Research Projects

A wide variety of research projects have been conducted at Summit Station since 1989. Initially established as a 'camp' for the collection of the Greenland Ice Sheet Project II (GISP2) ice core, seasonal campaigns were established to measure atmospheric components to improve the interpretation of the ice core records. The value of the location was readily recognized and further intensive measurement campaigns were initiated on a seasonal basis. Since that time, Summit Station has become an Arctic 'flagship' station as part of the Arctic Observing Network (AON) and the International Arctic Systems for Observing the Atmosphere (IASOA) network.

The following project summaries are developed from plans that are submitted every year to CPS. The data presented in the summaries below is from the Arctic Research Mapping Application (ARMAP). Use the filter below to view the research projects by project season.

 
Displaying 1 - 14 of 14

2013-2018 UNAVCO Community Proposal Geodesy Advancing Geosciences and EarthScope: The GAGE Facility

PI Institute/Department Email
Miller, Meghan
UNAVCO
Science Summary

The GAGE Facility: Geodesy Advancing Geosciences and EarthScope Cooperative Agreement (CA) supports advancement of cutting-edge community geodetic research around the world. Over the last two decades, space-based geodetic observations have enabled measurement of the motions of the Earth's surface and crust at many different scales, with unprecedented spatial and temporal detail and increased precision, leading to fundamental discoveries in continental deformation, plate boundary processes, the earthquake cycle, the geometry and dynamics of magmatic systems, continental groundwater storage and hydrologic loading. Space geodesy furthers research on earthquake and tsunami hazards, volcanic eruptions, coastal subsidence, wetlands health, soil moisture and groundwater distribution. Of particular importance are contributions to understanding of processes related to climate dynamics, including hurricane tracking and intensity, sea level rise, and changes in mountain glaciers and large polar ice sheets. As global population disproportionately increases in hazards-prone coastal and tectonically active regions of the US and across the globe, the societal relevance of quantifying, understanding, and potentially mitigating natural hazards grows. Geoscientists using global geodetic infrastructure coupled with leading edge techniques are well poised to advance basic research that is in the U.S. and global public interest as the challenges of living on a dynamic planet escalate. NSF-funded geodesy investigators are active on every continent, across a broad spectrum of the geosciences, and facilitated by data and engineering services that are now merged under the GAGE Facility. GAGE continues operations of: 1) the EarthScope Plate Boundary Observatory (PBO), an integrated set of geodetic networks that includes 1100 continuous GPS sites (with ~350 high-rate, low-latency data streams and ~125 surface meteorological sensors), 78 borehole strainmeters and seismometers, and 6 long-baseline laser strainmeters, and tiltmeters on several volcanoes; 2) global engineering and data services primarily to NSF-funded investigators who use terrestrial and satellite geodetic technologies in their research and provision of network operations support to community GPS networks and NASA's Global GNSS Network (GGN); and 3) Education and community outreach activities. NSF's Division of Polar Programs (PLR) contributes to the GAGE Facility support of PI research and GPS networks in Greenland and Antarctica. NASA contributes to the GAGE Facility to support the GGN and the activities of the IGS Central Bureau, which underlie the internationally coordinated reference frame products that make high-precision geodesy possible.

Collaborative Research: Integrated Characterization of Energy, Clouds, Atmospheric state, and Precipitation at Summit (ICECAPS)

PI Institute/Department Email
Bennartz, Ralf
U of Wisconsin, Madison
Walden, Von
Washington State University, Department of Civil and Environmental Engineering
Turner, David
National Oceanic & Atmospheric Administration
Shupe, Matthew
U of Colorado, Boulder, Cooperative Institute for Research in Environmental Sciences
Science Summary

