Abstract
Constraining the causes of past atmospheric methane variability is important for understanding links between methane and climate. Abrupt methane changes during the last deglaciation have been intensely studied for this purpose, but the relative importance of high-latitude and tropical sources remains poorly constrained. The methane interpolar concentration difference reflects past geographic emission variability, but existing records suffered from subtle but considerable methane production during analysis. Here, we report an ice-core-derived interpolar difference record covering the Last Glacial Maximum and deglaciation, with substantially improved temporal resolution, chronology and a critical correction for methane production in samples from Greenland. Using box models to infer latitudinal source changes, we show that tropical sources dominated abrupt methane variability of the deglaciation, highlighting their sensitivity to abrupt climate change and rapidly shifting tropical rainfall patterns. Northern extratropical emissions began increasing ~16,000 years ago, probably through wetland expansion and/or permafrost degradation induced by high-latitude warming, and contributed at most 25 Tg yr−1 (45% of the total emission increase) to the abrupt methane rise that coincided with rapid northern warming at the onset of the Bølling–Allerød interval. These constraints on deglacial climate–methane cycle interactions can improve the understanding of possible present and future feedbacks.
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Data availability
The [CH4], rIPD and box-model data are published on the Arctic Data Center, US Antarctic Program Data Center (USAP DC) and NOAA National Climatic Data Center. NEEM [CH4], WD [CH4] and GISP2 [CH4] data are publicly available and archived at https://doi.org/10.18739/A2ZC7RW3H and USAP DC 601737, the new CH4,xs data are archived at https://doi.org/10.18739/A2TM7229J, and the GISP2- and NEEM-derived rIPD results and four-box-model output are archived at https://doi.org/10.18739/A2PZ51N77 and USAP DC 601736. Additional GISP2 [CH4] data are archived at https://doi.org/10.18739/A2639K65M. Source data are provided with this paper.
Code availability
The code and data used to calculate the GISP2- and NEEM-derived rIPD records, run the four-box model and plot the results in Figs. 1–3 are archived and publicly available on Github at https://github.com/benryoung23/Riddell-Young_etal_2023.git.
Change history
02 January 2024
A Correction to this paper has been published: https://doi.org/10.1038/s41561-023-01370-5
References
Saunois, M. et al. The global methane budget 2000–2017. Earth Syst. Sci. Data 12, 1561–1623 (2020).
Feng, L., Palmer, P. I., Parker, R. J., Lunt, M. F. & Bösch, H. Methane emissions are predominantly responsible for record-breaking atmospheric methane growth rates in 2020 and 2021. Atmos. Chem. Phys. 23, 4863–4880 (2023).
Dean, J. F. et al. Methane feedbacks to the global climate system in a warmer world. Rev. Geophys. 56, 207–250 (2018).
Schuur, E. A. et al. Climate change and the permafrost carbon feedback. Nature 520, 171–179 (2015).
Ruppel, C. D. & Kessler, J. D. The interaction of climate change and methane hydrates. Rev. Geophys. 55, 126–168 (2017).
Cheng, C.-H. & Redfern, S. A. Impact of interannual and multidecadal trends on methane–climate feedbacks and sensitivity. Nat. Commun. 13, 3592 (2022).
Kleinen, T., Gromov, S., Steil, B. & Brovkin, V. Atmospheric methane underestimated in future climate projections. Environ. Res. Lett. 16, 094006 (2021).
Chappellaz, J., Barnola, J., Raynaud, D., Korotkevich, Y. S. & Lorius, C. Ice-core record of atmospheric methane over the past 160,000 years. Nature 345, 127–131 (1990).
Brook, E. J., Harder, S., Severinghaus, J., Steig, E. J. & Sucher, C. M. On the origin and timing of rapid changes in atmospheric methane during the last glacial period. Glob. Biogeochem. Cycles 14, 559–572 (2000).
Loulergue, L. et al. Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years. Nature 453, 383–386 (2008).
Bock, M. et al. Glacial/interglacial wetland, biomass burning, and geologic methane emissions constrained by dual stable isotopic CH4 ice core records. Proc. Natl Acad. Sci. USA 114, E5778–E5786 (2017).
Baumgartner, M. et al. High-resolution interpolar difference of atmospheric methane around the Last Glacial Maximum. Biogeosciences 9, 3961–3977 (2012).
Buizert, C. et al. The WAIS divide deep ice core WD2014 chronology—part 1: methane synchronization (68–31 ka BP) and the gas age–ice age difference. Clim. Past 11, 153-173 (2015).
Brook, E. J., Harder, S., Severinghaus, J. & Bender, M. Atmospheric methane and millennial-scale climate change. Geophys. Monogr. Ser. 112, 165–176 (1999).
