Sunlight-driven nitrate loss records Antarctic surface mass balance

Area of Science:

• * Paleoclimatology
• * Glaciology
• * Isotope Geochemistry

Background:

• * Standard proxies for Antarctic surface mass balance (SMB) reconstruction often lack accuracy and resolution in complex terrains away from ice dome summits.
• * Existing methods struggle to provide detailed SMB data in transition zones between ice domes and coastal areas.

Purpose of the Study:

• * To develop and validate a novel proxy for reconstructing past and present surface mass balance (SMB) in East Antarctica.
• * To improve the spatial and temporal resolution of SMB reconstructions, especially in under-sampled regions.

Main Methods:

• * Analysis of nitrogen isotopes in nitrate from ice cores across 114 sites in East Antarctica.
• * Application of the nitrogen isotope proxy to a shallow ice core from Aurora Basin North to reconstruct 700 years of SMB.
• * Comparison of reconstructed SMB with data from ice core density and upstream surface topography.

Main Results:

• * The nitrogen isotope proxy successfully reconstructed 700 years of SMB at Aurora Basin North, showing good agreement with independent methods.
• * The proxy provides SMB values that reflect the local environment in transition zones, independent of existing techniques.
• * Demonstrated the potential of this new proxy for broader application across East Antarctica.

Conclusions:

• * Photolytic fractionation of nitrogen isotopes in nitrate offers a robust and accurate proxy for Antarctic surface mass balance (SMB).
• * This new method enhances our ability to study past climate dynamics in complex Antarctic environments.
• * The proxy is particularly valuable for under-sampled transition zones, offering crucial data for climate modeling and ice sheet dynamics.