104 results on '"Jonkers L"'
Search Results
2. Coherent response of zoo‐ and phytoplankton assemblages to global warming since the Last Glacial Maximum
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Strack, T, Jonkers, L, Rillo, MC, Baumann, K‐H, Hillebrand, H, Kucera, M, Strack, T, Jonkers, L, Rillo, MC, Baumann, K‐H, Hillebrand, H, and Kucera, M
- Abstract
Aim: We are using the fossil record of different marine plankton groups to determine how their biodiversity has changed during past climate warming comparable to projected future warming. Location: North Atlantic Ocean and adjacent seas. Time series cover a latitudinal range from 75° N to 6° S. Time period: Past 24,000 years, from the Last Glacial Maximum (LGM) to the current warm period covering the last deglaciation. Major taxa studied: Planktonic foraminifera, dinoflagellates and coccolithophores. Methods: We analyse time series of fossil plankton communities using principal component analysis and generalized additive models to estimate the overall trend of temporal compositional change in each plankton group and to identify periods of significant change. We further analyse local biodiversity change by analysing species richness, species gains and losses, and the effective number of species in each sample, and compare alpha diversity to the LGM mean. Results: All plankton groups show remarkably similar trends in the rates and spatio-temporal dynamics of local biodiversity change and a pronounced non-linearity with climate change in the current warm period. Assemblages of planktonic foraminifera and dinoflagellates started to change significantly with the onset of global warming around 15,500 to 17,000 years ago and continued to change at the same rate during the current warm period until at least 5000 years ago, while coccolithophore assemblages changed at a constant rate throughout the past 24,000 years, seemingly irrespective of the prevailing temperature change. Main conclusions: Climate change during the transition from the LGM to the current warm period led to a long-lasting reshuffling of zoo- and phytoplankton assemblages, likely associated with the emergence of new ecological interactions and possibly a shift in the dominant drivers of plankton assemblage change from more abiotic-dominated causes during the last deglaciation to more biotic-dominated cause more...
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- 2024
Catalog
3. Coherent response of zoo‐ and phytoplankton assemblages to global warming since the Last Glacial Maximum.
- Author
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Strack, T., Jonkers, L., C. Rillo, M., Baumann, K.‐H., Hillebrand, H., and Kucera, M.
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LAST Glacial Maximum , *GLOBAL warming , *MARINE plankton , *SPECIES diversity , *GLACIAL melting , *FORAMINIFERA , *PHYTOPLANKTON - Abstract
Aim: We are using the fossil record of different marine plankton groups to determine how their biodiversity has changed during past climate warming comparable to projected future warming. Location: North Atlantic Ocean and adjacent seas. Time series cover a latitudinal range from 75° N to 6° S. Time period: Past 24,000 years, from the Last Glacial Maximum (LGM) to the current warm period covering the last deglaciation. Major taxa studied: Planktonic foraminifera, dinoflagellates and coccolithophores. Methods: We analyse time series of fossil plankton communities using principal component analysis and generalized additive models to estimate the overall trend of temporal compositional change in each plankton group and to identify periods of significant change. We further analyse local biodiversity change by analysing species richness, species gains and losses, and the effective number of species in each sample, and compare alpha diversity to the LGM mean. Results: All plankton groups show remarkably similar trends in the rates and spatio‐temporal dynamics of local biodiversity change and a pronounced non‐linearity with climate change in the current warm period. Assemblages of planktonic foraminifera and dinoflagellates started to change significantly with the onset of global warming around 15,500 to 17,000 years ago and continued to change at the same rate during the current warm period until at least 5000 years ago, while coccolithophore assemblages changed at a constant rate throughout the past 24,000 years, seemingly irrespective of the prevailing temperature change. Main conclusions: Climate change during the transition from the LGM to the current warm period led to a long‐lasting reshuffling of zoo‐ and phytoplankton assemblages, likely associated with the emergence of new ecological interactions and possibly a shift in the dominant drivers of plankton assemblage change from more abiotic‐dominated causes during the last deglaciation to more biotic‐dominated causes with the onset of the Holocene. [ABSTRACT FROM AUTHOR] more...
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- 2024
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4. Phase 4 of PAGES 2k: Hydroclimate of the common era
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Orsi, A., Falster, G., Kaushal, N., Jonkers, L., Jones, M., Henley, B., Eggleston, S., and Atwood, A.
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The climate of the past two thousand years (2k) provides context for current and future changes, and as such is vital for developing our understanding of the modern climate system. Previous PAGES 2k network phases emphasized temperature reconstructions, fundamentally improving our understanding of global climate changes over the Common Era. These reconstructions were featured in the Summary for Policymakers of the IPCC’s Sixth Assessment Report. Integration of this data with state-of-the-art Earth systems models, proxy system models and data assimilation yielded a more comprehensive understanding of the associated physical drivers and climate dynamics. Phase 4 of the PAGES 2k Network paves the way for a new level of understanding of the global water cycle. Our aim is to reconstruct hydroclimatic variability over the Common Era, from local to global spatial scales, at sub-annual to multi-centennial time scales, developing a process-level understanding of past hydroclimate events and variability. Our multi-faceted approach includes (1) developing new hydroclimate syntheses that are well-suited for data-model comparisons, (2) improving the interoperability and scope of existing data and model products, and (3) facilitating the translation of our science into evidence-based policy outcomes. In this presentation, we describe the progress to date, and focus the discussion on what a suitable hydroclimate proxy database should look like, both from the perspective of what data are available, and from what is a good target for model evaluation, using different regions of the world as case studies. PAGES 2k is an open community, and you are welcome to get involved., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023) more...
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- 2023
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5. Identifying hydro-sensitive coral δ18O records for improved high-resolution temperature and salinity reconstructions
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Thompson, D.M., Conroy, J.L., Konecky, B.L., Stevenson, S., DeLong, K.L., McKay, N., Reed, E.V., Jonkers, L., Carré, M., Diane Thompson, Jessica Conroy, and Samantha Stevenson
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corals ,TheoryofComputation_ANALYSISOFALGORITHMSANDPROBLEMCOMPLEXITY ,stable isotopes ,proxy system modelling - Abstract
Stable oxygen isotopic ratios in corals (δ18Ocoral) are commonly utilized to reconstruct climate variability beyond the limit of instrumental observations. These measurements provide constraints on past seawater temperature, due to the thermodynamics of isotopic fractionation, but also past salinity, as both salinity and seawater δ18O (δ18Osw) are similarly affected by precipitation/evaporation, advection, and other processes. We use historical observations, isotope-enabled model simulations, and the PAGES Iso2k database to assess the potential of δ18Ocoral to provide information on past salinity. Using ‘pseudocorals’ to represent δ18Ocoral as a function of observed or simulated temperature and salinity/δ18Osw, we find that δ18Osw contributes up to 89% of δ18Ocoral variability in the Western Pacific Warm Pool. Although uncertainty in the δ18Osw-salinity relationship influences the inferred salinity variability, corals from these sites could provide valuable δ18Osw reconstructions. Coordinated in situ monitoring of salinity and δ18Osw is vital for improving estimates of hydroclimatic change., {"references":["Konecky et al. (2020). Description of the Iso2K database used in this study."]} more...
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- 2022
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6. The foraminiferal response to climate stressors project: tracking the community response of planktonic foraminifera to historical climate change
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de Garidel-Thoron, T., Chaabane, S., Giraud, X., Meilland, J., Jonkers, L., Kucera, M., Brummer, G.-J. A., Grigoratou, M., Monteiro, F.M., Greco, M., Mortyn, P.G., Kuroyanagi, A., Howa, H., Beaugrand, G., Schiebel, R., de Garidel-Thoron, T., Chaabane, S., Giraud, X., Meilland, J., Jonkers, L., Kucera, M., Brummer, G.-J. A., Grigoratou, M., Monteiro, F.M., Greco, M., Mortyn, P.G., Kuroyanagi, A., Howa, H., Beaugrand, G., and Schiebel, R. more...
- Abstract
Planktonic Foraminifera are ubiquitous marine protozoa inhabiting the upper ocean. During life, they secrete calcareous shells, which accumulate in marine sediments, providing a geological record of past spatial and temporal changes in their community structure. As a result, they provide the opportunity to analyze both current and historical patterns of species distribution and community turnover in this plankton group on a global scale. The FORCIS project aims to unlock this potential by synthesizing a comprehensive global database of abundance and diversity observations of living planktonic Foraminifera in the upper ocean over more than 100 years starting from 1910. The database will allow for unravelling the impact of multiple global-change stressors acting on planktonic Foraminifera in historical times, using an approach that combines statistical analysis of temporal diversity changes in response to environmental changes with numerical modeling of species response based on their ecological traits. more...
