CPD Climate of the Past Discussions CPD Clim. Past Discuss. 1814-9359 Göttingen, Germany 10.5194/cpd-6-1453-2010 Rapid changes in ice core gas records – Part 1: On the accuracy of methane synchronisation of ice cores Köhler P. https://orcid.org/0000-0003-0904-8484 1 Alfred Wegener Institute for Polar and Marine Research, P.O. Box 120161, 27515 Bremerhaven, Germany 11 08 2010 6 4 1453 1471 Copyright: © 2010 P. Köhler 2010 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/preprints/6/1453/2010/cpd-6-1453-2010.html The full text article is available as a PDF file from https://cp.copernicus.org/preprints/6/1453/2010/cpd-6-1453-2010.pdf

Methane synchronisation is a concept to align ice core records during rapid climate changes of the Dansgaard/Oeschger (D/O) events onto a common age scale. However, atmospheric gases are recorded in ice cores with a log-normal-shaped age distribution probability density function, whose exact shape depends mainly on the accumulation rate on the drilling site. This age distribution effectively shifts the mid-transition points of rapid changes in CH<sub>4</sub> measured in situ in ice by about 58% of the width of the age distribution with respect to the atmospheric signal. A minimum dating uncertainty, or artefact, in the CH<sub>4</sub> synchronisation is therefore embedded in the concept itself, which was not accounted for in previous error estimates. This synchronisation artefact between Greenland and Antarctic ice cores is for GRIP and Byrd less than 40 years, well within the dating uncertainty of CH<sub>4</sub>, and therefore does not calls the overall concept of the bipolar seesaw into question. However, if the EPICA Dome C ice core is aligned via CH<sub>4</sub> to NGRIP this synchronisation artefact is in the most recent unified ice core age scale (Lemieux-Dudon et al., 2010) for LGM climate conditions of the order of three centuries and might need consideration in future gas chronologies.

 References Andersen, K.&nbsp;K., Ditlevsen, P.&nbsp;D., Rasmussen, S.&nbsp;O., Clausen, H.&nbsp;B., Vinther, B.&nbsp;M., Johnsen, S.&nbsp;J., and Steffensen, J.&nbsp;P.: Retrieving a common accumulation record from Greenland ice cores for the past 1800 years, J. Geophys. Res., 111, D15106, https://doi.org/10.1029/2005JD006765, 2006. Barker, S., Diz, P., Vantravers, M.&nbsp;J., Pike, J., Knorr, G., Hall, I.&nbsp;R., and Broecker, W.&nbsp;S.: Interhemispheric Atlantic seesaw response during the last deglaciation, Nature, 457, 1007–1102, <a href="http://dx.doi.org/10.1038/nature07770">https://doi.org/10.1038/nature07770</a>, 2009. Blunier, T. and Brook, E.&nbsp;J.: Timing of millennial-scale climate change in Antarctica and Greenland during the last glacial period, Science, 291, 109–112, 2001. Blunier, T., Chappellaz, J., Schwander, J., D{{ä}}llenbach, A., Stauffer, B., Stocker, T.&nbsp;F., Raynaud, D., Jouzel, J., Clausen, H.&nbsp;B., Hammer, C.&nbsp;U., and Johnsen, S.&nbsp;J.: Asynchrony of Antarctic and Greenland climate change during the last glacial period, Nature, 394, 739–743, 1998. Blunier, T., Spahni, R., Barnola, J.-M., Chappellaz, J., Loulergue, L., and Schwander, J.: Synchronization of ice core records via atmospheric gases, Clim. Past, 3, 325–330, https://doi.org/10.5194/cp-3-325-2007, 2007. Capron, E., Landais, A., Chappellaz, J., Schilt, A., Buiron, D., Dahl-Jensen, D., Johnsen, S.