References

Climate of the Past

Clim. Past

1814-9332

Copernicus Publications

Göttingen, Germany

10.5194/cp-8-609-2012

Centennial mineral dust variability in high-resolution ice core data from Dome C, Antarctica

Lambert

¹ ⁴ Bigler

² Steffensen

J. P.

² Hutterli

³ ⁵ Fischer

Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland

Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 København Ø, Denmark

British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK

now at: Korea Ocean Research and Development Institute, Ansan, Korea

now at: Tofwerk AG, Uttigenstrasse 22, 3600 Thun, Switzerland

22 03 2012

8 2 609 623

2012

This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/

This article is available from https://cp.copernicus.org/articles/8/609/2012/cp-8-609-2012.html

The full text article is available as a PDF file from https://cp.copernicus.org/articles/8/609/2012/cp-8-609-2012.pdf

Ice core data from Antarctica provide detailed insights into the characteristics of past climate, atmospheric circulation, as well as changes in the aerosol load of the atmosphere. We present high-resolution records of soluble calcium (Ca2+), non-sea-salt soluble calcium (nssCa2+), and particulate mineral dust aerosol from the East Antarctic Plateau at a depth resolution of 1 cm, spanning the past 800 000 years. Despite the fact that all three parameters are largely dust-derived, the ratio of nssCa2+ to particulate dust is dependent on the particulate dust concentration itself. We used principal component analysis to extract the joint climatic signal and produce a common high-resolution record of dust flux. This new record is used to identify Antarctic warming events during the past eight glacial periods. The phasing of dust flux and CO2 changes during glacial-interglacial transitions reveals that iron fertilization of the Southern Ocean during the past nine glacial terminations was not the dominant factor in the deglacial rise of CO2 concentrations. Rapid changes in dust flux during glacial terminations and Antarctic warming events point to a rapid response of the southern westerly wind belt in the region of southern South American dust sources on changing climate conditions. The clear lead of these dust changes on temperature rise suggests that an atmospheric reorganization occurred in the Southern Hemisphere before the Southern Ocean warmed significantly.

References 1

Abdi, H. and Williams, L. J.: Principal component analysis, Wiley Interdisciplinary Reviews: Computational Statistics, 2, 433–459, <a href="http://dx.doi.org/10.1002/wics.101">https://doi.org/10.1002/wics.101</a>, 2010.

Barker, S., Knorr, G., Edwards, R. L., Parrenin, F., Putnam, A. E., Skinner, L. C., Wolff, E., and Ziegler, M.: 800,000 Years of Abrupt Climate Variability, Science, 347, 0–5, <a href="http://dx.doi.org/10.1126/science.1203580">https://doi.org/10.1126/science.1203580</a>, 2011.

Bigler, M.: Hochaufloesende Spurenstoffmessungen an polaren Eisbohrkernen: Glazio-chemische und klimatische Prozessstudien, Ph.D. thesis, University of Bern, University of Bern, 2004.

Bigler, M., Röthlisberger, R., Lambert, F., Stocker, T. F., and Wagenbach, D.: Aerosol deposited in East Antarctica over the last glacial cycle: Detailed apportionment of continental and sea-salt contributions, J. Geophys. Res., 111, 1–14, <a href="http://dx.doi.org/10.1029/2005JD006469">https://doi.org/10.1029/2005JD006469</a>, 2006.

Bigler, M., Röthlisberger, R., Lambert, F., Wolff, E. W., Castellano, E., Udisti, R., Stocker, T. F., and Fischer, H.: Atmospheric decadal variability from high-resolution Dome C ice core records of aerosol constituents beyond the Last Interglacial, Quaternary Sci. Rev., 29, 324–337, <a href="http://dx.doi.org/10.1016/j.quascirev.2009.09.009">https://doi.org/10.1016/j.quascirev.2009.09.009</a>, 2010.

Blunier, T. and Brook, E. J.: Timing of millennial-scale climate change in Antarctica and Greenland during the last glacial period, Science, 291, 109–112, <a href="http://dx.doi.org/10.1126/science.291.5501.109">https://doi.org/10.1126/science.291.5501.109</a>, 2001.

