Atmospheric Deposition of Local Mineral Dust Delivers Phosphorus to the Greenland Ice Sheet

TL;DR

Mineral dust from nearby areas delivers phosphorus to the Greenland Ice Sheet, supporting algal growth and affecting ice melting.

Contribution

The study identifies local mineral dust as a source of phosphorus to the Greenland Ice Sheet, linking aerosol deposition to algal growth and ice albedo.

Findings

Aerosols collected on the Greenland Ice Sheet are primarily silicate minerals from local proglacial plains.

Phosphorus delivery via dust and snow supports algal cell densities consistent with observed blooms.

Airborne algae and fungi dominate eukaryotic communities in air and snow samples.

Abstract

Aerosol composition, size, and deposition rate determine
the impact
these particles have on cryosphere environments. Mineralogical, biological,
and geochemical characteristics of aerosols collected over two years
from the southwest Greenland Ice Sheet indicate that aerosols delivered
via dry deposition and in snow primarily consisted of silicate minerals,
with mean particle diameters of 1.01 ± 1.58 μm (2016) and
0.76 ± 0.87 μm (2017) for dry deposition and 2.4 ±
3.2 μm for dust delivered in snow (2017). The rare earth element
signature of the delivered dust was typical of nearby Greenlandic
lithologies, and combining this with other geochemical results and
airmass history modeling indicated that the airborne mineral dust
collected on-ice was likely from local emission sources,
namely nearby proglacial plains. Dust and snow deposition rates were
used to estimate phosphorus delivery to the ice surface at a rate
of 1.2 mg·m–2·year–1, which could fuel estimated pigmented glacier ice algal cell abundances
of 8.6 × 103 cells·mL–1, a
value consistent with glacier ice algal bloom cell densities documented
in the region. The eukaryotic communities in air and snow samples
were dominated by algae and fungi, respectively, with both sample
types also hosting various bacteria. These results suggest that the
airborne transfer of glacier ice and snow algae may be a method by
which fresh cryosphere surfaces become inoculated with these pigmented
organisms. Collectively, these findings highlight the biogeochemical
links between aerosols and the ice sheet surface, which have impacts
on glacier ice algal growth and the corresponding surface ice albedo
and melting.

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