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- 2022
7. Identifying Hydro‐Sensitive Coral δ 18 O Records for Improved High‐Resolution Temperature and Salinity Reconstructions
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Thompson, D. M., primary, Conroy, J. L., additional, Konecky, B. L., additional, Stevenson, S., additional, DeLong, K. L., additional, McKay, N., additional, Reed, E., additional, Jonkers, L., additional, and Carré, M., additional more...
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- 2022
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8. The last glacial ocean: The challenge of comparing multiproxy data synthesis with climate simulations
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Jonkers, L., Rehfeld, K., Kageyama, Masa, Kucera, M., Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Modélisation du climat (CLIM), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS) more...
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[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment - Abstract
International audience; The Last Glacial Maximum The Last Glacial Maximum (LGM; 23,000-19,000 years ago) is the most recent time in Earth's history with a fundamentally different climate from today. Thus, from a climate modeling perspective, the LGM is an ideal test case because of its radically different and quantitatively well-constrained boundary conditions. more...
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- 2021
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9. Determinants of Planktonic Foraminifera Calcite Flux: Implications for the Prediction of Intra‐ and Inter‐Annual Pelagic Carbonate Budgets
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Kiss, P., primary, Jonkers, L., additional, Hudáčková, N., additional, Reuter, R. T., additional, Donner, B., additional, Fischer, G., additional, and Kucera, M., additional
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- 2021
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10. Towards increased interoperability of paleoenvironmental observation data
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Bothe, Oliver, Rehfeld, K., Konecky, B., and Jonkers, L.
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010506 paleontology ,010504 meteorology & atmospheric sciences ,01 natural sciences ,0105 earth and related environmental sciences - Abstract
Data is an important foundation of scientific progress. It allows us to contrast hypotheses with observational evidence. Sharing and providing data openly have a long tradition in paleoenvironmental research, supported by repositories such as WDS-Paleo, PANGAEA,and Neotoma. more...
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- 2021
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11. Global climate goes regional, and vice versa: Reflecting on 14 years of the PAGES 2k Network
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Bothe, O., Rehfeld, K., Konecky, B., Jonkers, L., Bothe, O., Rehfeld, K., Konecky, B., and Jonkers, L.
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- 2021
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12. Phase 4 of the PAGES 2k Network: Hydroclimate of the Common Era
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Atwood, A., Bothe, O., Eggleston, S., Falster, G., Henley, B., Jones, M., Jonkers, L., Kaushal, N., Martrat, B., McGregor, H., Orsi, A., Phipps, S., and Sayani, H.
- Abstract
The PAGES 2k Network (pastglobalchanges.org/2k), founded in 2008, is one of the longest-running PAGES working groups. It has consistently achieved a high degree of community engagement and delivered significant datasets and publications. These have fundamentally improved our understanding of global climate changes through the Common Era. The 2k reconstructions of global temperature variability were featured in Figure 1 of the Summary for Policymakers of the IPCC’s Working Group I contribution to the Sixth Assessment Report (AR6; IPCC 2021). more...
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- 2022
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13. Identifying Hydro‐Sensitive Coral δ18O Records for Improved High‐Resolution Temperature and Salinity Reconstructions.
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Thompson, D. M., Conroy, J. L., Konecky, B. L., Stevenson, S., DeLong, K. L., McKay, N., Reed, E., Jonkers, L., and Carré, M.
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SALINITY ,SEAWATER salinity ,CORALS ,OXYGEN isotopes ,OCEAN temperature ,OCEAN currents - Abstract
Stable oxygen isotopic ratios in corals (δ18Ocoral) are commonly utilized to reconstruct climate variability beyond the limit of instrumental observations. These measurements provide constraints on past seawater temperature, due to the thermodynamics of isotopic fractionation, but also past salinity, as both salinity and seawater δ18O (δ18Osw) are similarly affected by precipitation/evaporation, advection, and other processes. We use historical observations, isotope‐enabled model simulations, and the PAGES Iso2k database to assess the potential of δ18Ocoral to provide information on past salinity. Using "pseudocorals" to represent δ18Ocoral as a function of observed or simulated temperature and salinity/δ18Osw, we find that δ18Osw contributes up to 89% of δ18Ocoral variability in the Western Pacific Warm Pool. Although uncertainty in the δ18Osw‐salinity relationship influences the inferred salinity variability, corals from these sites could provide valuable δ18Osw reconstructions. Coordinated in situ monitoring of salinity and δ18Osw is vital for improving estimates of hydroclimatic change. Plain Language Summary: Seawater salinity provides valuable information about the global water cycle, including changes in precipitation, evaporation, and ocean currents. However, scientists' understanding of recent salinity change is hampered by the limited coverage of salinity measurements. Tropical corals incorporate environmental information in their skeletons as they grow, providing indirect evidence of past ocean salinity. Quantitatively estimating salinity variations requires accounting both for temperature‐ and salinity‐driven influences on the stable oxygen isotope composition (δ18O) of the coral skeleton, as well as changes in the relationship between salinity and seawater δ18O. Through comparison with instrumental records and climate models, we find that corals in the western Pacific Ocean and eastern Indian Ocean are most likely to provide reliable salinity information across seasons, years, and decades. Finally, we find that direct seawater δ18O observations are critical to improve the salinity information obtained from corals. Key Points: Seawater δ18O contributes up to 89% of the coral δ18O variability, providing critical information about salinity variability and trendsThe inferred salinity contribution to coral δ18O values is highly dependent on the salinity‐δ18O linear regression slopeInterpretation of coral δ18O values should account for both temperature and hydrological influences, which may oppose one another [ABSTRACT FROM AUTHOR] more...
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- 2022
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14. High‐Resolution Mg/Ca and δ18O patterns in modern Neogloboquadrina pachyderma from the Fram Strait and Irminger Sea
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Livsey, C.M., Kozdon, R., Bauch, D., Brummer, G.-J. A., Jonkers, L., Orland, I., Hill, T.M., and Spero, H.J.
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Foraminifera [hole bearers] - Abstract
Neogloboquadrina pachyderma is the dominant species of planktonic foraminifera found in polar waters and is therefore invaluable for paleoceanographic studies of the high latitudes. However, the geochemistry of this species is complicated due to the development of a thick calcite crust in its final growth stage and atgreater depths within the water column. We analyzed the in situ Mg/Ca and δ 18O in discrete calcite zones using laser ablation‐inductively coupled plasma‐mass spectrometry, electron probe microanalysis, and secondary ion mass spectrometry within modern N. pachyderma shells from the highly dynamic Fram Strait and the seasonally isothermal/isohaline Irminger Sea. Here we compare shell geochemistry to the measured temperature, salinity, and δ18Osw in which the shells calcified to better understand the controls on N. pachyderma geochemical heterogeneity. We present a relationship between Mg/Ca and temperature in N. pachyderma lamellar calcite that is significantly different than published equations for shells that contained both crust and lamellar calcite. We also document highly variable secondary ion mass spectrometry δ18O results (up to a 3.3‰ range in single shells) on plankton tow samples which we hypothesize is due to the granular texture of shell walls. Finally, we document that the δ18O of the crust and lamellar calcite of N. pachyderma from an isothermal/isohaline environment are indistinguishable from each other, indicating that shifts in N. pachyderma δ18O are primarily controlled by changes in environmental temperature and/or salinity rather than differences in the sensitivities of the two calcite types to environmental conditions. more...
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- 2020
15. PaCTS 1.0: A Crowdsourced Reporting Standard for Paleoclimate Data
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Khider, D., primary, Emile‐Geay, J., additional, McKay, N. P., additional, Gil, Y., additional, Garijo, D., additional, Ratnakar, V., additional, Alonso‐Garcia, M., additional, Bertrand, S., additional, Bothe, O., additional, Brewer, P., additional, Bunn, A., additional, Chevalier, M., additional, Comas‐Bru, L., additional, Csank, A., additional, Dassié, E., additional, DeLong, K., additional, Felis, T., additional, Francus, P., additional, Frappier, A., additional, Gray, W., additional, Goring, S., additional, Jonkers, L., additional, Kahle, M., additional, Kaufman, D., additional, Kehrwald, N. M., additional, Martrat, B., additional, McGregor, H., additional, Richey, J., additional, Schmittner, A., additional, Scroxton, N., additional, Sutherland, E., additional, Thirumalai, K., additional, Allen, K., additional, Arnaud, F., additional, Axford, Y., additional, Barrows, T., additional, Bazin, L., additional, Pilaar Birch, S. E., additional, Bradley, E., additional, Bregy, J., additional, Capron, E., additional, Cartapanis, O., additional, Chiang, H.‐W., additional, Cobb, K. M., additional, Debret, M., additional, Dommain, R., additional, Du, J., additional, Dyez, K., additional, Emerick, S., additional, Erb, M. P., additional, Falster, G., additional, Finsinger, W., additional, Fortier, D., additional, Gauthier, Nicolas, additional, George, S., additional, Grimm, E., additional, Hertzberg, J., additional, Hibbert, F., additional, Hillman, A., additional, Hobbs, W., additional, Huber, M., additional, Hughes, A. L. C., additional, Jaccard, S., additional, Ruan, J., additional, Kienast, M., additional, Konecky, B., additional, Le Roux, G., additional, Lyubchich, V., additional, Novello, V. F., additional, Olaka, L., additional, Partin, J. W., additional, Pearce, C., additional, Phipps, S. J., additional, Pignol, C., additional, Piotrowska, N., additional, Poli, M.‐S., additional, Prokopenko, A., additional, Schwanck, F., additional, Stepanek, C., additional, Swann, G. E. A., additional, Telford, R., additional, Thomas, E., additional, Thomas, Z., additional, Truebe, S., additional, Gunten, L., additional, Waite, A., additional, Weitzel, N., additional, Wilhelm, B., additional, Williams, J., additional, Williams, J. J., additional, Winstrup, M., additional, Zhao, N., additional, and Zhou, Y., additional more...