In 2010, the observatory at Summit, Greenland, in the center of the Greenland Ice Sheet (GIS), was expanded to include a comprehensive suite of cloud-atmosphere observing instruments including microwave and infrared spectrometers, cloud radar, depolarization lidar, ceilometer, precipitation sensor, sodar, and a twice-daily radiosonde program. This observing effort was termed ICECAPS (Integrated Characterization of Energy, Clouds, Atmospheric state, and Precipitation at Summit). Continuation of the work was approved / funded late summer 2013 to allow for continuous operation, with moderate enhancements to include new precipitation measurements. Measurements from this expanded instrument suite will be used to derive critical baseline atmospheric data products including: Atmospheric State - tropospheric temperature, moisture, and wind profiles, Cloud Macrophysics - occurrence, vertical boundaries, temperature, Cloud Microphysics - phase, water content, and characteristic particle size, and Precipitation - type and rate. Together these products, when combined with similar ongoing measurements at Summit, can be used to study processes that impact the surface energy budget and precipitation at the site, as well as addressing questions related to atmospheric stability, cloud phase composition, and the persistence of stratiform clouds. It is further anticipated that these observations will continue to be used by a broad cross-section of the scientific community to promote understanding of GIS and Arctic climate, validate satellite observations, and evaluate model simulations. Graduate students play significant roles in most aspects of this project, gaining valuable experience with polar field work, operating instruments, and processing data. In addition, this research team has developed a unique education and outreach plan to work with students from local schools using simple, proxy instrumentation to help develop their understanding of atmospheric principles and observations, and to enhance the scientific curriculum in their schools via a wide range of outreach activities.

Collaborative Research: Science Coordination Office for Summit Station/ISI Observatory and the Greenland Traverse

PI Institute/Department Email
Hawley, Robert
Dartmouth College, Department of Earth Sciences
Dibb, Jack
U of New Hampshire, Institute for the Study of Earth, Oceans, and Space
Burkhart, John
U of California, Merced, School of Engineering
Science Summary

The Office of Polar Programs has been funding substantial scientific activities at Summit Station, Greenland for over twenty years. Summit Station hosts the Greenland Environmental Observatory (GEOSummit), a cooperation between the National Science Foundation (NSF) and the National Oceanographic and Atmospheric Administration with permission from the Danish Commission for Scientific Research in Greenland to provide long-term environmental measurements. Summit is the only high-elevation, free-tropospheric, inland environmental observatory in the Arctic which is manned throughout the year. Summit therefore fills a unique niche in the international scientific community’s global measurement capability. The Science Coordination Office (SCO) for Summit Station and the Greenland Ice Sheet serves in an advisory capacity to NSF’s Arctic Research Support and Logistics Program. SCO’s primary role is to present the needs and desires of the science community working on the Greenland Ice Sheet in discussions and decision making processes involving NSF, its primary logistics support contractor, and other stakeholders. The SCO also works with NSF, NSF’s contractor, and science teams to work out equitable and efficient use of resources, and strives to ensure that the wide range of science and support activities impact the pristine character of Summit as lightly as possible. SCO shares in the long-range goal of redeveloping Summit infrastructure in ways that will reduce long-term operation and maintenance costs, and reduce the emissions of pollutants by facilities on the station and the aircraft and traverse vehicles that visit. The SCO also helps coordinate visits to Summit for educational groups at all levels, from high school to post-graduate. The SCO will work closely with NSF and all relevant stakeholders in the design of a revitalized Summit Station where reducing operational and maintenance effort (and costs) will preserve the site for future science by reducing emissions. Additional scientific communities, including astronomy and astrophysics, have recently expressed interest in using Summit Station as an Arctic base for new observations. SCO will actively participate in discussions with all interested parties to develop a site plan to accommodate an influx of additional research activities while maintaining long-standing focus on climate-relevant research which requires clean air and snow conditions. SCO’s website is a keystone of communication to the science community, with several new features added over the past few years, including; a Google Earth based GIS recording activity in the region over the past 9 years, a virtual tour using Streetview images, a new ‘Working at Summit’ section that targets new investigators, a comprehensive bibliography of published work near Summit, and a quarterly newsletter. SCO will conduct a comprehensive overhaul of the web site to improve navigation, and will continue to add new features.

