Precipitation in the Central Amazon Basin: - The Isotopic Composition of Rain and Atmospheric Moisture at Belém and Manaus

Abstract

SUMMARYPossible causes of the seasonal differences in tne isotope pattern are discussed.

Application of Stable Isotope Tracer to Study Runoff Generation during Different Types of Rainfall Events

“…Several studies have investigated the temporal variations of precipitation isotopes in different types of rainfall events [14][15][16]. Factors affecting the temporal and spatial variation of precipitation…”

Seasonal variations in the stable oxygen isotope ratio of wood cellulose reveal annual rings of trees in a Central Amazon terra firme forest

“…In addition, the Intertropical Convergence Zone (ITCZ) affects the seasonality of δ 18 O prec in this region. When the ITCZ crosses the eastern margin of the Amazon basin, moisture from which 18 O has been depleted is pushed inland (Matsui et al 1983;Rozanski et al 1993). Thus, δ 18 O prec in the Amazon basin primarily originates from the Atlantic and is locally altered by the amount effect and the position of the ITCZ.…”

Comments

“…Henderson-Sellers et al's third isotopic result agrees with about half the published deforestation predictions ), but disagrees with Chen et al's results since decreased runoff would not be expected with increased atmospheric moisture convergence. Despite previous studies (e.g., Matsui et al 1983;Moreira et al 1997) suggesting that the isotopic signal of Amazonian deforestation would be most detectable in the dry season, Henderson-Sellers et al find only wet season signals. Overall, they conclude, "we cannot find any GCM (deforestation) simulation which agrees well with the isotope-derived changes in wet season Amazonian water cycling."…”