Articles | Volume 15, issue 6
https://doi.org/10.5194/cp-15-1939-2019
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/cp-15-1939-2019
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
15 Nov 2019
Research article |
| 15 Nov 2019
| 15 Nov 2019
A South Atlantic island record uncovers shifts in westerlies and hydroclimate during the last glacial
Svante Björck
CORRESPONDING AUTHOR
Department of Geology, Lund University, 22362 Lund, Sweden
Department of Geological Sciences and the Bolin Centre for Climate
Research, Stockholm University, 10691 Stockholm, Sweden
Jesper Sjolte
Department of Geology, Lund University, 22362 Lund, Sweden
Karl Ljung
Department of Geology, Lund University, 22362 Lund, Sweden
Florian Adolphi
Department of Geology, Lund University, 22362 Lund, Sweden
University of Bern, Physics Institute, Climate and Environmental Physics, Sidlerstrasse 5, 3012 Bern, Switzerland
Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland
Roger Flower
Department of Geography, University College London, London WC1E 6BT, UK
Rienk H. Smittenberg
Department of Geological Sciences and the Bolin Centre for Climate
Research, Stockholm University, 10691 Stockholm, Sweden
Malin E. Kylander
Department of Geological Sciences and the Bolin Centre for Climate
Research, Stockholm University, 10691 Stockholm, Sweden
Thomas F. Stocker
University of Bern, Physics Institute, Climate and Environmental Physics, Sidlerstrasse 5, 3012 Bern, Switzerland
Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland
Sofia Holmgren
Department of Geology, Lund University, 22362 Lund, Sweden
Hui Jiang
Key Laboratory of Geographic Information Science, East China Normal
University, 200062 Shanghai, PR China
Raimund Muscheler
Department of Geology, Lund University, 22362 Lund, Sweden
Yamoah K. K. Afrifa
School of Geography, Earth and Environmental Sciences, University of
Birmingham, Edgbaston, B15 2TT, UK
Jayne E. Rattray
Department of Biological Sciences, University of Calgary, Calgary,
Canada
Nathalie Van der Putten
Earth and Climate Cluster, Faculty of Science, Vrije Universiteit
Amsterdam, Amsterdam, the Netherlands
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Qin Tao, Cheng Shen, Raimund Muscheler, and Jesper Sjolte
Clim. Past, 21, 2561–2578, https://doi.org/10.5194/cp-21-2561-2025, https://doi.org/10.5194/cp-21-2561-2025, 2025
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Using model simulations and reconstructions over the last millennium, we identify distinct North Atlantic Oscillation-related winter climate responses following tropical versus extratropical eruptions, with improved model-data agreement in simulations that use the latest volcanic forcing. Our paleoclimate data–model comparison provides new evidence of volcanic climate impacts, which are strongly dependent on the choice of forcing dataset, model configuration, and eruption event selection.
Niklas Kappelt, Eric Wolff, Marcus Christl, Christof Vockenhuber, Philip Gautschi, and Raimund Muscheler
Clim. Past, 21, 1585–1594, https://doi.org/10.5194/cp-21-1585-2025, https://doi.org/10.5194/cp-21-1585-2025, 2025
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By measuring the radioactive decay of atmospherically produced 36Cl and 10Be in an ice core drilled in West Antarctica, we were able to determine the age of the deepest sample close to bedrock to be about 550 thousand years old. This means that the ice in this location, known as Skytrain Ice Rise, has survived several warm periods in the past, at least since marine isotope stage 11.
Lisa Claire Orme, Francis Ludlow, Natasha Langton, Jenny Kristina Sjӧstrӧm, Malin Kylander, Conor Murphy, Sean Pyne-O'Donnell, Jonathan Turner, Nannan Li, Sarah Jessica Davies, Fraser Mitchell, and John Alphonsus Matthews
EGUsphere, https://doi.org/10.5194/egusphere-2025-3737, https://doi.org/10.5194/egusphere-2025-3737, 2025
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The link between storms and volcanic eruptions in northwest Europe is investigated. Past storminess was reconstructed using sand deposits in a coastal peatbog from western Ireland. Together with similar records from northwest Europe this shows six periods of high storminess in the last 2500 years, coinciding roughly with the largest eruptions of this time. A record of past windiness for Ireland (600–1616CE) created from the “Irish Annals” supports enhanced storminess for 3 years after eruptions.
