242 results on '"Rohling, E. J."'
Search Results
2. Millennial atmospheric CO2 changes linked to ocean ventilation modes over past 150,000 years
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Yu, J., Anderson, R. F., Jin, Z. D., Ji, X., Thornalley, D. J. R., Wu, L., Thouveny, N., Cai, Y., Tan, L., Zhang, F., Menviel, L., Tian, J., Xie, X., Rohling, E. J., and McManus, J. F.
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- 2023
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3. Author Correction: Penultimate deglacial warming across the Mediterranean Sea revealed by clumped isotopes in foraminifera
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Rodríguez-Sanz, L., Bernasconi, S. M., Marino, G., Heslop, D., Müller, I. A., Fernandez, A., Grant, K. M., and Rohling, E. J.
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- 2021
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4. Last glacial atmospheric CO2 decline due to widespread Pacific deep-water expansion
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Yu, J., Menviel, L., Jin, Z. D., Anderson, R. F., Jian, Z., Piotrowski, A. M., Ma, X., Rohling, E. J., Zhang, F., Marino, G., and McManus, J. F.
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- 2020
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5. A 2000-Year Context for Modern Climate Change
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Maasch, K. A., Mayewski, P. A., Rohling, E. J., Stager, J. C., Karlén, W., Meeker, L. D., and Meyerson, E. A.
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- 2005
6. Estimating Plio‐Pleistocene North African Monsoon Runoff Into the Mediterranean Sea and Temperature Impacts.
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Heslop, D., Amarathunga, U., and Rohling, E. J.
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ANOXIC waters ,RUNOFF ,OXYGEN isotopes ,ICE sheets ,BOTTOM water (Oceanography) ,SAPROPEL ,MONSOONS - Abstract
Sapropels are dark, organic‐rich layers found in Mediterranean sediments that formed during periods of bottom water anoxia. While various mechanisms have been proposed to have caused anoxic conditions, a primary factor is considered to be water column stratification induced by freshwater runoff related to intensified North African monsoon precipitation during precession minima. Monsoon intensification also induced Green Sahara Periods that may have impacted North African hominin dispersal. In this study, we present a novel regression‐based deconvolution of a high‐resolution planktonic foraminiferal oxygen isotope record to estimate the combination of freshwater runoff reaching the eastern Mediterranean and associated surface warming of the water column over the past 5 million years. Sapropels are known to occur in clusters associated with periods of high orbital eccentricity. Our analysis reveals a consistent influence of orbital eccentricity in modulating the North African monsoon, and a possible shift in runoff source area induced by the initiation of Northern Hemisphere ice sheets. Our findings provide important insights into the role of the North African monsoon in shaping Mediterranean environmental changes over the past 5 million years. Plain Language Summary: We investigate long‐term changes in monsoon rains over North Africa, which annually result in freshwater flowing into the Mediterranean Sea. Over geological time, Earth's orbital variations have played a significant role in shaping the monsoon and, consequently, the quantity of freshwater entering the Mediterranean. Foraminifera, small marine organisms, record the oxygen isotope composition of their environment in their shells. Notably, the oxygen isotope balance in North African monsoon rains and the Mediterranean Sea differ, but eventually mix upon the freshwater entering into the Mediterranean. Our research combines a statistical analysis of oxygen isotope data preserved in foraminifera shells with a numerical model of the Mediterranean Sea, enabling us to estimate changes in monsoon freshwater input into the Mediterranean over the past 5 million years. This information not only enhances our understanding of monsoon evolution but also provides insights into the potential for hominin migrations in a more lush North African landscape characterized by higher rainfall than today. Key Points: We present quantitative estimates of Plio‐Pleistocene North African monsoon activity based on deconvolution of planktonic foraminiferal δ18OThrough the past 5 million years estimated monsoon activity is consistent with the expected pattern of orbital eccentricity modulationApparent monsoon strengthening at ∼2.6 Ma may be due to shifting runoff sources induced by Northern Hemisphere ice sheet initiation [ABSTRACT FROM AUTHOR]
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- 2023
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7. More efficient North Atlantic carbon pump during the Last Glacial Maximum
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Yu, J., Menviel, L., Jin, Z. D., Thornalley, D. J. R., Foster, G. L., Rohling, E. J., McCave, I. N., McManus, J. F., Dai, Y., Ren, H., He, F., Zhang, F., Chen, P. J., and Roberts, A. P.
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- 2019
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8. Penultimate deglacial warming across the Mediterranean Sea revealed by clumped isotopes in foraminifera
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Rodríguez-Sanz, L., Bernasconi, S. M., Marino, G., Heslop, D., Müller, I. A., Fernandez, A., Grant, K. M., and Rohling, E. J.
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- 2017
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9. Rapid Holocene Climate Changes in the Eastern Mediterranean
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Rohling, E. J., Casford, J., Abu-Zied, R., Cooke, S., Mercone, D., Thomson, J., Croudace, I., Jorissen, F. J., Brinkhuis, H., Kallmeyer, J., Wefer, G., and Hassan, Fekri A., editor
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- 2002
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10. Bipolar seesaw control on last interglacial sea level
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Marino, G., Rohling, E. J., Rodríguez-Sanz, L., Grant, K. M., Heslop, D., Roberts, A. P., Stanford, J. D., and Yu, J.
