Articles | Volume 18, issue 2
https://doi.org/10.5194/bg-18-423-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-18-423-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
19 Jan 2021
Research article |
| 19 Jan 2021
| 19 Jan 2021
Mg∕Ca, Sr∕Ca and stable isotopes from the planktonic foraminifera T. sacculifer: testing a multi-proxy approach for inferring paleotemperature and paleosalinity
UMR LOCEAN (IRD-CNRS-MNHN-Sorbonne Université), Centre IRD de
Nouméa, 101 Promenade Roger Laroque, Noumea 98848, New Caledonia
Alfred-Wegener-Institute, Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany
Gert Jan Reichart
Royal Netherlands Institute for Sea Research (NIOZ), Den Burg, Texel, the Netherlands
Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, the Netherlands
Christophe Menkes
UMR ENTROPIE (IRD, Université de la Réunion, CNRS, IFREMER, UNC), Centre
IRD de Nouméa, 101 Promenade Roger Laroque, Noumea 98848, New Caledonia
Morgan Mangeas
UMR ENTROPIE (IRD, Université de la Réunion, CNRS, IFREMER, UNC), Centre
IRD de Nouméa, 101 Promenade Roger Laroque, Noumea 98848, New Caledonia
Stephan Frickenhaus
Alfred-Wegener-Institute, Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany
Jelle Bijma
Alfred-Wegener-Institute, Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany
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Virginia Sánchez Barranco, Nienke C. J. van de Loosdrecht, Furu Mienis, Jasper M. de Goeij, Rick Hennekam, Gert-Jan Reichart, Jan-Berend Stuut, and Lennart J. de Nooijer
EGUsphere, https://doi.org/10.5194/egusphere-2025-4873, https://doi.org/10.5194/egusphere-2025-4873, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
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We studied how pollution from bays in Curaçao reaches nearby coral reefs and changes with seasons. By collecting suspended particulate matter at different locations during dry and wet seasons, we found that sheltered reefs receive more fine particles and pollutants, especially during rainy months, while exposed reefs are less affected. This shows that both location and seasonal rainfall determine reef vulnerability, highlighting the hidden impacts of human activity on these fragile ecosystems.
Elwyn de la Vega, Markus Raitzsch, Gavin L. Foster, Jelle Bijma, Ulysses S. Ninnemann, Michal Kucera, Tali Lea Babila, Jessica Crumpton Banks, Mohamed M. Ezat, and Audrey Morley
Biogeosciences, 22, 6765–6785, https://doi.org/10.5194/bg-22-6765-2025, https://doi.org/10.5194/bg-22-6765-2025, 2025
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The boron isotopic composition (δ11B) of foraminifera shells is an established proxy for the reconstruction of ocean pH. Applications to the Arctic oceans are however limited as robust calibrations in these regions are lacking. Here, we present a new calibration linking δ11B measured in two high-latitude foraminifera species to seawater pH. We show that the δ11B of the species analysed is well correlated with seawater pH and that this calibration can be applied to the paleorecord.
Carla Chevillard, Romain Le Gendre, Christophe Menkes, Takeshi Izumo, Bastien Pagli, Simon Van Wynsberge, and Sophie Cravatte
EGUsphere, https://doi.org/10.5194/egusphere-2025-5417, https://doi.org/10.5194/egusphere-2025-5417, 2025
This preprint is open for discussion and under review for Ocean Science (OS).
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To detect past marine heatwaves events and analyse their characteristics, scientists use one of the available sea surface temperature products, relying on different data ingested and procedures. Here, we compare marine heatwaves statistics computed using six products in the tropical Pacific over 1993–2021. We highlight significant differences and provide uncertainties. Our results advocate for the use of multiple products in marine heatwaves studies to increase the robustness of the conclusions.