Jesper Sjolte and Qin Tao
EGUsphere, https://doi.org/10.5194/egusphere-2025-2911, https://doi.org/10.5194/egusphere-2025-2911, 2025
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We have reconstructed past changes in North Atlantic climate by combining climate model output with tree-ring and ice core data. Our new data includes sea level pressure, temperature and precipitation on annual, seasonal and monthly time scales. The reconstruction captures changes in observed temperature over several hundred years across Greenland and Europe. This data can be used to study variations in climate and impacts of greenhouse gases, volcanic eruptions and variations in solar activity.
Tsai-Wen Lin, Tommaso Tesi, Jens Hefter, Hendrik Grotheer, Jutta Wollenburg, Florian Adolphi, Henning A. Bauch, Alessio Nogarotto, Juliane Müller, and Gesine Mollenhauer
Clim. Past, 21, 753–772, https://doi.org/10.5194/cp-21-753-2025, https://doi.org/10.5194/cp-21-753-2025, 2025
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In order to understand the mechanisms governing permafrost organic matter remobilization, we investigated organic matter composition during past intervals of rapid sea-level rise, of inland warming, and of dense sea-ice cover in the Laptev Sea. We find that sea-level rise resulted in widespread erosion and transport of permafrost materials to the ocean but that erosion is mitigated by regional dense sea-ice cover. Factors like inland warming or floods increase permafrost mobilization locally.
Markus Adloff, Aurich Jeltsch-Thömmes, Frerk Pöppelmeier, Thomas F. Stocker, and Fortunat Joos
Clim. Past, 21, 571–592, https://doi.org/10.5194/cp-21-571-2025, https://doi.org/10.5194/cp-21-571-2025, 2025
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We simulated how different processes affected the carbon cycle over the last eight glacial cycles. We found that the effects of interactive marine sediments enlarge the carbon fluxes that result from these processes, especially in the ocean, and alter various proxy signals. We provide an assessment of the directions of regional and global proxy changes that might be expected in response to different glacial–interglacial Earth system changes in the presence of interactive marine sediments.
Jakob Schwander, Thomas F. Stocker, Remo Walther, Samuel Marending, Tobias Erhardt, Chantal Zeppenfeld, and Jürg Jost
The Cryosphere, 18, 5613–5617, https://doi.org/10.5194/tc-18-5613-2024, https://doi.org/10.5194/tc-18-5613-2024, 2024
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The RADIX (Rapid Access Drilling and Ice eXtraction) optical dust logger is part of the exploratory 20 mm drilling system at the University of Bern and is inserted into the hole after drilling. Temperature and attitude sensors were successfully tested but not the dust sensor, as no RADIX hole reached the required bubble-free ice. In 2023, we tested the logger with an adapter for the deep borehole of the East Greenland Ice-core Project and obtained a good Late Glacial–Early Holocene dust record.
Arnaud Nicolas, Gesine Mollenhauer, Johannes Lachner, Konstanze Stübner, Maylin Malter, Jutta Wollenburg, Hendrik Grotheer, and Florian Adolphi
Clim. Past, 20, 2617–2628, https://doi.org/10.5194/cp-20-2617-2024, https://doi.org/10.5194/cp-20-2617-2024, 2024
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We use the authigenic 10Be/9Be record of a Laptev Sea sediment core for the period 8–14 kyr BP and synchronize it with the 10Be records from absolutely dated ice cores. We employed a likelihood function to calculate the ΔR values. A benthic ΔR value of +345±60 14C years was estimated, which corresponds to a marine reservoir age of 848±90 14C years. This new ΔR value was used to refine the age–depth model for core PS2458-4, establishing it as a potential reference chronology for the Laptev Sea.
Christian Wirths, Thomas F. Stocker, and Johannes C. R. Sutter
The Cryosphere, 18, 4435–4462, https://doi.org/10.5194/tc-18-4435-2024, https://doi.org/10.5194/tc-18-4435-2024, 2024
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We investigated the influence of several regional climate models on the Antarctic Ice Sheet when applied as forcing for the Parallel Ice Sheet Model (PISM). Our study shows that the choice of regional climate model forcing results in uncertainties of around a tenth of those in future sea level rise projections and also affects the extent of grounding line retreat in West Antarctica.
