Postdoctoral research fellow
School of Earth and Environment, University of Leeds, England
The microphysics of cloud formation and the impact of clouds on climate are some of the biggest unresolved questions in climate change research right now. As part of Ben Murray's research group at the University of Leeds in England, my work focuses on ice nucleation, which refers to the formation of ice crystals in clouds. Such crystals generally require a surface for nucleation, and in the atmosphere those surfaces are minute particles, or aerosols. We'd like to know more about how pollutants and particulate matter that get into the atmosphere influence climate through cloud processes. Will pollution lead to more or fewer clouds? How is that going to effect global temperatures? Right now we can't really say.
In the first week of November of last year, my colleague Samuel Dorsi and I traveled to Iceland. The overall goal of the trip was to find some fine-grained sediment smaller than 10 microns, which is material we think is going to get into the atmosphere, for later laboratory experimentation.
Glacial erosion produces very fine sediments, and along the southern coast of Iceland these sediments are spread out on extensive floodplains. Iceland is an extremely windy place, where powerful winds meet broad glacial floodplains. Huge amounts of dust get lofted into the atmosphere. These dust plumes are so large they can be seen in satellite images, streaming for hundreds of kilometers off the coast.
Working our way along the south coast of Iceland, we'd stop on the wide-open plains that lie between the glaciers and the North Atlantic. We'd hike out across pitch-black volcanic cobble and sand in search of deposits of fine sediments.
The retrieved samples are now safely stored in the freezer because we want to preserve the original composition and chemistry as much as possible. In the lab, we suspend the dust in tiny cloud droplets and observe the temperatures at which they freeze.
Results from our experiments can be used in atmospheric models and give us a better understanding of the effects of cloud on climate. For example, low, liquid-water clouds reflect a lot of solar radiation back to space and have a net cooling effect, but high clouds like cirrus are optically thin and let solar radiation in.