Articles | Volume 16, issue 1
https://doi.org/10.5194/os-16-221-2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/os-16-221-2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
14 Feb 2020
Research article |
| 14 Feb 2020
Decrease in 230Th in the Amundsen Basin since 2007: far-field effect of increased scavenging on the shelf?
Ole Valk
CORRESPONDING AUTHOR
Alfred Wegener Institute Helmholtz Centre for Polar and Marine
Research, 27570 Bremerhaven, Germany
Michiel M. Rutgers van der Loeff
Alfred Wegener Institute Helmholtz Centre for Polar and Marine
Research, 27570 Bremerhaven, Germany
Walter Geibert
Alfred Wegener Institute Helmholtz Centre for Polar and Marine
Research, 27570 Bremerhaven, Germany
Sandra Gdaniec
Department of Geological Sciences, Stockholm University, 106 91,
Stockholm, Sweden
S. Bradley Moran
College of Fisheries and Ocean Sciences, University of Alaska
Fairbanks, Fairbanks, AK 99775, USA
Kate Lepore
Department of Astronomy, Mount Holyoke College, South Hadley, MA 01075, USA
Robert Lawrence Edwards
Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN 55455, USA
Yanbin Lu
Earth Observatory of Singapore, Nanyang Technological University, Singapore 639798, Singapore
Viena Puigcorbé
Center for Marine Ecosystem Research, School of Science, Edith Cowan University, Joondalup, WA 6027, Australia
Nuria Casacuberta
Laboratory of Ion Beam Physics, ETH Zurich, 8093 Zurich, Switzerland
Institute of Biogeochemistry and Pollutant Dynamics, Environmental
Physics, ETH Zurich, 8092 Zurich, Switzerland
Ronja Paffrath
Max Planck Research Group for Marine Isotope Geochemistry, Institute for Chemistry and Biology of the Marine Environment, University of
Oldenburg, 26129 Oldenburg, Germany
William Smethie
Lamont-Doherty Earth Observatory, Palisades, NY 10964-8000, USA
Matthieu Roy-Barman
Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA – CNRS – UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
Related authors
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Anika Donner, Paul Töchterle, Christoph Spötl, Irka Hajdas, Xianglei Li, R. Lawrence Edwards, and Gina E. Moseley
Clim. Past, 19, 1607–1621, https://doi.org/10.5194/cp-19-1607-2023, https://doi.org/10.5194/cp-19-1607-2023, 2023
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This study investigates the first finding of fine-grained cryogenic cave minerals in Greenland, a type of speleothem that has been notably difficult to date. We present a successful approach for determining the age of these minerals using 230Th / U disequilibrium and 14C dating. We relate the formation of the cryogenic cave minerals to a well-documented extreme weather event in 1889 CE. Additionally, we provide a detailed report on the mineralogical and isotopic composition of these minerals.
Miguel Bartolomé, Ana Moreno, Carlos Sancho, Isabel Cacho, Heather Stoll, Negar Haghipour, Ánchel Belmonte, Christoph Spötl, John Hellstrom, R. Lawrence Edwards, and Hai Cheng
Clim. Past Discuss., https://doi.org/10.5194/cp-2023-54, https://doi.org/10.5194/cp-2023-54, 2023
Preprint under review for CP
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Reconstructing past temperatures at regional scales during the Common Era is necessary to place the current warming in the context of natural climate variability. We present a climate reconstruction based on eight stalagmites from four caves in the Pyrenees, NE Spain. These stalagmites were dated precisely and analysed for their oxygen isotopes, which appear dominated by temperature changes. Solar variability and major volcanic eruptions are the two main drivers of observed climate variability.
Charlotte Honiat, Gabriella Koltai, Yuri Dublyansky, R. Lawrence Edwards, Haiwei Zhang, Hai Cheng, and Christoph Spötl
Clim. Past, 19, 1177–1199, https://doi.org/10.5194/cp-19-1177-2023, https://doi.org/10.5194/cp-19-1177-2023, 2023
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A look at the climate evolution during the last warm period may allow us to test ground for future climate conditions. We quantified the temperature evolution during the Last Interglacial using a tiny amount of water trapped in the crystals of precisely dated stalagmites in caves from the southeastern European Alps. Our record indicates temperatures up to 2 °C warmer than today and an unstable climate during the first half of the Last Interglacial.