Bopp, L.: Dust impact on marine biota and atmospheric CO2 during glacial periods, Paleoceanography, 18, 1046, <a href="http://dx.doi.org/10.1029/2002PA000810">https://doi.org/10.1029/2002PA000810</a>, 2003.

Bouttes, N., Paillard, D., and Roche, D. M.: Impact of brine-induced stratification on the glacial carbon cycle, Clim. Past, 6, 575–589, <a href="http://dx.doi.org/10.5194/cp-6-575-2010">https://doi.org/10.5194/cp-6-575-2010</a>, 2010.

Bowen, H. J. M.: Environmental Chemistry of the Elements, Academic Press, London, 1979.

Delmonte, B., Petit, J. R., and Maggi, V.: Glacial to Holocene implications of the new 27000-year dust record from the EPICA Dome C (East Antarctica) ice core, Clim. Dynam., 18, 647–660, <a href="http://dx.doi.org/10.1007/s00382-001-0193-9">https://doi.org/10.1007/s00382-001-0193-9</a>, 2002.

Delmonte, B., Basile-Doelsch, I., Petit, J.-R., Maggi, V., Revel-Rolland, M., Michard, A., Jagoutz, E., and Grousset, F.: Comparing the Epica and Vostok dust records during the last 220,000 years: stratigraphical correlation and provenance in glacial periods, Earth-Sci. Rev., 66, 63–87, <a href="http://dx.doi.org/10.1016/j.earscirev.2003.10.004">https://doi.org/10.1016/j.earscirev.2003.10.004</a>, 2004.

Delmonte, B., Andersson, P. S., Hansson, M., Schöberg, H., Petit, J. R., Basile-Doelsch, I., and Maggi, V.: Aeolian dust in East Antarctica (EPICA-Dome C and Vostok): Provenance during glacial ages over the last 800 kyr, Geophys. Res. Lett., 35, 2–7, <a href="http://dx.doi.org/10.1029/2008GL033382">https://doi.org/10.1029/2008GL033382</a>, 2008.

Delmonte, B., Andersson, P. S., Schöberg, H., Hansson, M., Petit, J. R., Delmas, R., Gaiero, D. M., Maggi, V., and Frezzotti, M.: Geographic provenance of aeolian dust in East Antarctica during Pleistocene glaciations: preliminary results from Talos Dome and comparison with East Antarctic and new Andean ice core data, Quaternary Sci. Rev., 29, 256–264, <a href="http://dx.doi.org/10.1016/j.quascirev.2009.05.010">https://doi.org/10.1016/j.quascirev.2009.05.010</a>, 2010.

EPICA community members: One-to-one coupling of glacial climate variability in Greenland and Antarctica, Nature, 444, 195–198, <a href="http://dx.doi.org/10.1038/nature05301">https://doi.org/10.1038/nature05301</a>, 2006.

Fischer, H., Fundel, F., Ruth, U., Twarloh, B., Wegner, A., Udisti, R., Becagli, S., Castellano, E., Morganti, A., and Severi, M.: Reconstruction of millennial changes in dust emission, transport and regional sea ice coverage using the deep EPICA ice cores from the Atlantic and Indian Ocean sector of Antarctica, Earth Planet. Sc. Lett., 260, 340–354, <a href="http://dx.doi.org/10.1016/j.epsl.2007.06.014">https://doi.org/10.1016/j.epsl.2007.06.014</a>, 2007a.

Fischer, H., Siggaard-Andersen, M. L., Ruth, U., Röthlisberger, R., and Wolff, E. W.: Glacial/Interglacial changes in mineral dust and sea-salt records in polar ice cores: sources, transport, and deposition, Rev. Geophys., 45, RG1002, <a href="http://dx.doi.org/10.1029/2005RG000192">https://doi.org/10.1029/2005RG000192</a>, 2007b.

Fischer, H., Schmitt, J., Lüthi, D., Stocker, T. F., Tschumi, T., Parekh, P., Joos, F., Köhler, P., Völker, C., Gersonde, R., Barbante, C., Le Floch, M., Raynaud, D., Wolff, E.: The role of Southern Ocean processes in orbital and millennial CO2 variations – A synthesis, Quaternary Sci. Rev., 29, 193–205, <a href="http://dx.doi.org/10.1016/j.quascirev.2009.06.007">https://doi.org/10.1016/j.quascirev.2009.06.007</a>, 2010.

