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2,146 results on '"Leng, Melanie"'

1. Rapid rise in atmospheric CO2 marked the end of the Late Palaeozoic Ice Age

Author

Jurikova, Hana, Garbelli, Claudio, Whiteford, Ross, Reeves, Theodore, Laker, Gemma M., Liebetrau, Volker, Gutjahr, Marcus, Eisenhauer, Anton, Savickaite, Kotryna, Leng, Melanie J., Iurino, Dawid Adam, Viaretti, Marco, Tomašových, Adam, Zhang, Yuchen, Wang, Wen-qian, Shi, G. R., Shen, Shu-zhong, Rae, James W. B., and Angiolini, Lucia

Published
2025
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5. Sustained year-round oceanographic measurements from Rothera Research Station, Antarctica, 1997–2017

Author

Venables, Hugh, Meredith, Michael P., Hendry, Katharine R., ten Hoopen, Petra, Peat, Helen, Chapman, Alice, Beaumont, Jennifer, Piper, Rayner, Miller, Andrew J., Mann, Paul, Rossetti, Helen, Massey, Ali, Souster, Terri, Reeves, Simon, Fenton, Mairi, Heiser, Sabrina, Pountney, Sam, Reed, Sarah, Waring, Zoë, Clark, Marlon, Bolton, Emma, Mathews, Ryan, London, Hollie, Clement, Alice, Stuart, Emma, Reichardt, Aurelia, Brandon, Mark, Leng, Melanie, Arrowsmith, Carol, Annett, Amber, Henley, Sian F., and Clarke, Andrew

Published
2023
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6. Paleocene/Eocene carbon feedbacks triggered by volcanic activity.

Author

Kender, Sev, Bogus, Kara, Pedersen, Gunver K, Dybkjær, Karen, Mather, Tamsin A, Mariani, Erica, Ridgwell, Andy, Riding, James B, Wagner, Thomas, Hesselbo, Stephen P, and Leng, Melanie J

Abstract

The Paleocene-Eocene Thermal Maximum (PETM) was a period of geologically-rapid carbon release and global warming ~56 million years ago. Although modelling, outcrop and proxy records suggest volcanic carbon release occurred, it has not yet been possible to identify the PETM trigger, or if multiple reservoirs of carbon were involved. Here we report elevated levels of mercury relative to organic carbon-a proxy for volcanism-directly preceding and within the early PETM from two North Sea sedimentary cores, signifying pulsed volcanism from the North Atlantic Igneous Province likely provided the trigger and subsequently sustained elevated CO2. However, the PETM onset coincides with a mercury low, suggesting at least one other carbon reservoir released significant greenhouse gases in response to initial warming. Our results support the existence of 'tipping points' in the Earth system, which can trigger release of additional carbon reservoirs and drive Earth's climate into a hotter state.

Published
2021

10. Deep drilling reveals massive shifts in evolutionary dynamics after formation of ancient ecosystem

Author

Wilke, Thomas, Hauffe, Torsten, Jovanovska, Elena, Cvetkoska, Aleksandra, Donders, Timme, Ekschmitt, Klemens, Francke, Alexander, Lacey, Jack H, Levkov, Zlatko, Marshall, Charles R, Neubauer, Thomas A, Silvestro, Daniele, Stelbrink, Björn, Vogel, Hendrik, Albrecht, Christian, Holtvoeth, Jens, Krastel, Sebastian, Leicher, Niklas, Leng, Melanie J, Lindhorst, Katja, Masi, Alessia, Ognjanova-Rumenova, Nadja, Panagiotopoulos, Konstantinos, Reed, Jane M, Sadori, Laura, Tofilovska, Slavica, Van Bocxlaer, Bert, Wagner-Cremer, Friederike, Wesselingh, Frank P, Wolters, Volkmar, Zanchetta, Giovanni, Zhang, Xiaosen, and Wagner, Bernd

Subjects
Biological Sciences, Ecology, Evolutionary Biology, Earth Sciences, Geology, Biodiversity, Biological Evolution, Climate Change, Ecosystem, Fossils, Lakes
Abstract

The scarcity of high-resolution empirical data directly tracking diversity over time limits our understanding of speciation and extinction dynamics and the drivers of rate changes. Here, we analyze a continuous species-level fossil record of endemic diatoms from ancient Lake Ohrid, along with environmental and climate indicator time series since lake formation 1.36 million years (Ma) ago. We show that speciation and extinction rates nearly simultaneously decreased in the environmentally dynamic phase after ecosystem formation and stabilized after deep-water conditions established in Lake Ohrid. As the lake deepens, we also see a switch in the macroevolutionary trade-off, resulting in a transition from a volatile assemblage of short-lived endemic species to a stable community of long-lived species. Our results emphasize the importance of the interplay between environmental/climate change, ecosystem stability, and environmental limits to diversity for diversification processes. The study also provides a new understanding of evolutionary dynamics in long-lived ecosystems.

