Photolytic modification of seasonal nitrate isotope cycles in East Antarctica

Abstract. Nitrate in Antarctic snow has seasonal cycles nitrogen and oxygen isotopic ratios that reflect its sources atmospheric formation processes, as a result, nitrate archived ice should have great potential to record chemistry changes over thousands of years. However, sunlight strikes the surface results photolytic loss fractionation can completely obscure nitrate's original values. To gain insight into how photolysis overwrites cycles, we collected 244 samples along an 850 km transect East Antarctica during 2013–2014 CHICTABA traverse. The route's limited elevation change, consistent distance between coast high interior plateau, intermediate accumulation rates offered gentle environmental gradient ideal for studying competing pre- post-depositional influences on isotopes. We find isotopes are indeed notably modified by after deposition, drier sites more intense impacts. Still, imprint is present top 1–2 m snowpack likely preserved through archiving glacial at these sites. Despite this preservation, reconstructing past values from similar transitional regions will remain difficult challenge without having independent proxy correct changes. Nevertheless, function rate such if multiple years deposition aggregated remove application prove highly valuable own right.