The Summit of the Greenland Ice Sheet (72^oN, 38^oW), the highest elevation north of the Arctic Circle (3200 m) provides unique opportunities for making year-round measurements of the Earth's atmosphere. The relatively cold temperatures and low atmospheric water vapor associated with this location make it the clear site of choice for a number of measurements. This plan for a multidisciplinary environmental observatory at Summit is based on scientific input from two workshops (May 20-22, 1997 in Kangerlussuaq, Greenland and February 26, 1998 in Copenhagen, Denmark) and over 50 individual scientists. Five priority areas have been identified where a high-elevation site on the Greenland ice sheet is required for year-around measurements: i) ice-core interpretation, ii) tropospheric chemistry, iii) radiation, energy balance and boundary layer, iv) stratospheric observations, and v) atmospheric electricity. For these areas of research, the Summit site will provide unique data that cannot be developed at coastal Greenland or other arctic sites. In addition, two areas have been identified where year-around measurements at Summit would help complete an arctic network of measurement sites, and thus greatly enhance existing data: i) polar aeronomy and space sciences, and ii) seismic and geodetic measurements.

Summit was the site of two deep ice cores that give the climate history of the past 110,000 years in unprecedented detail, yet many of the parameters measured in the cores have not yet been quantitatively related to past atmospheric composition. Year-round measurements of snow and atmospheric properties are critical for developing the "transfer functions" needed to interpret these ice cores.

Summit is also a high priority site for studying perturbations to the Earth's current atmosphere. For example, one of the important questions is the extent to which anthropogenic nitrogen oxide emissions already have changed the remote troposphere from an ozone-consuming status into an ozone-producing status. Location of atmospheric chemistry monitoring systems at the highest elevation of the Greenland ice sheet is an excellent compliment to periodic aircraft campaigns that examine troposphere chemistry of high latitudes.

There are several strong motivations for making radiation measurements at Summit, including arctic meteorology, ice-sheet energy balance, atmospheric chemistry, remote sensing ground truth, climate modeling, global energy balance, ice sheet mass balance and European weather. For example, the stability of the ice sheet is determined to a great extent by the mass balance and hence energy budget at the surface. The energy budget of the dry snow zone of Greenland has so far been sporadically investigated, with the winter energy budget presently not known at all.

The Summit of Greenland is the only site in the northern polar region where high quality measurements of important stratospheric constituents can be made. The instruments require very low water content in the air and a high altitude location. Depletion of polar stratospheric ozone in the late winter and early spring seasons continues to be an important scientific issue for both hemispheres, with these global losses due in part to the intensified loss processes occurring in the polar region.

Atmospheric electricity measurements made at several km altitude on polar ice caps are uniquely valuable because they have noise levels that are only 1-10% of corresponding measurements at lower altitudes and lower latitudes. Summit is the only northern hemisphere site for such measurements, which would show effects on the global circuit of short-term decreases and long-term (solar cycle) changes in the galactic cosmic ray flux, as well as effects of solar proton events, and changes in magnetosphere-ionosphere convection.

The Earth's polar caps have traditionally provided researchers with a natural laboratory to study electrodynamic forcing and momentum transfer from the solar wind to the upper atmosphere. The high-latitude Summit site is ideally located for making optical, magnetic, and radio observations necessary to describe this interaction. Combined with Antarctic measurements, the potential exists for ground-breaking inter-hemispheric observations of magnetosphere-ionosphere coupling.

Seismic and geodetic measurements, of lower priority for implementation, would be part of a network to fill important data gaps. Continuous geodetic measurements would be an excellent compliment to the periodic measurements of vertical and horizontal movement, and help establish if movements are episodic or permanent.

All of the above measurements, with the exception of the seismic and geodetic measurements, could be made by a winter-over staff of four persons, plus two or possibly three support personnel. The current modular facility, which accommodated four personnel during the 1997-98 winter-over pilot project, would require expansion for both berthing and laboratory space for instruments. Year-round measurements could begin as early as summer 2000.

The U.S. National Science Foundation and the Danish Commission for Scientific Research in Greenland are considering development of science facility that would provide a year-round, long-term presence at the 3,200-m Summit Camp on the Greenland Ice Sheet (72^oN, 38^oW). This facility would give scientists from several disciplines access to a research site in the Northern Hemisphere that is unique for its high elevation, cold temperatures, high latitude and low water-vapor content. Summit has also been the site of glaciological and atmospheric research since 1989, when GISP2 and GRIP ice-coring activities began. This science plan gives a summary of the research interests expressed by over 50 individual scientists from the U.S. and Europe in either making measurements at Summit, or in using data from these measurements in their research.

Community input has been through two workshops, follow-up email from attendees to others in their field, and email to the NSF-OPP listserv. On May 20-22, 1997 the U.S. National Science Foundation (NSF) and the Danish Polar Center jointly supported a small workshop in Kangerlussuaq, Greenland to explore joint interest in science programs that could use a new winter-over capability at Summit. NSF requested researchers in all disciplines to identify the type of research projects that would be enhanced, for example, by measurements for a full annual cycle at the 3,200-m altitude or winter projects that require dark skies and clear conditions experienced at Summit. NSF invited proponents who represented wide segments of the community in each discipline to attend the workshop at the Kangerlussuaq International Science Center. Following that a workshop report and draft science plan was prepared and distributed to all who expressed interest. The Danish Commission hosted a European Summit Seminar in Copenhagen on February 26, 1998, at which representatives from NSF and the European Polar Board were also present, to discuss European interest in the proposed facility. At that meeting, preliminary information on the U.S. NSF's successful 1997-98 over-winter pilot project was presented. It was decided that efforts to realize the vision for the proposed facility should proceed and that the science plan should be completed.

 3.1. Summary of Prior Research Programs at Summit. Two deep ice cores drilled at the Summit of the Greenland ice sheet, the U.S. Greenland Ice Sheet Project Two (GISP2) and the European Greenland Ice Core Project (GRIP), have provided an unparalleled view of climatic and environmental change. Drilling began in 1989 and was completed to bedrock at GISP2 (3053 m) and GRIP (3029 m) in 1992 and 1993, respectively. The GRIP site was located at the present ice divide, and the GISP2 site was chosen over a bedrock plateau about 10 ice thicknesses (28 km) downstream to the west of the divide to obtain a flank-flow regime to compare with the GRIP divide flow. The actual GRIP deep core was preceded by drilling of the shallow EUROCORE at the same site. The GISP2 camp, site of the currently proposed environmental observatory, consisted of several surface structures, including: a 9-m by 18-m prefab building situated on top of 3.5-m pilings that acted as a meeting place, administrative office and cafeteria, an 18-m geodesic dome to house drilling activities, several temporary buildings and tents for berthing. The camp was equipped to accommodate about 55 people for up to 5 months per field season. Each year between 1989 and 1993, from early May until September, the GISP2 camp provided a base for the personnel working on the core drilling and associated science programs.

