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We gratefully acknowledge the Antartic Glaciology and Antarctic Meterology sections, Office of Polar Programs, of the United States National Science Foundation for support of this work.

NSF Grants Supporting this work:

1) NSF Award # 9904947 Antarctic Glaciology
Stable Isotope Studies at West Antarctic ITASE Sites
This collaborative proposal supports a project to perform stable isotope analyses of samples collected along the International Trans-Antarctic Scientific Expedition (ITASE) traverses which will begin during the 1999/2000 Antarctic field season. This work will focus on the spatial and temporal distribution of oxygen-18 and deuterium in West Antarctica (where data are particularly sparse) and the calibration of the isotope-climate relationship on a site-by-site basis, using instrumental and remote-sensing temperature histories. Specific objectives of this work which contribute to ITASE are: 1) to obtain detailed oxygen-18, deuterium and deuterium excess and stratigraphic histories in snowpits at most or all of the ITASE coring sites; 2) to provide direct calibration of the isotope-climate relationship at each site through a combination of direct (AWS) and indirect (passive microwave satellite) temperature measurements; 3) to obtain isotope profiles covering the last 200 years; and 4) to use the results to provide 200-year climate histories at high temporal and broad spatial resolution across West Antarctica that will allow testing of proposed relationships among isotopes, moisture source conditions, synoptic scale climatology, and site-specific meteorological parameters, and which will enhance our ability to interpret isotope records from older and deeper Antarctic ice cores

2) NSF Award # 0229416 Antarctic Glaciology
Temperature Variability of the Last 1000 years in East Antarctica
This award supports a pilot ice-core drilling and analysis program to test the feasibility of obtaining well-dated, high-resolution isotope and chemistry records from East Antarctica. Shallow ice cores will be obtained from two locations: 1) ~100 from South Pole towards North Victoria Land, as an extension of the Byrd Station-to-South Pole ITASE traverse [International Trans Antarctic Scientific Expedition]; 2) at Taylor Dome, near the original deep coring site. Each of these cores will be sampled at very high resolution (~1/2 cm) and analyzed for stable isotope (delta D or delta 18-O) at the University of Washington. The cores will also be analyzed for trace ions at the University of Maine, under separate funding. The resulting time series, if they can be well dated as we expect, will be used to calibrate against the instrumental temperature record, brightness temperature observations from satellites and operational weather forecast reanalysis data sets. Results from this calibration work will be used to help plan a program of larger scope, with the objective of mapping the spatial expression of climate variability in East Antarctica. A summary document will be produced and made available to the community to help with planning of related field programs (e.g. deep ice radar, firn radar profiling, atmospheric chemistry, ice coring, snow surface properties for satellite observations, ice surface elevation and mass balance).

3) NSF Award #0126161 Antarctic Meterology and Climatology
Remote Observations of Ice Sheet Surface Temperature: Toward Multi-Proxy Reconstruction of Antarctic Climate Variability
This project will develop spatially extended and statistically reliable estimates of Antarctic surface temperature variations over the past several centuries, using a multi-proxy calibration/verification approach that combines the climate signal in ice core, satellite remote sensing, and weather station data. Antarctica has been problematic from the point of view of large-scale paleoclimate reconstruction because of the paucity of long-term instrumental data, and the relatively low resolution of most ice cores. Several new developments, particularly the network of shallow (~100 meter) ice cores from the ongoing International Trans-Antarctic Scientific Expedition (ITASE) project will yield broad spatial coverage of annually resolved ice core physical properties, chemistry, and stable isotope data over more than a hundred years. Second, there are now over twenty years of microwave and infrared brightness temperatures available from satellites covering virtually all of Antarctica with seasonally resolved information that has been demonstrated to record the ice surface/near surface temperature with very reasonable precision and accuracy. Finally, higher quality microwave emission data from Advanced Microwave Scanning Radiometers (AMSR) with much finer spatial resolution and radiometric fidelity than those from previous sources will offer an improved view of longer term mean temperatures in Antarctica. The 40-year instrumental record and the shorter but spatially more comprehensive Automatic Weather Station network will be combined with seasonally-resolved 37-gigahertz satellite-based ice surface temperature estimates to reconstruct Antarctic-wide temperature patterns during the past forty years. The sparser Antarctic instrumental surface temperature data available back nearly to the beginning of the century will be added for longer-term, though quite spatially-restricted, cross-validation of these reconstructions. This cross-validation procedure has been used successfully with roughly century-long instrumental records at locations primarily in the Northern Hemisphere. The longer time scale will be approached through a cross-validation of the proxy-based pre-20th century surface temperature reconstructions using information on thermal emission from deeper in the firn that is contained in low-frequency passive microwave satellite measurements.

4) NSF Award Pending Antarctic Glaciology
Stable Isotope Studies at East Antarctic ITASE Sites
This award supports a project to obtain stable isotope profiles from shallow (<100 m) ice cores from East Antarctica, to add to the growing database of environmental proxy data collected under the auspices of the ITASE (International TransAntarctic Scientific Expedition) program. In Antarctica, the instrumental record of climate is particularly short (~40 years except in a few isolated locations on the coast), and ice core proxy data are the only means available for extending this record into the past. The use of stable isotopes of water (18-O/16-O and D/H ratios) from ice cores as proxies for temperature is well established for both very short (i.e. seasonal) and long timescales (centuries, millennia). Using multivariate regression methods and shallow ice cores from West Antarctica, a reconstruction of Antarctic climate over the last ~150 years has been developed which suggests the continent has been warming, on average, at a rate of ~0.2 K/century. Further improving these reconstructions is the chief motivation for further extending the US ITASE project. Ten to fifteen shallow (~ 100 m) from Victoria Land, East Antarctica will be obtained and analyzed. The core will be collected along a traverse route beginning at Taylor Dome and ending at the South Pole. Age-depth relationships for the cores will be determined through a combination of stable isotopes, visual stratigraphy and seasonal chemical signatures and marker horizons. Reconstructions of Antarctic climate obtained from these cores will be incorporated into the global network of paleoclimate information, which has been important in science, policy and educational contexts. The project will include graduate student and postdoctor$ field experience.