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- 2019
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16. Variability in the Northern North Atlantic and Arctic Oceans Across the Last Two Millennia: A Review
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Moffa‐Sánchez, P., primary, Moreno‐Chamarro, E., additional, Reynolds, D. J., additional, Ortega, P., additional, Cunningham, L., additional, Swingedouw, D., additional, Amrhein, D. E., additional, Halfar, J., additional, Jonkers, L., additional, Jungclaus, J. H., additional, Perner, K., additional, Wanamaker, A., additional, and Yeager, S., additional more...
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- 2019
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17. PaCTS v1.0:A crowdsourced reporting standard for paleoclimate Data
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Khider, D., Emile-Geay, Julien, Mckay, N.P., Gil, Y., Garijo, D., Ratnakar, V., Alonso-Garcia, M., Sebastian, B., Bothe, O., Brewer, P., Bunn, A., Chevalier, M., Csank, A., Dassié, E., DeLong, K., Felix, T., Francus, P., Frappier, A., Gray, W., Goring, S., Jonkers, L., Kahle, M., Kafman, D., Kehrwald, N., Martrat, B., McGregor, H., Richey, J., Schmittner, A., Thirumalai, E., Allen, K., Arnaud, F., Axford, Y., Barrows, T., Bazin, L., Pilaar Birch, S.E., Bardley, E., Bregy, J., Capron, Emilie, Cartapanis, O., Chiang, H.-W, Zhao, N., Zhou, Y., Khider, D., Emile-Geay, Julien, Mckay, N.P., Gil, Y., Garijo, D., Ratnakar, V., Alonso-Garcia, M., Sebastian, B., Bothe, O., Brewer, P., Bunn, A., Chevalier, M., Csank, A., Dassié, E., DeLong, K., Felix, T., Francus, P., Frappier, A., Gray, W., Goring, S., Jonkers, L., Kahle, M., Kafman, D., Kehrwald, N., Martrat, B., McGregor, H., Richey, J., Schmittner, A., Thirumalai, E., Allen, K., Arnaud, F., Axford, Y., Barrows, T., Bazin, L., Pilaar Birch, S.E., Bardley, E., Bregy, J., Capron, Emilie, Cartapanis, O., Chiang, H.-W, Zhao, N., and Zhou, Y. more...
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- 2019
18. PaCTS 1.0: A Crowdsourced Reporting Standard for Paleoclimate Data
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Khider, D, Emile-Geay, J, McKay, NP, Gil, Y, Garijo, D, Ratnakar, V, Alonso-Garcia, M, Bertrand, S, Bothe, O, Brewer, P, Bunn, A, Chevalier, M, Comas-Bru, L, Csank, A, Dassié, E, DeLong, K, Felis, T, Francus, P, Frappier, A, Gray, W, Goring, S, Jonkers, L, Kahle, M, Kaufman, D, Kehrwald, NM, Martrat, B, McGregor, H, Richey, J, Schmittner, A, Scroxton, N, Sutherland, E, Thirumalai, K, Allen, K, Arnaud, F, Axford, Y, Barrows, T ; https://orcid.org/0000-0003-2614-7177, Bazin, L, Pilaar Birch, SE, Bradley, E, Bregy, J, Capron, E, Cartapanis, O, Chiang, HW, Cobb, KM, Debret, M, Dommain, R, Du, J, Dyez, K, Emerick, S, Erb, MP, Falster, G, Finsinger, W, Fortier, D, Gauthier, N, George, S, Grimm, E, Hertzberg, J, Hibbert, F, Hillman, A, Hobbs, W, Huber, M, Hughes, ALC, Jaccard, S, Ruan, J, Kienast, M, Konecky, B, Le Roux, G, Lyubchich, V, Novello, VF, Olaka, L, Partin, JW, Pearce, C, Phipps, SJ, Pignol, C, Piotrowska, N, Poli, MS, Prokopenko, A, Schwanck, F, Stepanek, C, Swann, GEA, Telford, R, Thomas, E, Thomas, Z ; https://orcid.org/0000-0002-2323-4366, Truebe, S, von Gunten, L, Waite, A, Weitzel, N, Wilhelm, B, Williams, J, Williams, JJ, Winstrup, M, Zhao, N, Zhou, Y, Khider, D, Emile-Geay, J, McKay, NP, Gil, Y, Garijo, D, Ratnakar, V, Alonso-Garcia, M, Bertrand, S, Bothe, O, Brewer, P, Bunn, A, Chevalier, M, Comas-Bru, L, Csank, A, Dassié, E, DeLong, K, Felis, T, Francus, P, Frappier, A, Gray, W, Goring, S, Jonkers, L, Kahle, M, Kaufman, D, Kehrwald, NM, Martrat, B, McGregor, H, Richey, J, Schmittner, A, Scroxton, N, Sutherland, E, Thirumalai, K, Allen, K, Arnaud, F, Axford, Y, Barrows, T ; https://orcid.org/0000-0003-2614-7177, Bazin, L, Pilaar Birch, SE, Bradley, E, Bregy, J, Capron, E, Cartapanis, O, Chiang, HW, Cobb, KM, Debret, M, Dommain, R, Du, J, Dyez, K, Emerick, S, Erb, MP, Falster, G, Finsinger, W, Fortier, D, Gauthier, N, George, S, Grimm, E, Hertzberg, J, Hibbert, F, Hillman, A, Hobbs, W, Huber, M, Hughes, ALC, Jaccard, S, Ruan, J, Kienast, M, Konecky, B, Le Roux, G, Lyubchich, V, Novello, VF, Olaka, L, Partin, JW, Pearce, C, Phipps, SJ, Pignol, C, Piotrowska, N, Poli, MS, Prokopenko, A, Schwanck, F, Stepanek, C, Swann, GEA, Telford, R, Thomas, E, Thomas, Z ; https://orcid.org/0000-0002-2323-4366, Truebe, S, von Gunten, L, Waite, A, Weitzel, N, Wilhelm, B, Williams, J, Williams, JJ, Winstrup, M, Zhao, N, and Zhou, Y more...
- Abstract
The progress of science is tied to the standardization of measurements, instruments, and data. This is especially true in the Big Data age, where analyzing large data volumes critically hinges on the data being standardized. Accordingly, the lack of community-sanctioned data standards in paleoclimatology has largely precluded the benefits of Big Data advances in the field. Building upon recent efforts to standardize the format and terminology of paleoclimate data, this article describes the Paleoclimate Community reporTing Standard (PaCTS), a crowdsourced reporting standard for such data. PaCTS captures which information should be included when reporting paleoclimate data, with the goal of maximizing the reuse value of paleoclimate data sets, particularly for synthesis work and comparison to climate model simulations. Initiated by the LinkedEarth project, the process to elicit a reporting standard involved an international workshop in 2016, various forms of digital community engagement over the next few years, and grassroots working groups. Participants in this process identified important properties across paleoclimate archives, in addition to the reporting of uncertainties and chronologies; they also identified archive-specific properties and distinguished reporting standards for new versus legacy data sets. This work shows that at least 135 respondents overwhelmingly support a drastic increase in the amount of metadata accompanying paleoclimate data sets. Since such goals are at odds with present practices, we discuss a transparent path toward implementing or revising these recommendations in the near future, using both bottom-up and top-down approaches. more...
- Published
- 2019
19. Genetic and morphological divergence in the warm-water planktonic foraminifera genus Globigerinoides
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Morard, R., Füllberg, A., Brummer, G.-J. A., Greco, M., Jonkers, L., Wizemann, A., Weiner, A.K.M., Darling, K., Siccha, M., Ledevin, R., Kitazato, H., de Garidel-Thoron, T., de Vargas, C., Kucera, M., Morard, R., Füllberg, A., Brummer, G.-J. A., Greco, M., Jonkers, L., Wizemann, A., Weiner, A.K.M., Darling, K., Siccha, M., Ledevin, R., Kitazato, H., de Garidel-Thoron, T., de Vargas, C., and Kucera, M. more...
