Sunlight-driven nitrate loss records Antarctic surface mass balance

Standard proxies for reconstructing surface mass balance (SMB) in Antarctic ice cores are often inaccurate or coarsely resolved when applied to more complicated environments away from dome summits. Here, we propose an alternative SMB proxy based on photolytic fractionation of nitrogen isotopes in nitrate observed at 114 sites throughout East Antarctica. Applying this proxy approach to nitrate in a shallow core drilled at a moderate SMB site (Aurora Basin North), we reconstruct 700 years of SMB changes that agree well with changes estimated from ice core density and upstream surface topography. For the undersampled transition zones between dome summits and the coast, we show that this proxy can provide past and present SMB values that reflect the immediate local environment and are derived independently from existing techniques.

Automated summary

This article introduces an alternative proxy for surface mass balance (SMB) in Antarctic ice cores based on photolytic fractionation of nitrogen isotopes in nitrate. By applying this proxy approach to nitrate observed at 114 sites in East Antarctica, the authors reconstruct 700 years of SMB changes and provide SMB values that reflect the immediate local environment independently.