Giselle Utida, Francisco William Cruz, Mathias Vuille, Angela Ampuero, Valdir F. Novello, Jelena Maksic, Gilvan Sampaio, Hai Cheng, Haiwei Zhang, Fabio Ramos Dias de Andrade, and R. Lawrence Edwards
Clim. Past Discuss., https://doi.org/10.5194/cp-2023-2, https://doi.org/10.5194/cp-2023-2, 2023
Revised manuscript under review for CP
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In order to understand the ITCZ behavior during the past 3 k years over Northeastern Brazil, we reconstruct it based on oxygen stable isotopes of stalagmites in this area. There was a general increasing trend of aridity toward the present, mainly forced by the Atlantic and Pacific variabilities. We describe an ITCZ zonal behavior active around 1100 CE and the period from 1500 to 1750 CE. The dataset also records historical droughts that affected modern human population in this area of Brazil.
Simone Strydom, Roisin McCallum, Anna Lafratta, Chanelle L. Webster, Caitlyn M. O'Dea, Nicole E. Said, Natasha Dunham, Karina Inostroza, Cristian Salinas, Samuel Billinghurst, Charlie M. Phelps, Connor Campbell, Connor Gorham, Rachele Bernasconi, Anna M. Frouws, Axel Werner, Federico Vitelli, Viena Puigcorbé, Alexandra D'Cruz, Kathryn M. McMahon, Jack Robinson, Megan J. Huggett, Sian McNamara, Glenn A. Hyndes, and Oscar Serrano
Earth Syst. Sci. Data, 15, 511–519, https://doi.org/10.5194/essd-15-511-2023, https://doi.org/10.5194/essd-15-511-2023, 2023
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Seagrasses are important underwater plants that provide valuable ecosystem services to humans, including mitigating climate change. Understanding the natural history of seagrass meadows across different types of environments is crucial to conserving seagrasses in the global ocean. This dataset contains data extracted from peer-reviewed publications and highlights which seagrasses have been studied and in which locations and is useful for pointing out which need further investigation.
Paul Töchterle, Simon D. Steidle, R. Lawrence Edwards, Yuri Dublyansky, Christoph Spötl, Xianglei Li, John Gunn, and Gina E. Moseley
Geochronology, 4, 617–627, https://doi.org/10.5194/gchron-4-617-2022, https://doi.org/10.5194/gchron-4-617-2022, 2022
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Cryogenic cave carbonates (CCCs) provide a marker for past permafrost conditions. Their formation age is determined by Th / U dating. However, samples can be contaminated with small amounts of Th at formation, which can cause inaccurate ages and require correction. We analysed multiple CCCs and found that varying degrees of contamination can cause an apparent spread of ages, when samples actually formed within distinguishable freezing events. A correction method using isochrons is presented.
Helen Eri Amsler, Lena Mareike Thöle, Ingrid Stimac, Walter Geibert, Minoru Ikehara, Gerhard Kuhn, Oliver Esper, and Samuel Laurent Jaccard
Clim. Past, 18, 1797–1813, https://doi.org/10.5194/cp-18-1797-2022, https://doi.org/10.5194/cp-18-1797-2022, 2022
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We present sedimentary redox-sensitive trace metal records from five sediment cores retrieved from the SW Indian Ocean. These records are indicative of oxygen-depleted conditions during cold periods and enhanced oxygenation during interstadials. Our results thus suggest that deep-ocean oxygenation changes were mainly controlled by ocean ventilation and that a generally more sluggish circulation contributed to sequestering remineralized carbon away from the atmosphere during glacial periods.
Kathleen A. Wendt, Xianglei Li, R. Lawrence Edwards, Hai Cheng, and Christoph Spötl
Clim. Past, 17, 1443–1454, https://doi.org/10.5194/cp-17-1443-2021, https://doi.org/10.5194/cp-17-1443-2021, 2021
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In this study, we tested the upper limits of U–Th dating precision by analyzing three stalagmites from the Austrian Alps that have high U concentrations. The composite record spans the penultimate interglacial (MIS 7) with an average 2σ age uncertainty of 400 years. This unprecedented age control allows us to constrain the timing of temperature shifts in the Alps during MIS 7 while offering new insight into millennial-scale changes in the North Atlantic leading up to Terminations III and IIIa.
