A new method for high-resolution methane measurements on polar ice cores using continuous flow analysis

Area of Science:

• Paleoclimatology
• Atmospheric Chemistry
• Glaciology

Background:

• Methane (CH4) is a significant greenhouse gas, and its past atmospheric concentrations are crucial for understanding climate dynamics.
• Ice cores contain trapped air bubbles that serve as archives of past atmospheric composition, with CH4 variations used as climate proxies.
• Accurate, high-resolution CH4 measurements are essential for precisely dating ice cores and reconstructing past climate events.

Purpose of the Study:

• To introduce a novel, field-deployable method for semicontinuous methane detection in ice cores.
• To achieve higher temporal resolution in CH4 measurements compared to existing techniques.
• To improve the accuracy and precision of CH4 analysis in ice core studies.

Main Methods:

• Development and implementation of a continuous flow analysis (CFA) system for ice core analysis.
• Semicontinuous melting of ice core samples at a rate of 3.5 cm/min.
• On-line extraction of air from meltwater and subsequent analysis by gas chromatography (GC) for CH4 concentration.

Main Results:

• The CFA-CH4 method achieves a depth resolution of 15 cm with measurements every 3.5 minutes.
• The method demonstrates a reproducibility of 3%, yielding an absolute precision of 15 ppb for typical ice age CH4 concentrations.
• Measurements on an Antarctic ice core show significantly higher temporal resolution than traditional methods.

Conclusions:

• The new CFA-CH4 method offers a feasible and effective approach for high-resolution paleoclimate reconstructions.
• This advancement allows for more detailed analysis of rapid CH4 concentration changes in Earth's history.
• The technique has the potential to refine ice core dating and improve our understanding of methane cycle dynamics.