361 preliminary report; South African climates (Agulhas LGM density profile); 30 January-31 March 2016
- Author
-
Hall, Ian R., Hemming, Sidney R., Levay, Leah J., Barker, Stephen R., Berke, Melissa A., Luna Brentegani, Thibaut Caley, Alejandra Cartagena-Sierra, Charles, Christopher D., Coenen, Jason J., Crespin, Julien G., Franzese, Allison M., Jens Gruetzner, Han Xibin, Hins, Sophia K. V., Jimenez Espejo, Francisco J., Janna Just, Andreas Koutsodendris, Kaoru Kubota, Nambiyathodi Lathika, Norris, Richard D., Thiago Pereira dos Santos, Rebecca Robinson, Rolison, John M., Simon, Margit H., Deborah Tangunan, Jeroen van der Lubbe, Masako Yamane, Zhang Hucai, and Geology and Geochemistry more...
- Subjects
Africa ,Agulhas Current ,Algae ,Atlantic Meridional Overturning Circulation ,Atlantic Ocean ,Biostratigraphy ,Cenozoic ,Chemostratigraphy ,Climate effects ,Continental margin ,Cores ,Currents ,Expedition 361 ,Foraminifera ,IODP Site U1474 ,IODP Site U1475 ,IODP Site U1476 ,IODP Site U1477 ,IODP Site U1478 ,IODP Site U1479 ,Indian Ocean ,International Ocean Discovery Program ,Invertebrata ,Last glacial maximum ,Lithostratigraphy ,Magnetostratigraphy ,Marine sediments ,Microfossils ,Mozambique Channel ,Nannofossils ,Neogene ,Ocean circulation ,Ocean currents ,Paleo-oceanography ,Paleoclimatology ,Paleomagnetism ,Physical properties ,Plantae ,Pleistocene ,Pliocene ,Protista ,Quaternary ,Sediments ,South Atlantic ,Southeast Atlantic ,Southern Africa ,Tertiary ,SDG 14 - Life Below Water ,12 Stratigraphy, Historical Geology and Paleoecology - Abstract
International Ocean Discovery Program (IODP) Expedition 361 drilled six sites on the southeast African margin and in the Indian-Atlantic ocean gateway, southwest Indian Ocean, from 30 January to 31 March 2016. In total, 5175 m of core was recovered, with an average recovery of 102%, during 29.7 days of on-site operations. The sites, situated in the Mozambique Channel at locations directly influenced by discharge from the Zambezi and Limpopo River catchments, the Natal Valley, the Agulhas Plateau, and Cape Basin, were targeted to reconstruct the history of the greater Agulhas Current system over the past ∼5 my. The Agulhas Current is the strongest western boundary current in the Southern Hemisphere, transporting some 70 Sv of warm, saline surface water from the tropical Indian Ocean along the East African margin to the tip of Africa. Exchanges of heat and moisture with the atmosphere influence southern African climates, including individual weather systems such as extratropical cyclone formation in the region and rainfall patterns. Recent ocean model and paleoceanographic data further point at a potential role of the Agulhas Current in controlling the strength and mode of the Atlantic Meridional Overturning Circulation (AMOC) during the Late Pleistocene. Spillage of saline Agulhas water into the South Atlantic stimulates buoyancy anomalies that act as control mechanisms on the basin-wide AMOC, with implications for convective activity in the North Atlantic and global climate change. The main objectives of the expedition were to establish the sensitivity of the Agulhas Current to climatic changes during the Pliocene-Pleistocene, to determine the dynamics of the Indian-Atlantic gateway circulation during this time, to examine the connection of the Agulhas leakage and AMOC, and to address the influence of the Agulhas Current on African terrestrial climates and coincidences with human evolution. Additionally, the expedition set out to fulfill the needs of the Ancillary Project Letter, consisting of high-resolution interstitial water samples that will constrain the temperature and salinity profiles of the ocean during the Last Glacial Maximum. The expedition made major strides toward fulfilling each of these objectives. The recovered sequences allowed generation of complete spliced stratigraphic sections that span from 0 to between ∼0.13 and 7 Ma. This sediment will provide decadal- to millennial-scale climatic records that will allow answering the paleoceanographic and paleoclimatic questions set out in the drilling proposal. more...
29. Deep-water circulation changes lead North Atlantic climate during deglaciation
- Author
-
Muschitiello, Francesco, D'Andrea, William J, Schmittner, Andreas, Heaton, Timothy J, Balascio, Nicholas L, DeRoberts, Nicole, Caffee, Marc W, Woodruff, Thomas E, Welten, Kees C, Skinner, Luke C, Simon, Margit H, and Dokken, Trond M more...