Matthieu Roy-Barman, Lorna Foliot, Eric Douville, Nathalie Leblond, Fréderic Gazeau, Matthieu Bressac, Thibaut Wagener, Céline Ridame, Karine Desboeufs, and Cécile Guieu
Biogeosciences, 18, 2663–2678, https://doi.org/10.5194/bg-18-2663-2021, https://doi.org/10.5194/bg-18-2663-2021, 2021
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The release of insoluble elements such as aluminum (Al), iron (Fe), rare earth elements (REEs), thorium (Th) and protactinium (Pa) when Saharan dust falls over the Mediterranean Sea was studied during tank experiments under present and future climate conditions. Each element exhibited different dissolution kinetics and dissolution fractions (always lower than a few percent). Changes in temperature and/or pH under greenhouse conditions lead to a lower Th release and a higher light REE release.
Chao-Jun Chen, Dao-Xian Yuan, Jun-Yun Li, Xian-Feng Wang, Hai Cheng, You-Feng Ning, R. Lawrence Edwards, Yao Wu, Si-Ya Xiao, Yu-Zhen Xu, Yang-Yang Huang, Hai-Ying Qiu, Jian Zhang, Ming-Qiang Liang, and Ting-Yong Li
Clim. Past Discuss., https://doi.org/10.5194/cp-2021-20, https://doi.org/10.5194/cp-2021-20, 2021
Manuscript not accepted for further review
Yu-Te Hsieh, Walter Geibert, E. Malcolm S. Woodward, Neil J. Wyatt, Maeve C. Lohan, Eric P. Achterberg, and Gideon M. Henderson
Biogeosciences, 18, 1645–1671, https://doi.org/10.5194/bg-18-1645-2021, https://doi.org/10.5194/bg-18-1645-2021, 2021
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The South Atlantic near 40° S is one of the high-productivity and most dynamic nutrient regions in the oceans, but the sources and fluxes of trace elements (TEs) to this region remain unclear. This study investigates seawater Ra-228 and provides important constraints on ocean mixing and dissolved TE fluxes to this region. Vertical mixing is a more important source than aeolian or shelf inputs in this region, but particulate or winter deep-mixing inputs may be required to balance the TE budgets.
Xianglei Li, Kathleen A. Wendt, Yuri Dublyansky, Gina E. Moseley, Christoph Spötl, and R. Lawrence Edwards
Geochronology, 3, 49–58, https://doi.org/10.5194/gchron-3-49-2021, https://doi.org/10.5194/gchron-3-49-2021, 2021
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In this study, we built a statistical model to determine the initial δ234U in submerged calcite crusts that coat the walls of Devils Hole 2 (DH2) cave (Nevada, USA) and, using a 234U–238U dating method, extended the chronology of the calcite deposition beyond previous well-established 230Th ages and determined the oldest calcite deposited in this cave, a time marker for cave genesis. The novel method presented here may be used in future speleothem studies in similar hydrogeological settings.
Anne-Marie Wefing, Núria Casacuberta, Marcus Christl, Nicolas Gruber, and John N. Smith
Ocean Sci., 17, 111–129, https://doi.org/10.5194/os-17-111-2021, https://doi.org/10.5194/os-17-111-2021, 2021
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Atlantic Water that carries heat and anthropogenic carbon into the Arctic Ocean plays an important role in the Arctic sea-ice cover decline, but its pathways and travel times remain unclear. Here we used two radionuclides of anthropogenic origin (129I and 236U) to track Atlantic-derived waters along their way through the Arctic Ocean, estimating their travel times and mixing properties. Results help to understand how future changes in Atlantic Water properties will spread through the Arctic.
Maria-Elena Vorrath, Juliane Müller, Lorena Rebolledo, Paola Cárdenas, Xiaoxu Shi, Oliver Esper, Thomas Opel, Walter Geibert, Práxedes Muñoz, Christian Haas, Gerhard Kuhn, Carina B. Lange, Gerrit Lohmann, and Gesine Mollenhauer
Clim. Past, 16, 2459–2483, https://doi.org/10.5194/cp-16-2459-2020, https://doi.org/10.5194/cp-16-2459-2020, 2020
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We tested the applicability of the organic biomarker IPSO25 for sea ice reconstructions in the industrial era at the western Antarctic Peninsula. We successfully evaluated our data with satellite sea ice observations. The comparison with marine and ice core records revealed that sea ice interpretations must consider climatic and sea ice dynamics. Sea ice biomarker production is mainly influenced by the Southern Annular Mode, while the El Niño–Southern Oscillation seems to have a minor impact.