Collection and Analysis of GEOSummit Aerosols

PI Institute/Department Email
Cahill, Thomas
U of California, Davis, Department of Physics
Science Summary

Fine particles directly scatter and absorb sunlight, and depending on their size and composition can either heat or cool the Earth. They come from both natural sources like volcanoes, dust storms, and forest fires, and from man-made sources like industry, power plants and vehicles. Since a signature of their origin is imbedded in their composition, they can be tracked back to sources even thousands of miles away using meteorological models. Understanding the composition and sources of these fine particles is critical to developing better models of global climate change, but requires many years of observation. One of the best places to measure these fine particles in the atmosphere is at the Greenland Summit research station because the site is not near populated areas or the ocean which are sources of these particles. This renewal of an Arctic Observing Network project will extend sampling of these fine particles at the Greenland Summit site another 5 years. The results will be of value to global climate modelers and to atmospheric scientists. Undergraduate students will be involved in sample analysis. This program is unique in that the Greenland Summit site is the only high elevation Arctic site and thus responds to aerosols in the free troposphere, the region of the atmosphere that dominates long range transport. Since 2003, aerosols have been collected continuously in 8 size modes, 15 µm to 0.09 µm, on slowly rotating drums that allow for 12 hr. time resolution and an excellent match to the various transport patterns that bring aerosols into the Arctic. Since there is very little mass to analyze, the large synchrotron x-ray source at the Lawrence Berkeley Laboratory Advanced Light Source has been used to make the compositional analyses, yielding the lowest values of many aerosol species ever measured in the ambient atmosphere. The new program has several enhancements. Optical back scattering will allow measurement of the global albedo, which is important since aerosols are roughly responsible for 2/3 of the total uncertainty in global climate models. A new method has been added for measuring aerosol organic matter that will allow mass closure. In this protocol, the sum of all species equals the total mass present in each of the 8 size modes so that all aerosol mass can be accounted for in determination of the optical properties. The higher energy beams at the Stanford Synchrotron Radiation Light Source will now also be included, allowing the program to access heavier elements to better identify industrial sources. These data will be compared with other high elevation sites like the Mauna Loa Observatory in Hawaii to better track long-range transport of aerosols in the Northern hemisphere. A further benefit of these data is that they allow a measurement of how airborne particles get imbedded in the snow pack and eventually the ice cores collected at the Summit site. Thus, these measurements help explain the dust present over the past millennia, during both warm periods and ice ages.

Continued Core Atmospheric and Snow Measurements at the Summit, Greenland Environmental Observatory (Neumann)

PI Institute/Department Email
Neumann, Thomas
National Aeronautical and Space Administration, Goddard Space Flight Center
Science Summary

This NASA award supports the continuation and expansion of long-term measurements of the Arctic atmosphere, snow, and other Earth system components at the Summit, Greenland, Environmental Observatory (GEOSummit). The original measurement program began in 2003. Year-round measurements with at least 10 years in duration are required to observe and quantify the roles of large-scale, multiyear oscillations in oceanic and atmospheric circulation (e.g., Arctic Oscillation), snow accumulation, firn densification, and ice flow effects. The "Broader Impacts" of these observations are numerous and include the potential to transform understanding of the role of natural and anthropogenic aerosols in climate forcing, to improve climate models and the prediction of future Arctic environmental change, provide ground calibration for satellite measurements of ice sheet elevation, and to enhance the interpretation of ice core records of paleo-environmental variability.

Danish Automatic Weather Station

PI Institute/Department Email
Kern-Hansen, Claus
Danish Meteorological Institute
Science Summary

The Danish Meteorological Institute operates an Autonomous Weather Station (AWS) at Summit. This AWS is part of a network that provides forecasting and warning services as well as continuous monitoring of weather, sea state, climate, and related environmental conditions in the atmosphere, over land and in the sea.