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Interglacial periods -- Natural history ,Sea level -- Natural history ,Ocean-atmosphere interaction -- Natural history ,Environmental issues ,Science and technology ,Zoology and wildlife conservation - Abstract
A synthesis of new and existing data allows Heinrich Stadial 11 (HS11), a prominent Northern Hemisphere cold event, to be linked to the timing of peak sea-level rise during glacial termination T-II, whereas rapid sea-level rise in T-I is shown to clearly post-date Heinrich Stadial 1, so fundamentally different mechanisms seem to be at work during glacial terminations. Anatomy of a glacial termination A central goal of palaeoclimate research is that of deciphering the mechanisms responsible for major state shifts in the Earth system, such as between glacial and interglacial conditions. This has proven difficult enough even for the last glacial termination (T-I), much less termination II (T-II), which ended glacial conditions about 130,000 years ago. Gianluca Marino et al. use new and existing data to demonstrate a link, within uncertainties, between Heinrich Stadial 11 (HS11) -- a prominent Northern Hemisphere cold event -- and the timing of peak sea level rise during T-II. A strong Southern Hemisphere warming also occurred during HS11, consistent with the idea of a bipolar seesaw that would probably have promoted Antarctic ice sheet melting. In contrast, rapid sea level rise in T-1 clearly postdated Heinrich Stadial 1. Possibly in response to differing CO.sub.2 and insolation conditions during T-I and T-II, fundamentally different mechanisms seem to be at work in triggering glacial terminations. Our current understanding of ocean-atmosphere-cryosphere interactions at ice-age terminations relies largely on assessments of the most recent (last) glacial-interglacial transition.sup.1,2,3, Termination I (T-I). But the extent to which T-I is representative of previous terminations remains unclear. Testing the consistency of termination processes requires comparison of time series of critical climate parameters with detailed absolute and relative age control. However, such age control has been lacking for even the penultimate glacial termination (T-II), which culminated in a sea-level highstand during the last interglacial period that was several metres above present.sup.4. Here we show that Heinrich Stadial 11 (HS11), a prominent North Atlantic cold episode.sup.5,6, occurred between 135 [plus or minus] 1 and 130 [plus or minus] 2 thousand years ago and was linked with rapid sea-level rise during T-II. Our conclusions are based on new and existing.sup.6,7,8,9 data for T-II and the last interglacial that we collate onto a single, radiometrically constrained chronology. The HS11 cold episode.sup.5,6 punctuated T-II and coincided directly with a major deglacial meltwater pulse, which predominantly entered the North Atlantic Ocean and accounted for about 70 per cent of the glacial-interglacial sea-level rise.sup.8,9. We conclude that, possibly in response to stronger insolation and CO.sub.2 forcing earlier in T-II, the relationship between climate and ice-volume changes differed fundamentally from that of T-I. In T-I, the major sea-level rise clearly post-dates.sup.3,10,11 Heinrich Stadial 1. We also find that HS11 coincided with sustained Antarctic warming, probably through a bipolar seesaw temperature response.sup.12, and propose that this heat gain at high southern latitudes promoted Antarctic ice-sheet melting that fuelled the last interglacial sea-level peak., Author(s): G. Marino [sup.1] , E. J. Rohling [sup.1] [sup.2] , L. Rodríguez-Sanz [sup.1] , K. M. Grant [sup.1] , D. Heslop [sup.1] , A. P. Roberts [sup.1] , J. [...]
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- 2015
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11. Sea Surface and High-Latitude Temperature Sensitivity to Radiative Forcing of Climate over Several Glacial Cycles
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Rohling, E. J., Medina-Elizalde, M., Shepherd, J. G., Siddall, M., and Stanford, J. D.
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- 2012
12. Regional Synthesis of Mediterranean Atmospheric Circulation during the Last Glacial Maximum
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Kuhlemann, J., Rohling, E. J., Krumrei, I., Kubik, P., Ivy-Ochs, S., and Kucera, M.
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- 2008
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13. Plio-Pleistocene climate sensitivity evaluated using high-resolution CO2 records
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Martínez-Botí, M. A., Foster, G. L., Chalk, T. B., Rohling, E. J., Sexton, P. F., Lunt, D. J., Pancost, R. D., Badger, M. P. S., and Schmidt, D. N.
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- 2015
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14. Vertical density gradient in the eastern North Atlantic during the last 30,000 years
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Rogerson, M., Bigg, G. R., Rohling, E. J., and Ramirez, J.
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- 2012
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15. The sensitivity of the Antarctic Ice Sheet to a changing climate: past, present and future
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Noble, T. L., Rohling, E. J., Aitken, A. R. A., Bostock, H. C., Chase, Z., Gomez, N., Jong, L. M., King, M. A., Mackintosh, A. N., Mccormack, F. S., Mckay, R. M., Menviel, L., Phipps, S. J., Weber, M. E., Fogwill, C. J., Gayen, B., Golledge, N. R., Gwyther, D. E., Hogg, A. Mc C., Martos, Y. M., Pena‐molino, B., Roberts, J., Flierdt, T., and Williams, T.
- Abstract
The Antarctic Ice Sheet (AIS) is out of equilibrium with the current anthropogenic-enhanced climate forcing. Paleoenvironmental records and ice sheet models reveal that the AIS has been tightly coupled to the climate system during the past and indicate the potential for accelerated and sustained Antarctic ice mass loss into the future. Modern observations by contrast suggest that the AIS has only just started to respond to climate change in recent decades. The maximum projected sea level contribution from Antarctica to 2100 has increased significantly since the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report, although estimates continue to evolve with new observational and theoretical advances. This review brings together recent literature highlighting the progress made on the known processes and feedbacks that influence the stability of the AIS. Reducing the uncertainty in the magnitude and timing of the future sea level response to AIS change requires a multidisciplinary approach that integrates knowledge of the interactions between the ice sheet, solid Earth, atmosphere, and ocean systems and across time scales of days to millennia. We start by reviewing the processes affecting AIS mass change, from atmospheric and oceanic processes acting on short time scales (days to decades), through to ice processes acting on intermediate time scales (decades to centuries) and the response to solid Earth interactions over longer time scales (decades to millennia). We then review the evidence of AIS changes from the Pliocene to the present and consider the projections of global sea level rise and their consequences. We highlight priority research areas required to improve our understanding of the processes and feedbacks governing AIS change.
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- 2020
16. Sea-level and deep-sea-temperature variability over the past 5.3 million years
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Rohling, E. J., Foster, G. L., Grant, K. M., Marino, G., Roberts, A. P., Tamisiea, M. E., and Williams, F.
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- 2014
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17. Millennial atmospheric CO2changes linked to ocean ventilation modes over past 150,000 years
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Yu, J., Anderson, R. F., Jin, Z. D., Ji, X., Thornalley, D. J. R., Wu, L., Thouveny, N., Cai, Y., Tan, L., Zhang, F., Menviel, L., Tian, J., Xie, X., Rohling, E. J., and McManus, J. F.
- Abstract
Ice core measurements show diverse atmospheric CO2variations—increasing, decreasing or remaining stable—during millennial-scale North Atlantic cold periods called stadials. The reasons for these contrasting trends remain elusive. Ventilation of carbon-rich deep oceans can profoundly affect atmospheric CO2, but its millennial-scale history is poorly constrained. Here we present a well-dated high-resolution deep Atlantic acidity record over the past 150,000 years, which reveals five hitherto undetected modes of stadial ocean ventilation with different consequences for deep-sea carbon storage and associated atmospheric CO2changes. Our data provide observational evidence to show that strong and often volumetrically extensive Southern Ocean ventilation released substantial amounts of deep-sea carbon during stadials when atmospheric CO2rose prominently. By contrast, other stadials were characterized by weak ventilation via both Southern Ocean and North Atlantic, which promoted respired carbon accumulation and thus curtailed or reversed deep-sea carbon losses, resulting in diminished rises or even declines in atmospheric CO2. Our findings demonstrate that millennial-scale changes in deep-sea carbon storage and atmospheric CO2are modulated by multiple ocean ventilation modes through the interplay of the two polar regions, rather than by the Southern Ocean alone, which is critical for comprehensive understanding of past and future carbon cycle adjustments to climate change.
