An overview of early research programs and the development of GEOSummit
The Greenland Environmental Observatory at Summit was established in response to a demand for a facility capable of providing year-round resources and support for research on the summit of the Greenland Ice Sheet. Early research was related to ice core interpretation, but rapidly the unique nature of the site, and value of the facility as a ‘clean air’ climate facility became apparent. Researchers worked together with the NSF to develop a plan to preserve the unique attributes of the station and establish year-round staffing and logistical capabilities.
A draft science plan for a multidisciplinary environmental observatory at Summit developed in 1998 outlined five priority areas for research at Summit. The purpose of the document was to outline research programs that would attain the greatest benefit from the unique characteristics of the site location. As a result of the high elevation, high latitude, and low water vapor content the site has proven to be a valuable location for numerous multidisciplinary investigations including: sampling of globally transported atmospheric compounds, investigation of the snow-to-air transfer of atmospheric compounds, investigation of the complex photochemical cycling of reactive nitrogen species, detailed studies of the boundary layer and energy fluxes over the ice sheet, seismic measurements, magnetic measurements of the ionosphere, and also testing of remotely operated vehicles for glaciological measurements.
NSF-LTO Baseline Measurements
Beginning in the spring of 2003 the Office of Polar Programs (OPP) of the NSF funded a Long Term Observatory (NSF-LTO) initiating a year-round baseline measurement program at Summit. The primary purpose of the program is to expand existing intermittent measurements of Earth system components to year-round observations suitable for climate and atmospheric model input. Baseline variables measured include site meteorology, tropospheric chemistry, and surface snow chemistry and physical properties. The program is operated collaboratively between the University of California at Merced (UCM), the Desert Research Institute (DRi), and investigators from the Earth Systems Research Laboratory of the National Ocean and Atmospheric Administration (NOAA-ESRL).
A number of processes that could amplify atmospheric change need consistent measurements and systematic study. For example, recent evidence indicates that important atmospheric chemical constituents undergo temperature-dependent exchange with ice/snow, and that some species are photochemically transformed and/or produced within the sunlit surface snowpack. Because changes in Arctic atmospheric circulation are cyclic over 4-5 year or longer times, long-duration measurements are needed to understand circulation and to place observed changes in a long-term perspective. The atmospheric gas-phase and aerosol species being studied are all either sensitive indicators of anthropogenic impacts on regional and global atmospheric change, or are important chemically coupled species whose concentrations may be strongly influenced by changes in the Arctic, including changes in snow/ice surface temperatures, ice/snow cover, and atmospheric circulation. Related chemical measurements in the snow provide the needed link to investigate feedbacks between Arctic climate change, air-snow exchange, and atmospheric composition. Understanding this change requires a quantitative understanding of the environmental controls (e.g., temperature, radiation, humidity, ozone concentration) on air-snow feedbacks, and the impact of these processes on the entire Arctic atmosphere.
The measurements at GEOSummit have wide applicability for detecting, understanding and modeling Arctic change, and are responsive to a number of community initiatives, including the World Meteorological Organization’s Global Atmospheric Watch, SEARCH (A Study of Environmental Arctic Change) and other proposed initiatives. As such, this project provides the platform and baseline measurements for a wide number of scientists and individual research projects. There are at least three main broader impacts of the project. First and foremost, by definition an environmental observatory enhances infrastructure for research and education. Second GEOSummit serves as a vehicle to broadly disseminate scientific understanding of the Arctic system by making data and information widely available, both real time data and scientific understanding that is developed using those data. Third, education of the global community is an objective of the long-term measurements, using www-available data and educational materials.
