Articles | Volume 22, issue 16
https://doi.org/10.5194/bg-22-4187-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-22-4187-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| Highlight paper
| 
26 Aug 2025
Research article | Highlight paper |
| 26 Aug 2025
| 26 Aug 2025
Southern Hemisphere tree rings as proxies to reconstruct Southern Ocean upwelling
Earth Sciences New Zealand (formerly at GNS Science), Rafter Radiocarbon Laboratory, Te Awa Kairangi ki Tai / Lower Hutt, Aotearoa / New Zealand
Rachel Corran
Earth Sciences New Zealand (formerly at GNS Science), Rafter Radiocarbon Laboratory, Te Awa Kairangi ki Tai / Lower Hutt, Aotearoa / New Zealand
Sara E. Mikaloff-Fletcher
Earth Sciences New Zealand (formerly National Institute of Water and Atmospheric Research – NIWA), Te Whanganui-a-Tara / Wellington, Aotearoa / New Zealand
Erik Behrens
Earth Sciences New Zealand (formerly National Institute of Water and Atmospheric Research – NIWA), Te Whanganui-a-Tara / Wellington, Aotearoa / New Zealand
Rowena Moss
Earth Sciences New Zealand (formerly National Institute of Water and Atmospheric Research – NIWA), Te Whanganui-a-Tara / Wellington, Aotearoa / New Zealand
Gordon Brailsford
Earth Sciences New Zealand (formerly National Institute of Water and Atmospheric Research – NIWA), Te Whanganui-a-Tara / Wellington, Aotearoa / New Zealand
Andrew Lorrey
Earth Sciences New Zealand (formerly National Institute of Water and Atmospheric Research – NIWA), Te Whanganui-a-Tara / Wellington, Aotearoa / New Zealand
Margaret Norris
Earth Sciences New Zealand (formerly at GNS Science), Rafter Radiocarbon Laboratory, Te Awa Kairangi ki Tai / Lower Hutt, Aotearoa / New Zealand
Jocelyn Turnbull
Earth Sciences New Zealand (formerly at GNS Science), Rafter Radiocarbon Laboratory, Te Awa Kairangi ki Tai / Lower Hutt, Aotearoa / New Zealand
CIRES, University of Colorado at Boulder, Boulder, Colorado, USA
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Olga Albot, Joshua Ratcliffe, Richard Levy, Sebastian Naeher, Daniel King, Catherine Ginnane, Jocelyn Turnbull, Mary Jill Ira Banta, Christopher Wood, Jenny Dahl, Jannine Cooper, and Andy Phillips
EGUsphere, https://doi.org/10.5194/egusphere-2025-2949, https://doi.org/10.5194/egusphere-2025-2949, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
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Saltmarshes store carbon in their soils, contributing to climate change mitigation. We analysed five sites across Aotearoa New Zealand and found that carbon storage varies widely with land use and sediment inputs. Plant material was a major source of carbon in the soil and has been preserved for several centuries. Restoration increased soil carbon accumulation at two sites. These results improve national blue carbon estimates and highlight the role of saltmarshes as natural climate solutions.
Beata Bukosa, Sara Mikaloff-Fletcher, Gordon Brailsford, Dan Smale, Elizabeth D. Keller, W. Troy Baisden, Miko U. F. Kirschbaum, Donna L. Giltrap, Lìyǐn Liáng, Stuart Moore, Rowena Moss, Sylvia Nichol, Jocelyn Turnbull, Alex Geddes, Daemon Kennett, Dóra Hidy, Zoltán Barcza, Louis A. Schipper, Aaron M. Wall, Shin-Ichiro Nakaoka, Hitoshi Mukai, and Andrea Brandon
Atmos. Chem. Phys., 25, 6445–6473, https://doi.org/10.5194/acp-25-6445-2025, https://doi.org/10.5194/acp-25-6445-2025, 2025
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We used atmospheric measurements and inverse modelling to estimate New Zealand's carbon dioxide (CO2) emissions and removals from 2011 to 2020. Our study reveals that New Zealand's land absorbs more CO2 than previously estimated, particularly in areas dominated by indigenous forests. Our results highlight gaps in current national CO2 estimates and methods, suggesting a need for further research to improve emissions reports and refine approaches to track progress toward climate mitigation goals.
Bibhasvata Dasgupta, Malika Menoud, Carina van der Veen, Ingeborg Levin, Cora Veidt, Heiko Moossen, Sylvia Englund Michel, Peter Sperlich, Shinji Morimoto, Ryo Fujita, Taku Umezawa, Stephen Matthew Platt, Christine Groot Zwaaftink, Cathrine Lund Myhre, Rebecca Fisher, David Lowry, Euan Nisbet, James France, Ceres Woolley Maisch, Gordon Brailsford, Rowena Moss, Daisuke Goto, Sudhanshu Pandey, Sander Houweling, Nicola Warwick, and Thomas Röckmann
EGUsphere, https://doi.org/10.5194/egusphere-2025-2439, https://doi.org/10.5194/egusphere-2025-2439, 2025
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We combined long-term methane mole fraction and isotope measurements from eight laboratories that sample high-latitude stations to compare, offset correct and harmonise the datasets into a hemisphere merged timeseries. Because each laboratory uses slightly different methods, we adjusted the data to make it directly comparable. This allowed us to create a consistent record of atmospheric methane concentration and its isotopes from 1988 to 2023.