Viena Puigcorbé, Pere Masqué, and Frédéric A. C. Le Moigne
Earth Syst. Sci. Data, 12, 1267–1285, https://doi.org/10.5194/essd-12-1267-2020, https://doi.org/10.5194/essd-12-1267-2020, 2020
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The biological carbon pump is a mechanism by which the oceans capture atmospheric carbon dioxide thanks to microscopic marine algae. Quantifying its strength and efficiency is crucial to understand the global carbon budget and be able to forecast its trends. The radioactive pair 234Th : 238U has been extensively used for that purpose. This is a global compilation of carbon-to-234Th ratios (needed to convert the 234Th fluxes to carbon fluxes) that will contribute to improve our modeling efforts.
Gina E. Moseley, Christoph Spötl, Susanne Brandstätter, Tobias Erhardt, Marc Luetscher, and R. Lawrence Edwards
Clim. Past, 16, 29–50, https://doi.org/10.5194/cp-16-29-2020, https://doi.org/10.5194/cp-16-29-2020, 2020
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Abrupt climate change during the last ice age can be used to provide important insights into the timescales on which the climate is capable of changing and the mechanisms that drive those changes. In this study, we construct climate records for the period 60 to 120 ka using stalagmites that formed in caves along the northern rim of the European Alps and find good agreement with the timing of climate changes in Greenland and the Asian monsoon.
Hanying Li, Hai Cheng, Ashish Sinha, Gayatri Kathayat, Christoph Spötl, Aurèle Anquetil André, Arnaud Meunier, Jayant Biswas, Pengzhen Duan, Youfeng Ning, and Richard Lawrence Edwards
Clim. Past, 14, 1881–1891, https://doi.org/10.5194/cp-14-1881-2018, https://doi.org/10.5194/cp-14-1881-2018, 2018
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The
4.2 ka eventbetween 4.2 and 3.9 ka has been widely discussed in the Northern Hemsiphere but less reported in the Southern Hemisphere. Here, we use speleothem records from Rodrigues in the southwestern Indian Ocean spanning from 6000 to 3000 years ago to investigate the regional hydro-climatic variability. Our records show no evidence for an unusual climate anomaly between 4.2 and 3.9 ka. Instead, it shows a multi-centennial drought between 3.9 and 3.5 ka.
Gayatri Kathayat, Hai Cheng, Ashish Sinha, Max Berkelhammer, Haiwei Zhang, Pengzhen Duan, Hanying Li, Xianglei Li, Youfeng Ning, and R. Lawrence Edwards
Clim. Past, 14, 1869–1879, https://doi.org/10.5194/cp-14-1869-2018, https://doi.org/10.5194/cp-14-1869-2018, 2018
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The 4.2 ka event is generally characterized as an approximately 300-year period of major global climate anomaly. However, the climatic manifestation of this event remains unclear in the Indian monsoon domain. Our high-resolution and precisely dated speleothem record from Meghalaya, India, characterizes the event as consisting of a series of multi-decadal droughts between 3.9 and 4.0 ka rather than a singular pulse of multi-centennial drought as previously thought.
Géraldine Sarthou, Pascale Lherminier, Eric P. Achterberg, Fernando Alonso-Pérez, Eva Bucciarelli, Julia Boutorh, Vincent Bouvier, Edward A. Boyle, Pierre Branellec, Lidia I. Carracedo, Nuria Casacuberta, Maxi Castrillejo, Marie Cheize, Leonardo Contreira Pereira, Daniel Cossa, Nathalie Daniault, Emmanuel De Saint-Léger, Frank Dehairs, Feifei Deng, Floriane Desprez de Gésincourt, Jérémy Devesa, Lorna Foliot, Debany Fonseca-Batista, Morgane Gallinari, Maribel I. García-Ibáñez, Arthur Gourain, Emilie Grossteffan, Michel Hamon, Lars Eric Heimbürger, Gideon M. Henderson, Catherine Jeandel, Catherine Kermabon, François Lacan, Philippe Le Bot, Manon Le Goff, Emilie Le Roy, Alison Lefèbvre, Stéphane Leizour, Nolwenn Lemaitre, Pere Masqué, Olivier Ménage, Jan-Lukas Menzel Barraqueta, Herlé Mercier, Fabien Perault, Fiz F. Pérez, Hélène F. Planquette, Frédéric Planchon, Arnout Roukaerts, Virginie Sanial, Raphaëlle Sauzède, Catherine Schmechtig, Rachel U. Shelley, Gillian Stewart, Jill N. Sutton, Yi Tang, Nadine Tisnérat-Laborde, Manon Tonnard, Paul Tréguer, Pieter van Beek, Cheryl M. Zurbrick, and Patricia Zunino
Biogeosciences, 15, 7097–7109, https://doi.org/10.5194/bg-15-7097-2018, https://doi.org/10.5194/bg-15-7097-2018, 2018
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The GEOVIDE cruise (GEOTRACES Section GA01) was conducted in the North Atlantic Ocean and Labrador Sea in May–June 2014. In this special issue, results from GEOVIDE, including physical oceanography and trace element and isotope cyclings, are presented among 17 articles. Here, the scientific context, project objectives, and scientific strategy of GEOVIDE are provided, along with an overview of the main results from the articles published in the special issue.