Möller, L. et al. Independent variations of CH4 emissions and isotopic composition over the past 160,000 years. Nat. Geosci. 6, 885–890 (2013).
Hopcroft, P. O., Valdes, P. J., O’Connor, F. M., Kaplan, J. O. & Beerling, D. J. Understanding the glacial methane cycle. Nat. Commun. 8, 14383 (2017).
Rasmussen, S. O. et al. A stratigraphic framework for abrupt climatic changes during the last glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event stratigraphy. Quat. Sci. Rev. 106, 14–28 (2014).
Sherwood, O. A., Schwietzke, S., Arling, V. A. & Etiope, G. Global inventory of gas geochemistry data from fossil fuel, microbial and burning sources, version 2017. Earth Syst. Sci. Data 9, 639–656 (2017).
Sowers, T. Late quaternary atmospheric CH4 isotope record suggests marine clathrates are stable. Science 311, 838–840 (2006).
Bock, M. et al. Hydrogen isotopes preclude marine hydrate CH4 emissions at the onset of Dansgaard–Oeschger events. Science 328, 1686–1689 (2010).
Fischer, H. et al. Changing boreal methane sources and constant biomass burning during the last termination. Nature 452, 864–867 (2008).
Dyonisius, M. et al. Old carbon reservoirs were not important in the deglacial methane budget. Science 367, 907–910 (2020).
Petrenko, V. V. et al. Minimal geological methane emissions during the Younger Dryas–Preboreal abrupt warming event. Nature 548, 443–446 (2017).
Levine, J., Wolff, E., Hopcroft, P. O. & Valdes, P. J. Controls on the tropospheric oxidizing capacity during an idealized Dansgaard–Oeschger event, and their implications for the rapid rises in atmospheric methane during the last glacial period. Geophys. Res. Lett. 39, L12805 (2012).
Hmiel, B. et al. Preindustrial 14CH4 indicates greater anthropogenic fossil CH4 emissions. Nature 578, 409–412 (2020).
Weber, S., Drury, A., Toonen, W. & Van Weele, M. Wetland methane emissions during the Last Glacial Maximum estimated from PMIP2 simulations: climate, vegetation, and geographic controls. J. Geophys. Res. Atmos. 115, D06111 (2010).
Ringeval, B. et al. Response of methane emissions from wetlands to the Last Glacial Maximum and an idealized Dansgaard–Oeschger climate event: insights from two models of different complexity. Clim. Past 9, 149–171 (2013).
Kleinen, T., Mikolajewicz, U. & Brovkin, V. Terrestrial methane emissions from the Last Glacial Maximum to the preindustrial period. Clim. Past 16, 575–595 (2020).
Chappellaz, J. et al. Changes in the atmospheric CH4 gradient between Greenland and Antarctica during the Holocene. J. Geophys. Res. Atmos. 102, 15987–15997 (1997).
Rasmussen, R. A. & Khalil, M. Atmospheric methane in the recent and ancient atmospheres: concentrations, trends, and interhemispheric gradient. J. Geophys. Res. Atmos. 89, 11599–11605 (1984).
Dällenbach, A. et al. Changes in the atmospheric CH4 gradient between Greenland and Antarctica during the Last Glacial and the transition to the Holocene. Geophys. Res. Lett. 27, 1005–1008 (2000).
Mitchell, L., Brook, E., Lee, J. E., Buizert, C. & Sowers, T. Constraints on the late Holocene anthropogenic contribution to the atmospheric methane budget. Science 342, 964–966 (2013).
Beck, J. et al. Bipolar carbon and hydrogen isotope constraints on the Holocene methane budget. Biogeosciences 15, 7155–7175 (2018).
Yang, J.-W., Ahn, J., Brook, E. J. & Ryu, Y. Atmospheric methane control mechanisms during the early Holocene. Clim. Past 13, 1227–1242 (2017).
Lee, J. E. et al. Excess methane in Greenland ice cores associated with high dust concentrations. Geochim. Cosmochim. Acta 270, 409–430 (2020).
Legrand, M., Lorius, C., Barkov, N. & Petrov, V. Vostok (Antarctica) ice core: atmospheric chemistry changes over the last climatic cycle (160,000 years). Atmos. Environ. 22, 317–331 (1988).
Fung, I. et al. Three‐dimensional model synthesis of the global methane cycle. J. Geophys. Res. Atmos. 96, 13033–13065 (1991).
Brook, E. J., Sowers, T. & Orchardo, J. Rapid variations in atmospheric methane concentration during the past 110,000 years. Science 273, 1087–1091 (1996).
Valdes, P. J., Beerling, D. J. & Johnson, C. E. The ice age methane budget. Geophys. Res. Lett. 32, L02704 (2005).