Marjolaine Verret, Sebastian Naeher, Denis Lacelle, Catherine Ginnane, Warren Dickinson, Kevin Norton, Jocelyn Turnbull, and Richard Levy
EGUsphere, https://doi.org/10.5194/egusphere-2025-786, https://doi.org/10.5194/egusphere-2025-786, 2025
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15 million years ago, the McMurdo Dry Valleys of Antarctica were dominated by a tundra environment. In contrast, the modern environment is amongst the coldest and driest on Earth. Using a permafrost core, this paper investigates the shift from a tundra- to a bacteria-dominated landscape. By differentiating between ancient and modern organic material, we further our understanding of preservation of ancient organic material and its response and contribution to future climate change.
Christopher J. Roach, Joao Marcos A. C. de Souza, Erik Behrens, and Stephen J. Stuart
EGUsphere, https://doi.org/10.5194/egusphere-2024-1962, https://doi.org/10.5194/egusphere-2024-1962, 2024
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We have used a 5 km regional ocean model for New Zealand forced with a coarser resolution global model to project changes in under medium and high emissions scenarios. This is necessary since the global model is unable to resolve the small scale processes on the continental shelf which determine climate change may influence fisheries and aquaculture. We see the upper ocean warms at similar rates all around New Zealand, but that the deep ocean shows more rapid warming in the west and south.
Yusuf A. Bhatti, Laura E. Revell, Alex J. Schuddeboom, Adrian J. McDonald, Alex T. Archibald, Jonny Williams, Abhijith U. Venugopal, Catherine Hardacre, and Erik Behrens
Atmos. Chem. Phys., 23, 15181–15196, https://doi.org/10.5194/acp-23-15181-2023, https://doi.org/10.5194/acp-23-15181-2023, 2023
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Aerosols are a large source of uncertainty over the Southern Ocean. A dominant source of sulfate aerosol in this region is dimethyl sulfide (DMS), which is poorly simulated by climate models. We show the sensitivity of simulated atmospheric DMS to the choice of oceanic DMS data set and emission scheme. We show that oceanic DMS has twice the influence on atmospheric DMS than the emission scheme. Simulating DMS more accurately in climate models will help to constrain aerosol uncertainty.
Jonny Williams, Erik Behrens, Olaf Morgenstern, Peter Gibson, and Joao Teixeira
EGUsphere, https://doi.org/10.5194/egusphere-2023-1694, https://doi.org/10.5194/egusphere-2023-1694, 2023
Preprint withdrawn
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We use open-source cyclone tracking software and state-of-the-art climate models to characterise present-day tropical cyclones – TCs – in the South Pacific before moving on to estimate how they may change in the future. A robust result of this work is the projection of future intensification of TCs. However, the question of their future occurrence frequency is less clear. Under extreme future warming scenarios, we postulate a possible increase in power dissipation per TC of up to 25 %.
Georgia R. Grant, Jonny H. T. Williams, Sebastian Naeher, Osamu Seki, Erin L. McClymont, Molly O. Patterson, Alan M. Haywood, Erik Behrens, Masanobu Yamamoto, and Katelyn Johnson
Clim. Past, 19, 1359–1381, https://doi.org/10.5194/cp-19-1359-2023, https://doi.org/10.5194/cp-19-1359-2023, 2023
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Regional warming will differ from global warming, and climate models perform poorly in the Southern Ocean. We reconstruct sea surface temperatures in the south-west Pacific during the mid-Pliocene, a time 3 million years ago that represents the long-term outcomes of 3 °C warming, which is expected for the future. Comparing these results to climate model simulations, we show that the south-west Pacific region will warm by 1 °C above the global average if atmospheric CO2 remains above 350 ppm.
Peter Sperlich, Gordon W. Brailsford, Rowena C. Moss, John McGregor, Ross J. Martin, Sylvia Nichol, Sara Mikaloff-Fletcher, Beata Bukosa, Magda Mandic, C. Ian Schipper, Paul Krummel, and Alan D. Griffiths
Atmos. Meas. Tech., 15, 1631–1656, https://doi.org/10.5194/amt-15-1631-2022, https://doi.org/10.5194/amt-15-1631-2022, 2022
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We tested an in situ analyser for carbon and oxygen isotopes in atmospheric CO2 at Baring Head, New Zealand’s observatory for Southern Ocean baseline air. The analyser was able to resolve regional signals of the terrestrial carbon cycle, although the analysis of small events was limited by analytical uncertainty. Further improvement of the instrument performance would be desirable for the robust analysis of distant signals and to resolve the small variability in Southern Ocean baseline air.
