17O18O and 18O18O in ice core O2 from Greenland: implications to reconstruct past atmospheric photochemistry

Abundances of ¹⁷O¹⁸O and ¹⁸O¹⁸O (also called clumped isotopes and denoted by Δ₃₅ and Δ₃₆) of O₂  in firn and ice core air are novel tracers that can be useful to study past changes in atmospheric photochemistry and temperature. We present Δ₃₅ and Δ₃₆ values measured in firn and ice core air O₂ from North Greenland (NEEM; 77.45°N 51.06°W). The aim is to reconstruct the preindustrial-industrial, Holocene and glacial-interglacial variation in the tropospheric ozone photochemistry and temperature. Measurements of Δ₃₅ and Δ₃₆ are carried out using a high-resolution stable isotope ratio mass spectrometer Thermo Fisher 253 ULTRA[1]. Our measurements of Δ₃₅ and Δ₃₆  across past air, from archive samples, to the modern-day show significant changes in the atmospheric photochemistry via ozone burdening and stratospheric- tropospheric transport processes. We will present the measurement results along with a detailed discussion on the dominant process using explicit dynamic simulations of ∆₃₆ in the AC-GCM EMAC model [2,3,4].