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- 2023
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18. An Assessment of Earth's Climate Sensitivity Using Multiple Lines of Evidence
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Sherwood, S. C., Webb, M. J., Annan, J. D., Armour, K. C., Forster, P. M., Hargreaves, J. C., Hegerl, G., Klein, S. A., Marvel, K. D., Rohling, E. J., Watanabe, M., Andrews, T., Braconnot, P., Bretherton, C. S., Foster, G. L., Hausfather, Z., Heydt, A. S., Knutti, R., Mauritsen, Thorsten, Norris, J. R., Proistosescu, C., Rugenstein, M., Schmidt, G. A., Tokarska, K. B., Zelinka, M. D., Sherwood, S. C., Webb, M. J., Annan, J. D., Armour, K. C., Forster, P. M., Hargreaves, J. C., Hegerl, G., Klein, S. A., Marvel, K. D., Rohling, E. J., Watanabe, M., Andrews, T., Braconnot, P., Bretherton, C. S., Foster, G. L., Hausfather, Z., Heydt, A. S., Knutti, R., Mauritsen, Thorsten, Norris, J. R., Proistosescu, C., Rugenstein, M., Schmidt, G. A., Tokarska, K. B., and Zelinka, M. D.
- Abstract
We assess evidence relevant to Earth's equilibrium climate sensitivity per doubling of atmospheric CO2, characterized by an effective sensitivity S. This evidence includes feedback process understanding, the historical climate record, and the paleoclimate record. An S value lower than 2 K is difficult to reconcile with any of the three lines of evidence. The amount of cooling during the Last Glacial Maximum provides strong evidence against values of S greater than 4.5 K. Other lines of evidence in combination also show that this is relatively unlikely. We use a Bayesian approach to produce a probability density function (PDF) for S given all the evidence, including tests of robustness to difficult-to-quantify uncertainties and different priors. The 66% range is 2.6-3.9 K for our Baseline calculation and remains within 2.3-4.5 K under the robustness tests; corresponding 5-95% ranges are 2.3-4.7 K, bounded by 2.0-5.7 K (although such high-confidence ranges should be regarded more cautiously). This indicates a stronger constraint on S than reported in past assessments, by lifting the low end of the range. This narrowing occurs because the three lines of evidence agree and are judged to be largely independent and because of greater confidence in understanding feedback processes and in combining evidence. We identify promising avenues for further narrowing the range in S, in particular using comprehensive models and process understanding to address limitations in the traditional forcing-feedback paradigm for interpreting past changes.
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- 2020
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19. The Sensitivity of the Antarctic Ice Sheet to a Changing Climate: Past, Present, and Future
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Noble, T. L., primary, Rohling, E. J., additional, Aitken, A. R. A., additional, Bostock, H. C., additional, Chase, Z., additional, Gomez, N., additional, Jong, L. M., additional, King, M. A., additional, Mackintosh, A. N., additional, McCormack, F. S., additional, McKay, R. M., additional, Menviel, L., additional, Phipps, S. J., additional, Weber, M. E., additional, Fogwill, C. J., additional, Gayen, B., additional, Golledge, N. R., additional, Gwyther, D. E., additional, Hogg, A. McC., additional, Martos, Y. M., additional, Pena‐Molino, B., additional, Roberts, J., additional, van de Flierdt, T., additional, and Williams, T., additional
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- 2020
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20. Three million years of monsoon variability over the northern Sahara
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Larrasoaña, J. C., Roberts, A. P., Rohling, E. J., Winklhofer, M., and Wehausen, R.
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- 2003
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21. Sea-level fluctuations during the last glacial cycle
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Siddall, M., Rohling, E. J., Almogi-Labin, A., Hemleben, Ch., Meischner, D., Schmelzer, I., and Smeed, D. A.
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- 2003
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22. Rapid coupling between ice volume and polar temperature over the past 150,000 years
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Grant, K. M., Rohling, E. J., Bar-Matthews, M., Ayalon, A., Medina-Elizalde, M., Ramsey, Bronk C., Satow, C., and Roberts, A. P.
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- 2012
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23. Making sense of palaeoclimate sensitivity
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Rohling, E. J., Sluijs, A., Dijkstra, H. A., Köhler, P., van de Wal, R. S. W., von der Heydt, A. S., Beerling, D. J., Berger, A., Bijl, P. K., Crucifix, M., DeConto, R., Drijfhout, S. S., Fedorov, A., Foster, G. L., Ganopolski, A., Hansen, J., Hönisch, B., Hooghiemstra, H., Huber, M., Huybers, P., Knutti, R., Lea, D. W., Lourens, L. J., Lunt, D., Masson-Demotte, V., Medina-Elizalde, M., Otto-Bliesner, B., Pagani, M., Pälike, H., Renssen, H., Royer, D. L., Siddall, M., Valdes, P., Zachos, J. C., and Zeebe, R. E.
