WAIS Divide: Fluorimetry, Dust Logs, Climatology, Glaciology, Volcanology

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

Price/1142178 This award supports a project to continue the measurements of chlorophyll (Chl) and tryptophan (trp) in WAIS Divide ice down to 3330 m, or deeper if drilling continues below 3330 m. A new type of live/dead stain for microbes will be used to see if the decrease is related to the death rate of microbes responsible for the slow decrease of intensity with depth. Previous work on GISP2 ice has shown that methane concentrations in deeper sections of the core were an order of magnitude higher than the variations due to climate change. The conclusion from the prior work suggested that the methane spikes were due to methanogens at those depths that were metabolizing while frozen in the ice. With the Berkeley Fluorescence Spectrophotometer (BFS) measurements will be made on WAIS Divide ice at the National Ice Core Laboratory (NICL) to look for unusually large spikes of Trp and Chl that will inform gas chemists of the exact depths to look for gas anomalies (i.e., concentration spikes that may not be related to climate). In fluorimetric scanning of GISP2 ice at NICL, increases in Trp were found at many depths, corresponding to depths with nitrous oxide (N2O) spikes. Flow cytometry with excitation by a 405 nm laser will also be used to look for F420 autofluorescence emission at ~465 nm as a signature of methanogens. Previous measurements with the optical logger enabled many more volcanic ash layers to be found in the Dome C ice core than had been found with other methods. The recent discovery that logging of a freshly drilled borehole, to the bottom of WAIS Divide, resulted in a higher-resolution dust pattern and a far greater concentration of clearly resolvable volcanic ash layers than had been found in older boreholes is something that will be explored. Using these new ice core logging results, it will be possible to see if any ash layers coincide in time with volcanic ash layers that have been found at other sites and will strengthen existing evidence for a causal relationship between large volcanic eruptions and spikes in the dust log, indicative of abrupt climate changes. The intellectual merit of the work is that the data will contribute to a better understanding of the processes that contribute to gaseous impurities in the ice and to developing a better understanding of the link between global volcanism and climate. Finally, 47 micro-inclinometers are installed in the ice at various depths and lateral positions in optical modules that are frozen into the IceCube array. They have been recording tilt for nearly a year. These data will be analyzed for an additional three years which will provide an unique opportunity to study the shear-strain rate of a huge volume of cold glacial ice as a function of shear stress. The broader impacts of the work include the possibility of applications to Mars exploration, studies of life in ancient ice, oceanography, limnology, meteorology, climate and volcanology. The project will contribute to the education and training of a broad range of undergraduate and graduate students and post-docs from the U. S. and other countries.