Colloquium Series: Pratigya Polissar and Ann Pearson

Date: 

Monday, April 19, 2021, 12:00pm to 1:00pm

Location: 

Virtual
 

Presenting: Pratigya Polissar, Associate Professor in Ocean Sciences, UC Santa Cruz; Ann Pearson, Murray and Martha Ross Professor of Environmental Sciences; Harvard University

Title: Reconstructing pCO2 from carbon isotope fractionation in marine algae

Abstract: Carbon isotope ratios in algal organic matter have been used for decades as a CO2 paleobarometer.  Results from this proxy underpin estimates of Cenozoic CO2 and climate sensitivity.  Broad agreement between decreases in both proxy-derived CO  levels and global temperatures over the Cenozoic is tempered, however, by paleoclimate puzzles such as the “Miocene problem” of warm global temperatures but near-modern pCO2.  The existing framework for interpreting carbon isotopes in algae assumes a diffusive-like supply of CO2 to the cell, and that fixation by the enzyme RuBisCO is the primary source of isotopic fractionation.  Here we discuss recent advances from our labs that challenge these assumptions, and highlight additional factors such as irradiance that directly affect algal δ13C.  These new advances point towards a potential resolution for the “Miocene problem” and, combined with pH estimates from foraminifera boron isotopes, indicate a new path for determining changes in ocean carbon chemistry through time.

Zoom link: https://harvard.zoom.us/j/98884783575?pwd=ais5ek9MaGRQYy9ScEh3Zm5YdTRwQT09