Completion of the two ice coring programs opened a new era in paleoenvironmental investigation. These records provide the highest resolution, continuous, multi-parameter view of the last glacial-interglacial cycle produced thus far. The cores provide evidence of a wide variety of environments, including histories of fires, sea-ice extent, volcanic activity and storminess. The cores also record the frequency and magnitude of extreme events, and elusive cyclical components of the region's environment. Similarity of the GISP2 and GRIP records is compelling evidence that the stratigraphy of the ice at the Greenland Summit location is unaffected by extensive deformation from the surface to 2,790 m (110,000 years ago) and that even minor features of the records (e.g., 1-2 year onset and termination of climate- change events) are reliable. From these cores, we now know that the Earth has experienced large, rapid, regional to global climate oscillations through most of the last 110,000 years on a scale that human agricultural and industrial societies have not yet faced. These millenial-scale events represent quite large climate deviations: probably up to 20^oC in central Greenland, twofold changes in snow accumulation, 10-fold changes in wind-blown dust and sea-salt loading, roughly 100 ppbv in methane concentration, with cold, dry, dusty and low-methane conditions being correlated. The events often begin or end rapidly: changes equal to most of the glacial-interglacial differences commonly occur over decades, and some indicators, more sensitive to shifts in the pattern of atmospheric circulation, change in as little as 1-3 years.

Science weatherport used for summer atmospheric chemistry studies; Big House in background. Roger Bales Photo (1995)

The GISP2 and GRIP deep-drilling efforts also fostered development of an atmospheric and surface-snow sampling program as part of their field campaigns. From modest beginnings as a 1989 pilot-scale study, this program grew into a multifaceted investigation of the physical, chemical and meteorological processes determining air-to-snow transfer for several atmospheric species. In the 1991-93 field seasons, 20 research teams from the US and Europe were involved in the many aspects of this program. From 1994 to the present, after the completion of ice-core drilling, an international summer field program aimed at understanding both tropospheric chemistry and ice-atmosphere transfer functions has continued.

Several research teams have focused on aerosol-associated tracers to further our understanding of transport from natural and anthropogenic sources to Greenland. The isotopic distribution of lead in snow pits indicates a seasonal pattern of influence by different continental-scale anthropogenic source regions. North America emissions were found to be more important in fall and winter with Eurasian sources dominating in spring. Trace metal profiles suggest that the adoption of catalytic converters to reduce nitrous oxide (NO_x) emissions from automobiles has increased the emissions of platinum, palladium and rhodium into the atmosphere, through it is not yet clear that these metals will prove useful as tracers of regional emissions. Careful characterization of the composition and mineralogy of insoluble particles in Summit snow has shown that the present-day annual spring peak in continental dust is largely derived from the deserts of Asia, as has recently been shown for the large increase in dust loading during the last glacial maximum. Studies of a number of other aerosol and gaseous species have also been carried out at Summit, and a nitrogen-budget study is being done in summers 1998-99.

Unrelated to glaciology or atmospheric chemistry, a small cooperative research program between the University of Michigan and the Danish Meteorological Institute (DMI) was carried out in the Summit region to improve the spatial resolution of magnetic variation measurements in Greenland. The primarily focus is to resolve the temporal and spatial resolution of small scale propagating ionospheric current systems. 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. Thus a less-dense array was deployed in 1997 at Summit and at the Polar Ice and Training Facility (PITS).

 3.2. History of Winter-Over Observations on the Greenland Ice Sheet. The records from the GISP2 and GRIP cores have already been proven to contain evidence of unexpectedly rapid and dramatic shifts of climate, with changes in the composition of the ice signaling, or at least accompanying, most such climate shifts. Being able to quantitatively infer variations in atmospheric chemical processes from these changes in ice composition using an explicit transfer function will provide a powerful tool for examining the role of atmospherically based forcing in the climate system, as well as the response of the atmosphere to climate change. However, until 1997 all field experiments to develop and verify such models had been restricted to the summer months of May through August. A small team of researchers made similar measurements through the winter of 1997-1998 at the GISP2 camp, which began to address many of our current knowledge gaps regarding air-snow exchange processes at Summit through the greater portion of the year.

Modular Green House at Summit. Marijane England Photo (1997).

Under funding from the National Science Foundation Office of Polar Programs (NSF-OPP), the Polar Ice Coring Office, University of Nebraska-Lincoln (PICO-UNL) began planning for the facility and logistical support of the 1997-98 Summit winter-over project in October 1996, with the new facility delivered and ready for occupation by July 1, 1997. The new modular facility (ATCO Structures, Inc., Canada) consists of independent kitchen and laboratory units connected by berthing for four and common space (referred to as the Green House). A temporary structure was used as a heated shop and to house the 80 kW generator module. The GISP2 administrative and dining structure (the Big House) was only used for summer activities. The Green House, the new 80 kW generator module, 25,000 gallons of fuel, and all items required to build and stock the facility for winter and all supplies required for the winter project were delivered to the camp via Kangerlussuaq, Greenland, using Hercules LC-130 aircraft operated by the New York Air National Guard 109th Airlift Wing. The total flight hours required for shipping items specific to the winter-over were approximately 76 hours above routine summer operations.

Five priority areas have been identified where a high-elevation site on the Greenland ice sheet is required for year-around measurements (subsections 4.1-4.5). For these areas of research, the Summit site will provide unique data that cannot be developed at coastal Greenland or other arctic sites. In addition, two areas have been identified where year-around measurements at Summit would help complete an arctic network of measurement sites, and thus greatly enhance existing data.

4.1. Ice Core Interpretation. One of the primary goals motivating the collection of ice-core chemical records is the reconstruction of records of atmospheric chemistry in past times. To quantitatively interpret ice-core records we must know the 'transfer function' relating chemical concentrations in ice to those in the atmosphere. The first step of this inverse problem, using the snow composition to infer the composition of air over Summit, remains an open problem for most chemical species. We must understand how seasonal variations in snow accumulation, depositional processes, and the combination of tropospheric transport and chemical processing interact to determine the chemical composition of snow accumulating at Summit. Similar considerations apply to the use of variations in the stable isotopes of water in snow and ice as a paleothermometer. We must understand how parameters other than temperature, e.g. air-mass history and post-depositional exchange of vapor between air and snow, impact the isotopic signals that are preserved. This overarching goal of inverting ice-core records to time series of atmospheric composition and temperature, with quantitative estimates of uncertainty in the reconstruction, leads directly to a series of questions that can only be addressed through year-round sampling. However, so far nearly all field experiments to develop and verify transfer function models in Greenland have been restricted to the summer months of May through September. In order to understand how long-term changes are recorded in ice cores, we must improve our ability to separate effects of seasonal to interannual changes from the long-term signals.

Laboratory module used for measuring atmospheric hydrogen peroxide and formaldehyde, set about 0.5 km away from the main Summit camp. Roger Bales Photo (1995).

The primary research question motivating of these transfer-function studies is how are monthly and seasonal changes in concentrations of atmospheric species and fluxes to the snow reflected in the chemical record in snow and firn? Because atmospheric concentrations of most chemical species of interest in ice cores vary throughout the year, the seasonal pattern of snow deposition can greatly influence year-to-year changes in the concentrations found on the ice. Thus the first question becomes what is the seasonal pattern of snow accumulation at Summit?

