THE GLACIERS OF POPOCATEPETL VOLCANO (MEXICO) - CHANGES AND CAUSES

An updated inventory of Popocatepetl volcano's glaciers and field obse rvations for 1977-1992 is presented. Two glaciers (0.559 km(2)) and fo ur permafrost fields (0.239 km(2)) are reported here. Comparing new de scriptions of the Glaciar del Ventorrillo with previous descriptions, a systematic retreat pattern is identified. The average retreat rate ( in terms of terminus altitude) for 1906-1968 is nearly 7 m/year, advan ce rate 10 m/year for 1968-1978 and a response of glacier terminus is documented for 1978-1982 (at 40 m/year). Morphological changes are: a reduction of 25% in the glaciated area, and strong retreat of the Tezc alco Tongue. Glaciar Noroccidental is a stationary glacierette whose a rea was reduced by 12% in 34 years. Total glaciated area was reduced b y 22%. Permafrost fields are located around the glaciers and are the r emains of larger glaciers. Fluctuations are explained in terms of: (a) an increase of heat flow; (b) local climatic changes; (c) global clim atic changes; and (d) a combination of these. Further work is needed t o evaluate the role of the glaciers in the local environment, the impa ct of the local and global climate on them, the role they would play i n the case of explosive activity of Popocatepetl and its consequences. (C) 1997 INQUA/Elsevier Science Ltd.