Markus Adloff, Frerk Pöppelmeier, Aurich Jeltsch-Thömmes, Thomas F. Stocker, and Fortunat Joos
Clim. Past, 20, 1233–1250, https://doi.org/10.5194/cp-20-1233-2024, https://doi.org/10.5194/cp-20-1233-2024, 2024
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The Atlantic Meridional Overturning Circulation (AMOC) is an ocean current that transports heat into the North Atlantic. Over the ice age cycles, AMOC strength and its spatial pattern varied. We tested the role of heat forcing for these AMOC changes by simulating the temperature changes of the last eight glacial cycles. In our model, AMOC shifts between four distinct circulation modes caused by heat and salt redistributions that reproduce reconstructed long-term North Atlantic SST changes.
Bjorn Stevens, Stefan Adami, Tariq Ali, Hartwig Anzt, Zafer Aslan, Sabine Attinger, Jaana Bäck, Johanna Baehr, Peter Bauer, Natacha Bernier, Bob Bishop, Hendryk Bockelmann, Sandrine Bony, Guy Brasseur, David N. Bresch, Sean Breyer, Gilbert Brunet, Pier Luigi Buttigieg, Junji Cao, Christelle Castet, Yafang Cheng, Ayantika Dey Choudhury, Deborah Coen, Susanne Crewell, Atish Dabholkar, Qing Dai, Francisco Doblas-Reyes, Dale Durran, Ayoub El Gaidi, Charlie Ewen, Eleftheria Exarchou, Veronika Eyring, Florencia Falkinhoff, David Farrell, Piers M. Forster, Ariane Frassoni, Claudia Frauen, Oliver Fuhrer, Shahzad Gani, Edwin Gerber, Debra Goldfarb, Jens Grieger, Nicolas Gruber, Wilco Hazeleger, Rolf Herken, Chris Hewitt, Torsten Hoefler, Huang-Hsiung Hsu, Daniela Jacob, Alexandra Jahn, Christian Jakob, Thomas Jung, Christopher Kadow, In-Sik Kang, Sarah Kang, Karthik Kashinath, Katharina Kleinen-von Königslöw, Daniel Klocke, Uta Kloenne, Milan Klöwer, Chihiro Kodama, Stefan Kollet, Tobias Kölling, Jenni Kontkanen, Steve Kopp, Michal Koran, Markku Kulmala, Hanna Lappalainen, Fakhria Latifi, Bryan Lawrence, June Yi Lee, Quentin Lejeun, Christian Lessig, Chao Li, Thomas Lippert, Jürg Luterbacher, Pekka Manninen, Jochem Marotzke, Satoshi Matsouoka, Charlotte Merchant, Peter Messmer, Gero Michel, Kristel Michielsen, Tomoki Miyakawa, Jens Müller, Ramsha Munir, Sandeep Narayanasetti, Ousmane Ndiaye, Carlos Nobre, Achim Oberg, Riko Oki, Tuba Özkan-Haller, Tim Palmer, Stan Posey, Andreas Prein, Odessa Primus, Mike Pritchard, Julie Pullen, Dian Putrasahan, Johannes Quaas, Krishnan Raghavan, Venkatachalam Ramaswamy, Markus Rapp, Florian Rauser, Markus Reichstein, Aromar Revi, Sonakshi Saluja, Masaki Satoh, Vera Schemann, Sebastian Schemm, Christina Schnadt Poberaj, Thomas Schulthess, Cath Senior, Jagadish Shukla, Manmeet Singh, Julia Slingo, Adam Sobel, Silvina Solman, Jenna Spitzer, Philip Stier, Thomas Stocker, Sarah Strock, Hang Su, Petteri Taalas, John Taylor, Susann Tegtmeier, Georg Teutsch, Adrian Tompkins, Uwe Ulbrich, Pier-Luigi Vidale, Chien-Ming Wu, Hao Xu, Najibullah Zaki, Laure Zanna, Tianjun Zhou, and Florian Ziemen
Earth Syst. Sci. Data, 16, 2113–2122, https://doi.org/10.5194/essd-16-2113-2024, https://doi.org/10.5194/essd-16-2113-2024, 2024
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To manage Earth in the Anthropocene, new tools, new institutions, and new forms of international cooperation will be required. Earth Virtualization Engines is proposed as an international federation of centers of excellence to empower all people to respond to the immense and urgent challenges posed by climate change.