Reactive Nitrogen Photochemical Cycling
The importance of the rapid chemical cycling of compounds in surface snow was first appreciated in 1998 when researchers noticed unexpectedly high concentrations of chemicals associated with industrial pollution at Summit Station (Dibb, 1998; Munger, 1999). Since that time, seasonal investigations of the rapid cycling between the snowpack and the near-surface snow have demonstrated the reactive nature of the snow and it’s impact on the air above it. Subsequent investigations (Honrath, 1999, 2000, 2002; Ford, 2002) highlighted the photochemical cycling of reactive nitrogen compounds between the snow and air. Following up on collaborative projects in 1998, 1999, 2000, and 2002, a group of scientists from 7 different institutes are continuing to study the fate of some chemicals associated with air pollution which are transported to Greenland on global wind currents from North America, Asia, and Europe. These chemicals (nitric acid, for example) react to ultraviolet light hitting the sunlit snow, and begin other chemical processes, eventually releasing back into the air compounds that are hallmarks of air pollution. The project was the focus of a major summer campaign in 2003 and then a return to Summit in the spring of 2004 to examine the chemistry during the polar sunrise. In addition to the contributions made to understanding snow chemistry, this work suggests that reading some aspects of Greenland’s snow and ice record might be more complicated than was once thought. As scientists better understand these chemical interactions, they will be better able to read the climate history record of the ice cores taken from Summit. They also will better understand the record left in the snow surface from large-scale events such as volcanic eruptions or giant forest fires.
Energy Flux and Boundary Layer Meteorology
Investigators from ETH-Zurich are making year-round observations of the surface energy balance and turbulence in the boundary layer using an instrumented, 36-meter meteorological tower, a wind-profiler, a radiometer system to gain a better understanding of the earth’s surface heat balance and the structure of the boundary layer. Recent results from prior studies at Summit have been used to improve temperature and mass balance modeling over the ice sheet (Calanca, 2000; Wild, 2000). Radiation measurements are taken in accordance with specifications established by the Baseline Surface Radiation Network project of the Global Energy and Water Cycle Experiment (GEWEX). Data from Summit Station is included in the global network with the following objectives: i] To monitor the background (least influenced by immediate human activities which are regionally concentrated) shortwave and longwave radiative components and their changes with the best methods currently available; ii] to provide data for the calibration of satellite-based estimates of the surface radiative fluxes; iii] To produce high quality observational data to be used for validating the theoretical computations of radiative fluxes by models.
Transfer Function Investigations of Hydrogen Peroxide, Formaldehyde, and Nitrate
Preservation of seasonally varying compounds during the air-to-snow-to-ice transfer process are dependent on several variables including: seasonal concentration, annual accumulation, temperature, in situ physiochemical reactions, and temperature-dependent adsorption. To gain a more constrained estimation of the paleoatmospheric record of these compounds, a transfer function model capable of running in an inverse fashion is required. As a result of the availability of recent year-round measurements, increased understanding of these processes are being developed. Publications to result from this work include McConnell et al. (1997a, b; 1998), and Hutterli et al. (1999; 2001, 2002, 2003), Dassau et al. (2003), Burkhart et al. (2002) and Jacobi et al. (2002, 2004).
Using the well studied compounds hydrogen peroxide (H2O2) and formaldehyde (HCHO), investigators will evaluate and validate a model of air-snow exchange and the degree of spatial and temporal averaging needed to distinguish statistically significant changes in the concentrations of H2O2 over the past few hundred years. Their approach includes: 1] analysis and synthesis of ice-core data, 2] analysis of prior atmospheric and surface snow data, and 3] modeling of air-snow exchange processes and atmospheric chemistry for interpretation of concentrations in snow, firn, and ice. This study is greatly dependent on the availability of year-round measurements, previously unavailable.
In addition to H2O2 and HCHO, the preservation of nitrate is being investigated using the record of year-round surface snow concentrations in conjunction with the accumulation observations. The data from Summit have shown that nitrate is well preserved at the site, though may be subject to extensive post-depositional cycling (Burkhart, 2004).
Radiometer for Atmospheric Measurements At Summit (RAMAS)
The new microwave Radiometer for Atmospheric Measurements at Summit (RAMAS) has taken up preliminary operation at Summit Station and is now being prepared for continuous measurements. RAMAS covers the frequency band from 265 GHz to 280 GHz with an instantaneous bandwidth of currently 1 GHz. The main objective of RAMAS is to measure ozone (O3) and the key species of anthropogenic ozone destruction, chlorine monoxide (ClO). Measurements of nitrous oxide (N2O), an important dynamical tracer, will permit the separation of chemical and dynamical effects, while nitric acid (HNO3) will be monitored to study the processes of chlorine deactivation and stratospheric denitrification. Measurements of long-lived hydrocyanic acid (HCN) are aimed at a better understanding of photodissociation and may allow for a more detailed study of dynamical processes. Further species, H2O2, HO2, NO2 and SO2, will be measured on an experimental basis.
