Alaska: Reconstructing Central Alaskan Precipitation Variability and Atmospheric Circulation
The main goal of this project is to reconstruct the history of precipitation in Alaska during the last thousand years using ice core records of snow accumulation. The researchers plan to collect several new ice cores from the Mt. Hunter Plateau in the Alaska Range of Denali National Park and the new ice cores will be combined with an existing spatial array of ice cores in the region to map changes in the spatial patterns of precipitation. Because changes in atmospheric circulation patterns caused by ENSO and the Pacific Decadal Oscillation (PDO) affect where the precipitation falls, this spatial array of ice cores will provide a record of how these larger scale climate systems have varied during the last thousand years. The project will focus on determining the differences in the precipitation patterns at the Little Ice Age (approximately 200 to 600 years ago) and Medieval Climate Anomaly (approximately 800 to 1,200 years ago).
Greenland: Investigating Carbon-14 in Polar Firn and Ice
This project will investigate the potential of carbon-14 in ice cores as an absolute dating tool, as a tracer of the past cosmic ray flux and as a recorder of the past fossil fraction of the global methane budget. Cosmic ray particles produce carbon-14 from oxygen-16 directly within near-surface glacial ice and firn. This in-situ produced carbon-14 quickly reacts to form 14C-containing carbon dioxide, carbon monoxide, and methane in the ice matrix. Some or all of the resulting 14C-bearing gases may be lost from the firn to the atmosphere. The proposed work will provide a thorough characterization of in-situ cosmogenic 14C in glacial firn and shallow ice in the Summit region of Greenland. It will examine the retention of cosmogenic 14C in ice grains at all depth levels in the firn column, the partitioning of 14C between carbon dioxide, carbon monoxide, and methane, as well as the production rates and accumulation of cosmogenic 14C in shallow ice below firn close-off.
Greenland: Greenland Aerosols and Methane Records
This project will drill a 200-meter ice core at a low snow accumulation site in northeast Greenland during the spring of 2013. This core, along with similar archived core, will be used to obtain high resolution measurements of aerosols and methane concentrations in the ice, which, in turn, will allow a quantitative assessment of the impact of in-situ methane production on historical records of atmospheric methane in Greenland ice cores.
Alaska: McCall Glacier Ice Cores
The goal of this project is to analyze firn cores from McCall Glacier in the eastern Brooks Range of Alaska to better understand the processes of internal accumulation of ice within firn. The study will involve extracting firn cores from McCall Glacier to study their change over time to better understand the processes of internal accumulation of ice within firn and the effects of this process on the paleoclimate proxies they are using to interpret a previously drilled deep ice core. The plan is to take about 30 meters of core per year, as a series of about 5 m deep triplicate cores from 2 nearby locations.
Greenland: Closing the Isotope Hydrology at Summit
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. 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 (Greenland), Eureka (Ellesmere Island) and Reykjavik (Iceland). 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.
Greenland: Investigation of the Greenland Perennial Firn Aquifer
This project will provide the first efforts at measurement of a newly discovered component of the Greenland Ice Sheet mass balance. The perennial firn aquifer (PFA) stores liquid water in the subsurface firn year-round, including throughout the winter. It was discovered in April 2011, but there were no measurements made within the PFA, thus its volume estimate and even formation process are unknown except for those from modeling. This project will use a wide variety of techniques to provide the first measurements of liquid water storage in the PFA. Density profiles and even simple observations of PFA stratigraphy assessing the relative proportions of firn, water, and solid ice will provide valuable data needed to calculate the unknown mass of the PFA.