Science High in the Clouds Over Greenland

Fog bow over the Mobile Science Facility at Summit Station, Greenland  (July 2012). Photo: Dr. Brant Miller, University of Idaho There’s a lot of science taking place in the skies above Summit Station on Greenland. Von Walden, a professor at Washington State University, is leading a project called Integrated Characterization of Energy, Clouds, Atmospheric State, and Precipitation (ICECAPS) observatory. The data collected from this project will add to our understanding of the climates of the Greenland Ice Sheet and the wider Arctic region.

In the summer of 2010, Walden and the ICECAPS team installed a suite of sophisticated instruments to collect real-time cloud and atmospheric date. ICECAPS scientists will continue to collected data with the tools until 2018, giving them a long-term data set to investigate.

This month, Walden discusses the unique suite of scientific instrumentation installed and utilized by the ICECAPS team at Summit Station with Field Notes.

Von P. Walden in August 2013 with the NSF Mobile Science Facility is in the background. Photo: Von Walden

Field Notes (FN): What instruments has the ICECAPS observatory team installed at Summit Station, Greenland?

Von Walden (VW): We have four core instruments that work across the different parts of the electromagnetic spectrum. Two of the instruments—the LiDAR and radar—are what we call active remote sensing tools. They send out a pulse of radiation and look at what is reflected. LiDAR works in the visible spectrum by sending up little pulses of visible light to see where the clouds are.

Green LiDAR beam emanating from the Mobile Science Facility. Photo: Ed Stockard

The radar at Summit Station emits a radar pulse that is reflected off of the clouds. Our infrared and microwave instruments are passive remote sensing tools that look at what’s being emitted by the atmosphere and clouds.

If you had one of these instruments alone, you’d learn a lot about the atmosphere in Greenland. But having the suite of instruments makes for a very comprehensive view of what’s going on above you.

FN: Why is Summit Station an ideal place to collect atmospheric data?

VW: Summit is a unique place in the Arctic. It’s on top of the Greenland Ice Sheet and 3,200 meters above sea level. If you think about the Arctic, most of it is covered by the Arctic Ocean and at sea level. But Greenland is an enormous obstruction, if you will, to the air that’s circulating around the earth. So Greenland is very unique in the Arctic—it’s a very high, cold and dry place.

Moon rise at Summit Station, Greenland (including the Mobile Science Facility and the Swiss Tower). Photo: David Benson

FN: How were the instruments installed at the site?

VW: We were the first occupants at what’s called the Mobile Science Facility, or MSF, at Summit. This facility was constructed by the National Science Foundation to house different experiments. We shipped thousands of pounds of gear and instruments to Summit Station and proceeded to install them in to the building. Some of the instruments are mounted on the roof, but most of them are mounted inside the MSF and are pushed out through ports in the ceiling or the walls, essentially looking out from the building.

The MSF is this beautiful building that’s on skis because of the drifting that occurs every year. The winds at Summit cause the drifting of anything that’s on the surface. The skis serve two purposes. First, they lift the building off the surface a bit so that the air can flow underneath it, which minimizes some of the drifting.  Second, each year we turn off our instruments and Polar Field Services disconnects them from the building and moves the building to a new location. This allows us to smooth out the drift that was created the previous winter.

FN: What can the instruments tell us about the atmosphere and environmental changes in the Arctic?

VW: The ICECAPS experiment really has five different objectives.

First of all, we hope to find out how clouds and precipitation processes vary seasonally at Summit. We are also looking at how these properties are related to local and regional weather.

Secondly, what are the effects of the clouds in the atmosphere on the surface radiation budget, and how sensitive is it to changes in the atmosphere and clouds? This is very important for understanding how the Greenland Ice Sheet might be responding, in the long term, to global climate change.

We’re also interested in number three: how cloud and atmospheric properties vary at different Arctic sites. There are similar instrument suites in Barrow Alaska and Eureka Canada. So we are very keen to compare the measurements at Summit to these other locations that are at sea level.

We’re also interested in making measurements that serve as a baseline of the central Greenland Ice Sheet. Since these measurements have never been made before, we believe that it’s very important to make good, high-quality measurements to understand what the conditions are now. All indications are that climate change is occurring very rapidly in the Arctic and we might expect conditions in Greenland to change over the next few decades.

Lastly, we’re interested in the microphysical properties of the clouds—basically what they are made of. They aren’t just made of ice. There are a lot of ice crystals, but there is also a lot of liquid water in these clouds, what we call super-cool water droplets.

FN: Can you tell us about some interesting findings uncovered in the data produced by the ICECAPS instruments on Summit Station?

VW: We’ve found that clouds are quite persistent over Summit Station.

We also published a paper last year in Nature that showed the role of clouds at Summit in warming the surface during a melt event that occurred in July 2012. This was a period of time when the surface temperature actually got above freezing for the first time in 125 years.

We used that event as a case study for looking at the importance of the clouds. In particular, one of these super-cooled water clouds. With our instruments, we were able to show that the cloud warmed the surface, and that without the cloud cover that day the surface actually wouldn’t have gotten above freezing.

ICECAPS is a collaboration between Washington State University, the University of Idaho, the National Oceanic and Atmospheric Administration and others. It is supported by the National Science Foundation. For more information about ICECAPS and Von Walden’s cloud research at Summit Station, click here.  —Alicia Clarke