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- 2012
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24. An Assessment of Earth's Climate Sensitivity Using Multiple Lines of Evidence
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Sherwood, S. C., primary, Webb, M. J., additional, Annan, J. D., additional, Armour, K. C., additional, Forster, P. M., additional, Hargreaves, J. C., additional, Hegerl, G., additional, Klein, S. A., additional, Marvel, K. D., additional, Rohling, E. J., additional, Watanabe, M., additional, Andrews, T., additional, Braconnot, P., additional, Bretherton, C. S., additional, Foster, G. L., additional, Hausfather, Z., additional, von der Heydt, A. S., additional, Knutti, R., additional, Mauritsen, T., additional, Norris, J. R., additional, Proistosescu, C., additional, Rugenstein, M., additional, Schmidt, G. A., additional, Tokarska, K. B., additional, and Zelinka, M. D., additional
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- 2020
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25. PP33E-1768: Paleoceanographic Evolution of the Equatorial Indian Ocean during the Late Miocene (Invited)
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Clara Bolton, Claire Martinot, Emmeline Gray, Samuel Phelps, Kazuyo Tachikawa, Wolfgang Kuhnt, Ann Holbourn, Julia Lübbers, Laurence Vidal, Rohling, E. J., Katharine Grant, Gianluca Marino, Luc Beaufort, Corinne Sonzogni, Marta Garcia Molina, Nils Andersen, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Ocean and Earth Science [Southampton], University of Southampton-National Oceanography Centre (NOC), Leibniz Laboratory for Radiometric Dating and Stable Isotope Research, Christian-Albrechts-University, Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), and Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
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[SDU.STU]Sciences of the Universe [physics]/Earth Sciences - Abstract
International audience; During the late Miocene (~11-5 Ma), atmospheric pCO may have been 1 to 3 times pre-industrial values, and mean global temperatures were likely 3−4°C higher than today with reduced latitudinal gradients. Major ecosystem changes that took place during the late Miocene are consistent with falling global temperatures and decreasing pCO , but proxy evidence for these physical climate changes remains sparse because few continuous, orbital-resolution palaeoclimate records cover this interval. Recently, geographically widespread and major (~5-10°C) late Miocene sea surface cooling was revealed for the mid-and high-latitudes based on the U sea surface temperature (SST) proxy, however existing tropical SST records suggest only minor cooling in this interval (1-2°C). Here we present new multi-proxy geochemical and micropaleontological records of surface and deep ocean variability from IODP Site U1443, drilled in the equatorial Indian Ocean (5°N, 90°E) during Expedition 353, which span the interval 9.5 to 5 Ma. Surface ocean records from Site U1443 have the potential to resolve SST change at a "warm pool" tropical site, whilst also providing insight into long-term and orbital-scale changes in the Indian monsoon subsystem. SST estimates derived from Mg/Ca ratios in the surface-dwelling planktic foraminifer Trilobatus trilobus show ~4°C of cooling (from 3.8 to 2.5 mmol/mol Mg/Ca) between 8.5 and 6 Ma. Following a SST minimum at 6 Ma, reconstructed temperatures increase from 6 to 5 Ma, consistent with published extratropical SST records. SST estimates combined with paired foraminiferal δ O measurements reveal a 2‰ decrease in seawater δ O (δ O , uncorrected for ice-volume changes) between 8.5 and 6 Ma, and a subsequent increase between 6 and 5 Ma. Consistent with records from other sites, Site U1443 benthic δ O data show no long-term increase concurrent with the Mg/Ca-SST decrease. We also observe dynamic changes in coccolith mass, a proxy for cell size and/or calcification, on both million-year and more abrupt timescales, sometimes correlated to SST changes. On orbital timescales, our records show coeval cyclicity in SST, δ O , and export productivity proxies, suggesting that changes in monsoon strength affected upper water column structure and properties on these timescales during the late Miocene. 2 2 k 37 18 18 18 sw 18 18 sw
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- 2018
26. Correction: Corrigendum: Bipolar seesaw control on last interglacial sea level
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Marino, G., Rohling, E. J., Rodríguez-Sanz, L., Grant, K. M., Heslop, D., Roberts, A. P., Stanford, J. D., and Yu, J.
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- 2015
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27. New constraints on the Eastern Mediterranean δ18O:δD relationship
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Cox, K. A., Rohling, E. J., Schmidt, G. A., Schiebel, R., Bacon, S., Winter, D. A., Bolshaw, M., and Spero, H. J.
- Abstract
Previous work on oxygen and hydrogen isotope data from Eastern Mediterranean water samples has defined a mixing relationship in this region that is different from the world surface ocean. This prompted speculations about the hydrological processes in the Mediterranean region. We present new δ18O and δD data from the Eastern Mediterranean region and the East Greenland Current system, spanning a wide salinity range. These data define δ18O:δD relationships for both regions that are consistent with the world surface ocean δ18O:δD relationship, despite the highly evaporative conditions that prevail in the Mediterranean region. These new geochemical data have suggested that the world surface ocean &delta18O:δD relationship holds throughout almost the entire global salinity range.
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- 2018
28. Magnitudes of sea-level lowstands of the past 500,000 years
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Rohling, E. J., Fenton, M., Jorissen, F. J., Bertrand, P., Ganssen, G., and Caulet, J. P.
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- 1998
29. Lessons on climate sensitivity from past climate changes
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von der Heydt, A. S., Dijkstra, Hendrik, van de Wal, R. S. W., Caballero, R., Crucifix, M., Foster, G. L., Huber, M., Köhler, P., Rohling, E. J., Valdes, P. J., Ashwin, P., Bathiany, S., Berends, Tijn, van Bree, Loes, Ditlevsen, P., Ghil, M., Haywood, A., Katzav, J., Lohmann, G., Lohmann, J., Lucarini, V., Marzocchi, Alice, Pälike, H., Ruvalcaba Baroni, I., Simon, D., Sluijs, A., Stap, L. B., Tantet, A., Viebahn, J., Ziegler, M., Marine and Atmospheric Research, Sub Physical Oceanography, Dep Natuurkunde, Sub Dynamics Meteorology, Organic geochemistry, Paleomagnetism, Geochemistry, Tectonophysics, Marine palynology and palaeoceanography, Stratigraphy and paleontology, Climate and Environment, Marine and Atmospheric Research, Sub Physical Oceanography, Dep Natuurkunde, Sub Dynamics Meteorology, Organic geochemistry, Paleomagnetism, Geochemistry, Tectonophysics, Marine palynology and palaeoceanography, Stratigraphy and paleontology, Climate and Environment, Philosophy & Ethics, and UCL - SST/ELI/ELIC - Earth & Climate
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Climate tipping points ,Aquatic Ecology and Water Quality Management ,Atmospheric Science ,010504 meteorology & atmospheric sciences ,Climate commitment ,Climate change ,Present day ,Climate dynamics ,010502 geochemistry & geophysics ,Palaeoclimate ,01 natural sciences ,Proxy (climate) ,Atmospheric Sciences ,SDG 13 - Climate Action ,State dependence ,0105 earth and related environmental sciences ,Global and Planetary Change ,Forcing (recursion theory) ,SDG 13 – Klimaatactie ,Constraints on Climate Sensitivity (R Knutti, Section Editor) ,Aquatische Ecologie en Waterkwaliteitsbeheer ,Radiative forcing ,Climate sensitivity ,feedback processes ,13. Climate action ,Climatology ,Environmental science - Abstract
Over the last decade, our understanding of cli- mate sensitivity has improved considerably. The climate system shows variability on many timescales, is subject to non-stationary forcing and it is most likely out of equi- librium with the changes in the radiative forcing. Slow and fast feedbacks complicate the interpretation of geolog- ical records as feedback strengths vary over time. In the geological past, the forcing timescales were different than at present, suggesting that the response may have behaved differently. Do these insights constrain the climate sensitiv- ity relevant for the present day? In this paper, we review the progress made in theoretical understanding of climate sensitivity and on the estimation of climate sensitivity from proxy records. Particular focus lies on the background state dependence of feedback processes and on the impact of tipping points on the climate system. We suggest how to further use palaeo data to advance our understanding of the currently ongoing climate change.
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- 2016
30. Penultimate deglacial warming across the Mediterranean Sea revealed by clumped isotopes in foraminifera
- Author
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non-UU output of UU-AW members, Rodríguez-Sanz, L., Bernasconi, S. M., Marino, G., Heslop, D., Müller, I. A., Fernandez, A., Grant, K. M., Rohling, E. J., non-UU output of UU-AW members, Rodríguez-Sanz, L., Bernasconi, S. M., Marino, G., Heslop, D., Müller, I. A., Fernandez, A., Grant, K. M., and Rohling, E. J.
