Seasonal Sources of Biogenic Ice Nucleation Particles in the Arctic

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandling


The Arctic is particularly vulnerable to climate change, experiencing faster
warming than the global average. This warming leads to multiple negative
feedback processes like sea ice decline and retreating glaciers due to lower
reflectivity and a warmer temperature. Another crucial factor in the Arctic
climate budget is the extent, lifetime, and properties of clouds. Clouds play a
critical role in regulating the Arctic temperature by influencing heat
distribution and absorption, reflecting solar radiation, and trapping the heat
emitted by the Earth in the form of infrared radiation. Cloud formations are
mediated by aerosols, tiny particles suspended in the air. Aerosols, including
mineral dust and soot, serve as cloud condensation nuclei or ice nucleating
particles (INPs) below -15 °C. Bioaerosols, encompassing bacteria, fungal
spores, microalgae, cell fragments, and macromolecules, exhibit ice nucleation
activity (INA) at higher temperatures.
A recent report by the Intergovernmental Panel on Climate Change has
highlighted the largest uncertainties in calculating effective radiative forcing
change as aerosol-cloud interactions. Other research suggests that this
uncertainty is primarily driven by the lack of understanding of sources,
diversity, and activity of INA bioaerosols.
In response to these research gaps this thesis addresses the uncertainties
surrounding INA bioaerosols in the Arctic by examining their seasonal sources.
Our findings reveal a distinct seasonality in the bacterial atmospheric
community, with long-range transport dominating bioaerosols during winter
and early spring. In contrast, the summer period exhibits a shift to local
sources. In winter, sea ice emerges as an overlooked source of biogenic INPs,
while soil and streams play a crucial role as sources of highly active INPs in the
summer. These INPs can either be directly aerosolized into the atmosphere or
transported to the ocean, where melting sea ice and local production
contribute to an enrichment of INPs in the surface microlayer, readily available
for aerosolization during wave breaking and bubble bursting. Our
comprehensive study significantly contributes to our understanding of Arctic
microbial communities, their potential as producers of highly active INPs, and
the interactions influencing the distribution of these particles in air, soil, water, and ice environments. The significance of this research reaches into
considerations related to cloud formation, climate dynamics, and underscores
the importance of addressing the impact of changing environmental
conditions on biogenic INP concentrations and emissions in the Arctic. This
thesis establishes a solid foundation for future studies in this area.
Antal sider296
StatusUdgivet - 1 feb. 2024