ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-9-4145-2009 <sup>36</sup>Cl bomb peak: comparison of modeled and measured data Heikkilä U. 1 7 Beer J. 1 Feichter J. 2 Alfimov V. 3 Synal H.-A. 3 Schotterer U. 4 Eichler A. 4 Schwikowski M. 5 Thompson L. 6 EAWAG, Dübendorf, Switzerland Max Planck Institute for Meteorology, Hamburg, Germany Federal Institute of Technology (ETH) Zurich/Paul Scherrer Institute, Villigen, Switzerland Division of Climate and Environmental Physics, Physics Institute, University of Bern, Switzerland Paul Scherrer Institute, Villigen, Switzerland School of Earth Sciences, The Ohio State University, USA now at: Bjerknes Centre for Climate Research, Bergen, Norway 23 06 2009 9 12 4145 4156 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/9/4145/2009/acp-9-4145-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/9/4145/2009/acp-9-4145-2009.pdf

The extensive nuclear bomb testing of the fifties and sixties and the final tests in the seventies caused a strong <sup>36</sup>Cl peak that has been observed in ice cores world-wide. The measured <sup>36</sup>Cl deposition fluxes in eight ice cores (Dye3, Fiescherhorn, Grenzgletscher, Guliya, Huascarán, North GRIP, Inylchek (Tien Shan) and Berkner Island) were compared with an ECHAM5-HAM general circulation model simulation (1952–1972). We find a good agreement between the measured and the modeled <sup>36</sup>Cl fluxes assuming that the bomb test produced global <sup>36</sup>Cl input was ~80 kg. The model simulation indicates that the fallout of the bomb test produced <sup>36</sup>Cl is largest in the subtropics and mid-latitudes due to the strong stratosphere-troposphere exchange. In Greenland the <sup>36</sup>Cl bomb signal is quite large due to the relatively high precipitation rate. In Antarctica the <sup>36</sup>Cl bomb peak is small but is visible even in the driest areas. The model suggests that the large bomb tests in the Northern Hemisphere are visible around the globe but the later (end of sixties and early seventies) smaller tests in the Southern Hemisphere are much less visible in the Northern Hemisphere. The question of how rapidly and to what extent the bomb produced <sup>36</sup>Cl is mixed between the hemispheres depends on the season of the bomb test. The model results give an estimate of the amplitude of the bomb peak around the globe.

 References Andersen, K. K., Ditlevsen, P. D., Rasmussen, S. O., Clausen, H. B., Vinther, B. M., Johnsen, S. J., and Steffensen, J. P.: Retrieving a common accumulation record from Greenland ice cores for the past 1800 years, J. Geophys. Res., 111, D15106, doi:10.1029/2005JD006765, 2006. Blinov, A. Massonet, S., Sachsenhauser, H., Stan-Sion, C., Lazarev, V., Beer, J., Synal, H.-A., Kaba, M., Masarik, J., and Nolte, E.: An excess of $^36$Cl in modern atmospheric precipitation, Nucl. Inst. Meth. Phys. Res. B, 172, 537–544, 2000. Davis, S., Cecil, L. D., Zreda, M., and Moysey, S.: Chlorine-36, bromide and the origin of spring water, Chem. Geol., 179, 3–16, 2001. Delmas, R. J., Beer, J., Synal, H.-A., Muscheler, R., Petit, J.-R., and Pourchet, M.: Bomb-test $^36$Cl measurements in Vostok snow (Antarctica) and the use of $^36$Cl as a dating tool for deep ice cores, Tellus, 56B, 492–498, 2004. Dentener, F., Kinne, S., Bond, T., Boucher, O., Cofala, J., Generoso, S., Ginoux, P., Gong, S., Hoelzemann, J. J., Ito, A., Marelli, L., Penner, J. E., Putaud, J.-P., Textor, C., Schulz, M., van der Werf, G. R., and Wilson, J.: Emissions of primary aerosol and precursor gases in the years 2000 and 1750 prescribed data-sets for AeroCom, Atmos. Chem. Phys., 6, 4321–4344, 2006. Dyrssen, D. and Nyman, P. O.: Acta Radiol., 43, 421–427, 1955. Eichler, A., Schwikowski, M., Gäggeler, H., Furrer, V., Synal, H.