&nbsp;J., Jouzel, J., Lemieux-Dudon, B., Loulergue, L., Leuenberger, M., Masson-Delmotte, V., Meyer, H., Oerter, H., and Stenni, B.: Capron, E., Landais, A., Chappellaz, J., Schilt, A., Buiron, D., Dahl-Jensen, D., Johnsen, S. J., Jouzel, J., Lemieux-Dudon, B., Loulergue, L., Leuenberger, M., Masson-Delmotte, V., Meyer, H., Oerter, H., and Stenni, B.: Millennial and sub-millennial scale climatic variations recorded in polar ice cores over the last glacial period, Clim. Past, 6, 345–365, https://doi.org/10.5194/cp-6-345-2010, 2010. Chappellaz, J., Blunier, T., Raynaud, D., Barnola, J.&nbsp;M., Schwander, J., and Stauffer, B.: Synchronous changes in atmospheric CH<sub>4</sub> and Greenland climate between 40 and 8 kyr BP, Nature, 366, 443–445, 1993. Chappellaz, J., Blunier, T., Kints, S., D{ä}llenbach, A., Barnola, J.-M., Schwander, J., Raynaud, D., and Stauffer, B.: Changes in the atmospheric CH<sub>4</sub> gradient between Greenland and Antarctica during the Holocene, J.&nbsp;Geophys. Res., 102, 15987–15997, 1997. EPICA-community-members: One-to-one coupling of glacial climate variability in Greenland and Antarctica, Nature, 444, 195–198, https://doi.org/10.1038/nature05301, 2006. Goujon, C., Barnola, J.-M., and Ritz, C.: Modeling the densification of polar firn including heat diffusion: Application to close-off characteristics and gas isotopic fractionation for Antarctica and Greenland sites, J.&nbsp;Geophys. Res., 108, 4792, https://doi.org/10.1029/2002JD003319, 2003. Huybrechts, P., Rybak, O., Pattyn, F., Ruth, U., and Steinhage, D.: Ice thinning, upstream advection, and non-climatic biases for the upper 89{%} of the EDML ice core from a nested model of the Antarctic ice sheet, Clim. Past, 3, 577–589, https://doi.org/10.5194/cp-3-577-2007, 2007. Johnsen, S.&nbsp;J., Clausen, H.&nbsp;B., Dansgaard, W., Fuhrer, K., Gundestrup, N., Hammer, C.&nbsp;U., Iversen, P., Jouzel, J., Stauffer, B., and Steffensen, J.&nbsp;P.: Irregular glacial interstadials recorded in a new Greenland ice core, Nature, 359, 311–313, 1992. Joos, F. and Spahni, R.: Rates of change in natural and anthropogenic radiative forcing over the past 20 000 years, P. Natl. Acad. Sci. USA, 105, 1425–1430, https://doi.org/10.1073/pnas.0707386105, 2008. K{ö}hler, P., Fischer, H., and Schmitt, J.: Atmospheric \dcoo and its relation to \pcoo and deep ocean \dc during the late Pleistocene, Paleoceanography, 25, PA1213, <a href="http://dx.doi.org/10.1029/2008PA001703">https://doi.org/10.1029/2008PA001703</a>, 2010{a}. K{ö}hler, P., Knorr, G., Buiron, D., Lourantou, A., and Chappellaz, J.: Rapid changes in ice core gas records – Part 2: Understanding the rapid rise in atmospheric \coo at the onset of the Bølling/Allerød, Climate of the Past, p. in review, 2010{b}. Lemieux-Dudon, B., Blayo, E., Petit, J.-R., Waelbroeck, C., Svensson, A., Ritz, C., Barnola, J.-M., Narcisi, B.&nbsp;M., and Parrenin, F.: Consistent dating for Antarctic and Greenland ice cores, Quaternary Sci. Rev., 29, 8–20, <a href="http://dx.doi.org/10.1016/j.quascirev.2009.11.010">https://doi.org/10.1016/j.quascirev.2009.11.010</a>, 2010. Loulergue, L., Parrenin, F., Blunier, T., Barnola, J.