Konrad Steffen - US grants

This is for support for the International Symposium on Remote Sensing of Ice and Climate. The meeting is being sponsored by the International Glaciological Society, and co-sponsored by a number of other groups. This award is to support, in part, the publication of reviewed and accepted manuscripts comprising the proceedings of the symposium.

9321547 Key This three-year program will quantify the individual energy streams that make up the arctic surface radiation budget, and will relate the observed radiation distribution to synoptic-scale wind, pressure, and moisture patterns. It will be the first effort to produce a comprehensive radiation climatology for the Arctic. The arctic surface energy budget, particularly that of the Arctic Ocean, has been identified as a major component of the global climate system that is potentially sensitive to climate-scale perturbations due to feedback mechanisms involving the surface albedo, the stability of the lower troposphere, and water vapor transport. The project includes four main tasks: (1) The analysis of solar and long-wave radiation data obtained directly at manned observing sites in the arctic. (2) The calculation of radiative fluxes at the surface and at the top of the atmosphere using a satellite-based cloud data product from the International Satellite Cloud Climatology Project (ISCCP). (3) For selected months, the ISCCP-derived fluxes will be compared to the corresponding synoptic regime, and (4) a study to assess the effects of the sampling and analysis procedure on the radiation statistics and their temporal variability will be undertaken. ***

This award is for support for a 3 year program to assess the variation in the snow accumulation rate in northern Greenland. Previous work has shown that isotope records from shallow ice cores can be used to identify interannual and perhaps seasonal cycles of snow temperature and accumulation. In order to assess seasonal and interannual variability, the isotope temperature record requires calibration from in situ meteorologic measurements. On- going remote sensing research appears to show that interannual trends in brightness temperature can be used as proxy data for annual accumulation but this work requires calibration from ice core data in northern Greenland. Combining stable isotope measurements, remote sensing, and surface energy balance data will allow an assessment of how interannual and seasonal processes affect the magnitude and variability of snow accumulation. Meteorologic data collection stations will be established and five shallow ice cores will be drilled in a 400 km2 area around each of two stations, one in northeastern and one in northwestern Greenland. Argos satellite links will provide data transmission capability from each remote site. Grain size and temperature profiles, sublimation, and energy balance will be calculated using a one-dimensional energy and mass flux model.

ABSTRACT OPP-9703127 CURRY, JUDITH UNIVERSITY OF COLORADO This research project is a key component of a large, coordinated, multi-investigator program, Surface Heat Budget of the Arctic (SHEBA) Ocean. The research program will be conducted for 14 months from a ship frozen into the ice pack. These investigators will measure atmospheric conditions of the permanent ice cap of the Arctic Ocean from a scientifically instrumented C-130 aircraft during the Spring and Fall in conjunction with a NASA research program jointly conducted at the site. These researchers will determine the flux of incoming heat radiating onto the ice floe as a function of changing cloud conditions. Their results will help determine how atmospheric heating is coupled to adsorption of heat by the ice. These measurements are critical to understanding how heat is reflected or absorbed by the ice as it melts in the summer and thickens in the winter in response to seasonal variations in climate. The aircraft measurement program makes an essential contribution to the SHEBA team of researchers who will measure atmospheric variables with a large array of instruments on the ice floe and aircraft flying above as well as ice and ocean property measurements made on and below the ice floe. The combined set of measurements in SHEBA will allow refinement of climate models for the Arctic region. Those improved models will lead to better predictions of the climate and the permanence of the Arctic ice cap under a proposed global warming that could occur if atmospheric carbon dioxide levels are increased above present levels.

ABSTRACT

OPP-9907197 OPP-9907469 OPP-9907330
HONRATH, RICHARD DIBB, JACK ALBERT, MARY
MICH. TECH. UNIVERSITY UNIVERSITY NH CRREL

OPP-9907376 OPP-9907623 OPP-9907434
SHEPSON, PAUL BLAKE, DONALD ANASTASIO, CORT
PURDUE UNIVERSITY UC-IRVINE UC-DAVIS

OPP-9907314
STEFFAN, CONRAD
UNIVERSITY OF COLORADO

The PIs propose a field sampling program at the summit of the Greenland ice cap to examine the effects of energy from the sun on the chemistry of organic compounds contained in the interstitial air trapped in snow. The results of the research will be used to determine if the chemistry of the air/snow changes through time in response to fluctuations in light energy penetrating the snow. The study is critical to developing a method for interpreting ice core records for the history of atmospheric chemistry in the past. The photochemical process under study could lead to more accurate interpretations of past atmospheric conditions and provide better estimates of both natural and anthropogenic impacts on the atmosphere from changing climate or human activities. The results of the research will also provide evidence of the role of the Greenland ice sheet on modern atmospheric chemistry that will be critical to understanding how high-latitude processes affect the atmosphere.