Tropospheric water vapor content, a major constraint on ground-based microwave radiometry, is exceptionally low at Summit Station. Therefore year-round measurements with good temporal resolution will be possible for the first time in the Arctic. Other ground-based microwave radiometers in the Arctic, including all primary NDSC stations, are located below 600 m, where poor meteorological conditions impose longer measurement times and severely limit the temporal coverage.
The project is funded by the European Commission (Fifth framework programme) and supported the US National Science Foundation (NSF).
The objective of this research is to study the diurnal and seasonal ozone deposition to the year-round snowpack and investigate dependencies of ozone deposition on environmental and snow photochemical conditions. During the summer of 2003 and 2004 investigators used sensitive flux measurements by the tower gradient method and by measurements of ozone in the interstitial air.
Previous research in Polar Regions has demonstrated that chemical and physical interactions between the snowpack and the overlaying atmosphere have a substantial impact on the composition of the atmosphere (Helmig, 2002). Deposition and scavenging of gases and aerosols result in the accumulation of a chemical reservoir that subsequently, under conditions of increasing temperature and solar irradiance can turn into a photochemical reactor. These reactions result in the formation of radicals, the release of chemicals into the atmospheric surface layer, and consequently influence concentrations and budgets of important tropospheric trace gases. Recent observations of photochemical depletion of ozone in firn air, diurnal ozone trends in the surface layer, tethered balloon vertical profile data and estimates of photochemical ozone production all imply that ozone deposition to the snowpack depends on parameters including the quantity and composition of deposited trace gases, solar irradiance and snow temperature. Consequently, ozone surface fluxes in Polar Regions are expected to have snow photochemical, diurnal and seasonal dependencies and to overall be more complex and possibly larger than considerations in global atmospheric models. Current literature does not reflect these conditions and ozone flux estimates to year-round snow are contradictory and are suspected to have large errors.
Magnetometer Array on the Greenland Ice Cap (MAGIC)
The MAGIC project employs autonomous tri-axis fluxgate variometer instruments to study small scale ionospheric phenomena associated with various coupling process occurring at the interface between the solar wind and the earth’s magnetic field. In 1991-92, four autonomous, remote, magnetic data collection stations were established in an array around the GISP2 camp. Although the operation was terminated in 1997, it was found that when combined with coastal data, the Summit data were quite valuable for the analysis of the dynamic variations of the high latitude ionospheric current systems (Sitar, 1996,1998) Two improved stations deployed in 1997 at Summit Station and Raven camp and remain a central part of the current Greenland array (Clauer, 2002).
The GEOFON Program has been initiated in 1992 by the GeoForschungsZentrum (GFZ) Potsdam, the central geo science research institution in Germany. The GEOFON Program consists of three components, the permanent broadband seismological network, a varying number of mobile network deployments and the GEOFON Data Center. Within GFZ, GEOFON contributes to the Modular Earth Science Infrastructure as well as to the Geomonitoring, Lithospheric Structure and Natural Disaster research programs. Externally, bilateral cooperation links are established with more than 50 institutions worldwide.
At Summit, GEOFON maintains a seismometer that utilizes the data transmittance capabilities of the facility to transmit data regularly to the global network. This instrument is visited annually for regular maintenance; however, the station science support staff frequently download data and help with software upgrades.
NASA – “Tumbleweed Rover”
Testing of JPL’s “Tumbleweed Rover”, a 2 meter inflated ball containing an interior payload, occurred at Summit Station in the summer of 2003 and 2004. This site was ideal because it offered cold weather and 100’s of kilometers of long flat terrain that reasonably simulates climate conditions on the surface of Mars. The Tumbleweed Ball is a large, inflated ball that can be windblown and used to explore the surfaces of Mars, Venus, Titan, and perhaps Saturn’s moon Io (supersonic volcanic wind) and Neptune’s moon Triton (significant surface wind erosion). Summit station staff “launched” the instrument from the facility while NASA investigators followed its progress remotely.
