CReSIS Members Maximize Oppurtunities During the Greenland Field Season

News

By Katie Oberthaler
Winter 2008

The surrounding white expanse was far from that of a sandy palm beach, but for some CReSIS members, the ice sheets of Greenland provided a summer retreat. Six separate groups of CReSIS associates jettisoned warm weather for the glacial atmosphere between May and August to study an array of aspects about glacial behavior and composition.

Ilulissat Twin Otter Expedition – Radar Sounding from the Air

Twin Otter

Between June 26 and July 26, a team of CReSIS and NASA scientists stationed in Illulissat, Greenland, collected data on the ice thickness of the Jakobshavn Isbrae. The team used ice-penetrating radio waves to measure the bedrock depth and topography of a wide area of ice flying a Kenn Borek DHC-6 Twin Otter plane outfitted with a cutting-edge VHF radar system and twelve folded dipole antennas. These data will help scientists understand and model rapid changes within the Greenland ice sheets. This effort required a large team of scientists and engineers (see back page). The team first spent three weeks in Calgary, Canada, installing the radar and navigation devices onto the plane with the help of Dr. Carl Leuschen, Dr. Sarah Seguin, and graduate student Cameron Lewis. The operation then moved to Greenland to begin the aerial survey. Several improvements over prior experiments produced better data quality, but the trip still presented challenges. The summer melting season caused large pools of water to cover the ice’s surface. This resulted in heavy surface clutter in the returning radar signal. In the first few days, the team also had to troubleshoot the computer infrastructure, Polar Grid, which was developed and provided by Elizabeth City State University and Indiana University. “Despite all the setbacks, we were still able to get excellent data,” said Fernando Rodriguez-Morales, team leader. “I think we learned some lessons and we were all very happy with the final outcome.” The team hopes to make another trip next year to survey key outlet glaciers in western and eastern Greenland. Collecting data in March, for example, will allow the team to avoid the melting season and improve data quality.

Terry Evans Photography – Junction of Science and Art

Photographer Terry Evans visited the Ilulissat team at their base camp for one week to document the team’s work and capture images of the Jakobshavn Isbrae. Evans is currently assembling an exhibit for the Spencer Museum of Art at KU incorporating CReSIS activities in Greenland. Evans found the 24-hour sunlight disconcerting yet beneficial, as did the researchers. “All of my time markers were gone and in a way it was so freeing. I could get up in the middle of the night and photograph. The light didn’t change as fast as at home, and so it was good in a way, but it also was sort of confusing,” said Evans. The scope and size of the glacier also surprised Evans during her aerial photography sessions. “There were no human markers down there, so I was seeing ice bergs in the frozen fjord, and they could have been knee-high or they could have been forty stories tall,” she said. Although the scale confusion disappointed Evans at first, it edified her understanding of CReSIS’ research. Seeing CReSIS members at work in the field with the team directed the focus of her efforts. She noted, “The heart of the work that CReSIS is doing is this goal of measuring the depth of the glacier and the rate at which it’s melting. My own frustration in trying to see the scale of the glacier made me eventually realize that this is also the same challenge we have to understand the scale of climate change. These pictures represent that challenge.” “One of the things that fascinates me is that in a way we’re all gathering data to understand the glacier, CReSIS and I. There are lots of exhibits about climate change but not very many that actually combine science and art. What we’re hoping is this will make clear to people what CReSIS is doing,” said Evans. “A Greenland Glacier: The Scale of Climate Change” will be on display at the Spencer Museum from February 7, 2009, to May 24, 2009.

GAMBIT Testing – Preparations for Antarctic Work

A second CReSIS group also employed aerial geophysical methods in Greenland to assist researchers from Lamont-Doherty Earth Observatory in New York. CReSIS and Lamont Observatory partner through GAMBIT, an international research project studying the Gamburtsev Mountains, a massive sub-glacial mountain range in East Antarctica. Dr. David Braaten, deputy director of CReSIS, and Chris McMinn, electrical engineering undergraduate at KU, will travel to Antarctica from December 8, 2008, to February 9, 2009, to study how and why this mountain range formed. Similar to the Ilulissat experiment, Lamont researchers will operate the ice-penetrating radar in a Twin Otter plane over the ice sheet where the mountain range is buried. The radar system was successfully tested during a Greenland expedition this past summer. Since the Greenland test flights, Dr. Braaten and graduate student Mitch Oswald have been modifying the CReSISdeveloped software using the Greenland data. “There have been a couple different stages where I’ve had to go back and do it all over again because parts of the code were missing,” said Oswald. The final software code will produce more detailed echograms of the data collected in Antarctica.