Minjie Zheng, Hongyu Liu, Florian Adolphi, Raimund Muscheler, Zhengyao Lu, Mousong Wu, and Nønne L. Prisle
Geosci. Model Dev., 16, 7037–7057, https://doi.org/10.5194/gmd-16-7037-2023, https://doi.org/10.5194/gmd-16-7037-2023, 2023
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The radionuclides 7Be and 10Be are useful tracers for atmospheric transport studies. Here we use the GEOS-Chem to simulate 7Be and 10Be with different production rates: the default production rate in GEOS-Chem and two from the state-of-the-art beryllium production model. We demonstrate that reduced uncertainties in the production rates can enhance the utility of 7Be and 10Be as tracers for evaluating transport and scavenging processes in global models.
Chiara I. Paleari, Florian Mekhaldi, Tobias Erhardt, Minjie Zheng, Marcus Christl, Florian Adolphi, Maria Hörhold, and Raimund Muscheler
Clim. Past, 19, 2409–2422, https://doi.org/10.5194/cp-19-2409-2023, https://doi.org/10.5194/cp-19-2409-2023, 2023
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In this study, we test the use of excess meltwater from continuous flow analysis from a firn core from Greenland for the measurement of 10Be for solar activity reconstructions. We show that the quality of results is similar to the measurements on clean firn, which opens the possibility to obtain continuous 10Be records without requiring large amounts of clean ice. Furthermore, we investigate the possibility of identifying solar storm signals in 10Be records from Greenland and Antarctica.
Tobias Erhardt, Camilla Marie Jensen, Florian Adolphi, Helle Astrid Kjær, Remi Dallmayr, Birthe Twarloh, Melanie Behrens, Motohiro Hirabayashi, Kaori Fukuda, Jun Ogata, François Burgay, Federico Scoto, Ilaria Crotti, Azzurra Spagnesi, Niccoló Maffezzoli, Delia Segato, Chiara Paleari, Florian Mekhaldi, Raimund Muscheler, Sophie Darfeuil, and Hubertus Fischer
Earth Syst. Sci. Data, 15, 5079–5091, https://doi.org/10.5194/essd-15-5079-2023, https://doi.org/10.5194/essd-15-5079-2023, 2023
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The presented paper provides a 3.8 kyr long dataset of aerosol concentrations from the East Greenland Ice coring Project (EGRIP) ice core. The data consists of 1 mm depth-resolution profiles of calcium, sodium, ammonium, nitrate, and electrolytic conductivity as well as decadal averages of these profiles. Alongside the data a detailed description of the measurement setup as well as a discussion of the uncertainties are given.
Giulia Sinnl, Florian Adolphi, Marcus Christl, Kees C. Welten, Thomas Woodruff, Marc Caffee, Anders Svensson, Raimund Muscheler, and Sune Olander Rasmussen
Clim. Past, 19, 1153–1175, https://doi.org/10.5194/cp-19-1153-2023, https://doi.org/10.5194/cp-19-1153-2023, 2023
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The record of past climate is preserved by several archives from different regions, such as ice cores from Greenland or Antarctica or speleothems from caves such as the Hulu Cave in China. In this study, these archives are aligned by taking advantage of the globally synchronous production of cosmogenic radionuclides. This produces a new perspective on the global climate in the period between 20 000 and 25 000 years ago.
Robert Mulvaney, Eric W. Wolff, Mackenzie M. Grieman, Helene H. Hoffmann, Jack D. Humby, Christoph Nehrbass-Ahles, Rachael H. Rhodes, Isobel F. Rowell, Frédéric Parrenin, Loïc Schmidely, Hubertus Fischer, Thomas F. Stocker, Marcus Christl, Raimund Muscheler, Amaelle Landais, and Frédéric Prié
Clim. Past, 19, 851–864, https://doi.org/10.5194/cp-19-851-2023, https://doi.org/10.5194/cp-19-851-2023, 2023
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We present an age scale for a new ice core drilled at Skytrain Ice Rise, an ice rise facing the Ronne Ice Shelf in Antarctica. Various measurements in the ice and air phases are used to match the ice core to other Antarctic cores that have already been dated, and a new age scale is constructed. The 651 m ice core includes ice that is confidently dated to 117 000–126 000 years ago, in the last interglacial. Older ice is found deeper down, but there are flow disturbances in the deeper ice.