Published
2020

15. Stable oxygen isotopes reveal different thermal regimes during the Early Pliocene in the southern North Sea Basin: a multi-species approach.

Author

Cudennec, Jean-François, Schöne, Bernd R, Leng, Melanie, Harper, Elizabeth M, Gofas, Serge, Wesselingh, Frank P, and Johnson, Andrew L A

Subjects
OCEAN quahog, OXYGEN isotopes, OCEAN temperature, COLD (Temperature), STABLE isotopes
Abstract

Oxygen stable isotope (δ18O) analysis of marine biogenic carbonates is widely used to study the temperature at which the hard parts precipitated. This technique enables investigation of the environmental conditions experienced by carbonate-shelled organisms throughout their life. We used this approach on four bivalve species from the Coralline Crag Formation (Early Pliocene; UK), where warm- and cold-associated species co-occur in the Ramsholt Member. Our results reveal species-specific differences in reconstructed temperature. Two distinct climatic settings were identified: a cold setting with seafloor temperatures of 7.3 °C in winter and 12.4 °C in summer, and a warm one with seafloor temperatures of 10.4 °C in winter to above 14 °C in summer. These absolute temperatures were calculated using a modelled value of seawater δ18O (+0.1‰) that is open to question, but the disparity in temperatures exists whatever value is used. Interestingly, the reconstructed temperatures for some of the studied species align with those of their modern relatives: Arctica islandica records the coldest temperatures in this dataset, while Centrocardita squamulosa ampla indicates warmer conditions. Aequipecten opercularis , a eurythermal pectinid, exhibited the broadest range of temperatures. The interval during which the Coralline Crag was deposited (c. 4.4‒3.8 Ma) is generally regarded as relatively warm. However, the presence of A. islandica and the absolute seawater temperatures derived from shell δ18O suggest the occurrence of sufficiently long cool periods for the establishment and survival of this long-lived species. Data from specimens of C. squamulosa ampla and A. islandica collected from a single bed point to glacial/interglacial-type climate fluctuation. These results confirm that the presence of A. islandica is a marker for cold temperate environments. These results also confirm that assemblage information is not sufficient to determine palaeoclimatic conditions, and that reconstructed temperatures from shell δ18O can reveal time-averaging in fossil shell beds. [ABSTRACT FROM AUTHOR]

Published
2024
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24. Dynamics of sediment flux to a bathyal continental margin section through the Paleocene–Eocene Thermal Maximum

Author

Jones, Tom Dunkley, Manners, Hayley R, Hoggett, Murray, Turner, Sandra Kirtland, Westerhold, Thomas, Leng, Melanie J, Pancost, Richard D, Ridgwell, Andy, Alegret, Laia, Duller, Rob, and Grimes, Stephen T

Subjects
Earth Sciences, Physical Geography and Environmental Geoscience, Climate Change Science, Geology, Climate Action, Life on Land, Paleontology, Climate change science
Abstract

The response of the Earth system to greenhouse-gas-driven warming is of critical importance for the future trajectory of our planetary environment. Hyperthermal events - past climate transients with global-scale warming significantly above background climate variability - can provide insights into the nature and magnitude of these responses. The largest hyperthermal of the Cenozoic was the Paleocene-Eocene Thermal Maximum (PETM ∼ 56 Ma). Here we present new high-resolution bulk sediment stable isotope and major element data for the classic PETM section at Zumaia, Spain. With these data we provide a new detailed stratigraphic correlation to other key deep-ocean and terrestrial PETM reference sections. With this new correlation and age model we are able to demonstrate that detrital sediment accumulation rates within the Zumaia continental margin section increased more than 4-fold during the PETM, representing a radical change in regional hydrology that drove dramatic increases in terrestrial-to-marine sediment flux. Most remarkable is that detrital accumulation rates remain high throughout the body of the PETM, and even reach peak values during the recovery phase of the characteristic PETM carbon isotope excursion (CIE). Using a series of Earth system model inversions, driven by the new Zumaia carbon isotope record, we demonstrate that the silicate weathering feedback alone is insufficient to recover the PETM CIE, and that active organic carbon burial is required to match the observed dynamics of the CIE. Further, we demonstrate that the period of maximum organic carbon sequestration coincides with the peak in detrital accumulation rates observed at Zumaia. Based on these results, we hypothesise that orbital-scale variations in subtropical hydro-climates, and their subsequent impact on sediment dynamics, may contribute to the rapid climate and CIE recovery from peak-PETM conditions.