- Subjects
0403 Geology ,13. Climate action ,14. Life underwater ,0405 Oceanography ,0406 Physical Geography and Environmental Geoscience - Abstract
Constraining the response time of the climate system to changes in North Atlantic Deep Water (NADW) formation is fundamental to improving climate and Atlantic Meridional Overturning Circulation predictability. Here we report a new synchronization of terrestrial, marine, and ice-core records, which allows the first quantitative determination of the response time of North Atlantic climate to changes in high-latitude NADW formation rate during the last deglaciation. Using a continuous record of deep water ventilation from the Nordic Seas, we identify a ∼400-year lead of changes in high-latitude NADW formation ahead of abrupt climate changes recorded in Greenland ice cores at the onset and end of the Younger Dryas stadial, which likely occurred in response to gradual changes in temperature- and wind-driven freshwater transport. We suggest that variations in Nordic Seas deep-water circulation are precursors to abrupt climate changes and that future model studies should address this phasing. more...
30. Independent tephrochronological evidence for rapid and synchronous oceanic and atmospheric temperature rises over the Greenland stadial-interstadial transitions between ca. 32 and 40 ka b2k
- Author
-
Berben, Sarah M.P., Dokken, Trond M., Abbott, Peter M., Cook, Eliza, Sadatzki, Henrik, Simon, Margit H., and Jansen, Eystein
- Subjects
13. Climate action ,530 Physics ,550 Earth sciences & geology ,14. Life underwater
31. Leading role of ocean mixing in the Norwegian Sea for Dansgaard-Oeschger events.
- Author
-
Sadatzki, Henrik, Simon, Margit H., Muschitiello, Francesco, Berben, Sarah M. P., Friedrich, Tobias, Jansen, Eystein, Hajdas, Irka, Wacker, Lukas, and Dokken, Trond M.
- Subjects
- *
OCEANIC mixing , *SEA ice , *WATER masses , *WATER , *SEAS , *OCEAN dynamics - Abstract
Several studies have identified the Nordic Seas (NS) and the ice-ocean atmosphere interactions therein as a key-operating center to explain the pace and magnitude of the rapid climate fluctuations associated with Dansgaard-Oeschger cycles in the North Atlantic region. However, it remains elusive how cryosphere and ocean interactions evolved during the course of a D-O event and shaped temperature responses over Greenland. Here an overview of the sequence of events taking place in the eastern NS throughout Greenland interstadials (GI) 9 till 5 (40.4-32 ka BP) is presented. We use a unique high-resolution set of paired 42 radiocarbon (14C) ages on planktic foraminifera Neogloboquadrina pachyderma (sinistral) and 31 mixed benthic measurements (excluding Miliolid species) to reveal insights into the dynamics of cryosphere and ocean interactions. Based on foraminiferal subsurface and intermediate Δ¹⁴C ventilation reconstructions we find a stratified water column and sea-ice build up in the early stadial phases. Each Greenland Stadial (GS) is characterised by a gradual aging of the water masses and subsurface warming in the NS with planktic and benthic reservoir ages in the terminal phase of each GS up to 2500 yrs. A potential explanation for the observed pattern could be a slow interior upward mixing of older (warmer/saline), radiocarbon-depleted deep water to the surface which helps to erode the sea-ice cover in the final phases of each GS. The sea ice decline probably led to subsurface heat and marine CO2 release to the atmosphere in the transitional phase into GIs and thereby, contributing to the abrupt warming over Greenland. The processes we identify from the proxy data are in good qualitative agreement with results from an idealized model study. [ABSTRACT FROM AUTHOR] more...
- Published
- 2019
32. A multi-decadal record of oceanographic changes of the past ~150 years (1850-2015 AD) from North of Iceland.
- Author
-
Simon, Margit H., Muschitiello, Francesco, Tisserand, Amandine A., Olsen, Are, Moros, Matthias, Perner, Kerstin, Dokken, Trond M., and Jansen, Eystein
- Subjects
- *
UPWELLING (Oceanography) , *ATLANTIC multidecadal oscillation , *WATER currents , *WATER , *SURFACE reconstruction , *WATER masses - Abstract
Extending oceanographic data beyond the instrumental period is highly needed to better characterize and understand multidecadal to centennial natural ocean variability. Here we present new reconstructions from offshore North Iceland –a particularly important location in order to investigate changes in the i) southward fluxes of freshwater from the East Greenland Current, via the East Icelandic Current, ii) relative contribution of the Irminger Current water (temperature, salinity) to the North Icelandic Irminger Current (NIIC), and iii) shifts in the location of the North Atlantic Polar Front. The NIIC is one of the three main branches of Atlantic Water inflow to the Nordic Seas, playing a central role in the formation of Denmark Strait overflow water. However, as yet the NIIC is still poorly studied. In this study we present a new and well-dated multi-proxy record that allows multi-decadal reconstruction of surface, Atlantic-derived Subpolar Mode Water and Arctic Intermediate Water (AIW) mass changes on the western North Iceland shelf over the last ~150 years. The reconstruction overlaps with historical observations and the direct comparison reveals that the δ18O, Mg/Ca ratios and δ18Osw record of near surface-dwelling planktic foraminiferal Neogloboquadrina pachyderma (NPS) is reliably representing temperature and salinity fluctuations on the North Iceland shelf that links to large-scale atmospheric and oceanic changes in the North Atlantic region such as the Atlantic Multidecadal Oscillation. Moreover, our data suggest the variability in the δ13C record of NPS appear to reflect upwelling of nutrient-enriched AIW to the near surface layers during periods of stronger easterly winds and advection of more cold/fresh and nutrient-poor Polar surface waters to the North Iceland shelf–a mechanism that occurred, for example, during the Great Salinity anomaly in the late 1960´s. Finally, we show that geochemical proxies derived from the benthic foraminifera, Melonis barleeanus and Cassidulina neoteretis, track variability in AIW, matching and supporting the observed increase in temperature and salinity values around Iceland since the 1970´s. This study provides evidence that oceanographic proxies from North of Iceland can be used to reconstruct past regional shifts in water mass properties linked to decadal scale large-scale atmospheric and oceanographic changes beyond the instrumental record. [ABSTRACT FROM AUTHOR] more...