-A., Beer, J., Saurer, M., and Funk, M.: Glaciochemical dating of an ice core from upper Grenzgletscher (4200 m a.s.l.), J. Glaciol., 46, 507–515, 2000. Elmore, D., Tubbs, L. E., Newman, D., Ma, X. Z., Finkel, R., Nishiizumi, K., Beer, J., Oescher, H., and Andree, M.: $^36$Cl bomb pulse measured in a shallow ice core from Dye3, Greenland, Nature, 300, 735–737, 1982. Gates, W. L.: AMIP: The Atmospheric Model Intercomparison Project, B. Am. Meteorol. Soc., 73, 1962–1970, 1992. Glasstone, S. and Dolan, P. J.: The effects of nuclear weapons, United States Department of Defense and Energy Research and Development Administration, 3rd Edition, 1977. Green, J. R., Cecil, L. D., Synal, H.-A., Santos, J., Kreutz, K. J., and Wake, C. P.: A high resolution record of chlorine-36 nuclear-weapons-tests fallout from Central Asia, Nucl. Instrum. Meth. B, 223–224, 854–857, 2004. Field, C., Schmidt, G., Koch, D., and Salyk, C.: Modeling production and climate-related impacts on $^10$Be concentration in ice cores, J. Geophys. Res. 111, D15107, doi:10.1029/2005JD00640, 2006. Hagemann, S., Arpe, K., and Roeckner, E.: Evaluation of the hydrological cycle in the ECHAM5 model, J. Climate, 19, 16, 3810–3827, 2006. Heikkilä, U., Beer, J., and Feichter, J.: Modeling cosmogenic radionuclides 10Be and 7Be during the Maunder Minimum using the ECHAM5-HAM General Circulation Model, Atmos. Chem. Phys., 8, 2797–2809, 2008a. Heikkilä, U., Beer, J., and Alfimov, V.: Beryllium-10 and Beryllium-7 in precipitation in Dübendorf (440 m) and at Jungfraujoch (3580 m), Switzerland (1998–2005), J. Geophys. Res., 113, D11104, doi:10.1029/2007JD009160, 2008b. Holton, J., Haynes, P., McIntyre, M., Douglass, A., Rood, R., and Pfister, L.: Stratosphere-troposphere exchange, Rev. Geophys., 33, 403–439, 1995. Lal, D. and Peters, B.: Cosmic ray produced radioactivity on the Earth, Handbuch der Physik, XLVI/2, Springer-Verlag, New York, 551–612, 1967. Lukasczyk, C.: $^36$Cl im Grönlandeis, Diss. ETH No. 10688, http://e-collection.ethbib.ethz.ch/eserv/eth:22378/eth-22378-02.pdf, 201–203, 1994 (in German). Machta, L.: Radioactive fallout from nuclear weapons tests, USAEC, Oak Ridge, 369–391, 1963. Mahowald, N., Plumb, A., Rasch, P., del Corral, J., Sassi, F., and Heres, W.: Stratospheric transport in a three-dimensional isentropic coordinate model, J. Geophys. Res., 107(D15), 4254, doi:10.1029/2001JD001313, 2002. Masarik, J. and Beer, J.: Simulation of particle fluxes and cosmogenic nuclide production in the Earth's atmosphere, J. Geophys. Res., 104, 12099–12111, 1999. North Greenland Ice Core Project Members, High-resolution record of Northern Hemisphere extending into the last interglacial period, Nature, 431, 147–151, 2004. % Raisbeck, G., Yiou, F., Bourles, D., Lorius, C., Jouzel, J. and Barkov, N.I., Evidence for two intervals of enhanced $^10$Be deposition in Antarctic ice during the last glacial period, \it Nature 326, 273-277, 1987. Rehfeld, S. and Heimann, M.: Three dimensional atmospheric transport simulation of the radioactive tracers $^210$Pb, $^7$Be, $^10$Be and $^90$Sr, J. Geophys. Res., 100(D12), 26141–26161, 1995. Roeckner, E., Baeuml, G., Bonventura, L., Brokopf, R., Esch, M., Giorgetta, M., Hagemann, S., Kirchner, I., Kornblueh, L., Manzini, E., Rhodin, A., Schlese, U., Schulzweida, U., and Tompkins, A.: The atmospheric general circulation model ECHAM5. PART I: Model description, Report 349, Max Planck Institute for Meteorology, Hamburg, Germany, available at: http://www.mpimet.mpg.de, 2003. Röthlisberger, R., Mulvaney, R., Wolff, E. W., Hutterli, M. A., Bigler, M., de