Yasmina Ourradi, Gert-Jan Reichart, Sonja van Leeuwen, and Matthew Humphreys
EGUsphere, https://doi.org/10.5194/egusphere-2025-5050, https://doi.org/10.5194/egusphere-2025-5050, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
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We measured pH at high frequency for nearly a year at the Wadden Sea-North Sea interface. Biological activity mainly controls daily pH variations, while water exchange affects alkalinity. Dissolved inorganic carbon is influenced by both processes. Our research shows the Wadden Sea releases CO2 to the atmosphere. Understanding these patterns is crucial for predicting how coastal seas respond to changing climate and water conditions.
Romain Le Gendre, David Varillon, Sylvie Fiat, Régis Hocdé, Antoine de Ramon N'Yeurt, Serge Andréfouët, Jérôme Aucan, Sophie Cravatte, Maxime Duphil, Alexandre Ganachaud, Baptiste Gaudron, Elodie Kestenare, Vetea Liao, Bernard Pelletier, Alexandre Peltier, Anne-Lou Schaefer, Thomas Trophime, Simon Van Wynsberge, Yves Dandonneau, Michel Allenbach, and Christophe Menkes
Earth Syst. Sci. Data, 17, 5277–5301, https://doi.org/10.5194/essd-17-5277-2025, https://doi.org/10.5194/essd-17-5277-2025, 2025
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Due to ocean warming, coral reef ecosystems are strongly impacted by dystrophic events and corals experiencing increasing frequencies of bleaching events. In situ observation remains the best alternative for accurate characterization of trends and extremes in these shallow environments. This paper presents the coastal temperature dataset of the ReefTEMPS monitoring network, which spreads over multiple Pacific Island countries and territories (PICTs) in the western and central South Pacific.
Sarah Albernhe, Thomas Gorgues, Olivier Titaud, Patrick Lehodey, Christophe Menkes, and Anna Conchon
State Planet, 6-osr9, 4, https://doi.org/10.5194/sp-6-osr9-4-2025, https://doi.org/10.5194/sp-6-osr9-4-2025, 2025
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Micronekton are marine organisms gathering a wide diversity of taxa (crustaceans, fish, cephalopods) 2 to 20 cm in size. They are responsible for an important carbon export to the deep ocean and are the main prey for marine predators. We define provinces of homogeneous environmental parameters, representing areas of common micronekton biomass and vertical structure. We observe the evolution of the provinces in time from 1998 to 2023 to account for the seasonal to interannual variability.
Louise Delaigue, Gert-Jan Reichart, Li Qiu, Eric P. Achterberg, Yasmina Ourradi, Chris Galley, André Mutzberg, and Matthew P. Humphreys
Biogeosciences, 22, 5103–5121, https://doi.org/10.5194/bg-22-5103-2025, https://doi.org/10.5194/bg-22-5103-2025, 2025
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Our study analysed pH in ocean surface waters to understand how it fluctuates with changes in temperature, salinity, and biological activities. We found that temperature mainly controls daily pH variations, but biological processes also play a role, especially in affecting CO2 levels between the ocean and atmosphere. Our research shows how these factors together maintain the balance of ocean chemistry, which is crucial for predicting changes in marine environments.
Yannick F. Bats, Klaas G. J. Nierop, Alice Stuart-Lee, Joost Frieling, Linda van Roij, Gert-Jan Reichart, and Appy Sluijs
Biogeosciences, 22, 4689–4704, https://doi.org/10.5194/bg-22-4689-2025, https://doi.org/10.5194/bg-22-4689-2025, 2025
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In this study, we analyzed the molecular and stable carbon isotopic composition (δ13C) of pollen and spores (sporomorphs) that underwent chemical treatments that simulate diagenesis during fossilization. We show that the successive removal of sugars and lipids results in the depletion of 13C in the residual sporomorph, leaving rich aromatic compounds. This residual aromatic-rich structure likely represents diagenetically resistant sporopollenin, implying that diagenesis results in the depletion of 13C in pollen.