0135450
Steffan

The research is a collaborative effort between the University of Colorado, Boulder, the British Antarctic Survey, Cambridge, and the Jet Propulsion Laboratory. The Office of Polar Programs (OPP) at National Science Foundation and the National Aeronautical and Space Administration (NASA) will support the project. The Greenland Ice Sheet is thinning rapidly along its outlet glaciers and is contributing an estimated 0.13 mm/yr global sea level rise. Signs of its warming have been documented, including rising air temperature in its central part and retreating sea ice in its surrounding ocean. Extensive floating ice tongues in the northwest sector are ice undergoing massive rates of ablation from the surrounding warm ocean waters and are presently in a state of fragile equilibrium, but this ablation rate has never been measured. The Petermann Gletscher is the largest and most influential outlet glacier in northern Greenland, draining an area of 71,580 km2, with a discharge of 12 cubic km of ice per year. Remote sensing results suggest that its ice discharge exceeds that required to maintain the ice sheet interior in a state of mass equilibrium by 63%, and its grounding line is retreating at an anticipated rate at nearly one meter per year. Its floating ice tongue is only a few meters above sea level at the ice front, so it is highly vulnerable to ice thinning. If confirmed by in-situ observations and if this trend continues for several decades, the rate of thinning would be sufficient to threaten the stability and survival of the ice tongue. The Principal Investigators propose to do a detailed analysis of the glacier floating ice tongue in front of Petermann Gletscher that integrates key field observations with remote sensing data. The field program is designed to obtain the in-situ observations to confirm, validate, and calibrate the remote sensing estimates of basal melting, derive reliable estimates of surface melt from an energy balance model, observe changes in ice volume with precision, and understand the contribution of ice dynamics, surface melt and bottom melt to volume changes of floating ice. The experiment is will take place at the most crucial part of the glacier, the grounding line. Bottom melt rates are estimated to reach 25 m/yr near the grounding zone from remote sensing data, and 75% of the ice that crosses melts in contact with warm ocean waters in the first 20% area of floating ice. Basal melting will be measured in-situ over several time intervals using a novel phase-sensitive radar sounding system developed and tested by the British Antarctic Survey. At the surface, the energy budget of the ice will be characterized using a network of automated micrometeorological stations, and the results will be employed to determine how well surface melt can be predicted from an energy balance model and how much it changes with time. Remote sensing data that include strain rates from interferometric synthetic-aperture radar (InSAR), elevation changes from airborne laser altimetry, and ice thickness from airborne ice-radar sounding, will be employed to yield spatial estimates of basal melting to be compared with in-situ data. InSAR and Global Positioning Systems will be used to detect changes in flow rate with time. The results will provide invaluable insights into dynamics and climatic processes of northern Greenland glaciers.

This proposal will provide funds for the support of round trip air travel of approximately five graduate students from U.S. institutions to Beijing, China, to participate in the First Climate and Cryosphere International Science Conference.
The primary sponsor of the conference is the Climate and Cryosphere (CliC) project, which was established under the World Climate Research Programme (WCRP) and the Scientific Committee on Antarctic Research (SCAR) as a mechanism to coordinate the study of ice as an integral part of the global climate system.
The selection of recipients of the travel grant will be conducted by a panel of five recognized polar climate experts, from a pool of applicants who have an accepted abstract for the meeting. Selection criteria will include the scientific content of the abstract, geographic and other diversity considerations, and relevance to CliC project areas.
The principal investigator is the acknowledged leader of the U.S. polar research community, and has participated in a number of studies of both arctic and antarctic glaciology and climate. He has been responsible for many of the advances in our thinking about the climatic effects of the cryosphere.
The proposal furthers programmatic interests in involving young polar scientists with the international research community, and fostering scientific interaction at all levels.

Steffen/0732946

This award supports a field experiment, with partners from Chile and the Netherlands, to determine the state of health and stability of Larsen C ice shelf in response to climate change. Significant glaciological and ecological changes are taking place in the Antarctic Peninsula in response to climate warming that is proceeding at 6 times the global average rate. Following the collapse of Larsen A ice shelf in 1995 and Larsen B in 2002, the outlet glaciers that nourished them with land ice accelerated massively, losing a disproportionate amount of ice to the ocean. Further south, the much larger Larsen C ice shelf is thinning and measurements collected over more than a decade suggest that it is doomed to break up. The intellectual merit of the project will be to contribute to the scientific knowledge of one of the Antarctic sectors where the most significant changes are taking place at present. The project is central to a cluster of International Polar Year activities in the Antarctic Peninsula. It will yield a legacy of international collaboration, instrument networking, education of young scientists, reference data and scientific analysis in a remote but globally relevant glaciological setting. The broader impacts of the project will be to address the contribution to sea level rise from Antarctica and to bring live monitoring of climate and ice dynamics in Antarctica to scientists, students, the non-specialized public, the press and the media via live web broadcasting of progress, data collection, visualization and analysis. Existing data will be combined with new measurements to assess what physical processes are controlling the weakening of the ice shelf, whether a break up is likely, and provide baseline data to quantify the consequences of a breakup. Field activities will include measurements using the Global Positioning System (GPS), installation of automatic weather stations (AWS), ground penetrating radar (GPR) measurements, collection of shallow firn cores and temperature measurements. These data will be used to characterize the dynamic response of the ice shelf to a variety of phenomena (oceanic tides, iceberg calving, ice-front retreat and rifting, time series of weather conditions, structural characteristics of the ice shelf and bottom melting regime, and the ability of firn to collect melt water and subsequently form water ponds that over-deepen and weaken the ice shelf). This effort will complement an analysis of remote sensing data, ice-shelf numerical models and control methods funded independently to provide a more comprehensive analysis of the ice shelf evolution in a changing climate.