- Abstract
The planktonic foraminifera genus Globigerinoides provides a prime example of a species-rich genus in which genetic and morphological divergence are uncorrelated. To shed light on the evolutionary processes that lead to the present-day diversity of Globigerinoides, we investigated the genetic, ecological and morphological divergence of its constituent species. We assembled a global collection of single-cell barcode sequences and show that the genus consists of eight distinct genetic types organized in five extant morphospecies. Based on morphological evidence, we reassign the species Globoturborotalita tenella to Globigerinoides and amend Globigerinoides ruber by formally proposing two new subspecies, G. ruber albus n.subsp. and G. ruber ruber in order to express their subspecies level distinction and to replace the informal G. ruber “white” and G. ruber “pink”, respectively. The genetic types within G. ruber and Globigerinoides elongatus show a combination of endemism and coexistence, with little evidence for ecological differentiation. CT-scanning and ontogeny analysis reveal that the diagnostic differences in adult morphologies could be explained by alterations of the ontogenetic trajectories towards final (reproductive) size. This indicates that heterochrony may have caused the observed decoupling between genetic and morphological diversification within the genus. We find little evidence for environmental forcing of either the genetic or the morphological diversification, which allude to biotic interactions such as symbiosis, as the driver of speciation in Globigerinoides. more...
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- 2019
20. Highly replicated sampling reveals no diurnal vertical migration but stable species-specific vertical habitats in planktonic foraminifera
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Meilland, J., Siccha, M., Weinkauf, M.F.G., Jonkers, L., Morard, R., Baranowski, U., Baumeister, A., Bertlich, J., Brummer, G.-J. A., Debray, P., Fritz-Endres, T., Groeneveld, J., Magerl, L., Munz, P., Rillo, M.C., Schmidt, C., Takagi, H., Theara, G., Kucera, M., Meilland, J., Siccha, M., Weinkauf, M.F.G., Jonkers, L., Morard, R., Baranowski, U., Baumeister, A., Bertlich, J., Brummer, G.-J. A., Debray, P., Fritz-Endres, T., Groeneveld, J., Magerl, L., Munz, P., Rillo, M.C., Schmidt, C., Takagi, H., Theara, G., and Kucera, M. more...
- Abstract
Diurnal vertical migration (DVM) is a widespread phenomenon in the upper ocean, but it remains unclear to what degree it also involves passively transported micro- and meso-zooplankton. These organisms are difficult to monitor by in situ sensing and observations from discrete samples are often inconclusive. Prime examples of such ambiguity are planktonic foraminifera, where contradictory evidence for DVM continues to cast doubt on the stability of species vertical habitats, which introduces uncertainties in geochemical proxy interpretation. To provide a robust answer, we carried out highly replicated randomized sampling with 41 vertically resolved plankton net hauls taken within 26 hours in a confined area of 400 km2 in the tropical North Atlantic, where DVM in larger plankton occurs. Manual enumeration of planktonic foraminifera cell density consistently reveals the highest total cell concentrations in the surface mixed layer (top 50 m) and analysis of cell density in seven individual species representing different shell sizes, life strategies and presumed depth habitats reveals consistent vertical habitats not changing over the 26 hours sampling period. These observations robustly reject the existence of DVM in planktonic foraminifera in a setting where DVM occurs in other organisms. more...
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- 2019
21. PaCTS 1.0: A Crowdsourced Reporting Standard for Paleoclimate Data
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Khider, D., Emile-Geay, J., McKay, N. P., Gil, Y., Garijo, D., Ratnakar, V, Alonso-Garcia, M., Bertrand, S., Bothe, O., Brewer, P., Bunn, A., Chevalier, M., Comas-Bru, L., Csank, A., Dassie, E., DeLong, K., Felis, T., Francus, P., Frappier, A., Gray, W., Goring, S., Jonkers, L., Kahle, M., Kaufman, D., Kehrwald, N. M., Martrat, B., McGregor, H., Richey, J., Schmittner, A., Scroxton, N., Sutherland, E., Thirumalai, K., Allen, K., Arnaud, F., Axford, Y., Barrows, T., Bazin, L., Birch, S. E. Pilaar, Bradley, E., Bregy, J., Capron, E., Cartapanis, O., Chiang, H-W, Cobb, K. M., Debret, M., Dommain, R., Du, J., Dyez, K., Emerick, S., Erb, M. P., Falster, G., Finsinger, W., Fortier, D., Gauthier, Nicolas, George, S., Grimm, E., Hertzberg, J., Hibbert, F., Hillman, A., Hobbs, W., Huber, M., Hughes, A. L. C., Jaccard, S., Ruan, J., Kienast, M., Konecky, B., Le Roux, G., Lyubchich, V, Novello, V. F., Olaka, L., Partin, J. W., Pearce, C., Phipps, S. J., Pignol, C., Piotrowska, N., Poli, M-S, Prokopenko, A., Schwanck, F., Stepanek, C., Swann, G. E. A., Telford, R., Thomas, E., Thomas, Z., Truebe, S., von Gunten, L., Waite, A., Weitzel, N., Wilhelm, B., Williams, J., Winstrup, M., Zhao, N., Zhou, Y., Khider, D., Emile-Geay, J., McKay, N. P., Gil, Y., Garijo, D., Ratnakar, V, Alonso-Garcia, M., Bertrand, S., Bothe, O., Brewer, P., Bunn, A., Chevalier, M., Comas-Bru, L., Csank, A., Dassie, E., DeLong, K., Felis, T., Francus, P., Frappier, A., Gray, W., Goring, S., Jonkers, L., Kahle, M., Kaufman, D., Kehrwald, N. M., Martrat, B., McGregor, H., Richey, J., Schmittner, A., Scroxton, N., Sutherland, E., Thirumalai, K., Allen, K., Arnaud, F., Axford, Y., Barrows, T., Bazin, L., Birch, S. E. Pilaar, Bradley, E., Bregy, J., Capron, E., Cartapanis, O., Chiang, H-W, Cobb, K. M., Debret, M., Dommain, R., Du, J., Dyez, K., Emerick, S., Erb, M. P., Falster, G., Finsinger, W., Fortier, D., Gauthier, Nicolas, George, S., Grimm, E., Hertzberg, J., Hibbert, F., Hillman, A., Hobbs, W., Huber, M., Hughes, A. L. C., Jaccard, S., Ruan, J., Kienast, M., Konecky, B., Le Roux, G., Lyubchich, V, Novello, V. F., Olaka, L., Partin, J. W., Pearce, C., Phipps, S. J., Pignol, C., Piotrowska, N., Poli, M-S, Prokopenko, A., Schwanck, F., Stepanek, C., Swann, G. E. A., Telford, R., Thomas, E., Thomas, Z., Truebe, S., von Gunten, L., Waite, A., Weitzel, N., Wilhelm, B., Williams, J., Winstrup, M., Zhao, N., and Zhou, Y. more...
- Abstract
The progress of science is tied to the standardization of measurements, instruments, and data. This is especially true in the Big Data age, where analyzing large data volumes critically hinges on the data being standardized. Accordingly, the lack of community-sanctioned data standards in paleoclimatology has largely precluded the benefits of Big Data advances in the field. Building upon recent efforts to standardize the format and terminology of paleoclimate data, this article describes the Paleoclimate Community reporTing Standard (PaCTS), a crowdsourced reporting standard for such data. PaCTS captures which information should be included when reporting paleoclimate data, with the goal of maximizing the reuse value of paleoclimate data sets, particularly for synthesis work and comparison to climate model simulations. Initiated by the LinkedEarth project, the process to elicit a reporting standard involved an international workshop in 2016, various forms of digital community engagement over the next few years, and grassroots working groups. Participants in this process identified important properties across paleoclimate archives, in addition to the reporting of uncertainties and chronologies; they also identified archive-specific properties and distinguished reporting standards for new versus legacy data sets. This work shows that at least 135 respondents overwhelmingly support a drastic increase in the amount of metadata accompanying paleoclimate data sets. Since such goals are at odds with present practices, we discuss a transparent path toward implementing or revising these recommendations in the near future, using both bottom-up and top-down approaches. more...