Bastien Pagli, Takeshi Izumo, Alexandre Barboni, Carla Chevillard, Cyril Dutheil, Raphael Legrand, Christophe Menkes, Claire Rocuet, and Sophie Cravatte
EGUsphere, https://doi.org/10.5194/egusphere-2025-4166, https://doi.org/10.5194/egusphere-2025-4166, 2025
This preprint is open for discussion and under review for Ocean Science (OS).
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Marine heatwaves—periods of unusually warm ocean temperatures—are becoming more frequent and intense with climate change. These events can harm marine ecosystems, especially in vulnerable regions like French Polynesia. Here, we used satellite sea surface temperature data and ocean reanalysis to characterize past events. We investigated their characteristics, variability linked to ENSO, and the physical mechanisms driving their onset and decay across the region.
Evert de Froe, Christian Mohn, Karline Soetaert, Anna-Selma van der Kaaden, Gert-Jan Reichart, Laurence H. De Clippele, Sandra R. Maier, and Dick van Oevelen
EGUsphere, https://doi.org/10.5194/egusphere-2025-3385, https://doi.org/10.5194/egusphere-2025-3385, 2025
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Cold-water corals are important reef-building animals in the deep sea, and are found all over the world. So far, researchers have been mapping and predicting where cold-water corals can be found using video transects and statistics. This study provides the first process-based model in which corals are predicted based on ocean currents and food particle movement. The renewal of food by tidal currents close to the seafloor and corals proved essential in predicting where they can grow or not.
Shilpa Lal, Sophie Cravatte, Christophe Menkes, Jed Macdonald, Romain LeGendre, Ines Mangolte, Cyril Dutheil, Neil Holbrook, and Simon Nicol
EGUsphere, https://doi.org/10.5194/egusphere-2025-3281, https://doi.org/10.5194/egusphere-2025-3281, 2025
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This paper characterizes historical (1981–2023) marine heatwaves in the tropical southwestern Pacific, where they pose a challenge for marine resource dependent Islands. Heatwaves are distinguished as a function of their spatial extent, signature at the coast, and seasonality, to allow a better understanding of their impacts on ecosystems. Marine heatwaves are getting longer and more frequent, with greater spatial extents. Our results aim to inform the Pacific Islands on their vulnerability.
Jelle Bijma, Mathilde Hagens, Jens Hammes, Noah Planavsky, Philip A. E. Pogge von Strandmann, Tom Reershemius, Christopher T. Reinhard, Phil Renforth, Tim Jesper Suhrhoff, Sara Vicca, Arthur Vienne, and Dieter A. Wolf-Gladrow
EGUsphere, https://doi.org/10.5194/egusphere-2025-2740, https://doi.org/10.5194/egusphere-2025-2740, 2025
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Enhanced rock weathering is a nature based negative emission technology, that permanently stores CO2. It requires rock-flour to be added to arable land with the help of farmers. To be eligible for carbon credits calls for a simple but scientifically solid, so called, Monitoring, Reporting & Verification” (MRV). We demonstrate that the commonly used carbon-based accounting is ill-suited to close the balance in open systems such as arable land, and argue for cation-based accounting strategy.
Anna Cutmore, Nicole Bale, Rick Hennekam, Bingjie Yang, Darci Rush, Gert-Jan Reichart, Ellen C. Hopmans, and Stefan Schouten
Clim. Past, 21, 957–971, https://doi.org/10.5194/cp-21-957-2025, https://doi.org/10.5194/cp-21-957-2025, 2025
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As human activities lower marine oxygen levels, understanding the impact on the marine nitrogen cycle is vital. The Black Sea, which became oxygen-deprived 9600 years ago, offers key insights. By studying organic compounds linked to nitrogen cycle processes, we found that, 7200 years ago, the Black Sea's nitrogen cycle significantly altered due to severe deoxygenation. This suggests that continued marine oxygen decline could similarly alter the marine nitrogen cycle, affecting vital ecosystems.