Fuhrer, K., Wolff, E. W., and Johnsen, S. J.: Timescales for dust variability in the Greenland Ice Core Project(GRIP) ice core in the last 100,000 years, J. Geophys. Res., 104, 31043–31052, <a href="http://dx.doi.org/10.1029/1999JD900929">https://doi.org/10.1029/1999JD900929</a>, 1999.

Gaiero, D. M.: Dust provenance in Antarctic ice during glacial periods: From where in southern South America?, Geophys. Res. Lett., 34, 1–6, <a href="http://dx.doi.org/10.1029/2007GL030520">https://doi.org/10.1029/2007GL030520</a>, 2007.

Jouzel, J., Masson-Delmotte, V., Cattani, O., Dreyfus, G., Falourd, S., Hoffmann, G., Minster, B., Nouet, J., Barnola, J. M., Chappellaz, J., Fischer, H., Gallet, J. C., Johnsen, S., Leuenberger, M., Loulergue, L., Luethi, D., Oerter, H., Parrenin, F., Raisbeck, G., Raynaud, D., Schilt, A., Schwander, J., Selmo, E., Souchez, R., Spahni, R., Stauffer, B., Steffensen, J. P., Stenni, B., Stocker, T. F., Tison, J. L., Werner, M., and Wolff, E. W.: Orbital and millennial Antarctic climate variability over the past 800,000 years, Science, 317, 793–796, <a href="http://dx.doi.org/10.1126/science.1141038">https://doi.org/10.1126/science.1141038</a>, 2007.

Köhler, P. and Fischer, H.: Simulating low frequency changes in atmospheric CO2 during the last 740 000 years, Clim. Past, 2, 57–78, <a href="http://dx.doi.org/10.5194/cp-2-57-2006">https://doi.org/10.5194/cp-2-57-2006</a>, 2006.

Lässig, J. L., Cogliati, M. G., Bastanski, M. A., and Palese, C.: Wind characteristics in Neuquen , North Patagonia , Argentina, J. Wind Eng. Ind. Aerodyn., 79, 183–199, <a href="http://dx.doi.org/10.1016/S0167-6105(98)00110-X">https://doi.org/10.1016/S0167-6105(98)00110-X</a>, 1999.

Lambert, F., Delmonte, B., Petit, J. R., Bigler, M., Kaufmann, P. R., Hutterli, M. A., Stocker, T. F., Ruth, U., Steffensen, J. P., and Maggi, V.: Dust-climate couplings over the past 800,000 years from the EPICA Dome C ice core, Nature, 452, 616–619, <a href="http://dx.doi.org/10.1038/nature06763">https://doi.org/10.1038/nature06763</a>, 2008.

Lamy, F., Kilian, R., Arz, H. W., Francois, J.-P., Kaiser, J., Prange, M., and Steinke, T.: Holocene changes in the position and intensity of the southern westerly wind belt, Nat. Geosci., 3, 695–699, <a href="http://dx.doi.org/10.1038/ngeo959">https://doi.org/10.1038/ngeo959</a>, 2010.

Legrand, M. and Mayewski, P.: Glaciochemistry of polar ice cores: A review, Rev. Geophys., 35, 219–243, <a href="http://dx.doi.org/10.1029/96RG03527">https://doi.org/10.1029/96RG03527</a>, 1997.

Lisiecki, L. E. and Raymo, M. E.: A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records, Paleoceanography, 20, 1–17, <a href="http://dx.doi.org/10.1029/2004PA001071">https://doi.org/10.1029/2004PA001071</a>, 2005.

Loulergue, L., Schilt, A., Spahni, R., Masson-Delmotte, V., Blunier, T., Lemieux, B., Barnola, J.-M., Raynaud, D., Stocker, T. F., and Chappellaz, J.: Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years, Nature, 453, 383–386, <a href="http://dx.doi.org/10.1038/nature06950">https://doi.org/10.1038/nature06950</a>, 2008.