Hongyue Zhang, Jesper Sjolte, Zhengyao Lu, Jian Liu, Weiyi Sun, and Lingfeng Wan
Clim. Past, 19, 665–680, https://doi.org/10.5194/cp-19-665-2023, https://doi.org/10.5194/cp-19-665-2023, 2023
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Based on proxy data and modeling, the Arctic temperature has an asymmetric cooling trend with more cooling over the Atlantic Arctic than the Pacific Arctic during the Holocene, dominated by orbital forcing. There is a seasonal difference in the asymmetric cooling trend, which is dominated by the DJF (December, January, and February) temperature variability. The Arctic dipole mode of sea level pressure and sea ice play a major role in asymmetric temperature changes.
Jakob Schwander, Thomas F. Stocker, Remo Walther, and Samuel Marending
The Cryosphere, 17, 1151–1164, https://doi.org/10.5194/tc-17-1151-2023, https://doi.org/10.5194/tc-17-1151-2023, 2023
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RADIX (Rapid Access Drilling and Ice eXtraction) is a fast-access ice-drilling system for prospecting future deep-drilling sites on glaciers and polar ice sheets. It consists of a 40 mm rapid firn drill, a 20 mm deep drill and a logger. The maximum depth range of RADIX is 3100 m by design. The nominal drilling speed is on the order of 40 m h-1. The 15 mm diameter logger provides data on the hole inclination and direction and measures temperature and dust in the ice surrounding the borehole.
Erica Jaakkola, Antje Gärtner, Anna Maria Jönsson, Karl Ljung, Per-Ola Olsson, and Thomas Holst
Biogeosciences, 20, 803–826, https://doi.org/10.5194/bg-20-803-2023, https://doi.org/10.5194/bg-20-803-2023, 2023
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Increased spruce bark beetle outbreaks were recently seen in Sweden. When Norway spruce trees are attacked, they increase their production of VOCs, attempting to kill the beetles. We provide new insights into how the Norway spruce act when infested and found the emitted volatiles to increase up to 700 times and saw a change in compound blend. We estimate that the 2020 bark beetle outbreak in Sweden could have increased the total monoterpene emissions from the forest by more than 10 %.
Petter L. Hällberg, Frederik Schenk, Kweku A. Yamoah, Xueyuen Kuang, and Rienk H. Smittenberg
Clim. Past, 18, 1655–1674, https://doi.org/10.5194/cp-18-1655-2022, https://doi.org/10.5194/cp-18-1655-2022, 2022
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Using climate model simulations, we find that SE Asian tropical climate was strongly seasonal under Late Glacial conditions. During Northern Hemisphere winters, it was highly arid in this region that is today humid year-round. The seasonal aridity was driven by orbital forcing and stronger East Asian winter monsoon. A breakdown of deep convection caused a reorganized Walker Circulation and a mean state resembling El Niño conditions.
Janica C. Bühler, Josefine Axelsson, Franziska A. Lechleitner, Jens Fohlmeister, Allegra N. LeGrande, Madhavan Midhun, Jesper Sjolte, Martin Werner, Kei Yoshimura, and Kira Rehfeld
Clim. Past, 18, 1625–1654, https://doi.org/10.5194/cp-18-1625-2022, https://doi.org/10.5194/cp-18-1625-2022, 2022
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We collected and standardized the output of five isotope-enabled simulations for the last millennium and assess differences and similarities to records from a global speleothem database. Modeled isotope variations mostly arise from temperature differences. While lower-resolution speleothems do not capture extreme changes to the extent of models, they show higher variability on multi-decadal timescales. As no model excels in all comparisons, we advise a multi-model approach where possible.