Peter Kraal, Kristin A. Ungerhofer, Darci Rush, and Gert-Jan Reichart
EGUsphere, https://doi.org/10.5194/egusphere-2025-1870, https://doi.org/10.5194/egusphere-2025-1870, 2025
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Element cycles in oxygen-depleted areas such as upwelling areas inform future deoxygenation scenarios. The Benguela upwelling system shows strong decoupling of nitrogen and phosphorus cycling due to seasonal shelf anoxia. Anaerobic processes result in pelagic nitrogen loss as N2. At the same time, sediments are rich in fish-derived and bacterial phosphorus, with high fluxes of excess phosphate, altering deep-water nitrogen:phosphorus ratios. Such alterations can affect ocean functioning.
Szabina Karancz, Lennart J. de Nooijer, Bas van der Wagt, Marcel T. J. van der Meer, Sambuddha Misra, Rick Hennekam, Zeynep Erdem, Julie Lattaud, Negar Haghipour, Stefan Schouten, and Gert-Jan Reichart
Clim. Past, 21, 679–704, https://doi.org/10.5194/cp-21-679-2025, https://doi.org/10.5194/cp-21-679-2025, 2025
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Changes in upwelling intensity of the Benguela upwelling region during the last glacial motivated us to investigate the local CO2 history during the last glacial-to-interglacial transition. Using various geochemical tracers on archives from both subsurface and surface waters reveals enhanced storage of carbon at depth during the Last Glacial Maximum. An efficient biological pump likely prevented outgassing of CO2 from intermediate depth to the atmosphere.
Devika Varma, Laura Villanueva, Nicole J. Bale, Pierre Offre, Gert-Jan Reichart, and Stefan Schouten
Biogeosciences, 21, 4875–4888, https://doi.org/10.5194/bg-21-4875-2024, https://doi.org/10.5194/bg-21-4875-2024, 2024
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Archaeal hydroxylated tetraether lipids are increasingly used as temperature indicators in marine settings, but the factors influencing their distribution are still unclear. Analyzing membrane lipids of two thaumarchaeotal strains showed that the growth phase of the cultures does not affect the lipid distribution, but growth temperature profoundly affects the degree of cyclization of these lipids. Also, the abundance of these lipids is species-specific and is not influenced by temperature.
Charlotte Eich, Mathijs van Manen, J. Scott P. McCain, Loay J. Jabre, Willem H. van de Poll, Jinyoung Jung, Sven B. E. H. Pont, Hung-An Tian, Indah Ardiningsih, Gert-Jan Reichart, Erin M. Bertrand, Corina P. D. Brussaard, and Rob Middag
Biogeosciences, 21, 4637–4663, https://doi.org/10.5194/bg-21-4637-2024, https://doi.org/10.5194/bg-21-4637-2024, 2024
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Phytoplankton growth in the Southern Ocean (SO) is often limited by low iron (Fe) concentrations. Sea surface warming impacts Fe availability and can affect phytoplankton growth. We used shipboard Fe clean incubations to test how changes in Fe and temperature affect SO phytoplankton. Their abundances usually increased with Fe addition and temperature increase, with Fe being the major factor. These findings imply potential shifts in ecosystem structure, impacting food webs and elemental cycling.
Guangnan Wu, Klaas G. J. Nierop, Bingjie Yang, Stefan Schouten, Gert-Jan Reichart, and Peter Kraal
EGUsphere, https://doi.org/10.5194/egusphere-2024-3192, https://doi.org/10.5194/egusphere-2024-3192, 2024
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Estuaries store and process large amounts of carbon, making them vital to the global carbon cycle. In the Port of Rotterdam, we studied the source of organic matter (OM) in sediments and how it influences OM breakdown. We found that marine OM degrades faster than land OM, and human activities like dredging can accelerate this by exposing sediments to oxygen. Our findings highlight the impact of human activities on carbon storage in estuaries, which is key for managing estuarine carbon dynamics.