Many chemical species, typically those found in aerosols, are irreversibly deposited to the snow and undergo very little post-depositional change in concentration. Other species, typically those reactive species occurring as gases, are reversibly deposited and undergo post-depositional exchanges with the atmosphere. For reversibly deposited species such as acidic gases or photochemically produced hydrogen peroxide, the two primary questions are: i) to what extent do concentrations of these species present in the atmosphere and deposited to snow at Summit reflect transport from lower latitudes versus local processes and ii) how do post-depositional processes influence concentrations in snow, firn and ice? For aerosol-associated species, e.g. sulfate, metals or base cations, there are three primary questions: i) how do the aerosol concentrations and composition vary over the course of a year, ii) how do the source regions for air masses reaching Summit change throughout the year, and iii) what is the relative contribution of deposition by precipitation, fog, and dry deposition throughout the year? Also important for modeling post-depositional exchange are physical features of the snow and firn. Current questions are: i) what are the seasonal differences in snow and firn physical characteristics affecting transport of heat, momentum and mass, and ii) what are the rates of energy and vapor transport within the snow and firn over the year?

Though significant studies have been done over the past few years that increase our ability to interpret ice-core records of chemical species, the key limitation to making quantitative interpretation of the seasonally changing concentrations of most atmospheric species is the lack of year-round information for model calibration and evaluation. Recent work at South Pole illustrates the potential impact of sustained year-round measurements on ice-core interpretation. Results from the 1997-98 winter-over pilot project look very encouraging. Summit is the site of choice in the Northern Hemisphere for this work, with strong interest from both U.S. and European scientists. Summit is the site where we have the long-record, high-resolution ice cores, and is a site where NSF and EU have already made significant investments. This is the site where we must study the transfer function in order to realize full value from the cores.

4.2. Tropospheric chemistry. There is an obvious strong link between pressing questions stemming from anthropogenic perturbations to the Earth's current atmosphere and interpretation of past chemical changes in the ice-core record. Location of atmospheric chemistry monitoring systems at the highest elevation of the Greenland ice sheet offers a unique opportunity to combine specific studies motivated by climate questions to some of the most urgent questions related to the background tropospheric chemistry of the northern hemisphere.

One of the important questions is the extent to which anthropogenic nitrogen oxide emissions already have changed the remote troposphere from an ozone-consuming status into an ozone-producing status. There is evidence that tropospheric ozone (O₃) concentrations in the northern hemisphere have increased by approximately 1 percent per year over the past two decades; such increases contribute to greenhouse radiative forcing and could negatively affect biota. They further modify the concentration of hydroxyl radical (OH), the main atmospheric oxidant. The factors responsible for the ozone increase are, however, elusive. Global anthropogenic perturbations to the concentrations of NO_x are a possible explanation, but our current understanding of NO_x budgets in the remote troposphere is scant. Concentrations of OH in the global atmosphere could be perturbed in a major way by global increases in the concentrations of carbon monoxide (CO), methane (CH₄), O₃, and NO_x; however, even the sign of the perturbation is still a matter of debate. Oxidation by OH is main sink for atmospheric CO and CH₄, and in turn these two reactions are the principal sink for OH; positive feedbacks in the CO- CH₄-OH system could amplify the effects of anthropogenic influence on CO and CH₄ levels.

Balloon for twice daily atmospheric soundings, done as part of summer investigations of atmospheric chemistry at Summit. Roger Bales Photo (1993).

Atmospheric measurements in the Arctic allow one to probe the export of anthropogenic gases from the polluted continents to the global scale. Aircraft measurements during the NASA/ABLE-3 expeditions to the Arctic have documented NO_x concentrations sufficient to double regional ozone concentrations relative to a NO_x -free atmosphere, according to a photochemical model study. A major question then emerges as to the origin of NO_x in the Arctic. Both anthropogenic sources (mid-latitudes pollution, aircraft) and natural sources (wild fires, stratosphere) could be important; there is at this time no understanding of the relative contributions from these various sources.

Determining the sources and fate of chemical species requires us to consider both atmospheric transport and transformations. Examples of the questions include:

• What are the source regions and transport pathways for chemical species reaching the atmosphere over Summit? What chemical transformations occur en route?
• How do these source regions and transformations change with season? How do they change as global climate is altered?

Clearly, answers to these questions for certain chemical species will have great relevance to understanding northern-hemisphere and polar-tropospheric chemistry as well as to interpretation of ice cores. It is equally clear that surface-based atmospheric sampling at Summit can only address one part of the larger regional and global tropospheric chemistry questions. Such sampling will allow documentation of the current status of the atmosphere at one of the most-remote sites in the northern hemisphere. Information on atmospheric constituents ranging from insoluble particles to reactive gases is a key part of studies of the important removal processes operating over Summit. Full use of this information demands that the proposed program be integrated with other projects investigating and modeling tropospheric chemistry and those developing general circulation models (GCM's). For example, one proposed program that could greatly benefit from Summit measurements is Tropospheric Ozone Production about the Spring Equinox (TOPSE), a proposed airborne campaign that would make a series of biweekly flights into the Arctic around polar sunrise.

At present there is very strong interest in establishing and maintaining high-elevation northern hemisphere measurements on the part of the scientists who participated in the winter-over pilot project. It is expected that more scientists would join after the station was established.

4.3. Radiation, energy balance and boundary layer. There are several strong motivations for making radiation measurements at Summit, including: arctic meteorology, ice-sheet energy balance, atmospheric chemistry, remote sensing ground truth, climate modeling, global energy balance, ice sheet mass balance and European weather. Both U.S. and European scientists are interested in participating.

The stability of the two ice sheets, Greenland and Antarctica, is crucial for avoiding catastrophic sea-level changes. The present and future conditions of the ice sheets are, to great extent, determined by the mass balance and hence energy budget at the surface. The energy budget of the dry snow zone on the ice sheet is uniquely regulated by the high surface albedo, small atmospheric counter-radiation and small turbulent heat conduction from the atmosphere. Recently, it was discovered that relatively large sublimation/evaporation from the ice surface is responsible for the stability of the dry snow zone. These characteristics are a result of an exceptionally stable and relatively thick boundary layer covering the majority of the ice sheet. Since the boundary layer is the product of the interaction between the ice sheet and the atmosphere, these two largest glaciers of the world can be said to be capable of protecting their own existence. This capability, however, can be jeopardized by changing any of the above four features. One possibility is the increase of the atmospheric counter radiation as the result of the enhanced greenhouse effect. This change is expected to happen with much larger probability than the warming of the climate. It is urgently necessary to establish the present energy budget of the ice sheet and to monitor how it changes in the future.

Automatic weather station, part of the current network on the ice sheet. Konrad Steffen Photo.