Published
2018

26. Rapid rise in atmospheric CO2marked the end of the Late Palaeozoic Ice Age

Author

Jurikova, Hana, Garbelli, Claudio, Whiteford, Ross, Reeves, Theodore, Laker, Gemma M., Liebetrau, Volker, Gutjahr, Marcus, Eisenhauer, Anton, Savickaite, Kotryna, Leng, Melanie J., Iurino, Dawid Adam, Viaretti, Marco, Tomašových, Adam, Zhang, Yuchen, Wang, Wen-qian, Shi, G. R., Shen, Shu-zhong, Rae, James W. B., and Angiolini, Lucia

Abstract

Atmospheric CO2is thought to play a fundamental role in Earth’s climate regulation. Yet, for much of Earth’s geological past, atmospheric CO2has been poorly constrained, hindering our understanding of transitions between cool and warm climates. Beginning ~370 million years ago in the Late Devonian and ending ~260 million years ago in the Permian, the Late Palaeozoic Ice Age was the last major glaciation preceding the current Late Cenozoic Ice Age and possibly the most intense glaciation witnessed by complex lifeforms. From the onset of the main phase of the Late Palaeozoic Ice Age in the mid-Mississippian ~330 million years ago, the Earth is thought to have sustained glacial conditions, with continental ice accumulating in high to mid-latitudes. Here we present an 80-million-year-long boron isotope record within a proxy framework for robust quantification of CO2. Our record reveals that the main phase of the Late Palaeozoic Ice Age glaciation was maintained by prolonged low CO2, unprecedented in Earth’s history. About 294 million years ago, atmospheric CO2rose abruptly (4-fold), releasing the Earth from its penultimate ice age and transforming the Early Permian into a warmer world.

Published
2025
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37. Large Igneous Province Control on Ocean Anoxia and Eutrophication in the North Sea at the Paleocene–Eocene Thermal Maximum

Author

Mariani, Erica, primary, Kender, Sev, additional, Hesselbo, Stephen P., additional, Bogus, Kara, additional, Littler, Kate, additional, Riding, James B., additional, Leng, Melanie J., additional, Kemp, Simon J., additional, Dybkjær, Karen, additional, Pedersen, Gunver K., additional, Wagner, Thomas, additional, and Dickson, Alexander J., additional

Published
2024
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40. Insights into the evolution of the young Lake Ohrid ecosystem and vegetation succession from a southern European refugium during the Early Pleistocene

Author

Panagiotopoulos, Konstantinos, Holtvoeth, Jens, Kouli, Katerina, Marinova, Elena, Francke, Alexander, Cvetkoska, Aleksandra, Jovanovska, Elena, Lacey, Jack H., Lyons, Emma T., Buckel, Connie, Bertini, Adele, Donders, Timme, Just, Janna, Leicher, Niklas, Leng, Melanie J., Melles, Martin, Pancost, Richard D., Sadori, Laura, Tauber, Paul, Vogel, Hendrik, Wagner, Bernd, and Wilke, Thomas

Published
2020
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41. ​​South Georgia marine productivity over the past 15 ka and implications for glacial evolution​

Author

Wilkin, Jack T.R., Kender, Sev, Dejardin, Rowan, Allen, Claire S., Peck, Victoria L., Swann, George E.A., McClymont, Erin L., Scourse, James D., Littler, Kate, Leng, Melanie J., Wilkin, Jack T.R., Kender, Sev, Dejardin, Rowan, Allen, Claire S., Peck, Victoria L., Swann, George E.A., McClymont, Erin L., Scourse, James D., Littler, Kate, and Leng, Melanie J.