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- 2019
22. Variable habitat depth of the planktonic foraminifera Neogloboquadrina pachyderma in the northern high latitudes explained by sea-ice and chlorophyll concentration
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Greco, Mattia, Jonkers, L., Kretschmer, Kerstin, Bijma, Jelle, Kučera, Michal, Greco, Mattia, Jonkers, L., Kretschmer, Kerstin, Bijma, Jelle, and Kučera, Michal
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- 2019
23. PaCTS 1.0:A Crowdsourced Reporting Standard for Paleoclimate Data
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Khider, D., Emile-Geay, Julien, Mckay, N.P., Gil, Y., Garijo, D., Ratnakar, V., Alonso-Garcia, M., Bertrand, S., Bothe, O., Brewer, P., Bunn, A., Chevalier, M., Comas-Bru, L., Csank, A., Dassié, E., DeLong, K., Felis, Thomas, Francus, P., Frappier, A., Gray, W., Goring, S., Jonkers, L., Kahle, M., Kaufman, Darrell, Capron, Emilie, Williams, J, Winstrup, Mai, Zhao, N., Zhou, Y., Khider, D., Emile-Geay, Julien, Mckay, N.P., Gil, Y., Garijo, D., Ratnakar, V., Alonso-Garcia, M., Bertrand, S., Bothe, O., Brewer, P., Bunn, A., Chevalier, M., Comas-Bru, L., Csank, A., Dassié, E., DeLong, K., Felis, Thomas, Francus, P., Frappier, A., Gray, W., Goring, S., Jonkers, L., Kahle, M., Kaufman, Darrell, Capron, Emilie, Williams, J, Winstrup, Mai, Zhao, N., and Zhou, Y. more...
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- 2019
24. Seasonal patterns of shell ␣ux, d18O and d13C of small and large N. pachyderma (s) and G. bulloides in the subpolar North Atlantic
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Jonkers, L., van Heuven, S., Zahn, R., Peeters, F.J.C., Earth and Climate, and Amsterdam Global Change Institute
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SDG 14 - Life Below Water - Abstract
Past water column stratification can be assessed through comparison of the δ18O of different planktonic foraminiferal species. The underlying assumption is that different species form their shells simultaneously, but at different depths in the water column. We evaluate this assumption using a sediment trap time-series of Neogloboquadrina pachyderma (s) and Globigerina bulloides from the NW North Atlantic. We determined fluxes, δ18O and δ13C of shells from two size fractions to assess size-related effects on shell chemistry and to better constrain the underlying causes of isotopic differences between foraminifera in deep-sea sediments. Our data indicate that in the subpolar North Atlantic differences in the seasonality of the shell flux, and not in depth habitat or test size, determine the interspecies Δδ18O. N. pachyderma (s) preferentially forms from early spring to late summer, whereas the flux of G. bulloides peaks later in the season and is sustained until autumn. Likewise, seasonality influences large and small specimens differently, with large shells settling earlier in the season. The similarity of the seasonal δ18O patterns between the two species indicates that they calcify in an overlapping depth zone close to the surface. However, their δ13C patterns are markedly different (>1‰). Both species have a seasonally variable offset from δ13C DIC that appears to be governed primarily by temperature, with larger offsets associated with higher temperatures. The variable offset from δ13CDIC implies that seasonality of the flux affects the fossil δ13C signal, which has implications for reconstruction of the past oceanic carbon cycle. © 2013 American Geophysical Union. All Rights Reserved. more...
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- 2013
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25. Project start-up: theory and practice : MSC-APB Greenfield Brewery Project Mongolia: Heineken
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Jonkers, L., Jonkers, L., Jonkers, L., and Jonkers, L.
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- 2007
26. Chamber formation leads to Mg/Ca banding in the planktonic foraminifer Neogloboquadrina pachyderma
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Jonkers, L., Buse, B., Brummer, G.-J. A., Hall, I.R., Jonkers, L., Buse, B., Brummer, G.-J. A., and Hall, I.R.
- Abstract
Many species of planktonic foraminifera show distinct banding in the intratest distribution of Mg/Ca. This heterogeneity appears biologically controlled and thus poses a challenge to Mg/Ca paleothermometry. The cause of this banding and its relation with chamber formation are poorly constrained and most of what we know about intratest Mg/Ca variability stems from culture studies of tropical, symbiont-bearing foraminifera. Here we present data on the non-spinose, symbiont-barren Neogloboquadrina pachyderma from the subpolar North Atlantic where wintertime mixing removes vertical gradients in temperature and salinity. This allows investigation of biologically controlled Mg/Ca intratest variability under natural conditions. We find that intratest Mg/Ca varies between <0.1 and 7 mmol/mol, even in winter specimens. High Mg/Ca bands occur at the outer edge of the laminae, indicating reduced Mg removal at the end of chamber formation. Our data thus provide new constraints on the timing of the formation of such bands and indicate that their presence is intrinsic to the chamber formation process.Additionally, all specimens are covered with an outer crust consisting of large euhedral crystals. The composition of the crust is similar to the low Mg/Ca bands in the laminar calcite in winter and summer specimens, indicating a tight biological control on crust formation and composition. Nevertheless, despite high intratest variability, the median Mg/Ca of summertime tests is higher than that of wintertime tests. This provides support for Mg/Ca paleothermometry, but to improve the accuracy of paleotemperature estimates biological effects on Mg incorporation need to be better accounted for. more...
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- 2016
27. Icebergs not the trigger for North Atlantic cold events
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Barker, Stephen, Chen, J., Gong, Xun, Jonkers, L., Knorr, Gregor, Thornalley, D., Barker, Stephen, Chen, J., Gong, Xun, Jonkers, L., Knorr, Gregor, and Thornalley, D.
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- 2015
28. Seasonal stratification, shell flux and oxygen isotope dynamics of left-coiling N. pachyderma and T. quinqueloba in the western sub-polar North Atlantic
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Jonkers, L., Brummer, G.J.A., Peeters, F.J.C., Aken, H.M., de Jong, F., and Marine Biogeology
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SDG 14 - Life Below Water - Abstract
We present an almost 3 year long time series of shell fluxes and oxygen isotopes of left-coiling Neogloboquadrina pachyderma and Turborotalita quinqueloba from sediment traps moored in the deep central Irminger Sea. We determined their response to the seasonal change from a deeply mixed water column with occasional deep convection in winter to a thermally stratified water column with a surface mixed layer (SML) of around 50 m in summer. Both species display very low fluxes during winter with a remnant summer population holding out until replaced by a vital population that seeds the subsequent blooms. This annual population overturning is marked by a 0.7‰ increase in δ18O in both species. The shell flux of N. pachyderma peaks during the spring bloom and in late summer, when stratification is close to its minimum and maximum, respectively. Both export periods contribute about equally and account for >95% of the total annual flux. Shell fluxes of T. quinqueloba show only a single broad pulse in summer, thus following the seasonal stratification cycle. The δ18O of N. pachyderma reflects temperatures just below the base of the seasonal SML without offset from isotopic equilibrium. The δ18O pattern of T. quinqueloba shows a nearly identical amplitude and correlates highly with the δ18O of N. pachyderma. Therefore T. quinqueloba also reflects temperature near the base of the SML but with a positive offset from isotopic equilibrium. These offsets contrast with observations elsewhere and suggest a variable offset from equilibrium calcification for both species. In the Irminger Sea the species consistently show a contrast in their flux timings. Their flux-weighted δd18O will thus dominantly be determined by seasonal temperature differences at the base of the SML rather than by differences in their depth habitat. Consequently, their sedimentary δd18O may be used to infer the seasonal contrast in temperature at the base of the SML. © Copyright 2010 by the American Geophysical Union. more...
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- 2010
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29. Lunar periodicity in the shell flux of planktonic foraminifera in the Gulf of Mexico
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Jonkers, L., primary, Reynolds, C. E., additional, Richey, J., additional, and Hall, I. R., additional
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- 2015
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30. Global analysis of seasonality in the shell flux of extant planktonic Foraminifera
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Jonkers, L., primary and Kučera, M., additional
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- 2015
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31. Supplementary material to "Global analysis of seasonality in the shell flux of extant planktonic foraminifera"
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Jonkers, L., primary and Kučera, M., additional
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- 2015
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32. DNA from Nails for Genetic Analyses in Large-Scale Epidemiologic Studies
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Hogervorst, J.G.F., Hogervorst, J.G.F., Godschalk, R.W.L., van den Brandt, P.A., Weijenberg, M.P., Verhage, B.A.J., Jonkers, L., Goessens, J., Simons, C.C.J.M., Vermeesch, J.R., van Schooten, F.J., Schouten, L.J., Hogervorst, J.G.F., Hogervorst, J.G.F., Godschalk, R.W.L., van den Brandt, P.A., Weijenberg, M.P., Verhage, B.A.J., Jonkers, L., Goessens, J., Simons, C.C.J.M., Vermeesch, J.R., van Schooten, F.J., and Schouten, L.J. more...