Joost Frieling, Linda van Roij, Iris Kleij, Gert-Jan Reichart, and Appy Sluijs
Biogeosciences, 20, 4651–4668, https://doi.org/10.5194/bg-20-4651-2023, https://doi.org/10.5194/bg-20-4651-2023, 2023
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We present a first species-specific evaluation of marine core-top dinoflagellate cyst carbon isotope fractionation (εp) to assess natural pCO2 dependency on εp and explore its geological deep-time paleo-pCO2 proxy potential. We find that εp differs between genera and species and that in Operculodinium centrocarpum, εp is controlled by pCO2 and nutrients. Our results highlight the added value of δ13C analyses of individual micrometer-scale sedimentary organic carbon particles.
Laura Pacho, Lennart de Nooijer, and Gert-Jan Reichart
Biogeosciences, 20, 4043–4056, https://doi.org/10.5194/bg-20-4043-2023, https://doi.org/10.5194/bg-20-4043-2023, 2023
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We analyzed Mg / Ca and other El / Ca (Na / Ca, B / Ca, Sr / Ca and Ba / Ca) in Nodosariata. Their calcite chemistry is markedly different to that of the other calcifying orders of foraminifera. We show a relation between the species average Mg / Ca and its sensitivity to changes in temperature. Differences were reflected in both the Mg incorporation and the sensitivities of Mg / Ca to temperature.
Niels J. de Winter, Daniel Killam, Lukas Fröhlich, Lennart de Nooijer, Wim Boer, Bernd R. Schöne, Julien Thébault, and Gert-Jan Reichart
Biogeosciences, 20, 3027–3052, https://doi.org/10.5194/bg-20-3027-2023, https://doi.org/10.5194/bg-20-3027-2023, 2023
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Mollusk shells are valuable recorders of climate and environmental changes of the past down to a daily resolution. To explore this potential, we measured changes in the composition of shells of two types of bivalves recorded at the hourly scale: the king scallop Pecten maximus and giant clams (Tridacna) that engaged in photosymbiosis. We find that photosymbiosis produces more day–night fluctuation in shell chemistry but that most of the variation is not periodic, perhaps recording weather.
Rick Hennekam, Katharine M. Grant, Eelco J. Rohling, Rik Tjallingii, David Heslop, Andrew P. Roberts, Lucas J. Lourens, and Gert-Jan Reichart
Clim. Past, 18, 2509–2521, https://doi.org/10.5194/cp-18-2509-2022, https://doi.org/10.5194/cp-18-2509-2022, 2022
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The ratio of titanium to aluminum (Ti/Al) is an established way to reconstruct North African climate in eastern Mediterranean Sea sediments. We demonstrate here how to obtain reliable Ti/Al data using an efficient scanning method that allows rapid acquisition of long climate records at low expense. Using this method, we reconstruct a 3-million-year North African climate record. African environmental variability was paced predominantly by low-latitude insolation from 3–1.2 million years ago.
Carolien M. H. van der Weijst, Koen J. van der Laan, Francien Peterse, Gert-Jan Reichart, Francesca Sangiorgi, Stefan Schouten, Tjerk J. T. Veenstra, and Appy Sluijs
Clim. Past, 18, 1947–1962, https://doi.org/10.5194/cp-18-1947-2022, https://doi.org/10.5194/cp-18-1947-2022, 2022
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The TEX86 proxy is often used by paleoceanographers to reconstruct past sea-surface temperatures. However, the origin of the TEX86 signal in marine sediments has been debated since the proxy was first proposed. In our paper, we show that TEX86 carries a mixed sea-surface and subsurface temperature signal and should be calibrated accordingly. Using our 15-million-year record, we subsequently show how a TEX86 subsurface temperature record can be used to inform us on past sea-surface temperatures.