Giulia Sinnl, Mai Winstrup, Tobias Erhardt, Eliza Cook, Camilla Marie Jensen, Anders Svensson, Bo Møllesøe Vinther, Raimund Muscheler, and Sune Olander Rasmussen
Clim. Past, 18, 1125–1150, https://doi.org/10.5194/cp-18-1125-2022, https://doi.org/10.5194/cp-18-1125-2022, 2022
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A new Greenland ice-core timescale, covering the last 3800 years, was produced using the machine learning algorithm StratiCounter. We synchronized the ice cores using volcanic eruptions and wildfires. We compared the new timescale to the tree-ring timescale, finding good alignment both between the common signatures of volcanic eruptions and of solar activity. Our Greenlandic timescales is safe to use for the Late Holocene, provided one uses our uncertainty estimate.
Santos J. González-Rojí, Martina Messmer, Christoph C. Raible, and Thomas F. Stocker
Geosci. Model Dev., 15, 2859–2879, https://doi.org/10.5194/gmd-15-2859-2022, https://doi.org/10.5194/gmd-15-2859-2022, 2022
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Different configurations of physics parameterizations of a regional climate model are tested over southern Peru at fine resolution. The most challenging regions compared to observational data are the slopes of the Andes. Model configurations for Europe and East Africa are not perfectly suitable for southern Peru. The experiment with the Stony Brook University microphysics scheme and the Grell–Freitas cumulus parameterization provides the most accurate results over Madre de Dios.
Tobias Erhardt, Matthias Bigler, Urs Federer, Gideon Gfeller, Daiana Leuenberger, Olivia Stowasser, Regine Röthlisberger, Simon Schüpbach, Urs Ruth, Birthe Twarloh, Anna Wegner, Kumiko Goto-Azuma, Takayuki Kuramoto, Helle A. Kjær, Paul T. Vallelonga, Marie-Louise Siggaard-Andersen, Margareta E. Hansson, Ailsa K. Benton, Louise G. Fleet, Rob Mulvaney, Elizabeth R. Thomas, Nerilie Abram, Thomas F. Stocker, and Hubertus Fischer
Earth Syst. Sci. Data, 14, 1215–1231, https://doi.org/10.5194/essd-14-1215-2022, https://doi.org/10.5194/essd-14-1215-2022, 2022
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The datasets presented alongside this manuscript contain high-resolution concentration measurements of chemical impurities in deep ice cores, NGRIP and NEEM, from the Greenland ice sheet. The impurities originate from the deposition of aerosols to the surface of the ice sheet and are influenced by source, transport and deposition processes. Together, these records contain detailed, multi-parameter records of past climate variability over the last glacial period.
Jiamei Lin, Anders Svensson, Christine S. Hvidberg, Johannes Lohmann, Steffen Kristiansen, Dorthe Dahl-Jensen, Jørgen Peder Steffensen, Sune Olander Rasmussen, Eliza Cook, Helle Astrid Kjær, Bo M. Vinther, Hubertus Fischer, Thomas Stocker, Michael Sigl, Matthias Bigler, Mirko Severi, Rita Traversi, and Robert Mulvaney
Clim. Past, 18, 485–506, https://doi.org/10.5194/cp-18-485-2022, https://doi.org/10.5194/cp-18-485-2022, 2022
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We employ acidity records from Greenland and Antarctic ice cores to estimate the emission strength, frequency and climatic forcing for large volcanic eruptions from the last half of the last glacial period. A total of 25 volcanic eruptions are found to be larger than any eruption in the last 2500 years, and we identify more eruptions than obtained from geological evidence. Towards the end of the glacial period, there is a notable increase in volcanic activity observed for Greenland.
Tanya J. R. Lippmann, Michiel H. in 't Zandt, Nathalie N. L. Van der Putten, Freek S. Busschers, Marc P. Hijma, Pieter van der Velden, Tim de Groot, Zicarlo van Aalderen, Ove H. Meisel, Caroline P. Slomp, Helge Niemann, Mike S. M. Jetten, Han A. J. Dolman, and Cornelia U. Welte
Biogeosciences, 18, 5491–5511, https://doi.org/10.5194/bg-18-5491-2021, https://doi.org/10.5194/bg-18-5491-2021, 2021
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This paper is a step towards understanding the basal peat ecosystem beneath the North Sea. Plant remains followed parallel sequences. Methane concentrations were low with local exceptions, with the source likely being trapped pockets of millennia-old methane. Microbial community structure indicated the absence of a biofilter and was diverse across sites. Large carbon stores in the presence of methanogens and in the absence of methanotrophs have the potential to be metabolized into methane.
