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LSCE: PhD position on reconstruction of the global biosphere productivity during the last deglaciation  

See attached..

PhD position on reconstruction of the global biosphere productivity during the last deglaciation

Project Description

The concentration of atmospheric carbon dioxide (CO₂) changed more than 100 ppm over transitions between glacial and interglacial periods (deglaciations) during Quaternary. Among others, the role of global biosphere (terrestrial and marine realms) on the deglacial CO2 changes remains uncertain. In modern climate, the global biosphere uptakes nearly half of atmospheric carbon emitted by anthropogenic activity via photosynthesis (global biosphere productivity), the largest single carbon flux between atmosphere and the biosphere. However, it is challenging to estimate the past global biosphere productivity from local reconstructions as they are often based on indirect geochemical tracers and exhibit spatial heterogeneities. Instead, the triple oxygen isotope composition of air oxygen (¹⁷Δ of O₂) preserved in polar ice cores has been proposed as unique tracer of global biosphere productivity of the past. Recent study carried out at LSCE and University of Copenhagen revealed that the global photosynthesis was reduced during the last eight glacial intervals relative to modern value. Nevertheless, the quantitative interpretation of the ¹⁷Δ of O₂ data is still complicated because of large uncertainties in the biosphere processes that fractionate the triple O₂ isotopes.

contact

Ji-Woong YANG (ji-woong.yang@lsce.ipsl.fr) and Didier Roche (Didier.roche@lsce.ipsl.fr)

These_announce_v2_EN.docx (18 Ko)

A. Mazaud, dépêche du 12/04/2023