Lüthi, D., Le Floch, M., Bereiter, B., Blunier, T., Barnola, J.-M., Siegenthaler, U., Raynaud, D., Jouzel, J., Fischer, H., Kawamura, K., and Stocker, T. F.: High-resolution carbon dioxide concentration record 650,000–800,000 years before present, Nature, 453, 379–382, <a href="http://dx.doi.org/10.1038/nature06949">https://doi.org/10.1038/nature06949</a>, 2008.

Maher, B. A., Prospero, J. M., Mackie, D., Gaiero, D., Hesse, P. P., and Balkanski, Y.: Global connections between aeolian dust, climate and ocean biogeochemistry at the present day and at the last glacial maximum, Earth-Sci. Rev., 99, 61–97, <a href="http://dx.doi.org/10.1016/j.earscirev.2009.12.001">https://doi.org/10.1016/j.earscirev.2009.12.001</a>, 2010.

Mahowald, N. M., Muhs, D. R., Levis, S., Rasch, P. J., Yoshioka, M., Zender, C. S., and Luo, C.: Change in atmospheric mineral aerosols in response to climate: Last glacial period, preindustrial, modern, and doubled carbon dioxide climates, J. Geophys. Res., 111, D10202, <a href="http://dx.doi.org/10.1029/2005JD006653">https://doi.org/10.1029/2005JD006653</a>, 2006a.

Mahowald, N. M., Yoshioka, M., Collins, W. D., Conley, A. J., Fillmore, D. W., and Coleman, D. B.: Climate response and radiative forcing from mineral aerosols during the last glacial maximum, pre-industrial, current and doubled-carbon dioxide climates, Geophys. Res. Lett., 33, 2–5, <a href="http://dx.doi.org/10.1029/2006GL026126">https://doi.org/10.1029/2006GL026126</a>, 2006b.

Martin, J. H., Gordon, R. M., and Fitzwater, S. E.: Iron in Antarctic waters, Nature, 345, 156–158, <a href="http://dx.doi.org/10.1038/345156a0">https://doi.org/10.1038/345156a0</a>, 1990.

Martin, J. H., Gordon, R. M., and Fitzwater, S. E.: The Case for Iron, Limnol. Oceanogr., 36, 1793–1802, 1991.

Martínez-Garcia, A., Rosell-Melé, A., Geibert, W., Gersonde, R., Masqué, P., Gaspari, V., and Barbante, C.: Links between iron supply, marine productivity, sea surface temperature, and CO2 over the last 1.1 Ma, Paleoceanography, 24, 1–14, <a href="http://dx.doi.org/10.1029/2008PA001657">https://doi.org/10.1029/2008PA001657</a>, 2009.

Martínez-Garcia, A., Rosell-Melé, A., Jaccard, S. L., Geibert, W., Sigman, D. M., and Haug, G. H.: Southern Ocean dust – climate coupling over the past four million years, Nature, 476, 312–315, <a href="http://dx.doi.org/10.1038/nature10310">https://doi.org/10.1038/nature10310</a>, 2011.

Martrat, B., Grimalt, J. O., Shackleton, N. J., de Abreu, L., Hutterli, M. A., and Stocker, T. F.: Four climate cycles of recurring deep and surface water destabilizations on the Iberian margin., Science (New York, N.Y.), 317, 502–507, <a href="http://dx.doi.org/10.1126/science.1139994">https://doi.org/10.1126/science.1139994</a>, 2007.

Mayewski, P. A., Meeker, L. D., Whitlow, S., Twickler, M. S., Morrison, M. C., Bloomfield, P., Bond, G. C., Alley, R. B., Gow, A. J., Meese, D. A., Grootes, P. M., Ram, M., Taylor, K. C., and Wumkes, W.: Changes in Atmospheric Circulation and Ocean Ice Cover over the North Atlantic During the Last 41,000 Years, Science, 263, 1747–1751, <a href="http://dx.doi.org/10.1126/science.263.5154.1747">https://doi.org/10.1126/science.263.5154.1747</a>, 1994.

Miller, R. L. and Tegen, I.: Climate Response to Soil Dust Aerosols, J. Climate, 11, 3247–3267, <a href="http://dx.doi.org/10.1175/1520-0442(1998)011<3247:CRTSDA>2.0.CO;2">https://doi.org/10.1175/1520-0442(1998)011<3247:CRTSDA>2.0.CO;2</a>, 1998.