Angelis, M. Hansson, M. E., Steffensen, J. P., and Udisti, R.: Limited dechlorination of sea-salt aerosols during the last glacial period: Evidence from the European Project for Ice Coring in Antarctica (EPICA) Dome C ice core, J. Geophys. Res. 108(D16), 4526, doi:10.1029/2003JD003604, 2003. % Sachsenhauser, H., Zerle, L., Beer, J., Masarik, J. and Nolte, E., Atmospheric transport of cosmogenic radionuclides, \it Wengen, ?. Schlosser, P., Stute, M., Dörr, H., Sonntag, C., and Münnich, K. O.: Tritium/<sup>3</sup>He dating of shallow groundwater, Earth Planet. Sci. Lett., 89, 353–362, 1988. Schotterer, U., Schwarz, P. and Rajner, V.: From pre-bomb levels to industrial times: A complete tritium record from an alpine ice core and its relevance for environmental studies, IAEA-SM-349/55, 1997a. Schotterer, U., Fröhlich, K., Gäggeler, H. W., Sandjordj, S., and Stichler, W.: Isotope records from Mongolian and Alpine ice cores as climate indicators, Clim. Change, 36, 519–530, 1997b. Schwikowski, M., Brütsch, S., Gäggeler, H., and Schotterer, U.: A high-resolution air chemistry record from an Alpine ice core: Fiescherhorn glacier, Swiss Alps, J. Geophys. Res., 104(D11), 13709–13719, 1999. Steinhilber, F., Abreu, J. A., and Beer, J.: Solar modulation during the Holocene, Astrophys. Space Sci. Trans., 4, 1–6, 2008. Stier, P., Feichter, J., Kinne, S., Kloster, S., Vignati, E., Wilson, J., Ganzeveld, L., Tegen, I., Werner, M., Balkanski, Y., Schulz, M., Boucher, O., Minikin, A., and Petzold, A.: The aerosol-climate model ECHAM5-HAM, Atmos. Chem. Phys., 5, 1125–1156, 2005. Stohl, A., Bonasoni, P., Cristofanelli, P., Collins, W., Feichter, J., Frank, A., Forster, C., Gerasopoulos, E., Gäggeler, H., James, P., Kentarchos, T., Kromp-Kolb, H., Krüger, B., Land, C., Meloen, J., Papayannis, A., Priller, A., Seibert, P., Sprenger, M., Roelofs, G. J., Scheel, H.E., Schnabel, C., Siegmund, P., Tobler, L., Trickl, T., Wernli, H., Wirth, V., Zanis, P., and Zerefos, C.: Stratosphere–troposphere exchange: A review, and what we have learnt from STACCATO, J. Geophys. Res., 108(D12), 8516, doi:10.1029/2002JD002490, 2003. Synal, H.-A., Beer, J., Bonani, G., Suter, M., and Wölfli, W.: Atmospheric transport of bomb-produced $^36$Cl, Nucl. Instr. Meth., B52, 483–488, 1990. Thompson, L. G., Mosley-Thompson, E., Davis, M. E., Lin, P. N., Dai, J., Bolzan, J. F., and Yao, T.: A 1000 year climate ice-core record from the Guliya ice cap, China: its relationship to global climate variability, Ann. Glaciol., 21, 175–181, 1995a. Thompson, L. G., Mosley-Thompson, E., Davis, M. E., Lin, P.-N., Henderson, K. A., Cole-Dai, J., Bolzan, J. F., and Liu, K.-B.: Late glacial stage and Holocene tropical ice core records from Huascarán, Peru, Science, 269, 46–50, 1995b. Thompson, L. G., Mosley-Thopson, E., Davis, M. E., Henderson, K. A., Brecher, H. H., Zagorodnov, V. S., Mashiotta, T. A., Ping-Nan, L., Mikhalenko, V. N., Hardy, D. R., and Beer, J.: Kilimanjaro ice core records: evidence of Holocene climate change in tropical Africa, Science, 289, 589–593, doi:10.1126/science.1073198, 2002. Timmreck, C., Graf, H.-F., and Feichter, J.: Simulation of Mt. Pinatubo volcanic aerosol with the Hamburg Climate Model ECHAM4, Theor. Appl. Climatol., 62, 85–108, 1999. Usoskin, I. G., Alanko–Huotari, K., Kovaltsov, G. A., and Mursula, K.: Heliospheric modulation of cosmic rays: Monthly reconstruction of 1951–2004, J. Geophys. Res., 110, A12108, doi:10.1029/2005JA011250, 2005. Zerle, L., Faestermann, T., Knie, K., Korschinek, G., Nolte, E., Beer, J., and Schotterer, U.: The $^41$Ca bomb pulse and atmospheric transport of radionuclides, J. Geophys. Res., 102(D16), 19517–19527, 1997.