Observations have shown a relationship between increased summer ice velocity and increased meltwater production over several years on the western slope of the Greenland Ice Sheet. This doctoral dissertation research project will map the spatial distribution of moulins (vertical conduits that transmit surface meltwater to the bed of the ice sheet) based on high-resolution satellite imagery within a 1,100 square-km area of the inland ice northeast of Jakobshavn/Ilulissat, West Greenland (at a latitude of roughly 70-degrees N). The doctoral student will compare observed moulin locations to historical moulin locations as identified on a topographical map based on 1985 aerial photography in order to identify changes in moulin distribution over time. A multivariate regression model will be derived to explain moulin density across the study area. Subglacial water pressures, determined from moulin density, will be translated into basal sliding speed using sliding laws previously validated for alpine glaciers. The seasonal melt-acceleration phenomenon then will be modeled using a coupled thermodynamic ice sheet model under both present day and future climatic conditions, with the latter including a simulated increase in surface meltwater production. The primary goal of this project is to model the physical basis of the observed melt-induced acceleration of ice flow and predict how this mechanism will influence ice sheet dynamics in the future. The secondary goal of the project is to identify changes in moulin distribution over time. Moulin distribution will be determined via feature extraction from high resolution (with roughly one meter pixels) commercial satellite imagery.

Sea-level rise is a highly relevant societal concern. The estimated sea-level rise contribution from glaciers and ice sheets currently is based primarily on surface mass balance and ignores the possible influence of changing ice velocity, with increased ice loss related to increased iceberg calving. This project therefore will directly address the need to improve basic understanding of the potential sea-level rise contribution due to accelerated ice flow in the Greenland Ice Sheet. The products of this project will be maps of moulin density and of the magnitude and spatial distribution of basal slide within the study area. This project will provide new insights regarding the influence of meltwater on the ice dynamics of ice sheets by contributing novel models of surface hydrology (i.e moulin density) as well as basal slide (the relation between subglacial water pressure and ice velocity at the ice-bedrock interface). The parameterizations and conceptual advances made in this project likely will be useful for the alpine glacier community as well. This project will apply these theoretical advances to probe the physical basis of the observed correlation between ice surface velocity and duration of summer melt on the western flank of the Greenland Ice Sheet. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.

The stable isotopic records from the Greenland Ice Sheet are the gold standard for understanding climate variations in the Arctic on decadal to millennial scales. While the basic tenets that underlie interpretation of isotopic information appear robust in a mean sense, meteorological and glaciological processes can confound simple interpretations. Processes of concern are variations in moisture sources, cloud processes, surface ablation, blowing snow and vapor diffusion in the firn. The project objectives are to resolve fundamental uncertainties in the controls on the isotopic composition of the ice sheet through a 3-year measurement campaign at Summit, Eureka and Reykjavik. The project will use measurements and modeling to evaluate 1) the degree to which oxygen isotopic composition and deuterium excess of snow capture variations in moisture sources versus cloud microphysical conditions, and 2) the degree to which blowing snow and vapor diffusion within the firn confound accurate interpretation of variability in the isotopic record. Continuous measurements of the isotopic composition of water vapor and daily measurements of the isotopic composition of freshly-fallen and blowing snow will be made at Summit, Eureka and Reykjavik. These will be combined with measurements of the amount, size distribution, and approximate habit of falling and blowing snow, turbulence measurements to evaluate snow lofting, surface latent heat flux (ablation and frost) and energy balance, and remote sensing of polar clouds and atmospheric structure. High-resolution firn cores will be drilled to reconcile the detailed isotopic measurements and modeling with glaciological records. The new isotope measurements will jump start an emerging international pan-Arctic cooperative network of isotope measurements, which complements Arctic observations under existing Arctic Observing Network activities. The advanced measurements at Summit enhance the site as a comprehensive observatory for monitoring and understanding Arctic change.