NGRIP community members: High-resolution record of Northern Hemisphere climate extending into the last interglacial period, Nature, 431, 147–151, <a href="http://dx.doi.org/10.1038/nature02805">https://doi.org/10.1038/nature02805</a>, 2004.

Rankin, A. M., Auld, V., and Wolff, E. W.: Frost flowers as a source of fractionated sea salt aerosol in the polar regions, Geophys. Res. Lett., 27, 3469, <a href="http://dx.doi.org/10.1029/2000GL011771">https://doi.org/10.1029/2000GL011771</a>, 2000.

Revel-Rolland, M., Dedeckker, P., Delmonte, B., Hesse, P., Magee, J., Basiledoelsch, I., Grousset, F., and Bosch, D.: Eastern Australia: A possible source of dust in East Antarctica interglacial ice, Earth Planet. Sc. Lett., 249, 1–13, <a href="http://dx.doi.org/10.1016/j.epsl.2006.06.028">https://doi.org/10.1016/j.epsl.2006.06.028</a>, 2006.

Ridgwell, A. J.: Implications of the glacial CO2 "iron hypothesis" for Quaternary climate change, Geochem. Geophy. Geosy., 4, 1–10, <a href="http://dx.doi.org/10.1029/2003GC000563">https://doi.org/10.1029/2003GC000563</a>, 2003.

Röthlisberger, R., Bigler, M., Hutterli, M., Sommer, S., Stauffer, B., Junghans, H. G., and Wagenbach, D.: Technique for continuous high-resolution analysis of trace substances in firn and ice cores, Environ. Sci. Technol, 34, 338–342, <a href="http://dx.doi.org/10.1021/es9907055">https://doi.org/10.1021/es9907055</a>, 2000.

Röthlisberger, R., Mulvaney, R., Wolff, E. W., Hutterli, M. A., Bigler, M., Sommer, S., and Jouzel, J.: Dust and sea salt variability in central East Antarctica (Dome C) over the last 45 kyrs and its implications for southern high-latitude climate, Geophys. Res. Lett., 29, 1-5, <a href="http://dx.doi.org/10.1029/2002GL015186">https://doi.org/10.1029/2002GL015186</a>, 2002.

Röthlisberger, R., Bigler, M., Wolff, E. W., Joos, F., Monnin, E., and Hutterli, M. A.: Ice core evidence for the extent of past atmospheric CO2 change due to iron fertilisation, Geophys. Res. Lett., 31, 2–5, <a href="http://dx.doi.org/10.1029/2004GL020338">https://doi.org/10.1029/2004GL020338</a>, 2004.

Ruth, U., Wagenbach, D., Bigler, M., Steffensen, J. P., Röthlisberger, R., and Miller, H.: High resolution microparticle profiles at NGRIP: case studies of the calcium-dust relationship, Ann. Glaciol., 35, 237–242, 2002.

Ruth, U., Wagenbach, D., Steffensen, J. P., and Bigler, M.: Continuous record of microparticle concentration and size distribution in the central Greenland NGRIP ice core during the last glacial period, J. Geophys. Res., 108, 1–12, <a href="http://dx.doi.org/10.1029/2002JD002376">https://doi.org/10.1029/2002JD002376</a>, 2003.

Ruth, U., Barbante, C., Bigler, M., Delmonte, B., Fischer, H., Gabrielli, P., Gaspari, V., Kaufmann, P., Lambert, F., Maggi, V., Marino, F., Petit, J.-R., Udisti, R., Wagenbach, D., Wegner, A., and Wolff, E. W: Proxies and measurement techniques for mineral dust in Antarctic ice cores, Environ. Sci. Technol., 42, 5675–5681, <a href="http://dx.doi.org/10.1021/es703078z">https://doi.org/10.1021/es703078z</a>, 2008.

Sassen, K., Demott, P. J., Prospero, J. M., and Poellot, M. R.: Saharan dust storms and indirect aerosol effects on clouds?: CRYSTAL-FACE results, Geophys. Res. Lett., 30, 1–4, <a href="http://dx.doi.org/10.1029/2003GL017371">https://doi.org/10.1029/2003GL017371</a>, 2003.