- Published
- 2017
31. The timing of Mediterranean sapropel deposition relative to insolation, sea-level and African monsoon changes
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Grant, K. M., Grimm, R., Mikolajewicz, U., Marino, G., Ziegler, M., Rohling, E. J., Stratigraphy and paleontology, Stratigraphy & paleontology, Stratigraphy and paleontology, and Stratigraphy & paleontology
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Archeology ,010504 meteorology & atmospheric sciences ,Evolution ,Eastern Mediterranean ,Precession ,010502 geochemistry & geophysics ,Monsoon ,01 natural sciences ,Marine Isotope Stage 5 ,Behavior and Systematics ,African monsoon ,Insolation ,Sea level ,14. Life underwater ,Glacial period ,Sapropels ,Meltwater ,Ecology, Evolution, Behavior and Systematics ,Holocene ,0105 earth and related environmental sciences ,Global and Planetary Change ,Ecology ,Meltwater pulses ,Geology ,Sapropel ,Oceanography ,Archaeology ,13. Climate action ,Climatology ,Ice sheets - Abstract
The Mediterranean basin is sensitive to global sea-level changes and African monsoon variability on orbital timescales. Both of these processes are thought to be important to the deposition of organic-rich sediment layers or 'sapropels' throughout the eastern Mediterranean, yet their relative influences remain ambiguous. A related issue is that an assumed 3-kyr lag between boreal insolation maxima and sapropel mid-points remains to be tested. Here we present new geochemical and ice-volume-corrected planktonic foraminiferal stable isotope records for sapropels S1 (Holocene), S3, S4, and S5 (Marine Isotope Stage 5) in core LC21 from the southern Aegean Sea. The records have a radiometrically constrained chronology that has already been synchronised with the Red Sea relative sea-level record, and this allows detailed examination of the timing of sapropel deposition relative to insolation, sea-level, and African monsoon changes. We find that sapropel onset was near-synchronous with monsoon run-off into the eastern Mediterranean, but that insolation-sapropel/monsoon phasings were not systematic through the last glacial cycle. These latter phasings instead appear to relate to sea-level changes. We propose that persistent meltwater discharges into the North Atlantic (e.g., at glacial terminations) modified the timing of sapropel deposition by delaying the timing of peak African monsoon run-off. These observations may reconcile apparent model-data offsets with respect to the orbital pacing of the African monsoon. Our observations also imply that the previous assumption of a systematic 3-kyr lag between insolation maxima and sapropel midpoints may lead to overestimated insolation-sapropel phasings. Finally, we surmise that both sea-level rise and monsoon run-off contributed to surface-water buoyancy changes at times of sapropel deposition, and their relative influences differed per sapropel case, depending on their magnitudes. Sea-level rise was clearly important for sapropel S1, whereas monsoon forcing was more important for sapropels S3, S4, and S5.
- Published
- 2016
32. Last glacial atmospheric CO2decline due to widespread Pacific deep-water expansion
- Author
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Yu, J., Menviel, L., Jin, Z. D., Anderson, R. F., Jian, Z., Piotrowski, A. M., Ma, X., Rohling, E. J., Zhang, F., Marino, G., and McManus, J. F.
- Abstract
Ocean circulation critically affects the global climate and atmospheric carbon dioxide through redistribution of heat and carbon in the Earth system. Despite intensive research, the nature of past ocean circulation changes remains elusive. Here we present deep-water carbonate ion concentration reconstructions for widely distributed locations in the Atlantic Ocean, where low carbonate ion concentrations indicate carbon-rich waters. These data show a low-carbonate-ion water mass that extended northward up to about 20° S in the South Atlantic at 3–4 km depth during the Last Glacial Maximum. In combination with radiocarbon ages, neodymium isotopes and carbon isotopes, we conclude that this low-carbonate-ion signal reflects a widespread expansion of carbon-rich Pacific deep waters into the South Atlantic, revealing a glacial deep Atlantic circulation scheme different than commonly considered. Comparison of high-resolution carbonate ion records from different water depths in the South Atlantic indicates that this Pacific deep-water expansion developed from approximately 38,000 to 28,000 years ago. We infer that its associated carbon sequestration may have contributed critically to the contemporaneous decline in atmospheric carbon dioxide, thereby helping to initiate the glacial maximum.
- Published
- 2020
- Full Text
- View/download PDF
33. Sequestration of carbon in the deep Atlantic during the last glaciation
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Yu, J., Menviel, L., Jin, Z. D., Thornalley, D. J. R., Barker, S., Marino, G., Rohling, E. J., Cai, Y., Zhang, F., Wang, X., Dai, Y., Chen, P., Broecker, W. S., Yu, J., Menviel, L., Jin, Z. D., Thornalley, D. J. R., Barker, S., Marino, G., Rohling, E. J., Cai, Y., Zhang, F., Wang, X., Dai, Y., Chen, P., and Broecker, W. S.
- Abstract
Atmospheric CO2 concentrations declined markedly about 70,000 years ago, when the Earth's climate descended into the last glaciation. Much of the carbon removed from the atmosphere has been suspected to have entered the deep oceans, but evidence for increased carbon storage remains elusive. Here we use the B/Ca ratios of benthic foraminifera from several sites across the Atlantic Ocean to reconstruct changes in the carbonate ion concentration and hence the carbon inventory of the deep Atlantic across this transition. We find that deep Atlantic carbonate ion concentration declined by around 25 mu mol kg(-1) between similar to 80,000 and 65,000 years ago. This drop implies that the deep Atlantic carbon inventory increased by at least 50 Gt around the same time as the amount of atmospheric carbon dropped by about 60 Gt. From a comparison with proxy records of deep circulation and climate model simulations, we infer that the carbon sequestration coincided with a shoaling of the Atlantic meridional overturning circulation. We thus conclude that changes in the Atlantic Ocean circulation may have played an important role in reductions of atmospheric CO2 concentrations during the last glaciation, by increasing the carbon storage in the deep Atlantic.