Carolien M. H. van der Weijst, Josse Winkelhorst, Wesley de Nooijer, Anna von der Heydt, Gert-Jan Reichart, Francesca Sangiorgi, and Appy Sluijs
Clim. Past, 18, 961–973, https://doi.org/10.5194/cp-18-961-2022, https://doi.org/10.5194/cp-18-961-2022, 2022
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A hypothesized link between Pliocene (5.3–2.5 million years ago) global climate and tropical thermocline depth is currently only backed up by data from the Pacific Ocean. In our paper, we present temperature, salinity, and thermocline records from the tropical Atlantic Ocean. Surprisingly, the Pliocene thermocline evolution was remarkably different in the Atlantic and Pacific. We need to reevaluate the mechanisms that drive thermocline depth, and how these are tied to global climate change.
Alice E. Webb, Didier M. de Bakker, Karline Soetaert, Tamara da Costa, Steven M. A. C. van Heuven, Fleur C. van Duyl, Gert-Jan Reichart, and Lennart J. de Nooijer
Biogeosciences, 18, 6501–6516, https://doi.org/10.5194/bg-18-6501-2021, https://doi.org/10.5194/bg-18-6501-2021, 2021
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The biogeochemical behaviour of shallow reef communities is quantified to better understand the impact of habitat degradation and species composition shifts on reef functioning. The reef communities investigated barely support reef functions that are usually ascribed to conventional coral reefs, and the overall biogeochemical behaviour is found to be similar regardless of substrate type. This suggests a decrease in functional diversity which may therefore limit services provided by this reef.
Julie Meilland, Michael Siccha, Maike Kaffenberger, Jelle Bijma, and Michal Kucera
Biogeosciences, 18, 5789–5809, https://doi.org/10.5194/bg-18-5789-2021, https://doi.org/10.5194/bg-18-5789-2021, 2021
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Planktonic foraminifera population dynamics has long been assumed to be controlled by synchronous reproduction and ontogenetic vertical migration (OVM). Due to contradictory observations, this concept became controversial. We here test it in the Atlantic ocean for four species of foraminifera representing the main clades. Our observations support the existence of synchronised reproduction and OVM but show that more than half of the population does not follow the canonical trajectory.
Indah Ardiningsih, Kyyas Seyitmuhammedov, Sylvia G. Sander, Claudine H. Stirling, Gert-Jan Reichart, Kevin R. Arrigo, Loes J. A. Gerringa, and Rob Middag
Biogeosciences, 18, 4587–4601, https://doi.org/10.5194/bg-18-4587-2021, https://doi.org/10.5194/bg-18-4587-2021, 2021
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Organic Fe speciation is investigated along a natural gradient of the western Antarctic Peninsula from an ice-covered shelf to the open ocean. The two major fronts in the region affect the distribution of ligands. The excess ligands not bound to dissolved Fe (DFe) comprised up to 80 % of the total ligand concentrations, implying the potential to solubilize additional Fe input. The ligands on the shelf can increase the DFe residence time and fuel local primary production upon ice melt.
Jutta E. Wollenburg, Jelle Bijma, Charlotte Cremer, Ulf Bickmeyer, and Zora Mila Colomba Zittier
Biogeosciences, 18, 3903–3915, https://doi.org/10.5194/bg-18-3903-2021, https://doi.org/10.5194/bg-18-3903-2021, 2021
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Cultured at in situ high-pressure conditions Cibicides and Cibicidoides taxa develop lasting ectoplasmic structures that cannot be retracted or resorbed. An ectoplasmic envelope surrounds their test and may protect the shell, e.g. versus carbonate aggressive bottom water conditions. Ectoplasmic roots likely anchor the specimens in areas of strong bottom water currents, trees enable them to elevate themselves above ground, and twigs stabilize and guide the retractable pseudopodial network.
