Authors: Martinez-FrÍAs, J.¹; Delgado, A.²; MillÁN, M.³; Reyes, E.²; Rull, F.⁴; Travis, D.⁵; Garcia, R.⁶; LÓPez-Vera, F.⁷; RodrÍGuez-Losada, J.⁸; Martin-Rubi, J.⁹; Raya, J.²; Santoyo, E.¹⁰

Source: Journal of Atmospheric Chemistry, Volume 52, Number 2, October 2005 , pp. 185-202(18)

Publisher: Springer

Abstract:

Specific studies about the stable isotope composition (¹⁸O/¹⁶O and D/H) of atmospheric icy conglomerations are still scarce. The present work offers, for the first time, a very detailed analysis of oxygen and hydrogen isotopic signatures of unusually large ice conglomerations, or “megacryometeors”, that fell to the ground in Spain during January 2000. The hydrochemical analysis is based on the bulk isotopic composition and systematic selective sampling (deuterium isotopic mapping) of eleven selected specimens. δ¹⁸O and δD (V-SMOW) of all samples fall into the Meteoric Water Line matching well with typical tropospheric values. The distribution of the samples on Craig's line suggests either a variation in condensation temperature and/or different residual fractions of water vapour (Rayleigh processes). Three of the largest megacryometeors exhibited unequivocally distinctive negative values (δ¹⁸O = −17.2%₀ and δD = −127 %₀ V-SMOW), (δ¹⁸O = −15.6%₀ and δD = −112%₀ V-SMOW) and (δ¹⁸O = −14.4%₀ and δD = −100%₀ V-SMOW), suggesting an atmospheric origin typical of the upper troposphere. Theoretical calculations indicate that the vertical trajectory of growth was lower than 3.2 km. During the period in which the fall of megacryometeors occurred, anomalous atmospheric conditions were observed to exist: a substantial lowering of the tropopause with a deep layer of saturated air below, ozone depression and strong wind shear. Moreover, these large ice conglomerations occurred during non-thunderstorm conditions, suggesting an alternative process of ice growth was responsible for their formation.

Keywords: hydrogen and oxygen isotopes; ice conglomeration; megacryometeors; tropopause

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s10874-005-2007-7

Affiliations: 1: Planetary Geology Laboratory, Centro de Astrobiologia CSIC-INTA), Associated to the NASA Astrobiology Institute, Ctra de Ajalvir, km 4, 28850, Torrejón de Ardoz, Madrid, Spain, Email: martinezfrias@mncn.csic.es 2: Estacion Experimental del Zaidin, CSIC, Prof. Albareda, 1, 18008, Granada, Spain, 3: Fundación CEAM, Parque Tecnológico de Paterna, C/Charles Darwin, 14, 46980, Valencia, Spain, 4: Planetary Geology Laboratory, Centro de Astrobiologia CSIC-INTA), Associated to the NASA Astrobiology Institute, Ctra de Ajalvir, km 4, 28850, Torrejón de Ardoz, Madrid, Spain, 5: Department of Geography and Geology, University of Wisconsin-Whitewater, Whitewater, WI, 53190, USA, 6: Museo Nacional de Ciencias Naturales, (CSIC), José Gutiérrez Abascal, 2, 28006, Madrid, Spain, 7: Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain, 8: Dep. Edafología y Geología, Fac. Biología, U. La Laguna, 38206, La Laguna (Tenerife), I. Canarias, Spain, 9: Laboratorios IGME, La Calera, 1, 28760, Tres Cantos, Madrid, Spain, 10: Centro de Investigación en Energía, Universidad Nacional Autónoma de México, Priv. Xochicalco s/n Apdo, Postal 34, Temixco, Mor. 62580, Mexico,

Publication date: 2005-10-01

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• By this author: Martinez-FrÍAs, J. ;  Delgado, A. ;  MillÁN, M. ;  Reyes, E. ;  Rull, F. ;  Travis, D. ;  Garcia, R. ;  LÓPez-Vera, F. ;  RodrÍGuez-Losada, J. ;  Martin-Rubi, J. ;  Raya, J. ;  Santoyo, E.

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