Cheng, H. et al. Climate variations of Central Asia on orbital to millennial timescales. Sci. Rep. 6, 36975 (2016).
Seltzer, A. M. et al. Does δ18O of O2 record meridional shifts in tropical rainfall? Clim. Past 13, 1323–1338 (2017).
Wang, X. et al. Millennial‐scale precipitation changes in southern Brazil over the past 90,000 years. Geophys. Res. Lett. 34, L23701 (2007).
Kanner, L. C., Burns, S. J., Cheng, H. & Edwards, R. L. High-latitude forcing of the South American summer monsoon during the last glacial. Science 335, 570–573 (2012).
Rhodes, R. H. et al. Enhanced tropical methane production in response to iceberg discharge in the North Atlantic. Science 348, 1016–1019 (2015).
Bard, E., Rostek, F., Turon, J.-L. & Gendreau, S. Hydrological impact of Heinrich events in the subtropical northeast Atlantic. Science 289, 1321–1324 (2000).
Salgueiro, E. et al. Past circulation along the western Iberian margin: a time slice vision from the last glacial to the Holocene. Quat. Sci. Rev. 106, 316–329 (2014).
Johnsen, S. J. et al. Oxygen isotope and palaeotemperature records from six Greenland ice‐core stations: Camp Century, Dye‐3, GRIP, GISP2, Renland and NorthGRIP. J. Quat. Sci. 16, 299–307 (2001).
Cruz, F. W. et al. Insolation-driven changes in atmospheric circulation over the past 116,000 years in subtropical Brazil. Nature 434, 63–66 (2005).
Berger, A. Long-term variations of daily insolation and Quaternary climatic changes. J. Atmos. Sci. 35, 2362–2367 (1978).
Clark, P. U. et al. Global climate evolution during the last deglaciation. Proc. Natl Acad. Sci. USA 109, E1134–E1142 (2012).
Thirumalai, K., Clemens, S. C. & Partin, J. W. Methane, monsoons, and modulation of millennial‐scale climate. Geophys. Res. Lett. 47, e2020GL087613 (2020).
Clark, P. U., Alley, R. B. & Pollard, D. Northern Hemisphere ice-sheet influences on global climate change. Science 286, 1104–1111 (1999).
Broecker, W. S. Paleocean circulation during the last deglaciation: a bipolar seesaw? Paleoceanography 13, 119–121 (1998).
Kleinen, T., Gromov, S., Steil, B. & Brovkin, V. Atmospheric methane since the Last Glacial Maximum was driven by wetland sources. Clim. Past 19, 1081–1099 (2023).
Cheng, H., Sinha, A., Wang, X., Cruz, F. W. & Edwards, R. L. The global paleomonsoon as seen through speleothem records from Asia and the Americas. Clim. Dyn. 39, 1045–1062 (2012).
Buizert, C. et al. Greenland‐wide seasonal temperatures during the last deglaciation. Geophys. Res. Lett. 45, 1905–1914 (2018).
Denton, G. H., Alley, R. B., Comer, G. C. & Broecker, W. S. The role of seasonality in abrupt climate change. Quat. Sci. Rev. 24, 1159–1182 (2005).
Lambeck, K., Rouby, H., Purcell, A., Sun, Y. & Sambridge, M. Sea level and global ice volumes from the Last Glacial Maximum to the Holocene. Proc. Natl Acad. Sci. USA 111, 15296–15303 (2014).
Winterfeld, M. et al. Deglacial mobilization of pre-aged terrestrial carbon from degrading permafrost. Nat. Commun. 9, 3666 (2018).
Hopcroft, P. O., Valdes, P. J. & Kaplan, J. O. Bayesian analysis of the glacial–interglacial methane increase constrained by stable isotopes and Earth system modeling. Geophys. Res. Lett. 45, 3653–3663 (2018).
Buizert, C. et al. Precise interpolar phasing of abrupt climate change during the last ice age. Nature 520, 661–665 (2015).
Mayewski, P. A. et al. Major features and forcing of high‐latitude Northern Hemisphere atmospheric circulation using a 110,000‐year‐long glaciochemical series. J. Geophys. Res. Oceans 102, 26345–26366 (1997).
Schüpbach, S. et al. Greenland records of aerosol source and atmospheric lifetime changes from the Eemian to the Holocene. Nat. Commun. 9, 1476 (2018).
Martin, K. C. et al. Bipolar impact and phasing of Heinrich-type climate variability. Nature 617, 100–104 (2023).
Mitchell, L. E., Brook, E. J., Sowers, T., McConnell, J. R. & Taylor, K. Multidecadal variability of atmospheric methane, 1000–1800 CE. J. Geophys. Res. Biogeosci. 116, G02007 (2011).