Ove H. Meisel, Joshua F. Dean, Jorien E. Vonk, Lukas Wacker, Gert-Jan Reichart, and Han Dolman
Biogeosciences, 18, 2241–2258, https://doi.org/10.5194/bg-18-2241-2021, https://doi.org/10.5194/bg-18-2241-2021, 2021
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Arctic permafrost lakes form thaw bulbs of unfrozen soil (taliks) beneath them where carbon degradation and greenhouse gas production are increased. We analyzed the stable carbon isotopes of Alaskan talik sediments and their porewater dissolved organic carbon and found that the top layers of these taliks are likely more actively degraded than the deeper layers. This in turn implies that these top layers are likely also more potent greenhouse gas producers than the underlying deeper layers.
Markus Raitzsch, Jelle Bijma, Torsten Bickert, Michael Schulz, Ann Holbourn, and Michal Kučera
Clim. Past, 17, 703–719, https://doi.org/10.5194/cp-17-703-2021, https://doi.org/10.5194/cp-17-703-2021, 2021
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At approximately 14 Ma, the East Antarctic Ice Sheet expanded to almost its current extent, but the role of CO2 in this major climate transition is not entirely known. We show that atmospheric CO2 might have varied on 400 kyr cycles linked to the eccentricity of the Earth’s orbit. The resulting change in weathering and ocean carbon cycle affected atmospheric CO2 in a way that CO2 rose after Antarctica glaciated, helping to stabilize the climate system on its way to the “ice-house” world.
Sophie Cravatte, Guillaume Serazin, Thierry Penduff, and Christophe Menkes
Ocean Sci., 17, 487–507, https://doi.org/10.5194/os-17-487-2021, https://doi.org/10.5194/os-17-487-2021, 2021
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The various currents in the southwestern Pacific Ocean contribute to the redistribution of waters from the subtropical gyre equatorward and poleward. The drivers of their interannual variability are not completely understood but are usually thought to be related to well-known climate modes of variability. Here, we suggest that oceanic chaotic variability alone, which is by definition unpredictable, explains the majority of this interannual variability south of 20° S.
Siham de Goeyse, Alice E. Webb, Gert-Jan Reichart, and Lennart J. de Nooijer
Biogeosciences, 18, 393–401, https://doi.org/10.5194/bg-18-393-2021, https://doi.org/10.5194/bg-18-393-2021, 2021
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Foraminifera are calcifying organisms that play a role in the marine inorganic-carbon cycle and are widely used to reconstruct paleoclimates. However, the fundamental process by which they calcify remains essentially unknown. Here we use inhibitors to show that an enzyme is speeding up the conversion between bicarbonate and CO2. This helps the foraminifera acquire sufficient carbon for calcification and might aid their tolerance to elevated CO2 level.
Linda K. Dämmer, Lennart de Nooijer, Erik van Sebille, Jan G. Haak, and Gert-Jan Reichart
Clim. Past, 16, 2401–2414, https://doi.org/10.5194/cp-16-2401-2020, https://doi.org/10.5194/cp-16-2401-2020, 2020
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The compositions of foraminifera shells often vary with environmental parameters such as temperature or salinity; thus, they can be used as proxies for these environmental variables. Often a single proxy is influenced by more than one parameter. Here, we show that while salinity impacts shell Na / Ca, temperature has no effect. We also show that the combination of different proxies (Mg / Ca and δ18O) to reconstruct salinity does not seem to work as previously thought.
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Short summary
Results from a data set acquired from living foraminifera T. sacculifer collected from surface waters are presented, allowing us to establish a new Mg/Ca–Sr/Ca–temperature equation improving temperature reconstructions. When combining equations, δ18Ow can be reconstructed with a precision of ± 0.5 ‰, while successive reconstructions involving Mg/Ca and δ18Oc preclude salinity reconstruction with a precision better than ± 1.69. A new direct linear fit to reconstruct salinity could be established.
Results from a data set acquired from living foraminifera T. sacculifer collected from surface...
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