Concentrations of organic carbon, elemental carbon and mineral dust in the snow cover between 2016 and 2024 at Sonnblick Observatory, Austria

Light-absorbing aerosols, including elemental carbon and mineral dust, reduce the albedo of snow covers after deposition. This enhances melting, reducing the duration of the snow cover. Mineral dust additionally introduces various elements to the deposition area, e.g., Fe and Ca. In thermal-optical analysis, which is frequently applied to snow samples after melting and filtration over quartz fibre filters, these Fe-oxides contained in mineral dust lead to a bias in the classification of elemental and organic carbon [1]. Especially for remote environments like glaciers, the correct quantification of both compounds is of interest.

We quantify organic and elemental carbon (OC and EC) via thermal-optical analysis (TOA) in the snow cover collected at the glaciers surrounding the remote high-altitude Global Atmosphere Watch station Sonnblick Observatory (3106 m a.s.l.), located in the Austrian Alps. Samples were collected between 2016 and 2024 with a resolution of 20 cm, providing a continuous data set covering 9 years. We identify samples, which contain mineral dust, using the temperature dependent change of optical properties as previously described and assess the Fe loading directly from TOA data for the current data set. Up to 44 % of samples in the annually collected snow covers were identified to be affected by mineral dust, which is deposited after long-range transport. To counter the influence of mineral dust on OC and EC data, we evaluate those samples using a linear approach and quantify the changes in OC and EC concentrations in the annual snow covers when considering or neglecting the influence of mineral dust on TOA. We analyse the corrected EC data for trends.

Using elemental data of the snow samples collected at Sonnblick Observatory and approaches from literature, we discuss the possibility to deduce the mineral dust loading directly from TOA data.

[1] Kau, D., et al. (2022). Thermal–optical analysis of quartz fiber filters loaded with snow samples–determination of iron based on interferences caused by mineral dust. Atmospheric Measurement Techniques, 15(18), 5207-5217.