Supplementary material to “New Aircraft Will Survey Ice Sheets to Understand Rapid Change”

David Braaten, Center for Remote Sensing of Ice Sheets, University of Kansas, Lawrence

Citation:
Braaten, D. (2007), New aircraft will survey ice sheets to understand rapid change, Eos Trans. AGU, 88(38), 371. [Full Article (pdf)]

Center for Remote Sensing of Ice Sheets (CReSIS)

Observations of the Greenland and Antarctic ice sheets from space, aircraft and the surface have shown a rapid loss of ice mass during the past decade that has contributed to sea level rise. The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC, 2007) acknowledges that the latest sea level rise assessments for various emissions scenarios do not take into account the rapid changes in ice sheet mass flux that have been observed recently.

A Science and Technology Center (STC) funded by the National Science Foundation (NSF) was established in 2005 to better understand this behavior and predict the future contribution of the ice sheets to global sea level rise. This STC, the Center for Remote Sensing of Ice Sheets (CReSIS), is an interdisciplinary center that brings together engineers and scientists with the common goal of understanding the rapid changes occurring in some ice sheet regions. CReSIS is developing sensors and uncrewed aerial vehicles (UAVs) suitable for polar operations, conducting field experiments in Greenland and Antarctica, and developing theoretical and numerical models to better understand the mass balance of the polar ice sheets and their contributions to sea level change. Of particular interest to CReSIS is understanding the substantial speedup of glaciers in Greenland (Rignot and Kanagaratnam, 2006) and Antarctica (Thomas et al., 2004), and the rapid ice retreat and ice elevation change around the margins of Greenland (Krabill et al., 2000). Most of these rapid changes cannot be adequately explained with current ice sheet models due to the lack of critical information on boundary conditions, especially at the ice-bed interface. While it is likely that some of the rapid changes observed are tied to external forcings related to climate change, the actual quantative mechanisms behind the changes are poorly understood. Ice sheet models have the potential to provide quantative assessments of these rapid changes, but they first require more detailed information on conditions at the base of the ice, shear margins, and the grounding line. Without this information, our knowledge of ice sheet response to a warming environment through numerical modeling is critically limited.

CReSIS is led by the University of Kansas and has five university partners in the U.S. (The Ohio State University, The University of Maine, Penn State University, Elizabeth City State University, and Haskell Indian Nations University), and five collaborating university partners aboard (University of Copenhagen, Technical University of Denmark, University of Tasmania, University College-London, and University of Iceland). NASA’s Jet Propulsion Lab and Goddard Space Flight Center have also involved their ice sheet research programs in CReSIS’ mission. CReSIS is working toward its main scientific goal within a structure that integrates observations, science objectives, developing technologies, and numerical models. CReSIS also has education, diversity and knowledge transfer goals that include training the next generation of scientists and engineers, attracting students from underrepresented groups to careers in science and engineering, and providing a forum for policymakers to understand the impacts of climate change on the ice sheets.

Observations of temporal variation of the ice sheets have been too infrequent to ascertain whether the current changes constitute normal ice-sheet variability or indicate a transition into a new mode. The situation is made all the more complicated because of a lack of information on key boundary conditions, and uncertainties and controversy regarding the dynamics of fast ice flow. Current ice sheet models cannot account for the development of ice streams, the key dynamical feature of West Antarctica, nor is the spatial resolution in these models adequate to capture the dynamics of most of Greenland’s outlet glaciers. Incorporating detailed boundary condition information and the capability to capture fast-moving glaciers and ice streams into numerical models is critically important if scientists are to accurately predict the rate at which Greenland and Antarctica contribute to global sea level rise in coming decades. Since processes that trigger and control fast glacier flow are absent from the current ice sheet models used by the IPCC to predict future sea level rise, it is likely that the IPCC sea level rise projections are underestimating one of the most significant societal impacts of climate change in the coming decades.

Probing the Ice Sheets

Ice flow is modulated by the interplay of restraining forces acting at the sides and at the base, buttressing forces originating near the seaward margins, as well as by changes in climate affecting the balance between surface accumulation and ablation. The resistance to ice flow is controlled by many factors, including the physical dimensions of the ice sheet, internal temperature and crystalline fabric of the ice, and physical conditions and the ice-bed interface. Changes in ice flow must be driven by changes in the forces described above, and these changes can be triggered by climatic factors. Physical processes acting at the surface of the glacier and, to some extent, processes acting along the sides of the glacier are reasonably well understood and are efficiently studied using a suite of spaceborne, airborne and in situ measurement techniques. Due to measurement limitations, processes operating at the base of the ice sheet are less well understood.