Lee, J. E. et al. An 83 000-year-old ice core from Roosevelt Island, Ross Sea, Antarctica. Clim. Past 16, 1691–1713 (2020).
Buizert, C. et al. Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, northern Greenland. Atmos. Chem. Phys. 12, 4259–4277 (2012).
Seierstad, I. K. et al. Consistently dated records from the Greenland GRIP, GISP2 and NGRIP ice cores for the past 104 ka reveal regional millennial-scale δ18O gradients with possible Heinrich event imprint. Quat. Sci. Rev. 106, 29–46 (2014).
Mühl, M. et al. Methane, ethane, and propane production in Greenland ice core samples and a first isotopic characterization of excess methane. Clim. Past 19, 999–1025 (2023).
Buizert, C. et al. Antarctic surface temperature and elevation during the Last Glacial Maximum. Science 372, 1097–1101 (2021).
Schwander, J. & Stauffer, B. Age difference between polar ice and the air trapped in its bubbles. Nature 311, 45–47 (1984).
Rasmussen, S. O. et al. A first chronology for the North Greenland Eemian Ice Drilling (NEEM) ice core. Climate 9, 2713–2730 (2013).
Sigl, M. et al. The WAIS Divide deep ice core WD2014 chronology – Part 2: Annual-layer counting (0–31 ka BP). Clim. Past 12, 769–786 (2016).
Johnsen, S. Stable isotope homogenization of polar firn and ice. Isotopes Impurities Snow Ice 118, 210–219 (1977).
Simmonds, P. G. et al. The increasing atmospheric burden of the greenhouse gas sulfur hexafluoride (SF6). Atmos. Chem. Phys. 20, 7271–7290 (2020).
Rigby, M., Manning, A. & Prinn, R. Inversion of long-lived trace gas emissions using combined Eulerian and Lagrangian chemical transport models. Atmos. Chem. Phys. 11, 9887–9898 (2011).
Hall, B. et al. Improving measurements of SF6 for the study of atmospheric transport and emissions. Atmos. Meas. Tech. 4, 2441–2451 (2011).
Basu, S. et al. Estimating emissions of methane consistent with atmospheric measurements of methane and δ13C of methane. Atmos. Chem. Phys. 22, 15351–15377 (2022).
Lee, S.-Y., Chiang, J. C. H., Matsumoto, K. & Tokos, K. S. Southern Ocean wind response to North Atlantic cooling and the rise in atmospheric CO2: modeling perspective and paleoceanographic implications. Paleoceanography 26, PA1214 (2011).
Kaplan, J. O., Folberth, G. & Hauglustaine, D. A. Role of methane and biogenic volatile organic compound sources in late glacial and Holocene fluctuations of atmospheric methane concentrations. Global Biogeochem. Cycles 20, GB2016 (2006).
Levine, J. G., Wolff, E. W., Jones, A. E. & Sime, L. C. The role of atomic chlorine in glacial–interglacial changes in the carbon‐13 content of atmospheric methane. Geophys. Res. Lett. 38, L04801 (2011).
Murray, L. et al. Factors controlling variability in the oxidative capacity of the troposphere since the Last Glacial Maximum. Atmos. Chem. Phys. 14, 3589–3622 (2014).
Quiquet, A. et al. The relative importance of methane sources and sinks over the last interglacial period and into the last glaciation. Quat. Sci. Rev. 112, 1–16 (2015).
Acknowledgements
This work was supported by the US National Science Foundation (NSF) awards 1702920 (C.B., K.M.), 2102944 (C.B., K.M.) and 0806414 (E.B., C.B., J.R., J.E). The University of Bern gratefully acknowledges financial support by the Swiss National Science Foundation (no. 200020_172506: M.M., J.S., H.F. and 200020B_200328: M.M., J.S., H.F.). We thank the NSF Ice Core Facility (NICF) and the University of Copenhagen for their curation and preparation of the WD/GISP2 and NEEM ice-core samples used in this study, respectively. We also thank M. L. Kalk for his assistance in methane data measurement at Oregon State University.
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Methane data measured by J.R., J.L., J.E., K.M., B.R.-Y., E.B. and C.B.; excess methane data measured by B.R.-Y., K.M., J.L., M.M., J.S. and H.F.; gas age scale synchronization, rIPD calculation and box-model analysis by J.R., B.R.-Y., E.B., J.E. and J.L.; paper preparation by B.R.-Y. and E.B. All authors contributed to the final paper.
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Riddell-Young, B., Rosen, J., Brook, E. et al. Atmospheric methane variability through the Last Glacial Maximum and deglaciation mainly controlled by tropical sources. Nat. Geosci. 16, 1174–1180 (2023). https://doi.org/10.1038/s41561-023-01332-x
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DOI: https://doi.org/10.1038/s41561-023-01332-x
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