Haiwei Zhang, Hai Cheng, Yanjun Cai, Christoph Spötl, Gayatri Kathayat, Ashish Sinha, R. Lawrence Edwards, and Liangcheng Tan
Clim. Past, 14, 1805–1817, https://doi.org/10.5194/cp-14-1805-2018, https://doi.org/10.5194/cp-14-1805-2018, 2018
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The collapses of several Neolithic cultures in China are considered to have been associated with abrupt climate change during the 4.2 ka BP event; however, the hydroclimate of this event in China is still poorly known. Based on stalagmite records from monsoonal China, we found that north China was dry but south China was wet during this event. We propose that the rain belt remained longer at its southern position, giving rise to a pronounced humidity gradient between north and south China.
Florian Adolphi, Christopher Bronk Ramsey, Tobias Erhardt, R. Lawrence Edwards, Hai Cheng, Chris S. M. Turney, Alan Cooper, Anders Svensson, Sune O. Rasmussen, Hubertus Fischer, and Raimund Muscheler
Clim. Past, 14, 1755–1781, https://doi.org/10.5194/cp-14-1755-2018, https://doi.org/10.5194/cp-14-1755-2018, 2018
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The last glacial period was characterized by a number of rapid climate changes seen, for example, as abrupt warmings in Greenland and changes in monsoon rainfall intensity. However, due to chronological uncertainties it is challenging to know how tightly coupled these changes were. Here we exploit cosmogenic signals caused by changes in the Sun and Earth magnetic fields to link different climate archives and improve our understanding of the dynamics of abrupt climate change.
Maxi Castrillejo, Núria Casacuberta, Marcus Christl, Christof Vockenhuber, Hans-Arno Synal, Maribel I. García-Ibáñez, Pascale Lherminier, Géraldine Sarthou, Jordi Garcia-Orellana, and Pere Masqué
Biogeosciences, 15, 5545–5564, https://doi.org/10.5194/bg-15-5545-2018, https://doi.org/10.5194/bg-15-5545-2018, 2018
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The investigation of water mass transport pathways and timescales is important to understand the global ocean circulation. Following earlier studies, we use artificial radionuclides introduced to the oceans in the 1950s to investigate the water transport in the subpolar North Atlantic (SPNA). For the first time, we combine measurements of the long-lived iodine-129 and uranium-236 to confirm earlier findings/hypotheses and to better understand shallow and deep ventilation processes in the SPNA.
Marco van Hulten, Jean-Claude Dutay, and Matthieu Roy-Barman
Geosci. Model Dev., 11, 3537–3556, https://doi.org/10.5194/gmd-11-3537-2018, https://doi.org/10.5194/gmd-11-3537-2018, 2018
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We present an ocean model of the natural radioactive isotopes thorium-230 and protactinium-231. These isotopes are often used to investigate past ocean circulation and particle transport. They are removed by particles produced by plankton and from uplifted desert dust that is deposited into the ocean. We approach observed dissolved and adsorbed Th-230 and Pa-231 activities. The Pa-231 / Th-230 sedimentation ratio is reproduced as well; this quantity can be used as a proxy for ocean circulation.
Ny Riavo Gilbertinie Voarintsoa, Loren Bruce Railsback, George Albert Brook, Lixin Wang, Gayatri Kathayat, Hai Cheng, Xianglei Li, Richard Lawrence Edwards, Amos Fety Michel Rakotondrazafy, and Marie Olga Madison Razanatseheno
Clim. Past, 13, 1771–1790, https://doi.org/10.5194/cp-13-1771-2017, https://doi.org/10.5194/cp-13-1771-2017, 2017
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This research has been an investigation of two stalagmites from two caves in NW Madagascar to reconstruct the region's paleoenvironmental changes, and to understand the linkage of such changes to the dynamics of the ITCZ. Stable isotopes, mineralogy, and petrography suggest wetter climate conditions than today during the early and late Holocene, when the mean ITCZ was south, and drier during the mid-Holocene when the ITCZ was north.