Abstract

The subantarctic islands of South Georgia are located in the Southern Ocean, and they may be sensitive to future climate warming. However, due to a lack of well-dated subantarctic palaeoclimate archives, there is still uncertainty about South Georgia's response to past climate change. Here, we reconstruct primary productivity changes and infer Holocene glacial evolution by analysing two marine gravity cores: one near Cumberland Bay on the inner South Georgia shelf (GC673: ca. 9.5 to 0.3 cal. kyr BP) and one offshore of Royal Bay on the mid-shelf (GC666: ca. 15.2 cal. kyr BP to present). We identify three distinct benthic foraminiferal assemblages characterised by the dominance of Miliammina earlandi, Fursenkoina fusiformis, and Cassidulinoides parkerianus that are considered alongside foraminiferal stable isotopes and the organic carbon and biogenic silica accumulation rates of the host sediment. The M. earlandi assemblage is prevalent during intervals of dissolution in GC666 and reduced productivity in GC673. The F. fusiformis assemblage coincides with enhanced productivity in both cores. Our multiproxy analysis provides evidence that the latest Pleistocene to earliest Holocene (ca. 15.2 to 10.5 cal. kyr BP) was a period of high productivity associated with increased glacial meltwater discharge. The mid–late Holocene (ca. 8 to 1 cal. kyr BP), coinciding with a fall in sedimentation rates and lower productivity, was likely a period of reduced glacial extent but with several short-lived episodes of increased productivity from minor glacial readvances. The latest Holocene (from ca. 1 cal. kyr BP) saw an increase in productivity and glacial advance associated with cooling temperatures and increased precipitation which may have been influenced by changes in the southwesterly winds over South Georgia. We interpret the elevated relative abundance of F. fusiformis as a proxy for increased primary productivity which, at proximal site GC673, was forced by terrestrial runoff

Published
2024

42. A global compilation of diatom silica oxygen isotope records from lake sediment – trends and implications for climate reconstruction

Author

Meister, Philip, Alexandre, Anne, Bailey, Hannah, Barker, Philip, Biskaborn, Boris K., Broadman, Ellie, Cartier, Rosine, Chapligin, Bernhard, Couapel, Martine, Dean, Jonathan R., Diekmann, Bernhard, Harding, Poppy, Henderson, Andrew C. G., Hernandez, Armand, Herzschuh, Ulrike, Kostrova, Svetlana S., Lacey, Jack, Leng, Melanie J., Lücke, Andreas, Mackay, Anson W., Magyari, Eniko Katalin, Narancic, Biljana, Porchier, Cécile, Rosqvist, Gunhild, Shemesh, Aldo, Sonzogni, Corinne, Swann, George E. A., Sylvestre, Florence, Meyer, Hanno, Meister, Philip, Alexandre, Anne, Bailey, Hannah, Barker, Philip, Biskaborn, Boris K., Broadman, Ellie, Cartier, Rosine, Chapligin, Bernhard, Couapel, Martine, Dean, Jonathan R., Diekmann, Bernhard, Harding, Poppy, Henderson, Andrew C. G., Hernandez, Armand, Herzschuh, Ulrike, Kostrova, Svetlana S., Lacey, Jack, Leng, Melanie J., Lücke, Andreas, Mackay, Anson W., Magyari, Eniko Katalin, Narancic, Biljana, Porchier, Cécile, Rosqvist, Gunhild, Shemesh, Aldo, Sonzogni, Corinne, Swann, George E. A., Sylvestre, Florence, and Meyer, Hanno

Published
2024
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43. Large Igneous Province Control on Ocean Anoxia and Eutrophication in the North Sea at the Paleocene–Eocene Thermal Maximum

Author

Mariani, Erica, Kender, Sev, Hesselbo, Stephen P., Bogus, Kara, Littler, Kate, Riding, James B., Leng, Melanie J., Kemp, Simon J., Dybkjær, Karen, Pedersen, Gunver K., Wagner, Thomas, Dickson, Alexander J., Mariani, Erica, Kender, Sev, Hesselbo, Stephen P., Bogus, Kara, Littler, Kate, Riding, James B., Leng, Melanie J., Kemp, Simon J., Dybkjær, Karen, Pedersen, Gunver K., Wagner, Thomas, and Dickson, Alexander J.