-M., Spahni, R., Schilt, A., Raisbeck, G., and Chappellaz, J.: New constraints on the gas age-ice age difference along the EPICA ice cores, 0–50 kyr, Clim. Past, 3, 527–540, https://doi.org/10.5194/cp-3-527-2007, 2007. Lourantou, A., Lavrič, J.&nbsp;V., Köhler, P., Barnola, J.-M., Michel, E., Paillard, D., Raynaud, D., and Chappellaz, J.: Constraint of the \coo rise by new atmospheric carbon isotopic measurements during the last deglaciation, Global Biogeochem. Cy., 24, GB2015, https://doi.org/10.1029/2009GB003545, 2010. Monnin, E., Inderm{ü}hle, A., D{ä}llenbach, A., Fl{ü}ckiger, J., Stauffer, B., Stocker, T.&nbsp;F., Raynaud, D., and Barnola, J.-M.: Atmospheric CO<sub>2</sub> concentrations over the last glacial termination, Science, 291, 112–114, 2001. NorthGRIP-members: High-resolution record of Northern Hemisphere climate extending into the last interglacial period, Nature, 431, 147–151, 2004. Parrenin, F., Barnola, J.-M., Beer, J., Blunier, T., Castellano, E., Chappellaz, J., Dreyfus, G., Fischer, H., Fujita, S., Jouzel, J., Kawamura, K., Lemieux-Dudon, B., Loulergue, L., Masson-Delmotte, V., Narcisi, B., Petit, J.-R., Raisbeck, G., Raynaud, D., Ruth, U., Schwander, J., Severi, M., Spahni, R., Steffensen, J. P., Svensson, A., Udisti, R., Waelbroeck, C., and Wolff, E.: The EDC3 chronology for the EPICA Dome C ice core, Clim. Past, 3, 485–497, https://doi.org/10.5194/cp-3-485-2007, 2007. Ruth, U., Barnola, J.-M., Beer, J., Bigler, M., Blunier, T., Castellano, E., Fischer, H., Fundel, F., Huybrechts, P., Kaufmann, P., Kipfstuhl, S., Lambrecht, A., Morganti, A., Oerter, H., Parrenin, F., Rybak, O., Severi, M., Udisti, R., Wilhelms, F., and Wolff, E.: "EDML1": a chronology for the EPICA deep ice core from Dronning Maud Land, Antarctica, over the last 150 000 years, Clim. Past, 3, 475–484, https://doi.org/10.5194/cp-3-475-2007, 2007. Schwander, J., Barnola, J.-M., Andrié, C., Leuenberger, M., Ludin, A., Raynaud, D., and Stauffer, B.: The age of the air in the firn and the ice at Summit, Greenland, J. Geophys. Res., 98, 2831–2838, 1993. Spahni, R., Schwander, J., Fl{ü}ckiger, J., Stauffer, B., Chappellaz, J., and Raynaud, D.: The attenuation of fast atmospheric CH<sub>4</sub> variations recorded in polar ice cores, Geopys. Res. Lett., 30, 1571, https://doi.org/10.1029/2003GL017093, 2003. Spahni, R., Chappellaz, J., Stocker, T.&nbsp;F., Loulergue, L., Hausammann, G., Kawamura, K., Fl{ü}ckiger, J., Schwander, J., Raynaud, D., Masson-Delmotte, V., and Jouzel, J.: Atmospheric methane and nitrous oxide of the late Pleistocene from Antarctic ice cores, Science, 310, 1317–1321, https://doi.org/ 10.1126/science.1120132, 2005. Stenni, B., Masson-Delmotte, V., Johnsen, S., Jouzel, J., Longinelli, A., Monnin, E., R{ö}thlisberger, R., and Selmo, E.: An oceanic cold reversal during the last deglaciation, Science, 293, 2074–2077, 2001. Stocker, T.&nbsp;F. and Johnsen, S.&nbsp;J.: A minimum thermodynamic model for the bipolar seesaw, Paleoceanography, 18, 1087, https://doi.org/10.1029/2003PA000920, 2003. Svensson, A., Andersen, K. K., Bigler, M., Clausen, H. B., Dahl-Jensen, D., Davies, S. M., Johnsen, S. J., Muscheler, R., Parrenin, F., Rasmussen, S. O., Röthlisberger, R., Seierstad, I., Steffensen, J. P., and Vinther, B. M.: A 60 000 year Greenland stratigraphic ice core chronology, Clim. Past, 4, 47–57, https://doi.org/10.5194/cp-4-47-2008, 2008.