Paleo-pH, the carbonate system and climate variation: using boron isotope and B/Ca variations in foraminifera as proxies

• Grant number: 15/12409-6
• Support Opportunities: Regular Research Grants
• Start date: December 01, 2015
• End date: November 30, 2017
• Field of knowledge: Physical Sciences and Mathematics - Oceanography - Geological Oceanography
• Principal Investigator: Karen Badaraco Costa
• Grantee: Karen Badaraco Costa
• Host Institution: Instituto Oceanográfico (IO). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated researchers: Felipe Antonio de Lima Toledo

Abstract

The way the circulation and the chemistry of the oceans interact with the climate on a milenial scales, and how these interactions can be changed in response to increasing greenhouse gases, is gaining increasing attention from the scientific community. Through geochemical analyzes, carried out mainly in foraminifera preserved in marine sediments, it is possible to reconstruct the ocean circulation and the chemistry of the carbonate system in the past. The system carbonate in the ocean plays a key role in climate control on a glacial/interglacial scale. This system can be studied using six covariant parameters - pH [CO2], [HCO3-], [CO32-], total alkalinity (TA) and dissolved inorganic carbon (DIC). One of the proxies used when studying the carbonate system is the boron isotope (´11B), which provides information paleopH, since the isotopic composition of boron in the marine carbonate is pH dependent. In this project, we propose a study to determine the relation between pH (´11B) variation associated with the dissolution of events evidenced by the preservation of carbonate. To this objective ´11B analysis will be done on planktonic foraminifera tests of Globigerinoides ruber (w) and / or benthic foraminifera tests of Cibicidoides spp., found in samples of a high resolution sediment core from the Santos Basinfor the last year 28k, along with analysis of abundance and the degree of dissolution of foraminiferal species Hoeglundina elegans. Due to the high temporal resolution of this sediment cor, it will be possible to have a better resolution of the changes that occurred in the carbonate system, which will also allow a better understanding of the overall behavior of the carbon cycle. (AU)