GEOFON (GEOFOrschungsNetz - Geo Research Network)

PI Institute/Department Email
Strollo, Angelo
GeoForschungsZentrum Potsdam, GEOFON Program
Science Summary

Most knowledge about the deeper interior of the earth is derived from seismological records. Seismic waves generated by earthquakes travel through the globe and sample its major structures on the way. Important information about seismic velocities and densities, structural boundaries, mineral composition, temperature and pressure regimes etc are hidden in each recorded seismogram and can be retrieved by inverse methods. To obtain a complete picture, globally distributed high quality broadband seismological stations are required to record a full seismologically range in terms of frequency content (10**2 – 10**-6 Hz) and dynamic range (10**-9 – 10**-1 m/s). The technical equipment of the GEOFON network fullfills these requirements and is installed in 50 stations worldwide. (Near) real-time data transmission (via the Internet) from most stations makes the GEOFON data immediately available to the scientifc community and provides a perfect tool for rapid determination of earthquake source parameters for scientific purposes but also for earthquake and tsunami early warnings and for use by disaster management. Both near real-time and archive data are openly available to the community from the GEOFON Data Center and are shared with other national and international data centers such as the european ORFEUS Data Center in De Bilt (Netherlands) and the global FDSN/IRIS Data Center (Seattle, USA).

Greenland Cosmology Program

PI Institute/Department Email
Lubin, Philip
U of California, Santa Barbara, Physics Department
Science Summary

The millimeter wavelength sky is critical for understanding cosmological foregrounds in order to remove the galactic signature from the cosmological signature. This is especially important in searching for the gravity wave signature from the proposed inflationary era from polarization in the Cosmic Microwave Background (CMB). It is also much more interesting in its own right, than was anticipated even a few years ago, particularly with the recent Planck results. Our galaxy has two primary and very different emission mechanisms, namely synchrotron emission from high energy Cosmic Rays that dominates below 100 GHz and dust emission from heated interstellar dust grains that dominates above 100 GHz. It is critical that we have a series of very sensitive maps from 10-100 GHz to understand the synchrotron component of our galaxy to combine with the Planck high frequency dust maps from 100-900 GHz. The current WMAP and Planck maps at 23, 30, 40 and 70 GHz are insufficient, especially in polarization which neither satellite was specifically designed to measure and for which there is both insufficient sensitivity and serious systematic concerns. There are two major goals for the longer term effort in Greenland. One is to study the galactic foregrounds by making over about 50% of the sky AND to feed these maps and understanding into the deep cosmological maps we will make from Greenland at 30, 40 and eventually at 80 GHz to search for evidence of gravitational waves from the early universe. In order to do the latter (search for gravitational waves) researchers must do the former (characterize the galactic foregrounds) as so poignantly been shown by the recent Planck release. Greenland is one of the best observing sites and allow coverage of the northern hemisphere, which is less contaminated by the galaxy and is complimentary to southern hemisphere measurements at higher frequencies that study dust contaminated frequencies. A critical factor that is new is that the Planck data has recently shown that the higher frequency (about 100 GHz) polarization measurements are heavily contaminated by a much more complex dust emission than we had anticipated and at a higher level than anticipated. Since the atmosphere is quite absorptive above 100 GHz and essentially opaque above 300 GHz, with only a few observing frequency windows, in order to fully characterize the dust emission space based systems are needed. On the other hand the lower frequencies below 100 GHz are essentially completely open to observation from the ground with an exception being thr 60 GHz oxygen cluster but otherwise we can observe down to the ionospheric cutoff at 30 MHz. This will allow researchers to make much more detailed measurements of the galactic contamination from ground based measurements. Additionally the advantage of going into space compared to ground is only about a factor of 2 in system noise for the critical bands while at higher frequencies ground observations are much less sensitive than space both due to the increased opacity of the atmosphere and the decreased flux from the CMB at higher frequencies. These two effects give a strong science case to push to lower frequencies and to use the high altitude site in Greenland (Summit site) as an observing site. Another critical factor that favors observing at lower frequencies is that the technology we will use to make these measurements uses detectors that are extremely linear compared to the bolometers used at higher frequencies and thus atmospheric perturbations from water vapor fluctuations and pressure waves will be largely cancelled out to a much higher degree than bolometer based measurements allowing us to get polarization information on larger angular scales that is critical to understanding inflation and to measuring the ionization fraction of the universe (Tau). In the longer term we will want to duplicate the same system we build in Greenland in the Southern hemisphere to get complete sky coverage, possibly in Antarctica. This experiment will consist of a series of replicated telescopes using molds and technology the researchers have recently developed that allows for a staged approach with both short term results and long term observations. This data will be of use to not only the field of cosmology but to those who study galactic processes , high energy cosmic rays, galactic magnetic fields and even studies of the neutrino mass. This program has broad scientific implications and will place Denmark at the forefront of a critical area of cosmology.