- Published
- 2016
- Full Text
- View/download PDF
34. Lessons on Climate Sensitivity From Past Climate Changes
- Author
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Marine and Atmospheric Research, Sub Physical Oceanography, Dep Natuurkunde, Sub Dynamics Meteorology, Organic geochemistry, Paleomagnetism, Geochemistry, Tectonophysics, Marine palynology and palaeoceanography, Stratigraphy and paleontology, Climate and Environment, von der Heydt, A. S., Dijkstra, Hendrik, van de Wal, R. S. W., Caballero, R., Crucifix, M., Foster, G. L., Huber, M., Köhler, P., Rohling, E. J., Valdes, P. J., Ashwin, P., Bathiany, S., Berends, Tijn, van Bree, Loes, Ditlevsen, P., Ghil, M., Haywood, A., Katzav, J., Lohmann, G., Lohmann, J., Lucarini, V., Marzocchi, Alice, Pälike, H., Ruvalcaba Baroni, I., Simon, D., Sluijs, A., Stap, L. B., Tantet, A., Viebahn, J., Ziegler, M., Marine and Atmospheric Research, Sub Physical Oceanography, Dep Natuurkunde, Sub Dynamics Meteorology, Organic geochemistry, Paleomagnetism, Geochemistry, Tectonophysics, Marine palynology and palaeoceanography, Stratigraphy and paleontology, Climate and Environment, von der Heydt, A. S., Dijkstra, Hendrik, van de Wal, R. S. W., Caballero, R., Crucifix, M., Foster, G. L., Huber, M., Köhler, P., Rohling, E. J., Valdes, P. J., Ashwin, P., Bathiany, S., Berends, Tijn, van Bree, Loes, Ditlevsen, P., Ghil, M., Haywood, A., Katzav, J., Lohmann, G., Lohmann, J., Lucarini, V., Marzocchi, Alice, Pälike, H., Ruvalcaba Baroni, I., Simon, D., Sluijs, A., Stap, L. B., Tantet, A., Viebahn, J., and Ziegler, M.
- Published
- 2016
35. The timing of Mediterranean sapropel deposition relative to insolation, sea-level and African monsoon changes
- Author
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Stratigraphy and paleontology, Stratigraphy & paleontology, Grant, K. M., Grimm, R., Mikolajewicz, U., Marino, G., Ziegler, M., Rohling, E. J., Stratigraphy and paleontology, Stratigraphy & paleontology, Grant, K. M., Grimm, R., Mikolajewicz, U., Marino, G., Ziegler, M., and Rohling, E. J.
- Published
- 2016
36. The timing of Mediterranean sapropel deposition relative to insolation, sea-level and African monsoon changes
- Author
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Stratigraphy & paleontology, Stratigraphy and paleontology, Grant, K. M., Grimm, R., Mikolajewicz, U., Marino, G., Ziegler, M., Rohling, E. J., Stratigraphy & paleontology, Stratigraphy and paleontology, Grant, K. M., Grimm, R., Mikolajewicz, U., Marino, G., Ziegler, M., and Rohling, E. J.
- Published
- 2016
37. Enhanced productivity on the Iberian margin during glacial/interglacial transitions revealed by barium and diatoms
- Author
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THOMSON, J., NIXON, S., SUMMERHAYES, C. P., ROHLING, E. J., SCHONFELD, J., ZAHN, R., GROOTES, P., ABRANTES, F., GASPAR, L., and VAQUEIRO, S.
- Subjects
Geology, Stratigraphic -- Pleistocene ,Barium -- Research ,Glaciers -- Research ,Sedimentation and deposition -- Research ,Earth sciences - Abstract
The Portuguese margin is at a critical location for studies of the ocean's behaviour during glacial/interglacial climatic changes, and the rapid accumulation rates of the sediments enable high-resolution palaeoclimatic investigation. The sedimentary record of the past 350 ka has been investigated in a 35 m long core from 3.5 km water depth on the slope at 40 [degrees] N by geochemical, isotopic and micropalaeontological techniques. The Ca[CO.sub.3] content of this core as a function of time contains significant Milankovitch orbital frequencies of 18.8, 23.7, 38.0 and 100.6 ka, but these are driven primarily by dilution by clay-flux variations rather than by Ca[CO.sub.3] productivity variations. The largest signals in the productivity indicators [C.sub.org], Ba/Al and diatom abundance are all observed as simultaneous peaks at the oxygen isotope stage boundaries 10/9 and 6/5, with the signal magnitude in the order 10/9 [is greater than] 6/5 for all three indicators. Smaller coincident signals in [C.sub.org], Ba/Al but not diatoms are also observed at the oxygen isotope stage 2/1 boundary. Other less prominent peaks in the [C.sub.org] and Ba/Al profiles occur elsewhere, including Heinrich Event horizons, but these are not always simultaneous and none contain evidence of the dissolution-prone diatom microfossils. The 10/9, 6/5 and 2/1 oxygen isotope stage transitions represent the three most extreme glacial/interglacial sea level rises in the past 350 ky, possibly in the same sequence of magnitude, when sea level rose rapidly by 120+m from glacial low stands to interglacial high stands. The productivity signals at these transitions are contained within [is less than] 5 ka (including bioturbation). Keywords: Pleistocene, Iberian margin, sedimentation, oxygen isotopes, barium.
- Published
- 2000
38. Sequestration of carbon in the deep Atlantic during the last glaciation
- Author
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Yu, J., primary, Menviel, L., additional, Jin, Z. D., additional, Thornalley, D. J. R., additional, Barker, S., additional, Marino, G., additional, Rohling, E. J., additional, Cai, Y., additional, Zhang, F., additional, Wang, X., additional, Dai, Y., additional, Chen, P., additional, and Broecker, W. S., additional
- Published
- 2016
- Full Text
- View/download PDF
39. Snowball Earth ocean chemistry driven by extensive ridge volcanism during Rodinia breakup
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Gernon, T. M., primary, Hincks, T. K., additional, Tyrrell, T., additional, Rohling, E. J., additional, and Palmer, M. R., additional
- Published
- 2016
- Full Text
- View/download PDF
40. A new contribution to the Late Quaternary tephrostratigraphy of the Mediterranean: Aegean Sea core LC21
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Satow, C., Tomlinson, E. L., Grant, K. M., Albert, P. G., Smith, V. C., Manning, C. J., Ottolini, L., Wulf, S., Rohling, E. J., Lowe, J. J., Blockley, S. P. E., Menzies, M. A., Satow, C., Tomlinson, E. L., Grant, K. M., Albert, P. G., Smith, V. C., Manning, C. J., Ottolini, L., Wulf, S., Rohling, E. J., Lowe, J. J., Blockley, S. P. E., and Menzies, M. A.