Abstract

The Paleocene–Eocene Thermal Maximum (PETM) was a global hyperthermal event ∼56 Ma characterized by massive input of carbon into the ocean–atmosphere system and global warming. A leading hypothesis for its trigger is the emplacement of the North Atlantic Igneous Province (NAIP), with extensive extrusion/intrusion of igneous material into nearby sedimentary basins, forcing local uplift and warming-inducing carbon emissions. It remains unclear if oceanographic changes in the North Sea–Norwegian Sea–Arctic basins, such as anoxia and productivity, were causally linked to local NAIP uplift/activity, and at what time scales these perturbations occurred. To test mechanisms and time scales, we present geochemical proxies (XRF analysis, clay mineralogy, molybdenum isotopes, and pyrite framboid size distribution) in undisrupted marine sediment core E−8X located in the central North Sea. We find evidence for a rapid onset of anoxia/euxinia at the negative carbon isotope excursion from redox proxies, followed by a gradual drawdown of molybdenum/total organic carbon (Mo/TOC) during the PETM main phase indicative of tectonically-restricted basin likely from NAIP uplift. A short-lived increase in Mo, pyrite and TOC occurred during a precursor event associated with a sedimentary mercury pulse indicative of volcanic activity. We suggest thermal uplift and flood basalt volcanism tectonically restricted the North Sea and tipped it into an euxinic state via volcanic emission–oceanographic feedbacks inducing eutrophication. This fine temporal separation of tectonic versus climatic geochemical proxies, combined with pulsed NAIP volcanism, demonstrates that Large Igneous Province emplacements can, at least locally, result in ocean biogeochemical feedbacks operating on relatively short timescales.

Published
2024

44. Detrital input sustains diatom production off a glaciated Arctic coast

Author

Ng, Hong Chin, Hendry, Katharine R., Ward, Rachael, Woodward, E.M.S., Leng, Melanie J., Pickering, Rebecca A., Krause, Jeffrey W., Ng, Hong Chin, Hendry, Katharine R., Ward, Rachael, Woodward, E.M.S., Leng, Melanie J., Pickering, Rebecca A., and Krause, Jeffrey W.

Abstract

In the Arctic and subarctic oceans, the relatively low supply of silicon (compared to other nutrients) can make it limiting for the growth of diatoms, a fundamental building block of the oceanic food web. Glaciers release large quantities of dissolved silicon and dissolvable solid amorphous silica phases into high-latitude estuaries (fjords), but the role of these glacially-derived silica phases in sustaining diatom growth in the coastal and open-water sectors remains unknown. Here we show how stable and radiogenic silicon isotopes can be used together to address this question, using southwest Greenland as a case study. This study finds enhanced levels of detrital (i.e., mineral) amorphous silica, likely glacially-sourced, sustaining a large portion of diatom growth observed off the coast, revealing how the phytoplankton community can function during high-meltwater periods.

Published
2024

46. Hydroclimate changes in eastern Africa over the past 200,000 years may have influenced early human dispersal

Author

Schaebitz, Frank, Asrat, Asfawossen, Lamb, Henry F., Cohen, Andrew S., Foerster, Verena, Duesing, Walter, Kaboth-Bahr, Stefanie, Opitz, Stephan, Viehberg, Finn A., Vogelsang, Ralf, Dean, Jonathan, Leng, Melanie J., Junginger, Annett, Ramsey, Christopher Bronk, Chapot, Melissa S., Deino, Alan, Lane, Christine S., Roberts, Helen M., Vidal, Céline, Tiedemann, Ralph, and Trauth, Martin H.

Published
2021
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50. Extending the tephra and palaeoenvironmental record of the Central Mediterranean back to 430 ka: A new core from Fucino Basin, central Italy

Author

Giaccio, Biagio, Leicher, Niklas, Mannella, Giorgio, Monaco, Lorenzo, Regattieri, Eleonora, Wagner, Bernd, Zanchetta, Giovanni, Gaeta, Mario, Marra, Fabrizio, Nomade, Sébastien, Palladino, Danilo M., Pereira, Alison, Scheidt, Stephanie, Sottili, Gianluca, Wonik, Thomas, Wulf, Sabine, Zeeden, Christian, Ariztegui, Daniel, Cavinato, Gian Paolo, Dean, Jonathan R., Florindo, Fabio, Leng, Melanie J., Macrì, Patrizia, Niespolo, Elizabeth, Renne, Paul R., Rolf, Christian, Sadori, Laura, Thomas, Camille, and Tzedakis, Polychronis C.

Published
2019
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