Greenland Magnetometer Array

PI Institute/Department Email
Behlke, Rico
Technical University of Denmark, National Space Institute
Science Summary

The project plans to install a magnetometer at Summit Station to investigate geomagnetic variations in Central Greenland in support of two projects with complementary scientific aims: (1) Project IceBase is a high altitude geomagnetic survey to be proposed by a consortium around Goddard Space Flight Center to NASA to investigate the geothermal heat flux below the Greenland ice cap. The project aims at producing a Greenland-wide map of magnetic crust depth (Curie-depth), indicative for geothermal heat flux. The derived heat flux map is a boundary condition for ice sheet models to improve, among other things, estimates for global sea level rise due to melting of the Greenland ice sheet. Ground magnetometers are critical when correcting the survey data for natural geomagnetic time variations. Data from Summit Station, due to its location in Central Greenland, in combination with the below mentioned array, is crucial here. (2) The Greenland Magnetometer Array operated by DTU Space is a permanent array of some 15 magnetometer stations located on the Greenland East and West Coasts. The array is ideal for investigating the polar ionospheric current systems and processes related to the coupling of energy and momentum from the solar wind to the magnetosphere and ionosphere. Data is interpreted in combination with satellite data (e.g. NASA's Themis mission, ESA's Cluster mission), or with conjugate stations from Antarctica. The proposed Summit magnetometer experiment will, apart from improved geographical coverage, provide data from the electrically insulating ice cap. This data will be less affected by induced electric currents in surrounding oceans and underlying bedrock than the coastal stations, thus improving the scientific value of the array data as a whole.

NOAA Summit Clean Air Program

PI Institute/Department Email
Butler, James
National Oceanic & Atmospheric Administration, Global Monitoring Division
Science Summary

Researchers at NOAA’s Earth System Research Lab (ESRL) Global Monitoring Division (GMD) conduct continuous measurements of atmospheric composition at Summit Station to better understand changes occurring in the Arctic and Earth system. Continuous measurements include: 1. Halocarbon and other Atmospheric Trace Gases (HATS) Flasks: weekly to biweekly air sampling collection to measure trace gases that are important components of global halocarbon chemistry. These measurements have been ongoing since 2004. 2. Carbon Cycle Greenhouse Gas (CCGG) Flasks: weekly air sampling experiment to analyze levels of trace gases that are part of the global carbon cycle. These measurements were taken during winter of 1997-1998, 2000-2001, 2001-2002, and have been on-going since the 2003-2004 winter period. 3. In-situ Aerosol Sampling Suite: continual measurements of aerosol optical properties to determine aerosol radiative effects. These measurements were initiated in 2003 with an updated suite of instruments in 2009. 4. Surface ozone measurements: continual tropospheric air sampling efforts for ozone levels. These measurements were taken from 2000 to 2002, and from 2003 on. 5. Balloon-borne ozonesondes: measurements of year-round ozone atmospheric profiles. These measurements were first conducted during the late-winter of 2005. 6. In-situ Monitoring with the Chromatograph for Atmospheric Trace Species (CATS): a three-channel gas chromatograph performs hourly measurements of ozone depleting gases identified in the Montreal Protocol and amendments including nitrous oxide, sulfur hexafluoride, CFC-12, CFC-11, CFC-113, chloroform, methyl chloroform, and carbon tetrachloride. These measurements began in 2007. 7. Surface Meteorology: continuous measurements of surface meteorological properties to support both science and flight operations. These measurements have been continuous since summer 2005. 8. Surface Solar Radiation: continuous measurements of broadband solar and thermal radiation. These measurements began in 2013 with additional instruments added in 2016.