- Abstract
BACKGROUND: Nails contain genomic DNA that can be used for genetic analyses, which is attractive for large epidemiologic studies that have collected or are planning to collect nail clippings. Study participants will more readily participate in a study when asked to provide nail samples than when asked to provide a blood sample. In addition, nails are easy and cheap to obtain and store compared with other tissues. METHODS: We describe our findings on toenail DNA in terms of yield, quality, genotyping a limited set of SNPs with the Sequenom MassARRAY iPLEX platform and high-density genotyping with the Illumina HumanCytoSNP_FFPE-12 DNA array (>262,000 markers). We discuss our findings together with other studies on nail DNA and we compare nails and other frequently used tissue samples as DNA sources. RESULTS: Although nail DNA is considerably degraded, genotyping a limited set of SNPs with the Sequenom MassARRAY iPLEX platform (average sample call rate, 97.1%) and high-density genotyping with the Illumina HumanCytoSNP_FFPE chip (average sample call rate, 93.8%) were successful. CONCLUSIONS: Nails are a suitable source of DNA for genotyping in large-scale epidemiologic studies, provided that methods are used that are suitable or optimized for degraded DNA. For genotyping through (next generation) sequencing where DNA degradation is less of an issue, nails may be an even more attractive DNA source, because it surpasses other sources in terms of ease and costs of obtaining and storing the samples. IMPACT: It is worthwhile to consider nails as a source of DNA for genotyping in large-scale epidemiologic studies. See all the articles in this CEBP Focus section, "Biomarkers, Biospecimens, and New Technologies in Molecular Epidemiology." Cancer Epidemiol Biomarkers Prev; 23(12); 2703-12. (c)2014 AACR. more...
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- 2014
33. Lunar periodicity in the shell flux of some planktonic foraminifera in the Gulf of Mexico
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Jonkers, L., primary, Reynolds, C. E., additional, Richey, J., additional, and Hall, I. R., additional
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- 2014
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34. Seasonal Mg/Ca variability of N. pachyderma (s) and G. bulloides: Implications for seawater temperature reconstruction
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Jonkers, L., Jiménez-Amat, P., Mortyn, P.G., Brummer, G.-J.A., Jonkers, L., Jiménez-Amat, P., Mortyn, P.G., and Brummer, G.-J.A.
- Abstract
Given the importance of high-latitude areas in the ocean-climate system, there is need for a paleothermometer that is reliable at low temperatures. Here we assess the applicability of the Mg/Ca-temperature proxy in colder waters (5-10 degrees C) by comparing for the first time the seasonal Mg/Ca and delta O-18 cycles of N. pachyderma (s) and G. bulloides using a sediment trap time-series from the northern North Atlantic. While both species show indistinguishable seasonal delta O-18 patterns that clearly track the near surface temperature cycle, their Mg/Ca are very different. G. bulloides Mg/Ca is high (2.0-3.1 mmol/mol), but varies in concert with the seasonal temperature cycle. The Mg/Ca of N. pachyderma (s), on the other hand, is low (1.1-1.5 mmol/mol) and shows only a very weak seasonal cycle. The delta O-18 patterns indicate that both species calcify in the same depth zone. Consequently, depth habitat differences cannot explain the contrasting Mg/Ca patterns. The elevated Mg/Ca in pristine G. bulloides might be due to the presence of high Mg phases that are not preserved in fossil shells. The contrasting absence of a seasonal trend in the Mg/Ca of N. pachyderma (s) confirms other studies where calcification temperatures were less well constrained. The reason for this absence is not fully known, but may include species-specific vital effects. The very different seasonal patterns of both species' Mg/Ca underscore the importance of parameters other than temperature in controlling planktonic foraminiferal Mg/Ca. Our results therefore lend further caution in the interpretation of Mg/Ca-temperature reconstructions from high northern latitudes. more...
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- 2013
35. Temporal offsets between surface temperature, ice-rafting and bottom flow speed proxies in the glacial (MIS 3) northern North Atlantic
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Jonkers, L., Prins, M.A., Moros, M., Weltje, G.J., Troelstra, S.R., Brummer, G.J.A., Jonkers, L., Prins, M.A., Moros, M., Weltje, G.J., Troelstra, S.R., and Brummer, G.J.A.
- Abstract
Rapid climatic switches during marine isotope stage 3 (29-59 ka BP) are often attributed to ocean circulation changes caused by freshwater input into the North Atlantic through the melting of large amounts of icebergs and sea ice. However, recent studies have questioned this direct coupling between factors influencing the ocean-climate system. By combining multiple proxies from two mid depth northern North Atlantic sediment cores we assess temporal offsets and links between freshwater input and response of the near bottom flow as well as between near bottom flow and sea surface temperatures changes. Grain size, mineralogical and magnetic proxies for ice rafting and near-bottom flow speed, interpreted as indicators of freshwater input and deep circulation strength, consistently indicate a delay in the recovery of the deep circulation after freshwater perturbations. Sea surface temperature variability is inferred from foraminiferal assemblages and Mg/Ca and delta O-18 of Neogloboquadrina pachyderma s. The records show rapid switches towards higher temperatures following the ice-rafting events. Interestingly, near sea surface temperatures increased and decreased again during periods of accelerating bottom flow speed, likely reflecting the sudden release of heat from deeper in the water column, rather than circulation changes. Our data thus confirm the impact of freshwater forcing on the Atlantic deep circulation, but suggest that temperature variability at the surface was not directly linked to these circulation changes. more...
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- 2012
36. Encrustation and trace element composition of Neogloboquadrina dutertrei assessed from single chamber analyses - implications for paleotemperature estimates
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Jonkers, L., de Nooijer, L.J., Reichart, G.J., Zahn, R., Brummer, G.-J.A., Jonkers, L., de Nooijer, L.J., Reichart, G.J., Zahn, R., and Brummer, G.-J.A.
- Abstract
Crust formation is a common phenomenon in planktonic foraminifera. Because of their different formation mechanism and hence composition, crusts affect the overall test composition and therefore complicate the use of crust-bearing foraminifera in paleoceanography. Such species are often used to estimate subsurface paleotemperatures, and although the influence of encrustation on the trace element/Ca ratio is recognised, it has not been systematically explored between and within tests. Here we use laser ablation ICP-MS to assess the variability in trace element composition of the crust of Neogloboquadrina dutertrei within individual chambers, as well as the effect of compositional heterogeneity of the crust on whole test chemistry. Compositionally, the outer crust differs from inner layer by lower Mg/Ca and Mn/Ca, but is indistinguishable in Sr/Ca. Crust thickness decreases towards the younger chambers, and it may be entirely absent from the last chamber. In contrast to Mn/Ca and Sr/Ca, crustal Mg/Ca ratios show a tendency towards higher values on the younger chambers. These patterns in crust thickness and in crust Mg/Ca indicate that temperature is not the dominant factor controlling crust composition. Temperature estimates based on N. dutertrei, and presumably other crust-forming species too, are therefore biased towards too low values. Through comparison of modern and glacial tests, we show that this bias is not constant and that changes in crust thickness and/or in Mg/Ca values can spuriously suggest temperature changes. more...
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- 2012
37. Encrustation and trace element composition of <i>Neogloboquadrina dutertrei</i> assessed from single chamber analyses – implications for paleotemperature estimates
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Jonkers, L., primary, de Nooijer, L. J., additional, Reichart, G.-J., additional, Zahn, R., additional, and Brummer, G.-J. A., additional
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- 2012
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38. Encrustation and trace element composition of Neogloboquadrina dutertrei assessed from single chamber analyses, implications for paleotemperature estimates
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Jonkers, L., primary, de Nooijer, L. J., additional, Reichart, G.-J., additional, Zahn, R., additional, and Brummer, G.-J. A., additional
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- 2012
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39. Endosonography of Colorectal Diseases
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Tio, T. L., primary, Weijers, O., additional, Hulsman, F., additional, Jonkers, L., additional, Collins, E., additional, Sie, L. H., additional, and Tytgat, G. N. J., additional
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- 1992
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40. Identifying Hydro‐Sensitive Coral δ18O Records for Improved High‐Resolution Temperature and Salinity Reconstructions
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Thompson, D. M., Conroy, J. L., Konecky, B. L., Stevenson, S., DeLong, K. L., McKay, N., Reed, E., Jonkers, L., and Carré, M.