- Published
- 2019
33. International Ocean Discovery Program; Expedition 361 preliminary report; South African climates (Agulhas LGM density profile); 30 January-31 March 2016
- Author
-
Hall, Ian R., Hemming, Sidney R., LeVay, Leah J., Barker, Stephen R., Berke, Melissa A., Brentegani, Luna, Caley, Thibaut, Cartagena-Sierra, Alejandra, Charles, Christopher D., Coenen, Jason J., Crespin, Julien G., Franzese, Allison M., Gruetzner, Jens, Xibin, Han, Hins, Sophia K. V., Jimenez Espejo, Francisco J., Just, Janna, Koutsodendris, Andreas, Kubota, Kaoru, Lathika, Nambiyathodi, Norris, Richard D., Pereira dos Santos, Thiago, Robinson, Rebecca, Rolison, John M., Simon, Margit H., Tangunan, Deborah, van der Lubbe, Jeroen (H,) J. L., Yamane, Masako, and Hucai, Zhang more...
- Subjects
Historical Geology and Paleoecology ,Africa ,Agulhas Current ,Algae ,Atlantic Meridional Overturning Circulation ,Atlantic Ocean ,Biostratigraphy ,Cenozoic ,Chemostratigraphy ,Climate effects ,Continental margin ,Cores ,Currents ,Expedition 361 ,Foraminifera ,IODP Site U1474 ,IODP Site U1475 ,IODP Site U1476 ,IODP Site U1477 ,IODP Site U1478 ,IODP Site U1479 ,Indian Ocean ,International Ocean Discovery Program ,Invertebrata ,Last glacial maximum ,Lithostratigraphy ,Magnetostratigraphy ,Marine sediments ,Microfossils ,Mozambique Channel ,Nannofossils ,Neogene ,Ocean circulation ,Ocean currents ,Paleo-oceanography ,Paleoclimatology ,Paleomagnetism ,Physical properties ,Plantae ,Pleistocene ,Pliocene ,Protista ,Quaternary ,Sediments ,South Atlantic ,Southeast Atlantic ,Southern Africa ,Tertiary ,SDG 14 - Life Below Water ,12 Stratigraphy, Historical Geology and Paleoecology ,12 Stratigraphy - Abstract
International Ocean Discovery Program (IODP) Expedition 361 drilled six sites on the southeast African margin and in the Indian-Atlantic ocean gateway, southwest Indian Ocean, from 30 January to 31 March 2016. In total, 5175 m of core was recovered, with an average recovery of 102%, during 29.7 days of on-site operations. The sites, situated in the Mozambique Channel at locations directly influenced by discharge from the Zambezi and Limpopo River catchments, the Natal Valley, the Agulhas Plateau, and Cape Basin, were targeted to reconstruct the history of the greater Agulhas Current system over the past ∼5 my. The Agulhas Current is the strongest western boundary current in the Southern Hemisphere, transporting some 70 Sv of warm, saline surface water from the tropical Indian Ocean along the East African margin to the tip of Africa. Exchanges of heat and moisture with the atmosphere influence southern African climates, including individual weather systems such as extratropical cyclone formation in the region and rainfall patterns. Recent ocean model and paleoceanographic data further point at a potential role of the Agulhas Current in controlling the strength and mode of the Atlantic Meridional Overturning Circulation (AMOC) during the Late Pleistocene. Spillage of saline Agulhas water into the South Atlantic stimulates buoyancy anomalies that act as control mechanisms on the basin-wide AMOC, with implications for convective activity in the North Atlantic and global climate change. The main objectives of the expedition were to establish the sensitivity of the Agulhas Current to climatic changes during the Pliocene-Pleistocene, to determine the dynamics of the Indian-Atlantic gateway circulation during this time, to examine the connection of the Agulhas leakage and AMOC, and to address the influence of the Agulhas Current on African terrestrial climates and coincidences with human evolution. Additionally, the expedition set out to fulfill the needs of the Ancillary Project Letter, consisting of high-resolution interstitial water samples that will constrain the temperature and salinity profiles of the ocean during the Last Glacial Maximum. The expedition made major strides toward fulfilling each of these objectives. The recovered sequences allowed generation of complete spliced stratigraphic sections that span from 0 to between ∼0.13 and 7 Ma. This sediment will provide decadal- to millennial-scale climatic records that will allow answering the paleoceanographic and paleoclimatic questions set out in the drilling proposal. more...
- Published
- 2016
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.