The energy budget of the dry snow zone of Greenland has so far been sporadically investigated. It is necessary to establish a climatologically representative year-round scheme under the present climate and to follow how it might change in the coming decades. Winter energy budget is presently not known at all. For a summer period it was previously speculated that the negative net radiation keeps the surface cold and maintains the stable atmospheric stratification. Recent short-term measurements by ETH (Zurich) and the University of Innsbruck clearly showed a positive net radiation in summer at Summit. A question is how the stable stratification can be sustained with positive net radiation. The atmospheric radiation must be monitored on a long-term basis in a broad band as well as in relevant spectral ranges. Possible changes in spectral distributions of radiation are very important both for shortwave and longwave radiation. For the former, the effect of the aerosol is most important. For the latter, the co

Recent experiments also showed that radiative flux divergence plays a significant role for vertical variation in sensible heat flux. This divergence is presumably owing to the longwave outgoing radiation, although this must be clarified. There are also important discrepancies in the results between the Innsbruck and ETH groups, mainly in the surface albedo. Both campaigns were hampered by frequent ice condensation on radiometers. This problem was subsequently tackled by developing a new ventilation scheme for radiometers and the new campaign can give a firm answer to this problem. It is necessary to study the energy budget of the glacier surface not as a separate entity but as an integrated part of the investigation of the entire atmospheric boundary layer. The necessary methodology for this part of the investigation has been well tested at the ETH Camp on the west slope of the Greenland ice sheet and at the Summit GRIP camp.

There are a number of by-products and possibilities of contribution for others from this project. The characteristics of the turbulence that is an important part of the structure of the boundary layer is necessary for understanding gas exchange processes between the atmosphere and the ice surface. In this sense, Summit is about the only site in the Northern Hemisphere that satisfies all micrometeorological requirements. The surface is horizontal, uninterrupted and homogeneous, and is free of any horizontal obstructions and so can be used as a laboratory for micrometeorology with stable atmospheric stratification. The long-term observation of radiative fluxes is an invaluable contribution for the World Climate Research Program (WCRP)/Baseline Surface Radiation Network (BSRN). An accurate surface albedo monitored at Summit is necessary for validating the satellite-evaluated albedo, which is an important part of the Surface Radiation Budget Project (SRB) of the WCRP.

Depletion of polar stratospheric ozone in the late winter and early spring seasons continues to be an important scientific issue for both hemispheres. While the "ozone hole" has become an annual feature in the Southern Hemisphere, increased losses have also been detected in the Northern Hemisphere in recent years. Increased losses at mid-latitudes may be connected to the intensified loss processes occurring in the polar regions. In June 1998, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) jointly released the Executive Summary of the "Scientific Assessment of Ozone Depletion - 1998". Among the recent major scientific findings and observations are:

• At northern polar latitudes in six out of the last nine boreal winter-spring seasons, ozone has declined during some months by 25% to 30% below the 1960's average.
• Ozone losses in the stratosphere may have caused part of the observed cooling of the lower stratosphere in the polar and upper middle latitudes (about 0.6^oC per decade since 1979).
• The abundance of ozone-depleting substances in the stratosphere is expected to peak by the year 2000. However, when changing atmospheric conditions are combined with natural ozone variability, detecting the start of the ozone layer recovery may not be possible for perhaps another 20 years.

Monitoring the stratosphere will be very important also after 2000 when the largest chlorine loading of the stratosphere is expected, because some model calculations that include feedback effects show the largest Arctic ozone depletion will occur well after 2010. Further, the presently measured ozone loss is considerably larger than predicted from models, indicating that our understanding of the chemical processes involved are still incomplete.

The Network for the Detection of Stratospheric Change (NDSC) has been established because of observations of ozone losses and UV flux increases are now occurring globally (outside of the tropics). The work of this group of research stations, where ozone and key ozone-related parameters are measured, is complemented by satellite data. A goal of the network is to make observations through which changes in the physical and chemical state of the stratosphere can be determined and understood. In particular, to make the earliest possible identification of changes in the ozone layer and to discern the cause of these changes.

There are four primary NDSC stations in the Arctic: Eureka (80^oN, 86^oW), Ny Aalesund (79^oN, 12^oE), Thule (77^oN, 69^oW) and SondreStromfjord (69^oN, 51^oW). They are all located between sea level and 600 m; high atmospheric water vapor content at these elevations introduces the need for significant atmospheric correction. Various remote sensors would profit from a high altitude site, in particular passive microwave radiometers (PMR) and Fourier transform infrared spectrometers (FTIR). For the latter, the low frequency of cloud cover is also important. The Summit of Greenland at 3200 m above sea level is the highest altitude on Earth north of the Arctic Circle. This means that the total column amount of water above the Summit is the lowest anywhere in the Arctic, implying that the conditions for observations of the stratosphere using ground-based remote sensors of the PMR and FTIR type are unique. Further, cloud cover at Su

As a basic tool for measurements of stratospheric composition, the FTIR allows the nearly complete investigation of NO_y (reactive nitrogen). Among the other species it can detect are CH₄, N₂O, HNO₃ and the chlorine reservoir species HCl and ClONO₂. Measurements of the last two (hydrochloric acid and chlorine nitrate) show that their concentrations are markedly reduced in areas where elevated chlorine monoxide (ClO) concentrations are found. This anticorrelation is quantitatively consistent with the picture that HCl and ClONO₂ are converted to reactive chlorine.

The central questions concern the concentrations of various chemical species that are connected to stratospheric ozone depletion. Observations of stratospheric ClO will be important during the next decade or so as the amount of chlorofluorocarbons (CFC's) in the stratosphere is expected to peak and then begin to decrease. The amount of ClO does not depend on the amount of CFC alone, but also on the occurrence of polar stratospheric clouds that are inversely related to stratospheric temperature. There is an observed negative trend of these temperatures and, if this continues, may be due to decreasing ozone in the stratosphere and increasing carbon dioxide in the troposphere, ClO quantity and arctic ozone depletion may increase even with decreasing CFC in the stratosphere.

Observations of ClO from the ground are very important, but also very difficult due to interference from other atmospheric constituents. Vertically resolved (profiles) information on ClO can only be obtained with microwave sensors, which receive thermal emissions from the ClO molecules. This is of particular importance when observing the disturbed polar stratosphere where two distinct peaks for ClO appear near 20 and 35 km altitude. Such observations are only possible when the content of water vapor in the atmosphere above the microwave instrument is sufficiently low. Observing conditions have been estimated by using a set of summer-time radiosondes launched from Summit to calculate atmospheric opacities. The result shows that in summer favorable conditions exist for more than 50% of the time. However, since the water vapor in winter can be assumed to be much lower than in summer, observing time should approach 100% for the scientifically very important winter season. These numbers can be compared with th

4.5. Atmospheric electricity. Atmospheric electricity measurements made at several km altitude on polar ice caps are uniquely valuable because they have noise levels that are only 1-10% of corresponding measurements at lower altitudes and lower latitudes. Summit is the only northern hemisphere site for such measurements. Excellent data have been obtained at the South Pole in the past, but observations are not being made there at present. The justification is growing, however, for simultaneous observations at both Summit and South Pole.

The absence of radon, dust, and moisture inhomogeneities in the air above Summit means fewer conductivity inhomogeneities; therefore space charge inhomogeneities are minimized. The minimal vertical convection also minimizes the production of such inhomogeneities. When space charge inhomogeneities are moved around by winds, they are a strong source of electrical noise. Also, the high altitude and proximity to the magnetic poles result in higher atmospheric conductivity, and in a stronger signal to noise ratio. Observations at Summit would be free of local meteorological effects to a much greater extent than at low-altitude, low-latitude stations. They should give much clearer data on global scale variation in the global electric circuit. The previous, though limited measurements made at South Pole and Vostok had excellent signal/noise ratios in calm conditions, and yielded good data even with 20-knot winds.