Partnerships for polar science education and outreach in Greenland (JSEP) and Antarctica (JASE)

PI Institute/Department Email
Virginia, Ross
Dartmouth College, Institute of Arctic Studies
Science Summary

Earth's Polar Regions are undergoing rapid changes that have relevance to the entire world. Scientists are working to understand the causes and consequences of this change and have a critical role in communicating their findings with diverse stakeholders. The pace of polar change demands continuous investment in training and educating the next generation of polar professionals who are prepared to be leaders in academia, government, industry, and policy. The Joint Science Education Project (JSEP) and the Joint Antarctic School Expedition (JASE) are two NSF-sponsored polar-focused programs that provide significant opportunities for polar science outreach and for training the next generation of STEM professionals. JSEP, a project of the Joint Committee, was initiated in 2007 to educate students and teachers from Greenland, Denmark, and the U.S. The group spends three weeks in Greenland to study the causes and consequences of rapid environmental change. JASE, a project in collaboration with the Chilean Antarctic Institute (INACH), takes U.S. students to Antarctica to work alongside Chilean students and examine Antarctica's rapidly changing ecosystems. This project from Dartmouth College will continue leading the U.S. contributions to JSEP and JASE for the next four years, starting in April 2018. In addition to coordinating each field-based program for U.S. high school students, Dartmouth plans additional components to broaden the impact of these programs, including: sending a team of graduate student and faculty researchers with polar field experience to lead scientific components of JSEP and JASE; working with Greenlandic and Chilean educators to disseminate JSEP and JASE polar science outcomes to local audiences during the field-based expeditions; adapting JSEP and JASE polar science field activities for use in U.S. and international classrooms; providing training in cross-cultural science communication for diverse audiences to Dartmouth graduate students and the campus community; and assessing skill- and content-based outcomes for high school and graduate student participants in JSEP and JASE. As an outcome of a NSF IGERT grant to develop the Polar Environmental Change program and previous NSF funding for JSEP, Dartmouth has significant experience with science, outreach, and logistics of working in Kangerlussuaq and Summit, Greenland, and at INACH facilities on King George Island, Antarctica. A Dartmouth partnership with JSEP and JASE is a natural and synergistic collaborative opportunity to provide significant international polar science education and outreach to students from the U.S., Greenland, Denmark, and Chile, with broad impacts for international communities of stakeholders, future leaders, and polar scientists. This work will result in new models for place-based, inquiry-based, and cross-cultural STEM education that places students at multiple levels in mutually beneficial partnerships. Additionally, work with JSEP and JASE will emphasize indigenous perspectives on polar environmental change and evaluating its role in shaping the perspectives of participants. These models for interdisciplinary education and the extensive assessments conducted for all participants give this work significant intellectual merit in the fields of polar science and STEM education. Broader impacts include: building international networks of students, educators, stakeholders, future leaders, and polar scientists; increasing national capacity for science education, including cross-cultural and interdisciplinary perspectives on polar environmental change; and generating polar science educational tools and modules that are freely accessible to students and teachers in multiple languages. Benefits to the high school students, graduate students, and faculty at Dartmouth include: increased exposure to cutting-edge and field-based Arctic and Antarctic science; improved science communication skills; cross-cultural and international experience; greater facility in framing and communicating scholarship to meet the needs of Arctic communities; increased capacity for recognizing, assimilating, and communicating traditional knowledge; and skills for implementing programs to broaden impacts of their future scholarship. The graduate students will receive training in managing interdisciplinary research and outreach teams, and experience doing so in the field in Greenland, thereby contributing to their preparation as future leaders in polar science and policy.