CReSIS has taken on the challenge of developing sensors and platforms to provide time-efficient, three-dimensional, fine-resolution characterization of key regions and their basal conditions. Figure 1 illustrates how CReSIS will accomplish this by developing and deploying a variety of radar sensors and platforms to characterize the ice sheet from coarse to fine scale resolution, including ice thickness, near-surface and deep internal layers, ice crystalline fabric orientation, temperature profile, and the ice-bed interface including the presence or absence of liquid water. Calibration and ground-truth of the radar measurements are possible by utilizing existing deep ice core data sets, and CReSIS will also conduct shallow firn/ice coring and will operate a probe to rapidly measure the vertical density distribution in the upper firn. Seismic sensors will be used to characterize the sub-glacial characteristics (e.g., composition and fractures) as well as complementary ice column characterization.

Figure 1.
CReSIS is integrating observations, science hypotheses, new technology and ice sheet models to better understand rapid changes seen in the polar ice sheets and their impact on global sea level.

CReSIS is also developing a new V-tail UAV called Meridian (shown in figure 1), specifically designed to meet the demands of radar remote sensing and operation in polar regions. With lower vehicle cost and fuel consumption, the Meridian will extend the range and duration of remote sensing surveys, and will allow CReSIS to survey critical regions at very fine resolution. With an instrument payload (including antennas) of ~70 kg, miniaturization of existing radar sensors is necessary and this is a key technical objective of CReSIS.

Education Goals

An important goal of the Center is to educate and train a diverse population of graduate and undergraduate students in multidisciplinary polar science research, provide research opportunities for undergraduate students as a pathway to graduate education, and reach out to encourage K-12 students to pursue careers in science and engineering. Our education focus is to attract students to science and engineering through polar related topics and instill a sense of the importance of their work and the necessity to cross the boundaries of traditional disciplines. Graduate and undergraduate students are involved in CReSIS work in multidisciplinary research teams across the partner institutions, and have extensive learning opportunities through special events, seminars, relevant courses, and participation in conferences. Graduate students also have the opportunity to spend eight or more weeks abroad with one of the CReSIS international partners.

CReSIS is providing educational opportunities to K-12 students and teachers. Classroom visits, science nights, teacher workshops, and collaboration with a science museum are some of the activities that CReSIS is involved in to increase the interest in science and engineering, and to increase the ethnic diversity of students coming into these fields.

Community Involvement

CReSIS is actively reaching out to the broader scientific community to become engaged in guiding the Center, and is taking several steps to encourage wide involvement. To assure that the Center addresses the research interests of the broader scientific community, an external advisory group has been established. This group, comprised of scientists, engineers, educators and policy makers from universities, industry and government agencies, conducts a yearly review of the Center's accomplishments, strategic plan, and opportunities. CReSIS also routinely organizes and participates in workshops to solicit input on its initiatives. CReSIS has an equipment sharing policy for individuals outside of the Center, and has a data sharing policy that strives to make data sets available to the broader community within a year of a field experiment. CReSIS is also organizing forums with leading climate scientists and engineers to inform the general public and policy makers about the current state of the polar ice sheets, and the potential societal impacts that could result from continued rapid changes to the ice sheets.

Summary

CReSIS is a new Science and Technology Center established by NSF in 2005 to address an important issue facing society today: to understand and predict the role of polar ice sheets in sea level change. The problems associated with determining ice sheet mass balance and creating predictive models of ice sheet dynamics are scientifically and technologically complex, and require a sizeable group of interacting scientists and engineers working in the areas of technological innovation, data collection, and data analysis. CReSIS is educating and training a diverse population of graduate and undergraduate students in multidisciplinary polar science research, and is encouraging K-12 students to pursue careers in science and engineering. CReSIS will continue to seek input from the scientific community, and provide data sets to the community in a timely manner. More information about CReSIS is available at www.cresis.ku.edu.

References

Acknowledgment

This research was supported by the National Science Foundation under grant number 0424589.