Global variations in the atmospheric electric circuit include both terrestrial and extraterrestrial modulation of the current flow. The terrestrial changes include day-to-day variability in the upward current flow from the low latitude thunderstorm generators, due to variability of the tropical mesoscale convection systems that drive the Hadley circulation. The mesoscale convection responds to changes in sea-surface temperature and to global warming. These generators maintain the ionosphere-Earth potential difference at about 250 kV. The extraterrestrial modulation is known from theory and is consistent with scattered, noisy observations. The solar wind modulates the galactic cosmic ray flux, which determines atmospheric conductivity. At high latitudes it also modulates the ionosphere-earth potential difference. The conductivity and the potential difference together control the downward current density (J_z) of a few picoamps per square meter that flows from the atmosphere to the surface. Solar

A number of data sets show correlations between changes in atmospheric dynamics, as part of regional weather and climate changes, and changes in J_z that are the result of changes in solar activity. The mechanism is thought to involve J_z control over the rate of accumulation of electrostatic charge on supercooled droplets at the tops of clouds. This appears to affect the rate of ice nucleation and precipitation, and of the albedo of the cloud systems, both of which are important for weather and climate change. But the database for evaluating the solar wind modulation of J_z is very scattered and noisy, and there is a need for accurate monitoring of J_z variations from one or more low noise sites. The measurements would provide an opportunity to study effects on the global circuit of short-term (Forbush) decreases and long-term (solar cycle) changes in the galactic cosmic ray flux, as well as effects of solar proton events, and changes in magnetosphere-ionosphere co

There are many other problems in atmospheric and space electricity for which continuous geoelectric monitoring is needed and for several decades the atmospheric electricity community has been advocating such monitoring. In conjunction with measurements elsewhere, these instruments don't just assess the effect of magnetospheric convection changes on the global circuit. They monitor ionospheric convection activity.

Recent research developments in atmospheric science have shown that there is reason to believe that the global circuit is an excellent global thermometer, possibly providing a single point method of monitoring global warming that does not suffer from the host of problems that ground level thermometry does. In addition, recent work has also shown a significant possibility that the global circuit acts to couple the magnetosphere and solar wind with the troposphere many orders of magnitude more strongly than anyone has previously believed. Long term acquisition of a high quality, digitally recorded atmospheric electricity database has become a matter of high scientific priority in the atmospheric sciences. It is well known that a substantially greater scientific return will be obtained by deploying a global network of such stations. However, there is much to be learned from a single station at Summit.

Aurora borealis in Greenland. Jorgen Taagholt Photo.

4.6. Polar aeronomy and space sciences. The Earth's polar caps have traditionally provided researchers with a natural laboratory to study electrodynamic forcing and momentum transfer from the solar wind to the upper atmosphere. The high-latitude Summit site is ideally located for making optical, magnetic, and radio observations necessary to describe this interaction. Because this site is geomagnetically conjugate with all-sky imagers, imaging riometers and HF radars deployed in Antarctica, the potential exists for ground-breaking interhemispheric observations of magnetosphere-ionosphere coupling.

High-latitude auroral arcs in particular provide researchers with a direct probe of distant plasma populations from several poorly understood magnetospheric regions such as the lobe, plasma sheet boundary layer, and the central plasma sheet. Well established incoherent scatter (IS) radar techniques to measure the source energy distribution associated with these auroral arcs have marked an elemental step forward in our understanding of the instantaneous state of the magnetosphere and of the contribution of the precipitating electrons to the global atmospheric energy budget. Unfortunately, IS radar techniques are incapable of describing the energy distribution at energies below 400 eV. Such low energies are typical for soft polar cap arcs, which are present roughly 50% of the time in the polar cap ionosphere.

Recent advances in monochromatic optical tomography hold the promise to adequately describe the energy distribution of such polar cap aurora by extending the analysis down to approximately 20 eV. A pathfinding experiment was conducted at the NSF Early Polar Cap Observatory (EPCO, Resolute Bay, NWT) and at the Canadian ASTRO Observatory (Eureka, NWT) wherein simultaneous pairs of all-sky images at 630.0 nm (atomic oxygen) were used to reconstruct the arc-related volume emission rate structure in a vertical plane of latitude versus altitude. Such analysis enables a description for the evolving energy distribution in the magnetosphere on a sufficiently short time scale to understand the interplay between closed field line source regions and field lines connected to the solar wind. Coordinated tomographic and IS radar data sets can also describe the composition of the neutral atmosphere in a plane of latitude/altitude -- a measurement heretofore unavailable. At least four fundamental questions may be answered

• Is there a characteristic or typical shape for polar cap arc energy distributions? How does a seemingly closed-field line regime migrate to such high latitudes?
• What is the relationship between the evolving polar cap arc and the background convection electric field?
• What is the relationship between the polar cap arc flow pattern, the magnetospheric topology, and ionospheric conductivity?
• How does polar cap atomic oxygen vary over latitude and altitude?

A primary research goal is to establish the capability of merging higher-energy IS radar estimates of the electron source energy distribution with the lower-energy tomographic estimates of the electron source energy distribution. A key result will be the first observations of electron density, plasma temperature, electric fields, and atomic oxygen volume emission rates in a common geophysical plane. This goal can be implemented by operating the existing Sondrestrom/Kangerlussuaq IS radar and co-located all-sky imager in coordination with an all-sky imager located at the Summit. The baseline between Sondrestrom/Kangerlussuaq and Summit camp is approximately 600 km, a distance ideal for high-fidelity tomographic reconstruction of polar cap arcs in 630.0 nm emission. The two stations are also within 4 degrees of the same geomagnetic latitude. Such a geometry is well suited to study the typically sun-aligned geometry of polar cap arcs.

For dedicated windows during the new moon period, the Sondrestrom/Kangerlussuaq IS radar will be used to perform magnetic East - West elevation scans and the Sondrestrom/Kangerlussuaq imager will be commanded to record 630.0 nm at the highest usable rate of image acquisition. During the winter-long experiment, NOAA satellite images will be used to pre-select intervals of clear skies at both stations so that IS radar data analysis can begin prior to the recovery of the Summit camp optical data. It is anticipated that over an entire winter-long period, several tens of arc events will be available for study.

Geological and glaciological studies in east Greenland. Jorgen Taagholt Photo.

4.7. Seismic & geodetic measurements. These would be part of a network to fill in important data gaps. Continuous geodetic measurements would be an excellent compliment to the periodic measurements of vertical and horizontal movement, and help establish if movements are episodic or gradual.

Previous investigations have found very little seismic activity under the interior of the Greenland Ice Sheet. Similarly, there have been very few earthquakes located under the Antarctic Ice Sheet, which raises question of why such activity is muted in these locations. Placement of a seismograph will facilitate determination of future earthquake locations and frequency under the Greenland ice sheet. A seismograph on the ice sheet will also contribute to the developing cooperation on earthquake study in the entire Arctic region. Until recently, these studies have been hampered by ineffective efforts in northern Russia. Seismically active zones are located in several coastal areas, but the general impression is that that earthquakes do not occur under the ice sheet. General seismic knowledge will be improved with a seismograph at Summit, but the more important result will be an increased knowledge regarding sub-ice sheet earthquakes. The recordings will tremendously improve the seismological knowledge of Greenland lithosphere characteristics. Based on past experience at other sites on the ice sheet a seismograph at Summit should be very sensitive, i.e. have good signal-to-noise characteristics.

