The Forest Effects on the Isotopic Composition of Rainfall in the Northwestern Amazon Basin

Author(s):Show less -

Ampuero, A. ^[1] ; Strikis, N. M. ^[1] ; Apaestegui, J. ^[2] ; Vuille, M. ^[3] ; Novello, V. F. ^[4] ; Espinoza, J. C. ^[5] ; Cruz, F. W. ^[4] ; Vonhof, H. ^[6] ; Mayta, V. C. ^[7] ; Martins, V. T. S. ^[4] ; Cordeiro, R. C. ^[1] ; Azevedo, V. ^[1] ; Sifeddine, A. ^[8]

Affiliation

^[1] Univ Fed Fluminense, Dept Geoquim, Niteroi, RJ - Brazil

^[2] Inst Geofis Peru, Lima - Peru

^[3] SUNY Albany, Dept Atmospher & Environm Sci, Albany, NY 12222 - USA

^[4] Univ Sao Paulo, Inst Geociencia, Sao Paulo - Brazil

^[5] Univ Grenoble Alpes, Inst Geosci Environm, Grenoble INP, IRD, CNRS, IGE, UMR 5001, Grenoble - France

^[6] Max Planck Inst Chem, Dept Climate Geochem, Mainz - Germany

^[7] Univ Sao Paulo, Dept Ciencias Atmosfer, IAG, Sao Paulo - Brazil

^[8] Sorbonne Univ, CNRS, IRD, UPMC, MNHN, UMR LOCEAN, Ctr IRD, Bondy - France

• Document type: Journal article
• Source: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES; v. 125, n. 4 FEB 27 2020.
• Web of Science Citations: 3

Abstract

In the Amazon basin, intense precipitation recycling across the forest significantly modifies the isotopic composition of rainfall (delta O-18, delta D). In the tropical hydrologic cycle, such an effect can be identified through deuterium excess (dxs), yet it remains unclear what environmental factors control dxs, increasing the uncertainty of dxs-based paleoclimate reconstructions. Here we present a 4-year record of the isotopic composition of rainfall, monitored in the northwestern Amazon basin. We analyze the isotopic variations as a function of the air mass history, based on atmospheric back trajectory analyses, satellite observations of precipitation upstream, leaf area index, and simulated moisture recycling along the transport pathway. We show that the precipitation recycling in the forest exerts a significant control on the isotopic composition of precipitation in the northwestern Amazon basin, especially on dxs during the dry season (r = 0.71). Applying these observations to existing speleothem and pollen paleorecords, we conclude that winter precipitation increased after the mid-Holocene, as the expansion of the forest allowed for more moisture recycling. Therefore, forest effects should be considered when interpreting paleorecords of past precipitation changes. (AU)

• FAPESP's process: 17/50085-3 - PIRE: climate research education in the Americas using tree-ring speleothem examples (PIRE-CREATE)
• Grantee: Francisco William da Cruz Junior
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 16/15807-5 - Paleoclimate and paleoenvironmental reconstructions over the last glacial period in the mid-west Brazil
• Grantee: Valdir Felipe Novello
• Support Opportunities: Scholarships in Brazil - Post-Doctoral