Written by Melissa Christensen, ASD
Case Study: Is Greenland Getting Darker?: National Science Foundation-Sponsored Research Project Uses ASD Instruments to Measure Climate Change
The Greenland ice sheet has experienced a recent period (since ~1990) of accelerating glacier melting, causing global sea level rise. Along with warming Arctic temperatures, Greenland’s melting may have been enhanced by a darkening snow surface, but scientists haven’t been able to determine if, and why, Greenland’s snow is getting darker due to the expense and difficulty of getting researchers out in the field. A darker snow surface absorbs solar radiation more quickly, warms up, and causes melting. The necessary research would focus not only on how much snow is falling, but also where it’s snowing, how much snow is melting, and whether and why the snow surface is darkening. The end goal is to determine how far sea level will rise in the next few decades to centuries, threatening many of America’s major coastal cities.
In 2016, a collaborative research group from Dartmouth College, The University of Maine and Boise State University, Idaho, sponsored by the National Science Foundation (NSF), began studying the recent changes in surface mass balance on the western Greenland ice sheet percolation zone.
In order to gather crucial data, Gabriel Lewis, Dartmouth College Ph.D. candidate, wrote a NSF Graduate Research Fellowship grant, as well as a Goetz Fellowship Grant from ASD, to borrow an ® and was awarded temporary use of the instrument for both field seasons.
“We knew we needed to measure albedo to find out if Greenland is getting darker as a result of more impurities from fossil fuel pollution in the snow, or if the darkening is from larger snow grain sizes from warmer temperatures, or if the satellite measurements are falsely indicating a darkening ice sheet,” said Lewis.
Lewis chose the ASD FieldSpec 4 because:
･ Unlike other spectroradiometers, the FieldSpec 4 can measure albedo (the ratio of incoming and outgoing radiation of the snow) at multiple frequencies (in this case, 350-2500 nanometers with high resolution and accuracy) for a more complete picture.
･ The FieldSpec 4 can also be used with a contact probe to measure the optical grain size of snow grains – a vital piece of information to determine if the snow has darkened.
･ The instrument is portable, making it easy to transport and use in the field.
･ The instrument came highly recommended by engineering colleagues at Dartmouth College.
The FieldSpec 4 instrument was used to measure albedo, as well as the optical grain size of the snow. Additionally, samples of snow were collected and analyzed to measure their dust and soot impurities. Through laboratory analysis back at Dartmouth, the group was able to measure the quantity of impurities, their origin and whether their creation was natural or man-made.
Though the research project has yet to be completed, the preliminary results exhibit a statistically significant correlation between the snow grain size and albedo, and no statistically significant correlation between the impurities and albedo. There is great agreement between the NSF-sponsored research project’s measurements and both NASA satellites and computer climate models. Most of the measurements fall within the expected uncertainty from the samples and locations processed so far and the team is eager to collect more data.
“It’s great to know we are on the right track. I am very excited to take the FieldSpec 4 back into the field this spring and expand on some of the correlations we’ve already noticed,” commented Lewis. “From my work last summer, it is clear the ASD FieldSpec 4 albedo measurements in Greenland agree nicely with many of the satellite and climate model measurements -which is wonderful.”
In April 2017, Lewis and his team will return to Greenland to gather additional measurements over the course of eight weeks. From there, the final research data will be compiled to determine whether or not current climate models need to be altered to better predict the future of the Greenland ice sheet, including what is specifically causing the snow to melt or become darker (e.g. grain size, pollution, warmth, etc.).
Lewis concludes, “climate change is not up for discussion. It is real. It is happening, and we have all the data to prove it. The data I am helping to gather and analyze will help us understand the impact of climate change on Greenland, and what it means for the future of the planet.”