Only twice before has a seismograph been used on the Greenland ice sheet; at Camp Century and at Inge Lehmann station, both in the northern part of Greenland. The use was limited to a very short time at Camp Century and only one year (1966-67) at Inge Lehmann. These sensors were very sensitive, but use was discontinued due to high costs. A seismograph has been operated successfully at the South Pole station in Antarctica for many years.

Repeated geodetic measurements using three methods (tidal gravimeter, global positioning system (GPS), and synthetic aperture radar (SAR)) will enable determination of the motion of selected points. GPS and SAR positioning experiments are intended to give a much denser time series than is now available; i.e. weekly or in 17-day increments. Expansion of data collection from every summer to year round will address two concerns. First is the question of whether the flow process, which seems regular in the longer annual time scale, also turns out to be regular on shorter time scales, or do surges occur? Secondly, the more frequent measurements of surface points will give information on the consolidation of accumulated snow. Repeated GPS measurements will also assist in measuring electromagnetic wave propagation through the ionosphere and troposphere, which will give information on ionosphere density variations and atmospheric vapor variations. A tidal gravimeter has not previously been placed on the Greenland

Logistic costs for operations at Summit demand that any research program be carefully integrated in order to maximize scientific return by reducing duplication of effort. While we have discussed the different research activities as if they were decoupled issues, it should be obvious that this division is only for convenience. There would be a number of shared measurements, especially in the first four areas. In the following subsections we present a functional description of the resource needs. For example, several of the investigations will require a common meteorological database to interpret results. Resource needs are described for the six main measurement areas. Seismic and geodetic measurements are not included.

5.1. Research Activities.

Ice-core interpretation: i) collect daily surface snow samples, ii) collect weekly samples from snow pits, iii) observe and document all instances of falling and blowing snow, iv) examine crystal morphology during these events to estimate the fractions of new vs. old snow involved, v) make manual snow depth and density measurements at multiple locations after each snowfall or blowing snow event vi) maintain automatic snow depth gauges, vii) calibrate and maintain continuous instruments for selected atmospheric chemistry measurements (e.g. hydrogen peroxide, formaldehyde), viii) maintain aerosol sampling systems and change filters at least daily (for analysis of e.g., soluble ions, anthropogenic trace metals). ix) make continuous micrometeorology measurements sufficient to model energy fluxes and measure snow and firn temperatures for model validation.

Tropospheric chemistry: i) maintain continuous instruments for selected atmospheric chemistry measurements (e.g. ozone), ii) collect weekly canister samples of air for analysis of hydrocarbons and halocarbons in U.S. and European laboratories, iii) maintain aerosol sampling systems and change filters at least daily (e.g., natural radionuclides, carbonaceous aerosols), iv) make daily balloon soundings.

Radiation, energy balance and boundary layer: Carry out an initial two-year measurement of direct, diffuse, and reflected-solar radiation, global radiation, longwave down and up-welling radiation, net radiation, sunphotometry with designated filters for the aerosol-optical depth, sensible and latent heat fluxes and the flux into the snow cover. This will involve: i) continued operation of automatic weather stations now at Summit, upgrading instruments as needed, ii) deploy and operate a well-calibrated far-infrared spectrometer that is equipped with short-wave filters for the spectral radiation, iii) deploy and operate a mid-infrared spectrometer system to determine temperature and water vapor profiles in the bottom few kilometers of the atmosphere (automatic versions of these instruments have been built for the DOE ARM program), iv) occasionally check the weather station, and check that the viewing port of the far-infrared spectrometer is clear of snow and ice, v) instrument a 50-m tower at five levels w

Stratospheric observations: deploy two dedicated instruments and operate over the long term: i) passive microwave radiometer, and ii) FTIR. The PMR instrument should operate in a different frequency range compared to (e.g. the ground-based instruments in Ny Ålesund). The frequency range should take advantage of the much better observing conditions at Summit. 250 to 300 GHz, was already successfully used at a similar site in inland Antarctica could be considered. In addition to the key species, O₃ and ClO, other important constituents can be observed such as HO₂, N₂O, HNO₃, and NO₂.

Atmospheric electricity: ii) deploy and maintain instrumentation to measure Jz and Ez (weight a few kg) in dual identical arrays around 1 km apart to measure the electric field, the air/earth current and possibly the conductivity, iii) do a daily functionality check on instrumentation, iv) log weather comments, v) check instruments for snow build-up, de-ice field mill rotors to see if any insulators need de-icing (monthly).

Polar aeronomy and space science: Install a weatherized digital 630.0 nm all-sky imager on the roof of Summit site laboratory (30 kg). Operate this imager during the winter-over period simultaneous with routine operation of the Sondrestrom IS radar and all-sky camera. The Summit imager will be automated and require only occasional changeout of magnetic data tape and cleaning of accumulated snow from the external optical dome.

5.2. Personnel. Some combination of shared and dedicated project personnel will be needed to staff the proposed facility. All of the routine and most of the intensive measurements and sampling programs envisioned could be accomplished by a field party of at least four personnel, plus two or possibly three support personnel (including a mechanic for diesels and snowmobiles). This will require a high degree of cooperation among investigators, and particularly those in the field at any given time; but experience over the past year indicates that it is a realistic expectation. Logistically, the benefits of keeping the field party as small as possible are tremendous. Following the 1997-98 model, all personnel (science technicians and facility support personnel) would participate in basic station maintenance functions as well as scientific measurements. Logistics personnel would be selected taking into consideration their scientific/technical backgrounds and interest in the work to be completed.

Special campaigns or other science programs at Summit will require additional personnel for short lengths of time; every effort should be made to stagger such campaigns in order to keep camp loading even and avoid large increases in required support (structures, vehicles, personnel, etc.). In the U.S., agencies like NOAA have very little to offer in terms of facilities costs, but can make a long-term commitment to run measurement programs. We should explore if NOAA personnel could help staff a winter-over facility, as they now do at South Pole station. We recommend that the support personnel be funded separately from any science proposal. A contact in Sondrestrom will also be required, as well as someone authorized to arrange interservice agreements and transport of cargo and personnel between the US or Europe and Greenland during supply/re-supply periods. PICO or a similar logistics contractor should be tasked with these details. A science program coordinator could make these arrangements, but would need

Ice-core interpretation: 1 person full time, with a second person available for safety reasons during field measurements.

Tropospheric chemistry: 0.5 person full time.

Radiation, energy balance and boundary layer: 1 person full time.

Stratospheric observations: 1 full-time scientist needs to install, tune and operate the passive microwave sensor; this phase might last for one year. Later the instrument can operate nearly automatically and will require only little support from a local engineer, typically a few hours per week.

Atmospheric electricity: 0.25-0.5 person full time.

Polar aeronomy and space science: occasional. (8 hr/month) to change magnetic tapes, verify video signal, and clean snow off of external optical dome.