Synthetic Aperture Radar Remote Vehicle
This project is lead by researchers at the University of Kansas who are developing vehicle-mounted synthetic aperture radar (SAR) for use in measuring polar ice sheets. The team tested this method using tracked ATVs and a remote controlled snow machine at Summit Station in 2004 and may potentially redeploy in 2005. This research project involves the innovative application of information technology in the development and deployment of intelligent radar sensors for measuring key glaciological parameters. Radar instrumentation will consist of a SAR system that can operate in bistatic or monostatic mode. One important application of the SAR will be in the determination of basal conditions, particularly the presence and distribution of basal water. Basal water lubricates the ice/bed interface, enhancing flow, and increasing the amount of ice discharged into the ocean. Another application of the SAR will be to measure ice thickness and map internal layers in both shallow and deep ice. Information on near-surface internal layers will be used to estimate the average, recent accumulation rate, while the deeper layers provide a history of past accumulation and flow rates. The system will be developed to collect, process and analyze data in real time and in conjunction with a priori information derived from archived sources. The combined real time and archived information will be used onboard the vehicles to select and generate an optimum sensor configuration. This project thus involves innovative research in intelligent systems, sounding radars and ice sheet modeling.
Max-DOAS – J. Stutz, UCLA
A recently awarded proposal to develop a new generation multi-axis differential optical absorption spectrometer (MAX-DOAS) to continually measure concentrations of the important trace species formaldehyde (HCHO), nitrous acid (HONO), nitric oxide (NO2), and halogen oxides in the Arctic will use Summit Station to house the instrument. The instrument will augment ongoing observations at GEOSummit as part of the NSF-LTO baseline measurement program.
Deep drill testing – Taylor / Koci, DRI
As part of the inland West Antarctic Ice Sheet (WAIS) drilling program, researchers and engineers from DRI and the University of Wisconsin will be utilizing the Summit Station facility to conduct Deep Ice Sheet Coring (DISC) tests. It is expected that a team of ~20 individuals will be at Summit during the summer 2005 season. Furthermore, power requirements will place an additional demand of 1.5 kW on the power supply grid. This project will require close cooperation between on-site staff, the SCO, and project team members to assure that activities will not infringe on current, established observational and experimental campaigns.
Organic Carbon Aerosols – Bergin
Atmospheric aerosols are of concern due to their ability to influence climate by altering the radiation balance of the Earth and due to the fact that they are harmful to human health. Ice core concentrations of OC and specific organic compounds have the potential to yield information on the past influence of carbonaceous aerosols on climate as well as the sources of these aerosols. Before ice core concentrations of carbonaceous compounds related to particulate matter deposition can be evaluated, it is important to determine the link between the concentrations in air and snow. Preliminary results of water insoluble particulate organic carbon (IPOC) in a snow pit from Summit, Greenland show a decrease of ~ 50% in IPOC concentrations in the top 50 cm, hinting that early post depositional processes may be very important. We will measure the concentrations of particulate organic carbon, elemental carbon, and specific organic compounds that serve as source tracers in the air, surface snow, and snow pits. Overall, the proposed research will yield insights into the processes that influence the concentrations of particulate carbon in the air and snow at Summit, Greenland. These results will serve as the groundwork for future modeling, laboratory and field studies that will focus on the deposition, and transformation of particulate organic compounds in snow.
UV-VIS Radiation measurements – B. Lefer, University of Houston
In addition to the current UV monitoring being conducted at Summit as part of the baseline measurement program, a proposal to install a total sky imager and direct beam spectroradiometer has been submitted. Also as a part of this program, an actinic flux radiometer would be installed on-site for snow profiling to better understand the light attenuation properties of snow. The instrumentation would yield important information related to long-term changes in total UV radiation at Summit. The measurements are designed to complement the existing measurements and to provide characterization of the optical properties of clouds and aerosols to expand our understanding of the photochemical environment at Summit.
Polar Mesopheric Cloud Observations – J. Kelly, SRI
Summit provides an ideal location for the study of Polar Mesopheric Clouds (PMC) as a result of the high elevation and latitude and low water vapor. Observation of PMCs would be possible approximately 50% of the time, representing a two-fold increase over any other arctic observatory. Installation of a Rayleigh lidar operating at 532 nm using high power laser and telescope/photon counting receiver has been proposed. Summertime operation of the instrument would focus on PMC research, however, the instrument could be operational year-round measuring stratospheric clouds and temperature during the winter months.