🏔️ Mont Blanc ice has archived European aerosols since the last deglaciation

A study published in PNAS Nexus documents for the first time the evolution in Europe of different aerosols (sea salt, dust, biotic particles) over the past 12,000 years.

These measurements of ¹⁸O and various chemical compounds come from an ice core drilled at 4,300 m (about 14,100 ft) near the summit of Mont Blanc and dated, among other methods, using ¹⁴C. This unique archive makes it possible to document the aerosol-climate relationship outside polar regions, here in Western Europe.


Atmospheric aerosol, fine liquid or solid particles in the atmosphere, is a key player in regional climate that remains poorly understood. Ice simultaneously archives past climate and aerosols. However, until now, the study of glacial records has not allowed examination of the aerosol-climate relationship since the last glaciation, except in polar regions. This lack of data at mid-latitudes is crucial for Europe, which, in addition to climate fluctuations, experienced anthropogenic pressure well before the start of the industrial era, with changes in land use over the last millennia of the Holocene by early agricultural societies.

Carbon-14 measurement and past temperature profile

Scientists from 3 countries and 2 French laboratories (see box) identified a drilling site on a glacier in the French Alps that has archived the evolution of aerosols in Europe over the past ~12,000 years.

Unlike ice sites often located in a pass, this new drilling is situated on a flat summit, which minimizes the strong stresses due to glacier flow on ice near the bedrock, a phenomenon that disturbs the climate record beyond a few thousand years. This new ice core was dated using argon from air bubbles and the identification of lead pollution during Roman antiquity for the most recent part, by measuring ¹⁴C on organic matter and the ¹⁸O profile for the beginning of the Holocene.

Strong increase in marine aerosols and decrease in biogenic particle concentrations

Chemical analysis of this ice shows an increase in sea salt and dust concentrations over Western Europe during cold climate periods, which corresponds to a strengthening of westerly winds and greater dust emissions likely originating from the Sahara.

It also indicates a decrease in concentrations of biogenic particles during cold climate periods, implying a notable reduction in European vegetation cover.