5.3. Laboratory Space. The increased requirements on the Summit facility suggested in this plan will require an expansion of the existing facility. Requirements for an increased population at the facility would require additional modular units similar to the 1997-98 ATCO facility (Green House). The Big House has a limited useful life and should not be considered as a viable facility for use in planning unless significant work is completed on the facility.

Ice-core interpretation: 2.5 by 6 m area in lab, plus 3.5 by 3.5 m area by tower (same as 1997-98).

Tropospheric chemistry: 2.5 by 4 m area in lab, plus 3.5 by 3.5 m area by tower (same as 1997-98; shared with ice-core interpretation).

Radiation, energy balance and boundary layer: 2 m of floor space for the far-infrared spectrometer. 1 m for BSRN data acquisition and management

Stratospheric observations: i) For passive microwave radiometer (500-700 kg instrument), two rooms, one for the compressor unit 1 sq. meter with sonic insulation and a temperature controlled fan outside and a second room 3 by 3 meters, with a window made of styrofoam. ii) For FTIR, 2 by 4 meters with "window" in the roof. Both rooms should be temperature stabilized to approximately 2K.

Atmospheric electricity: Space for computer, and for test equipment used in daily checks.

Polar aeronomy and space science: Provide bulkhead penetration for imager control and data cables, as well as for the GPS antenna cable. Mating connectors will be provided for bulkhead panel from imager PI. About 21 units (81 cm) of standard rack mounted equipment space will be required for GSE electronics, computer, and monitor. The weight of the external imaging system is approximately 30 kg and the weight of the internal rack-mounted equipment is estimated at 30 kg.

5.4. Power. We recommend that the clean-power concept used for recent investigations be retained, with the possibility for pollution-sensitive sampling being conducted at a remote camp powered by photovoltaics, or by wind-power generation if feasible. It should be possible to maintain the clean sampling site 10 km distant, to allow commuting on an as needed basis. Based on the following information, the maximum power requirement for science is in the range of 15-20 kW. The new four-person modular structure, big house and any other camp structures, plus monitoring instruments, should continue to be powered by diesel generators.

Ice-core interpretation: Same as for 1997-98 pilot project. (2.5 kW at tower and 1.5 kW in lab)

Tropospheric chemistry: Same as for 1997-98 pilot project. (2.5 kW at tower and 1.5 kW in lab)

Radiation, energy balance and boundary layer: 500 W for the far-infrared spectrometer, 500 W for 50-m micrometeorology tower and 150 W for radiosounding (all 110 VAC)

Stratospheric observations: i) passive microwave radiometer, 3.5 kW, 220 VAC, 50 Hz; ii) FTIR, < 4 kW.

Atmospheric electricity: A few hundred watts.

Polar aeronomy and space science: The imager system should consume no more than 200 W at 110 Vac.

5.5. Data and Communications. We recommend that the approach used during the 1997-98 winter-over project be continued. The communications equipment consisted of radio, telex and satellite phone. New means of voice and electronic data transmission should be investigated to enhance communications and sharing of data. Each of the science personnel should have a dedicated computer for data analysis, plus a separate computer for communications. Additional computers will be needed for operation and receiving data from the science instruments.

Ice-core interpretation: Enter, download and examine data daily, transmit summaries to U.S. and European laboratories weekly, and send out full data sets on re-supply flights.

Tropospheric chemistry: Enter, download and examine data daily, transmit summaries to U.S. and European laboratories weekly, and send out full data sets on re-supply flights.

Radiation, energy balance and boundary layer: Enter, download and examine data daily, transmit summaries to U.S. and European laboratories weekly, and send out full data sets on re-supply flights.

Stratospheric observations: Download and examine data daily and send out full data sets on re-supply flights. For continuous operation of the passive microwave radiometer (24 hours/day) the data rate will be of the order of 30 Mb/day. A limited preprocessing of the data in near real time might be possible, however it would still be required to transmit all the collected data at least on a weekly basis for final processing.

Atmospheric electricity: Download and backup data weekly and send out full data sets on re-supply flights. Each array generates sixteen 16-bit words per second for a total of thirty-two 16-bit words per second plus time tags (8 bytes) for a total of 72 bytes per second (576 bps). Data will be stored in a dedicated computer plus a data recorder.

Polar aeronomy and space science: 100 kB summary keograms (time sequential vertical samples of multiple all-sky images) should be made available to remote PIs. Full raw image data sets should be sent out on resupply flights.

5.5. Special Requirements. An additional piece of heavy equipment could be required for snow removal to augment and back up the aging Caterpillar 931. Fuel requirements are estimated at 25,000 gallons for diesel fuel Arctic and aviation fuels.

Ice-core interpretation: 30-m tower, already on site.

Tropospheric chemistry: 30-m tower, already on site.

Radiation, energy balance and boundary layer: 50-m tower.

Stratospheric observations: The passive microwave radiometer consists of several sub-units, allowing for an easy transportation by small aircraft. The sensor will be operated inside a laboratory building, and will observe through a vertical window extending from 0.90 m to 1.90 m above the floor and a width of 0.5 m, this opening will be covered by a piece of Styrofoam (3 to 5 cm thick) for insulation and weather protection (Styrofoam is highly transparent for mm-waves). Typical laboratory temperature and humidity ranges are acceptable. The instrument needs approximately once per week an absolute calibration. For this procedure liquid nitrogen is required (< 10 liters per calibration). The FTIR requires access to a platform offering a 360-degree view to allow the tracking of the sun or the moon. The sun/moon tracker has to be mounted outside the building and will need some regular maintenance. Also, the FTIR will need approximately 4 L of liquid nitrogen per day, and the microwave sensor may need a few

Atmospheric electricity: Instrumentation is mounted a few meters above the surface on wooden poles in the upwind, clean air direction. Deployment of the instrumentation would involve dual identical arrays around 1 km apart. Each instrument will consist of a 43 cm diameter sphere, a 1/4 hp motor and an electronics box approximately 48 cm x 61 cm x 30 cm in an insulated buried vault. Both instruments will be tied by cable to station ac power and a data recording PC. Packed for shipping, the electronics plus test equipment and the associated crates will weigh about 400 kg and occupy about 2 cubic meters. This estimate does not include the lumber for the tower and the large cable spools. The installation will require about ten 5 m x 10 cm x 10 cm posts, and about 1.2 km each of ac power and signal transmission cables.

Polar aeronomy and space science: External imager should be wind protected by tripod tie-downs.

5.6. Re-supply. We recommend using C-130 support for major set up and re-supply of fuel and other heavy, bulky items. This could be done in the "summer", May through September period. Twin Otter support could then be used nearly year around for change of personnel and winter re-supply. Expanding the facility and taking in supplies and fuel for the winter would require an additional 64 to 72 LC-130 flight hours above routine summer operations. A larger science crew and the possibility of rotating crews will necessitate two to four additional Twin Otter flights during the winter.