Olivier Aumont, Marco van Hulten, Matthieu Roy-Barman, Jean-Claude Dutay, Christian Éthé, and Marion Gehlen
Biogeosciences, 14, 2321–2341, https://doi.org/10.5194/bg-14-2321-2017, https://doi.org/10.5194/bg-14-2321-2017, 2017
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The marine biological carbon pump is dominated by the vertical transfer of particulate organic carbon (POC) from the surface ocean to its interior. In this study, we explore the impacts of a variable composition of this organic matter using a global ocean biogeochemical model. We show that accounting for a variable lability of POC increases POC concentrations by up to 2 orders of magnitude in the ocean's interior. Furthermore, the amount of carbon that reaches the sediments is twice as large.
Amelie Driemel, Eberhard Fahrbach, Gerd Rohardt, Agnieszka Beszczynska-Möller, Antje Boetius, Gereon Budéus, Boris Cisewski, Ralph Engbrodt, Steffen Gauger, Walter Geibert, Patrizia Geprägs, Dieter Gerdes, Rainer Gersonde, Arnold L. Gordon, Hannes Grobe, Hartmut H. Hellmer, Enrique Isla, Stanley S. Jacobs, Markus Janout, Wilfried Jokat, Michael Klages, Gerhard Kuhn, Jens Meincke, Sven Ober, Svein Østerhus, Ray G. Peterson, Benjamin Rabe, Bert Rudels, Ursula Schauer, Michael Schröder, Stefanie Schumacher, Rainer Sieger, Jüri Sildam, Thomas Soltwedel, Elena Stangeew, Manfred Stein, Volker H Strass, Jörn Thiede, Sandra Tippenhauer, Cornelis Veth, Wilken-Jon von Appen, Marie-France Weirig, Andreas Wisotzki, Dieter A. Wolf-Gladrow, and Torsten Kanzow
Earth Syst. Sci. Data, 9, 211–220, https://doi.org/10.5194/essd-9-211-2017, https://doi.org/10.5194/essd-9-211-2017, 2017
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Our oceans are always in motion – huge water masses are circulated by winds and by global seawater density gradients resulting from different water temperatures and salinities. Measuring temperature and salinity of the world's oceans is crucial e.g. to understand our climate. Since 1983, the research icebreaker Polarstern has been the basis of numerous water profile measurements in the Arctic and the Antarctic. We report on a unique collection of 33 years of polar salinity and temperature data.
Marco van Hulten, Rob Middag, Jean-Claude Dutay, Hein de Baar, Matthieu Roy-Barman, Marion Gehlen, Alessandro Tagliabue, and Andreas Sterl
Biogeosciences, 14, 1123–1152, https://doi.org/10.5194/bg-14-1123-2017, https://doi.org/10.5194/bg-14-1123-2017, 2017
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We ran a global ocean model to understand manganese (Mn), a biologically essential element. Our model shows that (i) in the deep ocean, dissolved [Mn] is mostly homogeneous ~0.10—0.15 nM. The model reproduces this with a threshold on MnO2 of 25 pM, suggesting a minimal particle concentration is needed before aggregation and removal become efficient.
(ii) The observed distinct hydrothermal signals are produced by assuming both a strong source and a strong removal of Mn near hydrothermal vents.
Stef Vansteenberge, Sophie Verheyden, Hai Cheng, R. Lawrence Edwards, Eddy Keppens, and Philippe Claeys
Clim. Past, 12, 1445–1458, https://doi.org/10.5194/cp-12-1445-2016, https://doi.org/10.5194/cp-12-1445-2016, 2016
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The use of stalagmites for last interglacial continental climate reconstructions in Europe has been successful in the past; however to expand the geographical coverage, additional data from Belgium is presented. It has been shown that stalagmite growth, morphology and stable isotope content reflect regional and local climate conditions, with Eemian optimum climate occurring between 125.3 and 117.3 ka. The start the Weichselian is expressed by a stop of growth caused by a drying climate.
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Short summary
After 2007 230Th decreased significantly in the central Amundsen Basin. This decrease is accompanied by a circulation change, indicated by changes in salinity. Ventilation of waters is most likely not the reason for the observed depletion in 230Th as atmospherically derived tracers do not reveal an increase in ventilation rate. It is suggested that these interior waters have undergone enhanced scavenging of Th during transit from Fram Strait and the Barents Sea to the central Amundsen Basin.
After 2007 230Th decreased significantly in the central Amundsen Basin. This decrease is...