Regina Gonzalez Moguel, Felix Vogel, Sébastien Ars, Hinrich Schaefer, Jocelyn C. Turnbull, and Peter M. J. Douglas
Atmos. Chem. Phys., 22, 2121–2133, https://doi.org/10.5194/acp-22-2121-2022, https://doi.org/10.5194/acp-22-2121-2022, 2022
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Evaluating methane (CH4) sources in the Athabasca oil sands region (AOSR) is crucial to effectively mitigate CH4 emissions. We tested the use of carbon isotopes to estimate source contributions from key CH4 sources in the AOSR and found that 56 ± 18 % of CH4 emissions originated from surface mining and processing facilities, 34 ± 18 % from tailings ponds, and 10 ± < 1 % from wetlands, confirming previous findings and showing that this method can be successfully used to partition CH4 sources.
Brian Nathan, Stefanie Kremser, Sara Mikaloff-Fletcher, Greg Bodeker, Leroy Bird, Ethan Dale, Dongqi Lin, Gustavo Olivares, and Elizabeth Somervell
Atmos. Chem. Phys., 21, 14089–14108, https://doi.org/10.5194/acp-21-14089-2021, https://doi.org/10.5194/acp-21-14089-2021, 2021
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The MAPM project showcases a method to improve estimates of PM2.5 emissions through an advanced statistical technique that is still new to the aerosol community. Using Christchurch, NZ, as a test bed, measurements from a field campaign in winter 2019 are incorporated into this new approach. An overestimation from local inventory estimates is identified. This technique may be exported to other urban areas in need.
Laia Comas-Bru, Kira Rehfeld, Carla Roesch, Sahar Amirnezhad-Mozhdehi, Sandy P. Harrison, Kamolphat Atsawawaranunt, Syed Masood Ahmad, Yassine Ait Brahim, Andy Baker, Matthew Bosomworth, Sebastian F. M. Breitenbach, Yuval Burstyn, Andrea Columbu, Michael Deininger, Attila Demény, Bronwyn Dixon, Jens Fohlmeister, István Gábor Hatvani, Jun Hu, Nikita Kaushal, Zoltán Kern, Inga Labuhn, Franziska A. Lechleitner, Andrew Lorrey, Belen Martrat, Valdir Felipe Novello, Jessica Oster, Carlos Pérez-Mejías, Denis Scholz, Nick Scroxton, Nitesh Sinha, Brittany Marie Ward, Sophie Warken, Haiwei Zhang, and SISAL Working Group members
Earth Syst. Sci. Data, 12, 2579–2606, https://doi.org/10.5194/essd-12-2579-2020, https://doi.org/10.5194/essd-12-2579-2020, 2020
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This paper presents an updated version of the SISAL (Speleothem Isotope Synthesis and Analysis) database. This new version contains isotopic data from 691 speleothem records from 294 cave sites and new age–depth models, including their uncertainties, for 512 speleothems.
Haeyoung Lee, Edward J. Dlugokencky, Jocelyn C. Turnbull, Sepyo Lee, Scott J. Lehman, John B. Miller, Gabrielle Pétron, Jeong-Sik Lim, Gang-Woong Lee, Sang-Sam Lee, and Young-San Park
Atmos. Chem. Phys., 20, 12033–12045, https://doi.org/10.5194/acp-20-12033-2020, https://doi.org/10.5194/acp-20-12033-2020, 2020
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To understand South Korea's CO2 emissions and sinks as well as those of the surrounding region, we used flask-air samples collected for 2 years at Anmyeondo (36.53° N, 126.32° E; 46 m a.s.l.), South Korea, for analysis of observed 14C in atmospheric CO2 as a tracer of fossil fuel CO2 contribution (Cff). Here, we showed our observation result of 14C and Cff. SF6 and CO can be good proxies of Cff in this study, and the ratio of CO to Cff was compared to a bottom-up inventory.
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Co-editor-in-chief
This study combines an impressive dataset of tree ring radiocarbon measurements to quantify the balance between upwelling-related CO2 degassing from and CO2 uptake by the Southern Ocean, which is a crucial flux of of carbon between atmosphere and ocean and an important component of our climate system. These results benefit the broad climatology community both for its approach and for its important conclusions about the latitudinal variability in CO2 flux in the Southern Ocean.
This study combines an impressive dataset of tree ring radiocarbon measurements to quantify the...
Short summary
The Southern Ocean carbon sink is a balance between two opposing forces: CO2 absorption at mid-latitudes and CO2 outgassing at high latitudes. Radiocarbon analysis can be used to constrain the latter, as upwelling waters outgas old CO2, diluting atmospheric radiocarbon content. We present tree-ring radiocarbon measurements from Aotearoa / New Zealand and Chile. We show that low radiocarbon in Aotearoa / New Zealand’s Motu Ihupuku / Campbell Island is linked to outgassing in the critical Antarctic Southern Zone.
The Southern Ocean carbon sink is a balance between two opposing forces: CO2 absorption at...
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