- Abstract
Stable oxygen isotopic ratios in corals (δ18Ocoral) are commonly utilized to reconstruct climate variability beyond the limit of instrumental observations. These measurements provide constraints on past seawater temperature, due to the thermodynamics of isotopic fractionation, but also past salinity, as both salinity and seawater δ18O (δ18Osw) are similarly affected by precipitation/evaporation, advection, and other processes. We use historical observations, isotope‐enabled model simulations, and the PAGES Iso2k database to assess the potential of δ18Ocoralto provide information on past salinity. Using ‘‘pseudocorals’’ to represent δ18Ocoralas a function of observed or simulated temperature and salinity/δ18Osw, we find that δ18Oswcontributes up to 89% of δ18Ocoralvariability in the Western Pacific Warm Pool. Although uncertainty in the δ18Osw‐salinity relationship influences the inferred salinity variability, corals from these sites could provide valuable δ18Oswreconstructions. Coordinated in situ monitoring of salinity and δ18Oswis vital for improving estimates of hydroclimatic change. Seawater salinity provides valuable information about the global water cycle, including changes in precipitation, evaporation, and ocean currents. However, scientists' understanding of recent salinity change is hampered by the limited coverage of salinity measurements. Tropical corals incorporate environmental information in their skeletons as they grow, providing indirect evidence of past ocean salinity. Quantitatively estimating salinity variations requires accounting both for temperature‐ and salinity‐driven influences on the stable oxygen isotope composition (δ18O) of the coral skeleton, as well as changes in the relationship between salinity and seawater δ18O. Through comparison with instrumental records and climate models, we find that corals in the western Pacific Ocean and eastern Indian Ocean are most likely to provide reliable salinity information across seasons, years, and decades. Finally, we find that direct seawater δ18O observations are critical to improve the salinity information obtained from corals. Seawater δ18O contributes up to 89% of the coral δ18O variability, providing critical information about salinity variability and trendsThe inferred salinity contribution to coral δ18O values is highly dependent on the salinity‐δ18O linear regression slopeInterpretation of coral δ18O values should account for both temperature and hydrological influences, which may oppose one another Seawater δ18O contributes up to 89% of the coral δ18O variability, providing critical information about salinity variability and trends The inferred salinity contribution to coral δ18O values is highly dependent on the salinity‐δ18O linear regression slope Interpretation of coral δ18O values should account for both temperature and hydrological influences, which may oppose one another more...
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- 2022
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41. PaCTS 1.0: A Crowdsourced Reporting Standard for Paleoclimate Data
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Khider, D., Emile‐Geay, J., McKay, N. P., Gil, Y., Garijo, D., Ratnakar, V., Alonso‐Garcia, M., Bertrand, S., Bothe, O., Brewer, P., Bunn, A., Chevalier, M., Comas‐Bru, L., Csank, A., Dassié, E., DeLong, K., Felis, T., Francus, P., Frappier, A., Gray, W., Goring, S., Jonkers, L., Kahle, M., Kaufman, D., Kehrwald, N. M., Martrat, B., McGregor, H., Richey, J., Schmittner, A., Scroxton, N., Sutherland, E., Thirumalai, K., Allen, K., Arnaud, F., Axford, Y., Barrows, T., Bazin, L., Pilaar Birch, S. E., Bradley, E., Bregy, J., Capron, E., Cartapanis, O., Chiang, H.‐W., Cobb, K. M., Debret, M., Dommain, R., Du, J., Dyez, K., Emerick, S., Erb, M. P., Falster, G., Finsinger, W., Fortier, D., Gauthier, Nicolas, George, S., Grimm, E., Hertzberg, J., Hibbert, F., Hillman, A., Hobbs, W., Huber, M., Hughes, A. L. C., Jaccard, S., Ruan, J., Kienast, M., Konecky, B., Le Roux, G., Lyubchich, V., Novello, V. F., Olaka, L., Partin, J. W., Pearce, C., Phipps, S. J., Pignol, C., Piotrowska, N., Poli, M.‐S., Prokopenko, A., Schwanck, F., Stepanek, C., Swann, G. E. A., Telford, R., Thomas, E., Thomas, Z., Truebe, S., Gunten, L., Waite, A., Weitzel, N., Wilhelm, B., Williams, J., Williams, J. J., Winstrup, M., Zhao, N., and Zhou, Y. more...
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13. Climate action ,550 Earth sciences & geology ,15. Life on land - Abstract
The progress of science is tied to the standardization of measurements, instruments, and data. This is especially true in the Big Data age, where analyzing large data volumes critically hinges on the data being standardized. Accordingly, the lack of community‐sanctioned data standards in paleoclimatology has largely precluded the benefits of Big Data advances in the field. Building upon recent efforts to standardize the format and terminology of paleoclimate data, this article describes the Paleoclimate Community reporTing Standard (PaCTS), a crowdsourced reporting standard for such data. PaCTS captures which information should be included when reporting paleoclimate data, with the goal of maximizing the reuse value of paleoclimate data sets, particularly for synthesis work and comparison to climate model simulations. Initiated by the LinkedEarth project, the process to elicit a reporting standard involved an international workshop in 2016, various forms of digital community engagement over the next few years, and grassroots working groups. Participants in this process identified important properties across paleoclimate archives, in addition to the reporting of uncertainties and chronologies; they also identified archive‐specific properties and distinguished reporting standards for new versus legacy data sets. This work shows that at least 135 respondents overwhelmingly support a drastic increase in the amount of metadata accompanying paleoclimate data sets. Since such goals are at odds with present practices, we discuss a transparent path toward implementing or revising these recommendations in the near future, using both bottom‐up and top‐down approaches. more...
42. Sea Surface Temperatures and Paleoenvironmental Variability in the Central Mediterranean During Historical Times Reconstructed Using Planktonic Foraminifera
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Rodolfo Sprovieri, Serena Ferraro, Alessandro Incarbona, Lukas Jonkers, Giorgio Tranchida, and Incarbona, A., Jonkers, L., Ferraro, S., Sprovieri, R., Tranchida, G.
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Foraminifera ,Mediterranean climate ,Atmospheric Science ,Oceanography ,biology ,Paleontology ,Plankton ,biology.organism_classification ,Geology ,artificial neural network, industrial era, modern analog technique, Sicily channel, SST reconstruction, transfer function - Abstract
The ongoing anthropogenic‐induced warming assessment requires a robust background from regional sea surface temperature (SST) reconstructions. Planktonic foraminifera have yielded valuable insights into late Quaternary SST dynamics, but the techniques to estimate SST from fossil assemblages have only rarely been used in very recent sedimentary records (the last 2,000 years). Here we use two transfer function methods, modern analog technique and artificial neural networks, to reconstruct SST variability in two cores from the Central Mediterranean Sea that span the last five centuries. Both cores show similar and considerable changes in the planktonic foraminifera assemblages. However, the inferred mean annual SSTs only varied in a narrow range, in agreement with instrumental data that go back to 1850 CE. Our reconstructions extend this time frame and indicate that SST variability did not exceed 1.5 °C over the past three centuries. Rather than temperature, we suggest that the changes in the assemblages reflect switches between sea surface winter/spring productivity and a deep winter mixed layer, due to the atmosphere/ocean interplay that governs different productivity modes in neighboring mesoscale gyres. more...
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- 2019
43. The global genetic diversity of planktonic foraminifera reveals the structure of cryptic speciation in plankton.
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Morard R, Darling KF, Weiner AKM, Hassenrück C, Vanni C, Cordier T, Henry N, Greco M, Vollmar NM, Milivojevic T, Rahman SN, Siccha M, Meilland J, Jonkers L, Quillévéré F, Escarguel G, Douady CJ, de Garidel-Thoron T, de Vargas C, and Kucera M more...
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- Genetic Speciation, DNA Barcoding, Taxonomic, Foraminifera genetics, Foraminifera classification, Genetic Variation, Plankton genetics, Plankton classification
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The nature and extent of diversity in the plankton has fascinated scientists for over a century. Initially, the discovery of many new species in the remarkably uniform and unstructured pelagic environment appeared to challenge the concept of ecological niches. Later, it became obvious that only a fraction of plankton diversity had been formally described, because plankton assemblages are dominated by understudied eukaryotic lineages with small size that lack clearly distinguishable morphological features. The high diversity of the plankton has been confirmed by comprehensive metabarcoding surveys, but interpretation of the underlying molecular taxonomies is hindered by insufficient integration of genetic diversity with morphological taxonomy and ecological observations. Here we use planktonic foraminifera as a study model and reveal the full extent of their genetic diversity and investigate geographical and ecological patterns in their distribution. To this end, we assembled a global data set of ~7600 ribosomal DNA sequences obtained from morphologically characterised individual foraminifera, established a robust molecular taxonomic framework for the observed diversity, and used it to query a global metabarcoding data set covering ~1700 samples with ~2.48 billion reads. This allowed us to extract and assign 1 million reads, enabling characterisation of the structure of the genetic diversity of the group across ~1100 oceanic stations worldwide. Our sampling revealed the existence of, at most, 94 distinct molecular operational taxonomic units (MOTUs) at a level of divergence indicative of biological species. The genetic diversity only doubles the number of formally described species identified by morphological features. Furthermore, we observed that the allocation of genetic diversity to morphospecies is uneven. Only 16 morphospecies disguise evolutionarily significant genetic diversity, and the proportion of morphospecies that show genetic diversity increases poleward. Finally, we observe that MOTUs have a narrower geographic distribution than morphospecies and that in some cases the MOTUs belonging to the same morphospecies (cryptic species) have different environmental preferences. Overall, our analysis reveals that even in the light of global genetic sampling, planktonic foraminifera diversity is modest and finite. However, the extent and structure of the cryptic diversity reveals that genetic diversification is decoupled from morphological diversification, hinting at different mechanisms acting at different levels of divergence., (© 2024 The Authors. Biological Reviews published by John Wiley & Sons Ltd on behalf of Cambridge Philosophical Society.) more...
