Ice sheets and nitrogen

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Glaciology

Background:

• Snow and ice are critical regulators of the nitrogen cycle, limiting land-atmosphere and ocean-atmosphere exchanges.
• Polar ice sheets store approximately 260 Tg N, primarily as nitrate in Antarctica.
• Ice cores provide invaluable historical data on nitrogen cycle variability and anthropogenic disturbances.

Purpose of the Study:

• To analyze historical nitrogen deposition and atmospheric concentrations using ice core records.
• To assess the impact of human activities on the global nitrogen cycle.
• To understand the role of snowpack photolysis in nitrogen emissions.

Main Methods:

• Analysis of nitrogen compounds (nitrate, ammonium) in ice cores from polar and mid-latitude regions.
• Interpretation of ice core data to reconstruct past atmospheric concentrations of nitrogen species.
• Investigation of nitrate photolysis in snowpack and its impact on regional NOx emissions.

Main Results:

• Nitrous oxide concentrations have increased by 20% in the last 200 years, reaching unprecedented levels.
• Greenland ice cores show a 2-3 fold increase in nitrate concentrations, particularly from the 1950s to 1980s, linked to NOx emissions.
• Antarctic ice shows no significant recent trends in nitrate or ammonium, but natural variations are noteworthy.
• Snowpack nitrate photolysis contributes significantly to regional NOx re-emissions.

Conclusions:

• Ice core data demonstrate significant anthropogenic influence on the global nitrogen cycle, evidenced by rising greenhouse gases and nitrogen deposition.
• Regional emission inventories can be validated and constrained using ice core records from various latitudes.
• Snowpack processes, such as nitrate photolysis, play a crucial role in the atmospheric chemistry of snow-covered regions.