Tropospheric Ozone During the Last Interglacial

The history of tropospheric O-3, an important atmospheric oxidant, is poorly constrained because of uncertainties in its historical budget and a dearth of independent records. Here, we estimate the mean tropospheric O-3 burden during the Last Interglacial period (LIG; 115 to 130 thousand years ago) using a record of the clumped isotopic composition of O-2 (i.e., Delta(36) values) preserved in Antarctic ice. The measured LIG Delta(36) value is 0.03 +/- 0.02 parts per thousand (95% CI) higher than the late pre-industrial Holocene (PI; 1,590-1,850 CE) value and corresponds to a modeled 9% reduction in LIG tropospheric O-3 burden (95% CI: 3%-15%), caused in part by a substantial reduction in biomass burning emissions during the LIG relative to the PI. These results are consistent with the hypothesis that late-Pleistocene megafaunal extinctions caused woody and grassy fuels to accumulate on land, leading to enhanced biomass burning in the preindustrial Holocene.

Automated summary

Using Antarctic ice records, we estimated the tropospheric ozone burden during the last interglacial period and found a reduction compared to the late pre-industrial Holocene. This is consistent with the hypothesis of reduced biomass burning caused by the extinction of megafauna.