Interpretation of the small grains in the inclusions of ice cores

TL;DR

This paper investigates the origin of small grains in Antarctic ice core inclusions, proposing they originate from atmospheric ions that coagulate and diffuse downward, with implications for understanding Earth's past climate and particle influx.

Contribution

It introduces a model explaining small grain formation from atmospheric ions and links it to Earth's orbital variations and isotope distributions.

Findings

Small grains likely originate from atmospheric ions in the upper atmosphere.

Inclusions are more abundant during cold Pleistocene periods.

Large grains are terrestrial and have variable mass distributions.

Abstract

The origin of the grains with diameters less than 4 micron from the inclusions in Antarctic ice cores is discussed. It is proposed that these grains were initiated by ions stopped in the upper atmosphere. The ions form molecules, which coagulate and diffuse downwards. These processes give rise to a characteristic mass spectrum of the small grains. Inclusions in ice were abundant during cold periods of the Pleistocene. This supports a model in which the influx of particles is large when Earth's orbit stays within a disk shaped cloud around the Sun. The production of such a cloud may favor light atoms. This should e.g. be apparent in the isotope distribution of Magnesium from the small grains. The large grains, which have a variable mass distribution, are terrestrial.