Quantifying Firn Compaction and its Implications for Altimetry-based Mass Balance Estimates of the Greenland Ice Sheet

PI Institute/Department Email
Abdalati, Waleed
National Aeronautical and Space Administration, Goddard Space Flight Center
Science Summary

The Greenland ice sheet (GrIS) contains enough ice to raise sea levels by 7 meters if it were to disappear entirely. Although total loss of the ice sheet is not a concern for the foreseeable future, accurately measuring the total mass balance — accumulation minus loss —of the GrIS remains a critical scientific objective for determining the ice sheet’s present day contributions to sea level rise. Greenland's mass was in near balance in the mid-1990s, but has experienced an increasingly negative mass balance since then with a current annual mass loss of approximately 0.46 - 0.75mm of sea-level equivalent (SLE) per year. The year 2012 proved an "extreme" melt year in Greenland with a single-year loss of 1.59 mm SLE, owing in part to surface mass balance (loss from surface melting) that was three standard deviations below the long-term mean. Light Detection and Ranging (LiDAR) altimetry is one of the primary approaches used to compute mass changes on the GrIS, in part because of its high spatial resolution and sampling capabilities when compared to other approaches such as gravimetry and radar altimetry. The Ice, Cloud and Land Elevation Satellite (ICESat) was used to successfully estimate mass balance for Greenland during much of the last decade. ICESat's successor ICESat-2 is scheduled to launch in 2017 and will continue ICESat's legacy of space-based lidar remote sensing of the Greenland and Antarctic ice sheets. In addition, airborne laser altimetry has been used to estimate ice sheet mass balance and outlet glacier changes since 1991. Such an airborne lidar is fundamental to Operation IceBridge (OIB), which is dedicated to filling the elevation change measurement gap between ICESat and ICESat-2. An unavoidable source of uncertainty in altimetry-based mass balance measurements is the conversion from volume change into mass. One of the primary components of this volume change is firn compaction: the rate at which fresh snow is compressed into glacial ice on the surface of a glacier. At elevations below the equilibrium line, snow melts out entirely to glacial ice each summer, and a density of pure ice may be assumed to calculate changes in mass. However, approximately 80% of the GrIS lies within the accumulation zone, where firn compaction must be accurately measured or modeled in order to perform this volume-to-mass conversion effectively. Direct compaction measurements are spatially and temporally extremely sparse on the GrIS and nonexistent in some large regions, so models remain the primary source for compaction adjustments in mass balance measurements. Most firn compaction models were created and parameterized assuming long-term steady state climate conditions, namely that accumulation and mean temperature remain nearly constant over components of ice sheet elevation change for long time periods, an assumption that held true for much of Greenland only a few decades ago. Some of the current models include considerations for melt, percolation and refreezing, but maintain many of the same steady-state assumptions in the underlying physical characterizations of snow forming into ice. The models not only tend to disagree with each other when run under identical steady-state conditions, but also exhibit a broad range of future behaviors when forced with the transient variables of a changing climate. Each model was created and validated against varying levels of field data spanning different regions and time periods. Without a consistently measured validation dataset, it is nearly impossible to determine which compaction models are most correct when estimating firn compaction across a vast region. One of the most widely-cited firn compaction models used during ICESat-1 to calculate mass balance in Greenland estimated that the rate of firn compaction changed by as much as ± 2.5-13.5 cm yr-1 across nearly three quarters of Greenland’s accumulation zone in the six years spanning 2002-2007. This estimated change in compaction rate dwarfs the ±0.4 cm yr-1 measurement accuracy in the baseline science requirements currently proposed for NASA’s upcoming ICESat-2 mission. To successfully calculate the current and future mass balance of Greenland, accurate and timely field measurements are needed to more precisely constrain firn compaction rates across the GrIS.

Responsive Autonomous Rovers to Enable Polar Science

PI Institute/Department Email
Ray, Laura
Dartmouth College, Thayer School of Engineering
Science Summary