Schwartz, S. E.: The whitehouse effect-shortwave radiative forcing of climate by anthropogenic aerosols: an overview, J. Aerosol. Sci., 27, 359–382, <a href="http://dx.doi.org/10.1016/0021-8502(95)00533-1">https://doi.org/10.1016/0021-8502(95)00533-1</a>, 1996.

Sigman, D. M., Hain, M. P., and Haug, G. H.: The polar ocean and glacial cycles in atmospheric CO(2) concentration, Nature, 466, 47–55, <a href="http://dx.doi.org/10.1038/nature09149">https://doi.org/10.1038/nature09149</a>, 2010.

Steffensen, J. P., Andersen, K. K., Bigler, M., Clausen, H. B., Dahl-Jensen, D., Fischer, H., Goto-Azuma, K., Hansson, M., Johnsen, S. J., Jouzel, J., Masson-Delmotte, V., Popp, T., Rasmussen, S. O., Röthlisberger, R. R., Stauffer, U., Siggaard-Andersen, B., Sveinbjörnsdóttir, M. L., Arny, E., Svensson, A., and White, J. W. C.: High-resolution Greenland ice core data show abrupt climate change happens in few years, Science, 321, 680–684, <a href="http://dx.doi.org/10.1126/science.1157707">https://doi.org/10.1126/science.1157707</a>, 2008.

Stocker, T. F. and Johnsen, S. J.: A minimum thermodynamic model for the bipolar seesaw, Paleoceanography, 18, 1087–1089, <a href="http://dx.doi.org/10.1029/2003PA000920">https://doi.org/10.1029/2003PA000920</a>, 2003.

Sugden, D. E., McCulloch, R. D., Bory, A. J.-M., and Hein, A. S.: Influence of Patagonian glaciers on Antarctic dust deposition during the last glacial period, Nat. Geosci., 2, 281–285, <a href="http://dx.doi.org/10.1038/ngeo474">https://doi.org/10.1038/ngeo474</a>, 2009.

Tegen, I.: Modeling the mineral dust aerosol cycle in the climate system, Quaternary Sci. Rev., 22, 1821–1834, <a href="http://dx.doi.org/10.1016/S0277-3791(03)00163-X">https://doi.org/10.1016/S0277-3791(03)00163-X</a>, 2003.

Tegen, I., Lacis, A., and Fung, I.: The influence on climate forcing of mineral aerosols from disturbed soils, Nature, 380, 419–422, <a href="http://dx.doi.org/10.1038/380419a0">https://doi.org/10.1038/380419a0</a>, 1996.

Watson, A. J., Bakker, D. C., Ridgwell, A. J., Boyd, P. W., and Law, C. S.: Effect of iron supply on Southern Ocean CO2 uptake and implications for glacial atmospheric CO2, Nature, 407, 730–733, <a href="http://dx.doi.org/10.1038/35037561">https://doi.org/10.1038/35037561</a>, 2000.

Winckler, G. and Fischer, H.: 30,000 years of cosmic dust in Antarctic ice, Science, 313, 491, <a href="http://dx.doi.org/10.1126/science.1127469">https://doi.org/10.1126/science.1127469</a>, 2006.

Wolff, E. W., Fischer, H., Fundel, F., Ruth, U., Twarloh, B., Littot, G. C., Mulvaney, R., Röthlisberger, R., de Angelis, M., Boutron, C. F., Hansson, M., Jonsell, U., Hutterli, M. A., Lambert, F., Kaufmann, P., Stauffer, B., Stocker, T. F., Steffensen, J. P., Bigler, M., Siggaard-Andersen, M. L., Udisti, R., Becagli, S., Castellano, E., Severi, M., Wagenbach, D., Barbante, C., Gabrielli, P., and Gaspari, V.: Southern Ocean sea-ice extent, productivity and iron flux over the past eight glacial cycles, Nature, 440, 491–496, <a href="http://dx.doi.org/10.1038/nature04614">https://doi.org/10.1038/nature04614</a>, 2006.

Wolff, E., Fischer, H., and Röthlisberger, R.: Glacial terminations as southern warmings without northern control, Nat. Geosci., 2, 206–209, <a href="http://dx.doi.org/10.1038/NGEO442">https://doi.org/10.1038/NGEO442</a>, 2009.