Frerk Pöppelmeier, David J. Janssen, Samuel L. Jaccard, and Thomas F. Stocker
Biogeosciences, 18, 5447–5463, https://doi.org/10.5194/bg-18-5447-2021, https://doi.org/10.5194/bg-18-5447-2021, 2021
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Chromium (Cr) is a redox-sensitive element that holds promise as a tracer of ocean oxygenation and biological activity. We here implemented the oxidation states Cr(III) and Cr(VI) in the Bern3D model to investigate the processes that shape the global Cr distribution. We find a Cr ocean residence time of 5–8 kyr and that the benthic source dominates the tracer budget. Further, regional model–data mismatches suggest strong Cr removal in oxygen minimum zones and a spatially variable benthic source.
Loïc Schmidely, Christoph Nehrbass-Ahles, Jochen Schmitt, Juhyeong Han, Lucas Silva, Jinwha Shin, Fortunat Joos, Jérôme Chappellaz, Hubertus Fischer, and Thomas F. Stocker
Clim. Past, 17, 1627–1643, https://doi.org/10.5194/cp-17-1627-2021, https://doi.org/10.5194/cp-17-1627-2021, 2021
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Using ancient gas trapped in polar glaciers, we reconstructed the atmospheric concentrations of methane and nitrous oxide over the penultimate deglaciation to study their response to major climate changes. We show this deglaciation to be characterized by modes of methane and nitrous oxide variability that are also found during the last deglaciation and glacial cycle.
Nathalie Van der Putten, Florian Adolphi, Anette Mellström, Jesper Sjolte, Cyriel Verbruggen, Jan-Berend Stuut, Tobias Erhardt, Yves Frenot, and Raimund Muscheler
Clim. Past Discuss., https://doi.org/10.5194/cp-2021-69, https://doi.org/10.5194/cp-2021-69, 2021
Manuscript not accepted for further review
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In recent decades, Southern Hemisphere westerlies (SHW) moved equator-ward during periods of low solar activity leading to increased winds/precipitation at 46° S, Indian Ocean. We present a terrestrial SHW proxy-record and find stronger SHW influence at Crozet, shortly after 2.8 ka BP, synchronous with a climate shift in the Northern Hemisphere, attributed to a major decline in solar activity. The bipolar response to solar forcing is supported by a climate model forced by solar irradiance only.
Martina Messmer, Santos J. González-Rojí, Christoph C. Raible, and Thomas F. Stocker
Geosci. Model Dev., 14, 2691–2711, https://doi.org/10.5194/gmd-14-2691-2021, https://doi.org/10.5194/gmd-14-2691-2021, 2021
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Sensitivity experiments with the WRF model are run to find an optimal parameterization setup for precipitation around Mount Kenya at a scale that resolves convection (1 km). Precipitation is compared against many weather stations and gridded observational data sets. Both the temporal correlation of precipitation sums and pattern correlations show that fewer nests lead to a more constrained simulation with higher correlation. The Grell–Freitas cumulus scheme obtains the most accurate results.
Frerk Pöppelmeier, Jeemijn Scheen, Aurich Jeltsch-Thömmes, and Thomas F. Stocker
Clim. Past, 17, 615–632, https://doi.org/10.5194/cp-17-615-2021, https://doi.org/10.5194/cp-17-615-2021, 2021
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The stability of the Atlantic Meridional Overturning Circulation (AMOC) critically depends on its mean state. We simulate the response of the AMOC to North Atlantic freshwater perturbations under different glacial boundary conditions. We find that a closed Bering Strait greatly increases the AMOC's sensitivity to freshwater hosing. Further, the shift from mono- to bistability strongly depends on the chosen boundary conditions, with weaker circulation states exhibiting more abrupt transitions.
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Short summary
Southern Hemisphere westerlies play a key role in regulating global climate. A lake sediment record on a mid-South Atlantic island shows changes in the westerlies and hydroclimate 36.4–18.6 ka. Before 31 ka the westerlies shifted in concert with the bipolar seesaw mechanism in a fairly warm climate, followed by southerly westerlies and falling temperatures. After 27.5 ka temperatures dropped 3 °C with drier conditions and with shifting westerlies possibly triggering the variable LGM CO2 levels.
Southern Hemisphere westerlies play a key role in regulating global climate. A lake sediment...
