Variation in the isotopic composition of the central portion of the State of São Paulo and its interface with climatic systems

Author(s)

Vinícius dos Santos

• Document type: Master's Dissertation
• Press: Rio Claro. 2018-08-10.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Geociências e Ciências Exatas. Rio Claro
• Defense date: 2018-06-26
• Advisor: Didier Gastmans

Abstract

Stable isotopes of hydrogen ( 1 H/ 2 H) and oxygen ( 16 O/ 17 O/ 18 O) constitute excellent tracers of water movement through the hydrological cycle, and they have been used as an important tool to i nterpret climate controls on precipitation . In tropical areas, regional and local climatic factors faced as responsible for the variability observed on isotopic composition of precipitation. Based on the processes involved in the water isotopic transformat ions along it path through the hydrological cycle in continental areas, the main purpose of this master thesis was evaluate and understand which climatic factors are responsible for controlling the isotopic composition of the precipitation in the center of the state of São Paulo. The results demonstrate that the availability of moisture in the atmosphere , co mbined with moisture recirculation processes along the displacement of air masses that generate rain in the studied region , were the main key drivers responsible by the variability observed in isotopic composition of the precipitation, as demonstrated by the local meteoric lines ( δ 2 H = 8.15* δ 18 O + 14.25 ), values of d - excess up to 11‰ , and the seasonal effect, that is characterized by differences between more enriched precipitation during the dry season, characterized by val ues of δ 18 O = > - 4‰, and more depleted precipitation during wet season, with val ues of δ 18 O = < - 4‰ . Seasonal effects were observed during the events El Niños 1997 - 98 and 2014 - 16, as wel l as during the period of precipitation monitoring (2013 - 2017). The moisture recirculation processes are modulated by the action of atmospheric systems over the seasons, such as South Atlantic Convergence Zone (S ACZ ) , when there is large availability of mo isture in the atmosphere and the occurrence of large scale rainfall that depleted the isotopic composition of precipitation, and Cold Frontier ( C F) incursions together with advection movements in an atmosphere with lower moisture availability, during winte r, with the occurrence of convective rains that enrichment the precipitation isotopic composition. Thus, the work provides information and knowledge that can be applied in future hydrological models, given the effects of climate change on the hydrological cycle. (AU)

• FAPESP's process: 16/18735-5 - Isotopic composition of precipitation and its relationship with climatic variability in the southern central portion of São Paulo State (BR)
• Grantee: Vinícius dos Santos
• Support Opportunities: Scholarships in Brazil - Master