NEEM – Profiling Internal Ice Layers

From August 1 to August 18, Dennis Sundermeyer and Dr. Carl Leuschen traveled to central Greenland to conduct surface-based radar research at a drilling location called NEEM. The site is an effort led by The University of Copenhagen in collaboration with partners in 13 other countries. The international team is searching for ice samples from an age approximately 115,000 – 130,000 years ago known as the Eemian period. During this time, Greenland temperatures were 3 to 5 degrees warmer than today. This ancient climate could mirror
future conditions and improve understanding about the impact of future climate change on the North Atlantic region. While the core will provide detailed data at a single location, the echograms produced by CReSIS radar will allow scientists to extend this information over a
broader area and improve understanding of the ice’s age, movement patterns, and thickness. The CReSIS team surveyed the ice in a 10 by 10 kilometer grid at the NEEM region using Synthetic Aperture Radar (SAR). The radar mapped the layers down to the bedrock at 2,500 meters below the surface. The radar data were collected by towing a sled with an array of twelve antennas over the ice behind a Toyota Land Cruiser. A triangular aluminum frame of nine trusses, wood and fiberglass beams to support the antennas, and snowboards on the bottom comprised the sled. “We needed something that was light-weight and rigid and adaptable to different situations,” Sundermeyer said. The sled wasn’t the only malleable factor of the trip; Sundermeyer and Leuschen also had to adapt to setbacks. High winds tipping the sled, broken bearings on the Land Cruiser and electromagnetic interference from other electronic devices challenged the team. The team still collected accurate data on the glacial layers and bedrock topography at NEEM. They hope to continue similar work in other regions. In the future, Sundermeyer would like to survey between two drill locations hundreds of kilometers apart to better understand how the ice varies over.

Polar Grid – Supporting Data Collection Efforts

Many of the operations in Greenland could not have succeeded without the use of Polar Grid data processing systems. Polar Grid is a collaborative information transfer infrastructure developed by Elizabeth City State University (ECSU) and Indiana University (IU). The system is comprised of various clusters of computers, including laptops in field sites, base camps, and data centers at ECSU and IU. Networking between these sites provides increased power and celerity for real-time processing of Synthetic Aperture Radar (SAR) data collected by UAV and Twin Otter aerial surveys, as well as ground-based SAR, seismic, and gravity components. “All the computers are typically the exact same and they are mounted in a rack to house them,” Dr. Eric Akers of ECSU said about the clusters. “They are connected closely together so that they can perform many tasks.” Usually, small amounts of data processing can be achieved in the field. Most data must be shipped home to be fully processed. Increased data processing in the field by this Polar Grid configuration allows researchers to adjust their measurement strategies and understand their data faster. Polar Grid was on site at Ilulissat and NEEM this summer to provide this processing power. The group, which included Dr. Akers and Je’aime Powell of ESCU and Matt Link and Rich Knepper of IU, brought 8 nodes, or computers, to Ilulissat. They based their operation in the Ilulissat airplane hanger. The data were downloaded, backed-up and processed in the cluster after each flight. Polar Grid successfully maximized the data storage of nearly 13 Terabytes. “The data has to be shipped back home and this process is very dangerous because hard drives could be damaged,” explained Akers. Polar Grid provided an archival system to safeguard the data in the event of a hard drive corruption. At NEEM, Polar Grid served the same function but with a different configuration. The improved temporal processing in the field aided quick analysis of the ice layering and movement.

Leigh Stearns – Understanding Glacial Dynamics

Leigh Stearns also collected a multitude of information at the ice’s surface this summer. Stearns, who will join CReSIS and KU faculty in January, is a geologist at the University of Maine. Over the course of four expeditions between May and September, she trekked across the Helheim and Kangerluggsauq glaciers to position approximately 30 GPS units. Both outlet glaciers have undergone rapid changes in the past few years. Stearns detected their movements through a number of methods. The GPS units took measurements every five seconds on the glaciers to obtain glacial speed fluctuation. Unlike in past expeditions, Stearns will keep roughly 10 GPS units on the glacier during the winter when sparse data on glacial behavior are available. Stearns also placed time-lapse cameras in front of the glacier to detect iceberg calving events. Weather stations on the glacial surface measured surface melt. Preliminary analysis of oceanographic measurements show that warm water is entering the ice-covered fjord. If this water reaches the front of the glacier, it would cause melting. Stearns will study how this water circulates and interacts with the glacier in future research. “Finding new results always leads to a slew of more puzzling questions. I hope to continue the Greenland work that I've been doing the past few years, and engaging students and other researchers into this exciting field,” said Stearns. “With CReSIS, I plan on remaining active in field work, education and outreach, and improving glaciology models so we can constrain our sea level rise estimates.” Overall, the achievements of this summer’s Greenland field season will help CReSIS members analyze ice composition, movement, and depth in more detail as well as improve data management infrastructure. These data and their analysis will enhance future Greenland expeditions and the upcoming Antarctic field season. More details on all this work can be found on the CReSIS web site, http://cresis.ku.edu.