- Abstract
Tephra layers preserved in marine sediments can contribute to the reconstruction of volcanic histories and potentially act as stratigraphic isochrons to link together environmental records. Recent developments in the detection of volcanic ash (tephra) at levels where none is macroscopically visible (so-called ‘crypto-tephra’) have greatly enhanced the potential of tephrostratigraphy for synchronising environmental and archaeological records by expanding the areas over which tephras are found. In this paper, crypto-tephra extraction techniques allow the recovery of 8 non-visible tephra layers to add to the 9 visible layers in a marine sediment core (LC21) from the SE Aegean Sea to form the longest, single core record of volcanic activity in the Aegean Sea. Using a novel, shard-specific methodology, sources of the tephra shards are identified on the basis of their major and trace element single-shard geochemistry, by comparison with geochemical data from proximal Mediterranean volcanic stratigraphies. The results indicate that the tephra layers are derived from 14 or 15 separate eruptions in the last ca 161 ka BP: 9 from Santorini; 2 or 3 from Kos, Yali, or Nisyros; 2 from the Campanian province; and one from Pantelleria. The attributions of these tephra layers indicate that 1) inter-Plinian eruptions from Santorini may have produced regionally significant tephra deposits, 2) marine tephrostratigraphies can provide unique and invaluable data to eruptive histories for island volcanoes, and 3) tephra from both Pantelleria and Campania may be used to correlate marine records from the Aegean Sea to those from the Tyrrhenian, Adriatic and Ionian Seas.
- Published
- 2015
- Full Text
- View/download PDF
41. Precession and obliquity forcing of the freshwater budget over the Mediterranean
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Hydrologie, Landscape functioning, Geocomputation and Hydrology, Sub Physical Oceanography, Sub AW Strat PA OG 2e geldstroom, Stratigraphy and paleontology, Bosmans, J. H.C., Drijfhout, S. S., Tuenter, E., Hilgen, F. J., Lourens, L. J., Rohling, E. J., Hydrologie, Landscape functioning, Geocomputation and Hydrology, Sub Physical Oceanography, Sub AW Strat PA OG 2e geldstroom, Stratigraphy and paleontology, Bosmans, J. H.C., Drijfhout, S. S., Tuenter, E., Hilgen, F. J., Lourens, L. J., and Rohling, E. J.
- Published
- 2015
42. Paleoceanography of the Atlantic-Mediterranean exchange: overview and first quantitative assessment of climatic forcing
- Author
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Rogerson, M., Rohling, E. J., Bigg, G. R., and Ramirez, J.
- Abstract
The Mediterranean Sea provides a major route for heat and freshwater loss from the North Atlantic and thus is an important cause of the high density of Atlantic waters. In addition to the traditional view that loss of fresh water via the Mediterranean enhances the general salinity of the North Atlantic, and the interior of the eastern North Atlantic in particular, it should be noted that Mediterranean water outflowing at Gibraltar is in fact cooler than compensating inflowing water. The consequence is that the Mediterranean is also a region of heat loss from the Atlantic and contributes to its large-scale cooling. Uniquely, this system can be understood physically via the constraints placed on it by a single hydraulic structure: the Gibraltar exchange. Here we review the existing knowledge about the physical structure of the Gibraltar exchange today and the evidential basis for arguments that it has been different in the past. Using a series of quantitative experiments, we then test prevailing concepts regarding the potential causes of these past changes. We find that (1) changes in the vertical position of the plume of Mediterranean water in the Atlantic are controlled by the vertical density structure of the Atlantic; (2) a prominent Early Holocene "contourite gap" within the Gulf of Cadiz is a response to reduced buoyancy loss in the eastern Mediterranean during the time of "sapropel 1" deposition; (3) changes in buoyancy loss from the Mediterranean during MIS3 caused changes in the bottom velocity field in the Gulf of Cadiz, but we note that the likely cause is reduced freshwater loss and not enhanced heat loss; and (4) strong exchange at Gibraltar during Atlantic freshening phases implies that the Gibraltar exchange provides a strong negative feedback to reduced Atlantic meridional overturning. Given the very counterintuitive way in which the Strait of Gibraltar system behaves, we recommend that without quantitative supporting work, qualitative interpretations of how the system has responded to past external forcing are unlikely to be robust.
- Published
- 2012
43. The climate sensitivity parameter during the last 800 kyr - offsets due to transient effects and state dependency
- Author
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Köhler, Peter, van de Wal, R. S. W., Dijkstra, H., and Rohling, E. J.
- Abstract
The climate sensitivity parameter S is defined as the equilibrium change in global annual mean surface temperature ∆T per radiative forcing ∆R, S= ∆T/∆R. We here combine a data set of radiative forcing ∆R of greenhouse gases and albedo changes (Köhler et al., 2010) with an estimate of ∆T based on the deconvolution of benthic δ18O into sealevel and temperature (Bintanja et al., 2005) for the last 800 kyr. We show how S varies depending on the radiative forcing considered, e.g. if only ∆R of CO2 or ∆R of CO2+CH4+N2O or additionally ∆R of the albedo changes are taken into account. Furthermore we find, that for the LGM all calculated S, independent on the considered forcing ∆R is about 10-15% smaller than if calculated for the whole 800 kyr time window. We propose that this difference between the rather stable climate of the LGM and the whole 800 kyr is caused by transient effects and the state dependency of S. We identify based on thresholds in temporal changes in ∆T and ∆R relatively stable climates and separate the transient effect from state dependency in S. In a final application it is shown how the state dependency of S and assumptions on various slow and fast feedbacks are important for the functional relationship between ∆T and CO2 for the range in CO2 observed in the past 800 kyr and proposed in the future (2×CO2).
- Published
- 2012
44. New constraints on the Eastern Mediterranean δ18O:δD relationship
- Author
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Cox, K.-A., Rohling, E.-J., Schmidt, G., Schiebel, Ralf, Bacon, S., Winter, D.-A., Bolshaw, M., Spero, Howard, Institute of Experimental Physics, Otto-von-Guericke University [Magdeburg] (OVGU), Laboratoire de Planétologie et Géodynamique - Angers (LPG-ANGERS), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Oceanography Centre (NOC), University of California [Davis] (UC Davis), and University of California
- Subjects
[SDU]Sciences of the Universe [physics] - Abstract
International audience; Previous work on oxygen and hydrogen isotope data from Eastern Mediterranean water samples has defined a mixing relationship in this region that is different from the world surface ocean. This prompted speculations about the hydrological processes in the Mediterranean region. We present new δ18O and δD data from the Eastern Mediterranean region and the East Greenland Current system, spanning a wide salinity range. These data define δ18O:δD relationships for both regions that are consistent with the world surface ocean δ18O:δD relationship, despite the highly evaporative conditions that prevail in the Mediterranean region. These new geochemical data have suggested that the world surface ocean &delta18O:δD relationship holds throughout almost the entire global salinity range.
- Published
- 2011
45. Addendum: Plio-Pleistocene climate sensitivity evaluated using high-resolution CO2 records
- Author
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Martínez-Botí, M. A., primary, Foster, G. L., additional, Chalk, T. B., additional, Rohling, E. J., additional, Sexton, P. F., additional, Lunt, D. J., additional, Pancost, R. D., additional, Badger, M. P. S., additional, and Schmidt, D. N., additional
- Published
- 2015
- Full Text
- View/download PDF
46. Enhanced Mediterranean-Atlantic exchange during Atlantic freshening phases
- Author
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Rogerson, M., Colmenero-hidalgo, E., Levine, R. C., Rohling, E. J., Voelker, A. H. L., Bigg, G. R., Schoenfeld, J., Cacho, I., Sierro, F. J., Lowemark, L., Reguera, M. I., De Abreu, L., and Garrick, K.