5.7. Administration. It is recommended that the funded principal investigators form a steering committee, and that the steering committee designate two scientific coordinators (one each from U.S. and Europe) to organize annual workshops, maintain communications and coordination with the European programs, seek participation and coordination with other arctic scientific investigations, and act as official spokesman for the steering committee. The scientific coordinators should serve on a rotating basis, and supplemental funding should be provided for coordination. Prior experience has also shown that a considerable amount of time and effort must be spent dealing with logistic concerns and coordinating sampling efforts and requirements. While most of these issues can be dealt with in frequent exchanges among those involved, we also suggest providing supplemental funding to one investigator to be the focal point for coordinating field work and logistics with the logistics contractor (e.g. PICO). This

A possible scenario for cooperation would be for one or more European scientists to prepare a proposal within the EC Fifth RTD Framework Programme (Environment/Global Change) by about March 1999. The structure of these programs allows any foreign country to be a participant. It is desirable that the US scientists as a whole group would cooperate in the European project and vice versa. The main proposal from the European side would be on the same level as the scientific coordinator from the US. This two-person team would then take the responsibility to coordinate investigations. NSF has indicated that proposals requiring C-130 support from the Air National Guard (currently, all Greenland operations) must be submitted by February 15 for work in the subsequent year. Proposals requiring other field work must be submitted by August 1 for work in the subsequent year.

In the interim period before proposals are received and funded and a steering committee formed, the (modest) coordination needed, outside of that provided by NSF, could be done by an ad hoc committee designated by the scientists intending to submit proposals for participation in the program. Following is a four-year schedule.

The workshop consisted of a series of presentations on the history of winter-over activities on the ice sheet, logistics information, and the proposed scientific program:

Jorgen Taagholt, Danish Polar Center: Winter-over stations on the Greenland ice sheet
Leif Vanggaard, Danish Arctic Institute: Danish experiences in the selection and management of personnel for small arctic stations
Lt. Colonel Verle Johnston: 109th Airlift Wing Greenland Information
Atsumu Ohmura, ETH, Zurich:Energy and radiation budget on the surface at Summit.
Carl Christian Tscherning, professor, University of Copenhagen: 1) Earth-tide measurements, 2) Repeated position-determination using GPS, and 3) Maintenance of a network of SAR reflectors (or transponders, cf. DCRS proposal)
Niels Reeh, Danish Center for Remote Sensing: Vertical movement of the upper firn layers
Soren Gregersen, Kort & Matrikelstyrelsen, Copenhagen: Seismograph on Summit; seismicity and tectonics in Greenland
Naja Mikkelsen, Ministry for Environment and Energy Copenhagen: Paleoclimatic investigations: Past achievements and future challenges
Torben Stockflet Jorgensen, Danish Meteorological Institute: Microwave measurements related to the ozone layer
Frank Murcray, University of Denver: Remote sensing of the stratosphere and upper troposphere
Brian A. Tinsley, University of Texas at Dallas: Summit camp as an optimum site for measuring global electric circuit parameters relevant to global climate.
Jack Dibb, UNH (also UAz, CRREL, CMU, UW Milwaukee and UC Irvine): Relationships between air and snow chemistry in winter at summit Greenland
Roger Bales, University of Arizona: Ice core records and atmospheric photochemistry; also presentations for others not in attendance:
Eric Steig, INSTAR, Boulder: Stable isotope measurements in atmospheric water vapor at the Greenland Summit through the full seasonal cycle.
Mary Albert, CRREL:Snow properties and processes
NASA, PARCA:Program in Arctic Regional Climate Assessment
John Kelly, University of Alaska: Seasonal variation of atmospheric carbon dioxide and its relation to climate induced changes in northern vegetation
Peter Tans, NOAA Carbon Cycle Group: Measurements of atmospheric trace gases affecting earth's climate
Sam Oltmans, NOAA: Ozone and water vapor studies

Workshop attendees:

8.2. February, 1998 Workshop in Copenhagen. In agreement with the US National Science Foundation the Danish Commission for Scientific Research in Greenland hosted a European Summit Seminar in Copenhagen February 26, 1998, for discussing a European interest in all-year-round measurements at the unique Summit location, and with information about the US NSF's successful pilot project this winter 1997/98, where 4 persons were overwintering at Summit.

P. Hart Hansen, chairman of the Commission and host of the meeting, expressed the hope that the outcome of the meeting would provide a scientific background for a possible joint venture with the U.S. to undertake year-round studies at Summit. He hoped to be able to present the conclusions of the meeting to the European Polar Board, at their meeting in Copenhagen on March 13, 1998.

Clauer. NSF, said that one of the reasons for NSF to establish the overwintering facilities at Summit was the need for sampling snow all year round in order to determine the transfer function which should support the interpretations of the vital data from the deep ice cores in the global change research. The pilot experiment of running an all-year-round station has so far been a success, but very expensive. There is therefore a need for European co-financing in the future, even though the US interest for continuing science projects in Greenland is presently increasing.

N. Mikkelsen, chairperson, concluded that a White Paper for science projects at Summit had to be prepared based on Roger Bales report from the Kangerlussuaq meeting in May 1997 and the outcome of todays discussions, before the work with preparing actual proposals should be initiated.

Individual scientists presented projects to be carried out at Summit: Boundary layer micrometeorology (A. Ohmura), Stratosphere research (T. S. Jorgensen and K. F. Künzi), Seismic & geodetic measurements (C. C. Tscherning), Movements of the firn layers and the ice (N. Reeh), Seismicity & tectonics (S. Gregersen), Aerosol research (P. Wåhlin), Transfer functions from air to snow (J. L. Jaffrezo).

M. Holm, Greenland Home Rule, was pleased to advise that the Greenland Home Rule considers the Summit site to be ideal for scientific research. He stressed that Greenland has now scientific institutions of its own, and that they hope to be able to cooperate at the Summit site or on results from the site.

N. Mikkelsen opened for a general discussion of funding and possibilities for maintaining the camp site at Summit.

N. Gundestrup suggested that the various proposals should be compiled into one joint programme headed by one scientist from the US and one from Europe to coordinate the science and the financing.

Williams described the set up of the European Science Foundation and mentioned that the European Polar Board was established in 1995 by ESF. The Summit station is on the agenda for the European Polar Board meeting in Copenhagen on March 13 as an item under "large facilities". The European Polar Board has no funds at its disposal, but it could act as a coordinating body and further endorse the programme to various funding agencies.

Based on the discussions, a White Paper working group was established. From the US R. Bales was nominated with the support of J. Dibb and F. Murray. From the European side T. S. Jorgensen was suggested. It was suggested that R. Bales and T. S. Jorgensen should prepare a White Paper with a coherent and firm research plan for a scientific Summit programme on the basis of todays meeting and the May 1997 Summit meeting report.

N. Mikkelsen stated that the financial support for a Summit proposal needed clarification. With the endorsement of the Summit programme by the European Polar Board on March 13, 1998, she suggested that EU and national funding agencies could be approached and promises of commitment achieved not later than September 1999.

In conclusion the meeting had shown:

• that there was a keen interest in Summit science which calls for multinational cooperation.
• that there was a keen interest in keeping the Summit station operational in the future as the site was crucial for conducting a number of scientific investigation programmes.
• that the outcome of this meeting would be presented to the ESF European Polar Board at its meeting on March 13, 1998, with the hope that the Polar Board would endorse the Summit programme and thus facilitate further negotiations with funding agencies.
• that a White Paper with an outline of the Summit programme will be completed by fall 1998 by R. Bales and T. S. Jorgensen based on todays discussions and the Kangerlussuaq report from the May-97 meeting.

List of participants: