We are delighted to be working with The Institute for Climate and Atmospheric Science at the University of Leeds. The ice nucleation research team are conducting an 18-month research programme on the Greenland ice sheet. They will be sampling the ice sheet throughout their time there and as particulate contamination is a major concern we have shipp ed one of our Clean Hoods to the summit station.
Summit Station is a research platform at the summit of the Greenland ice sheet, it has been in operation since 1988. The National Science Foundation funds and manages the station in cooperation with the Government of Greenland. Located at 72° 36′ N latitude, and at an altitude of 10,600 feet with a mean annual air temperature of -31°!
The Institute researches the properties of aerosol particles in the Earth’s atmosphere and how these particles influence clouds through a combination of laboratory, field and numerical modelling studies.
Their work focuses on improving understanding of the fundamental role aerosols and clouds play in our planet’s climate system, which will ultimately lead to improved weather and climate models.
Project: The Integrated Characterization of Clouds, Energy, Atmospheric state, and Precipitation at Summit, Aerosol-Cloud Experiment (ICECAPS-ACE) funded by U.S. National Science Foundation and the U.K. Natural Environment Research Council.
The aim of this part of the project is to provide a better understanding of aerosol-cloud interactions over the Greenland Ice Sheet (GrIS) by investigating the sources and concentrations (including seasonal changes and episodic intrusions) of ice nucleating particles (INP) at Summit.
This will improve understanding of super-cooled liquid found within Arctic clouds. To do this we will measure INP concentrations as a function of activation temperature and season. These observations are crucial for improving the accuracy of weather and climate models over GrIS.
To measure INP concentrations at Summit we will use a filter-based technique which is similar to approaches already used in remote low-INP concentration environments comparable to Greenland. To collect the filters, we will deploy a robust commercial filter sampler (BGI PQ100 FRM Sampler) that adheres to the EPA Federal Reference Method for PM10 (particulate matter < 10 microns).
The PQ100 instrument will sample aerosol onto 0.4-µm track-etched polycarbonate filters. We will sample at 16.67 L min-1, the flow rate that the sampling head is optimized for. The aerosols will be removed from the filters into a small volume of water (typically 6 ml), by placing the filter into ultra-pure water in a clean container and agitating using a Vortex mixer.
The resulting suspension will then be used to quantify the INP concentration as a function of ice-activation temperature using a Nucleation by Immersed Particles Instrument (NIPI), which has been used in lab and field studies in the past. Using the suspension from the filter in this technique, we place an array of ~50 droplets of 1 µl volume onto a hydrophobic-coated surface.
The droplets are then cooled at a rate of 1 K min-1 while recording the freezing temperature of individual droplets using a digital camera. With knowledge of the volume of air that passed through the filter, we can use the freezing data to determine the INP concentration over a range of temperatures. INP are rare and so these experiments are susceptible to effects from contamination.
As such it is important that all procedures are carried out in a clean environment. Handling of samples and experiments will be carried out in a Vertical Laminar Flow Hood (Clean Environments CH1200V) to exclude particulate contaminants.Bethany Wyld | The Institute for Climate and Atmospheric Science