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- 2024
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44. ForCenS-LGM: a dataset of planktonic foraminifera species assemblage composition for the Last Glacial Maximum.
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Jonkers L, Mix A, Voelker A, Risebrobakken B, Smart CW, Ivanova E, Arellano-Torres E, Eynaud F, Naoufel H, Max L, Rossignol L, Simon MH, Martins MVA, Petró S, Caley T, Dokken T, Howard W, and Kucera M more...
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- Animals, Biodiversity, Ecosystem, Foraminifera, Zooplankton, Fossils
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Species assemblage composition of marine microfossils offers the possibility to investigate ecological and climatological change on time scales inaccessible using conventional observations. Planktonic foraminifera - calcareous zooplankton - have an excellent fossil record and are used extensively in palaeoecology and palaeoceanography. During the Last Glacial Maximum (LGM; 19,000 - 23,000 years ago), the climate was in a radically different state. This period is therefore a key target to investigate climate and biodiversity under different conditions than today. Studying LGM climate and ecosystems indeed has a long history, yet the most recent global synthesis of planktonic foraminifera assemblage composition is now nearly two decades old. Here we present the ForCenS-LGM dataset with 2,365 species assemblage samples collected using standardised methods and with harmonised taxonomy. The data originate from marine sediments from 664 sites and present a more than 50% increase in coverage compared to previous work. The taxonomy is compatible with the most recent global core top dataset, enabling direct investigation of temporal changes in foraminifera biogeography and facilitating seawater temperature reconstructions., (© 2024. The Author(s).) more...
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- 2024
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45. A multicentennial mode of North Atlantic climate variability throughout the Last Glacial Maximum.
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Prange M, Jonkers L, Merkel U, Schulz M, and Bakker P
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Paleoclimate proxy records from the North Atlantic region reveal substantially greater multicentennial temperature variability during the Last Glacial Maximum (LGM) compared to the current interglacial. As there was no obvious change in external forcing, causes for the increased variability remain unknown. Exploiting LGM simulations with a comprehensive coupled climate model along with high-resolution proxy records, we introduce an oscillatory mode of multicentennial variability, which is associated with moderate variations in the Atlantic meridional overturning circulation and depends on the large-scale salinity distribution. This self-sustained mode is amplified by sea-ice feedbacks and induces maximum surface temperature variability in the subpolar North Atlantic region. Characterized by a distinct climatic imprint and different dynamics, the multicentennial oscillation has to be distinguished from Dansgaard-Oeschger variability and emerges only under full LGM climate forcing. The potential of multicentennial modes of variability to emerge or disappear in response to changing climate forcing may have implications for future climate change. more...
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- 2023
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46. The FORCIS database: A global census of planktonic Foraminifera from ocean waters.
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Chaabane S, de Garidel-Thoron T, Giraud X, Schiebel R, Beaugrand G, Brummer GJ, Casajus N, Greco M, Grigoratou M, Howa H, Jonkers L, Kucera M, Kuroyanagi A, Meilland J, Monteiro F, Mortyn G, Almogi-Labin A, Asahi H, Avnaim-Katav S, Bassinot F, Davis CV, Field DB, Hernández-Almeida I, Herut B, Hosie G, Howard W, Jentzen A, Johns DG, Keigwin L, Kitchener J, Kohfeld KE, Lessa DVO, Manno C, Marchant M, Ofstad S, Ortiz JD, Post A, Rigual-Hernandez A, Rillo MC, Robinson K, Sagawa T, Sierro F, Takahashi KT, Torfstein A, Venancio I, Yamasaki M, and Ziveri P more...
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- Censuses, Climate Change, Oceans and Seas, Plankton, Foraminifera
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Planktonic Foraminifera are unique paleo-environmental indicators through their excellent fossil record in ocean sediments. Their distribution and diversity are affected by different environmental factors including anthropogenically forced ocean and climate change. Until now, historical changes in their distribution have not been fully assessed at the global scale. Here we present the FORCIS (Foraminifera Response to Climatic Stress) database on foraminiferal species diversity and distribution in the global ocean from 1910 until 2018 including published and unpublished data. The FORCIS database includes data collected using plankton tows, continuous plankton recorder, sediment traps and plankton pump, and contains ~22,000, ~157,000, ~9,000, ~400 subsamples, respectively (one single plankton aliquot collected within a depth range, time interval, size fraction range, at a single location) from each category. Our database provides a perspective of the distribution patterns of planktonic Foraminifera in the global ocean on large spatial (regional to basin scale, and at the vertical scale), and temporal (seasonal to interdecadal) scales over the past century., (© 2023. The Author(s).) more...
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- 2023
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47. Plankton response to global warming is characterized by non-uniform shifts in assemblage composition since the last ice age.
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Strack T, Jonkers L, C Rillo M, Hillebrand H, and Kucera M
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- Biodiversity, Global Warming, Temperature, Plankton, Foraminifera physiology
- Abstract
Biodiversity is expected to change in response to future global warming. However, it is difficult to predict how species will track the ongoing climate change. Here we use the fossil record of planktonic foraminifera to assess how biodiversity responded to climate change with a magnitude comparable to future anthropogenic warming. We compiled time series of planktonic foraminifera assemblages, covering the time from the last ice age across the deglaciation to the current warm period. Planktonic foraminifera assemblages shifted immediately when temperature began to rise at the end of the last ice age and continued to change until approximately 5,000 years ago, even though global temperature remained relatively stable during the last 11,000 years. The biotic response was largest in the mid latitudes and dominated by range expansion, which resulted in the emergence of new assemblages without analogues in the glacial ocean. Our results indicate that the plankton response to global warming was spatially heterogeneous and did not track temperature change uniformly over the past 24,000 years. Climate change led to the establishment of new assemblages and possibly new ecological interactions, which suggests that current anthropogenic warming may lead to new, different plankton community composition., (© 2022. The Author(s).) more...
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- 2022
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48. Author Correction: Complex spatio-temporal structure of the Holocene thermal maximum.
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Cartapanis O, Jonkers L, Moffa-Sanchez P, Jaccard SL, and de Vernal A
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- 2022
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49. Complex spatio-temporal structure of the Holocene Thermal Maximum.
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Cartapanis O, Jonkers L, Moffa-Sanchez P, Jaccard SL, and de Vernal A
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- Cold Temperature, Temperature, Climate, Climate Change
- Abstract
Inconsistencies between Holocene climate reconstructions and numerical model simulations question the robustness of climate models and proxy temperature records. Climate reconstructions suggest an early-middle Holocene Thermal Maximum (HTM) followed by gradual cooling, whereas climate models indicate continuous warming. This discrepancy either implies seasonal biases in proxy-based climate reconstructions, or that the climate model sensitivity to forcings and feedbacks needs to be reevaluated. Here, we analyze a global database of Holocene paleotemperature records to investigate the spatiotemporal structure of the HTM. Continental proxy records at mid and high latitudes of the Northern Hemisphere portray a "classic" HTM (8-4 ka). In contrast, marine proxy records from the same latitudes reveal an earlier HTM (11-7ka), while a clear temperature anomaly is missing in the tropics. The results indicate a heterogeneous response to climate forcing and highlight the lack of globally synchronous HTM., (© 2022. The Author(s).) more...
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- 2022
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50. Publisher Correction: A global database of Holocene paleotemperature records.
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Kaufman D, McKay N, Routson C, Erb M, Davis B, Heiri O, Jaccard S, Tierney J, Dätwyler C, Axford Y, Brussel T, Cartapanis O, Chase B, Dawson A, de Vernal A, Engels S, Jonkers L, Marsicek J, Moffa-Sánchez P, Morrill C, Orsi A, Rehfeld K, Saunders K, Sommer PS, Thomas E, Tonello M, Tóth M, Vachula R, Andreev A, Bertrand S, Biskaborn B, Bringué M, Brooks S, Caniupán M, Chevalier M, Cwynar L, Emile-Geay J, Fegyveresi J, Feurdean A, Finsinger W, Fortin MC, Foster L, Fox M, Gajewski K, Grosjean M, Hausmann S, Heinrichs M, Holmes N, Ilyashuk B, Ilyashuk E, Juggins S, Khider D, Koinig K, Langdon P, Larocque-Tobler I, Li J, Lotter A, Luoto T, Mackay A, Magyari E, Malevich S, Mark B, Massaferro J, Montade V, Nazarova L, Novenko E, Pařil P, Pearson E, Peros M, Pienitz R, Płóciennik M, Porinchu D, Potito A, Rees A, Reinemann S, Roberts S, Rolland N, Salonen S, Self A, Seppä H, Shala S, St-Jacques JM, Stenni B, Syrykh L, Tarrats P, Taylor K, van den Bos V, Velle G, Wahl E, Walker I, Wilmshurst J, Zhang E, and Zhilich S more...
- Abstract
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
- Published
- 2020
- Full Text
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