- Subjects
Gibraltar ,Last Glacial Maximum ,Mediterranean Outflow ,Atlantic ,Heinrich Event ,Mediterranean - Abstract
The Atlantic-Mediterranean exchange of water at Gibraltar represents a significant heat and freshwater sink for the North Atlantic and is a major control on the heat, salt and freshwater budgets of the Mediterranean Sea. Consequently, an understanding of the response of the exchange system to external changes is vital to a full comprehension of the hydrographic responses in both ocean basins. Here, we use a synthesis of empirical (oxygen isotope, planktonic foraminiferal assemblage) and modeling (analytical and general circulation) approaches to investigate the response of the Gibraltar Exchange system to Atlantic freshening during Heinrich Stadials (HSs). HSs display relatively flat W-E surface hydrographic gradients more comparable to the Late Holocene than the Last Glacial Maximum. This is significant, as it implies a similar state of surface circulation during these periods and a different state during the Last Glacial Maximum. During HS1, the gradient may have collapsed altogether, implying very strong water column stratification and a single thermal and delta O-18(water) condition in surface water extending from southern Portugal to the eastern Alboran Sea. Together, these observations imply that inflow of Atlantic water into the Mediterranean was significantly increased during HS periods compared to background glacial conditions. Modeling efforts confirm that this is a predictable consequence of freshening North Atlantic surface water with iceberg meltwater and indicate that the enhanced exchange condition would last until the cessation of anomalous freshwater supply into to the northern North Atlantic. The close coupling of dynamics at Gibraltar Exchange with the Atlantic freshwater system provides an explanation for observations of increased Mediterranean Outflow activity during HS periods and also during the last deglaciation. This coupling is also significant to global ocean dynamics, as it causes density enhancement of the Atlantic water column via the Gibraltar Exchange to be inversely related to North Atlantic surface salinity. Consequently, Mediterranean enhancement of the Atlantic Meridional Overturning Circulation will be greatest when the overturning itself is at its weakest, a potentially critical negative feedback to Atlantic buoyancy change during times of ice sheet collapse.
- Published
- 2010
47. Reconstructing the seafloor environment during sapropel formation using benthic foraminiferal trace metals, stable isotopes, and sediment composition
- Author
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Ní Fhlaithearta, S., Reichart, Gert-Jan, Jorissen, F. J., Fontanier, C., Rohling, E. J., Thomson, J., and de Lange, G. J.
- Published
- 2010
48. Reconstructing the seafloor environment during sapropel formation using benthic foraminiferal trace metals, stable isotopes, and sediment composition
- Author
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Fhlaithearta, Ní, Reichart, Gert-Jan, Jorissen, Frans, Fontanier, Christophe, Rohling, E.-J., Thomson, J., De Lange, Gert, Utrecht University [Utrecht], Laboratoire de Planétologie et Géodynamique - Angers (LPG-ANGERS), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and SRON Netherlands Institute for Space Research (SRON)
- Subjects
[SDU]Sciences of the Universe [physics] - Abstract
International audience; The evolution of productivity, redox conditions, temperature, and ventilation during the deposition of an Aegean sapropel (S1) is independently constrained using bulk sediment composition and high-resolution single specimen benthic foraminiferal trace metal and stable isotope data. The occurrence of benthic foraminifer, Hoeglundina elegans (H. elegans), through a shallow water (260 m) sapropel, permits for the first time a comparison between dissolved and particulate concentrations of Ba and Mn and the construction of a Mg/Ca–based temperature record through sapropel S1. The simultaneous increase in sedimentary Ba and incorporated Ba in foraminiferal test carbonate, (Ba/Ca)H. elegans, points to a close coupling between Ba cycling and export productivity. During sapropel deposition, sedimentary Mn content ((Mn/Al)sed) is reduced, corresponding to enhanced Mn2+ mobilization from sedimentary Mn oxides under suboxic conditions. The consequently elevated dissolved Mn2+ concentrations are reflected in enhanced (Mn/Ca)H. elegans levels. The magnitude and duration of the sapropel interruption and other short-term cooling events are constrained using Mg/Ca thermometry. Based on integrating productivity and ventilation records with the temperature record, we propose a two-mode hysteresis model for sapropel formation.
- Published
- 2010
49. Using benthic foraminifera to reconstruct the benthic environment during sapropel formation
- Author
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Fhlaithearta, Ní, Jorissen, Frans, Mason, P., De Lange, Gert, Rohling, E.-J., Reichart, Gert-Jan, Laboratoire de Planétologie et Géodynamique - Angers (LPG-ANGERS), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Istituto Nazionale di Fisica Nucleare, Sezione di Milano (INFN), Istituto Nazionale di Fisica Nucleare (INFN), Istituto Nazionale di Fisica Nucleare, Sezione di Padova (INFN, Sezione di Padova), SRON Netherlands Institute for Space Research (SRON), and Utrecht University [Utrecht]
- Subjects
[SDU]Sciences of the Universe [physics] - Abstract
Date du colloque: 03/2008; International audience
- Published
- 2008
50. A stratigraphically controlled multi-proxy chronostratigraphy for the Eastern Mediterranean
- Author
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Casford, J. S. L., Abu-Zied, R., Rohling, E. J., Cooke, S., Fontanier, C., Leng, M., Millard, A., and Thomson, J.
- Subjects
Stratigraphy ,Radiocarbon ,Mediterranean - Abstract
An Accelerator Mass Spectrometry (AMS) 14C dated multiparameter event stratigraphy is developed for the Aegean Sea on the basis of highly resolved (centimeter to subcentimeter) multiproxy data collected from four late glacial to Holocene sediment cores. We quantify the degree of proportionality and synchroneity of sediment accumulation in these cores and use this framework to optimize the confidence levels in regional marine, radiocarbon-based chronostratigraphies. The applicability of the framework to published, lower-resolution records from the Aegean Sea is assessed. Next this is extended into the wider eastern Mediterranean, using new and previously published high-resolution data from the northern Levantine and Adriatic cores. We determine that the magnitude of uncertainties in the intercore comparison of AMS 14C datings based on planktonic foraminifera in the eastern Mediterranean is of the order of ±240 years (2 SE). These uncertainties are attributed to synsedimentary and postsedimentary processes that affect the materials dated. This study also offers a background age control that allows for vital refinements to radiocarbon-based chronostratigraphy in the eastern Mediterranean, with the potential for similar frameworks to be developed for any other well-studied region.
- Published
- 2007
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