In order to determine the mass balance, and thus contribution to sea level, of the Earth’s ice sheets, researchers must understand the spatiotemporal variations in snow accumulation and firn compaction rates. The amount of snow that falls and accumulates from year-to-year across the ice sheets acts as a hydrological sink, lowering sea level, whereas ablation or melt that runs off acts to increase sea level. The total ice-sheet surface mass balance is primarily composed of the total mass of snow that accumulatedminus the mass of runoff from ice melt Subtracting the total ice mass lost through discharge at glacier calving fronts, known as the input-output method provides the ice-sheet mass balance. This project focuses on the positive component of mass balance: snow accumulation. The ice-sheet mass balance can also be measured by monitoring changes in surface elevation from satellite borne altimeters (e.g., NASA’s ICESat and upcoming ICESat-2, ESA’s CryoSat-2). The measured elevation change is used to determine the volumetric change, which must be converted to mass through knowledge of the density of the material gained or lost. Along the periphery of Greenland in the ablation zone, the change is easily attributed to solid ice, but in the interior, the conversion from volume to mass is less straightforward. The presence of a firn layer in the accumulation zone complicates conversion to mass for a few reasons. Firstly, firn is less dense than ice. The observed elevation change is the summation of change to the firn thickness and to the underlying ice column, which must be properly partitioned to adequately assign a density to the observed change. Secondly, variations in the firn compaction rate result in surface elevation fluctuations that are not the result of a mass change. Therefore, determining the ice-sheet mass balance requires a precise understanding of the spatiotemporal variations in snow accumulation and firn compaction rates, both of which are challenging to measure frequently and at large spatial scales. Snow accumulation varies substantially in time and space. While records of accumulation exist from ice cores and stake lines, their spatial coverage is sparse suggesting that they are inadequate for mass balance studies when used alone. Instead the core records have been used to calibrate climate model output, providing an important spatially and temporally complete accumulation history. Additionally, regional climate model surface mass balance products have been used in ice sheet-wide mass balance studies due to their complete spatiotemporal coverage. While these models are extremely useful for current and future mass balance assessment, field observations of snow accumulation are required to evaluate model ability over the ice sheets. While spatiotemporal measurements of snow accumulation are difficult and few, measurements of firn compaction are even rarer. For example, Arthern et al. (2010) measured vertical strain in the firn at hourly intervals over several years at three sites in Antarctica to investigate the controls on compaction rates as well as to evaluate different firn densification models. In Greenland, tracking the displacements of features observed using borehole optical stratigraphy over a single year at Summit provided measurements of the vertical compaction profile of the firn. Finally, repeat measurements of the firn density profile, derived using a neutron scattering technique, along a ~500 km traverse allowed Morris and Wingham (2011; 2014) to measure strain rates as a function of depth and develop a new densification equation based on their findings. The models developed by the aforementioned studies are tuned by data ranging from a few data points to a few 10s of sites, which limits their use outside of the surveyed areas. Thus, some ground-truthing of the temporal and spatial variability of compaction rates derived from firn densification models exists, but their evaluation would benefit from a method that can easily measure compaction rates over large areas. This project aims to expand our understanding of the spatiotemporal variations in snow accumulation and firn compaction rates by using GPR towed by an autonomous rover.

Surface Processes of the Greenland Ice Sheet Under a Warming Climate

PI Institute/Department Email
Steffen, Konrad
U of Colorado, Boulder, Cooperative Institute for Research in Environmental Sciences
Science Summary

A part of the NASA-sponsored PARCA (Program in Arctic Regional Climate Assessment) project, researchers on this NSF co-funded project have installed and are currently maintaining 18 Automatic Weather Stations (AWS). Each AWS is equipped with a number of instruments to sample the following: -air temperature, wind speed, wind direction, humidity, pressure -accumulation rate at high temporal resolution to identify and resolve individual storms -surface radiation balance in visible and infrared wavelengths -sensible and latent heat fluxes -snowpack conductive heat fluxes Hourly average data are transmitted via a satellite link (GOES or ARGOS) throughout the year. In addition, measurements are stored in solid state memory. The system is powered with two 100 Ah batteries, charged by a 10 or 20 W solar panel. The satellite data-link is powered by two separate 100 Ah batteries connected to a 20 W solar panel. This setup guarantees continuous data recordings and storage, even in the case of satellite transmission failure. The expected lifetime of the instrumentation is 5 years. PARCA GC-Net Automatic Weather Stations (AWS) are equipped with communication satellite transmitters that enable near-real time monitoring of weather conditions on the Greenland ice sheet. Transmission latency is as short as 4 minutes, typically 1-2 hours, and occasionally as long as 48 hours.