HR: 1340h
AN: PP13C-1415    [Abstracts]
TI: Correlating tidewater glacial meltwater discharge with El Niño-Southern Oscillation in Southern Alaska
AU: * Jaeger, J M
EM: jaeger@geology.ufl.edu
AF: Department of Geological Sciences University of Florida, PO Box 112120, Gainesville, FL 32611-2120, United States
AU: Cowan, E
EM: cowanea@appstate.edu
AF: Department of Geology Appalachian State University, P.O. Box 32067, Boone, NC 28608, United States
AU: Jackolski, C
EM: Jackolski@geol.niu.edu
AF: Department of Geology and Environmental Geosciences Northern Illinois University, 312 Davis Hall, Normal Rd, DeKalb, IL 60115-2854, United States
AU: Powell, R D
EM: ross@geol.niu.edu
AF: Department of Geology and Environmental Geosciences Northern Illinois University, 312 Davis Hall, Normal Rd, DeKalb, IL 60115-2854, United States
AU: Chapman, G
EM: chapmang@geology.ufl.edu
AF: Department of Geological Sciences University of Florida, PO Box 112120, Gainesville, FL 32611-2120, United States
AB: Over the past two decades coincident with Arctic climate warming, Alaskan glaciers have experienced significant volume loss with the resulting discharge substantially contributing to rising sea level. This thinning has occurred during a period of pronounced variability in regional climatology and oceanography. However, the meteorological parameters forcing melting have not been well established, as there are few annual records of meltwater discharge directly from large cliff-calving glaciers. To test how meltwater production varies in response to climate forcing, a multi-decadal proxy record of meltwater discharge was established for tidewater glaciers in Disenchantment Bay and in Muir Inlet, Glacier Bay National Park, southern coastal Alaska. 33 piston cores and 8 multicores were collected from 24 stations to measure annual sediment deposition rates over the last several decades. Sedimentary facies, physical properties, and short-lived radioisotopes were used to delineate summertime sediment deposition rates on fortnightly to annual time scales, as tidal and seasonal forcing create distinctly laminated (cyclopels) and annually varved deposits. Magnetic susceptibility, sortable silt, and sediment floc characteristics were used as proxies of meltwater plume competence. Complete varves were identified from cores collected in Disenchantment Bay for up to 22 years (1981-2003) and the period of highest and most variable summer layer thickness at Hubbard Glacier coincides with El Ni ñ o-dominated conditions in the North Pacific from 1990-1995 and a warm phase of the Pacific Decadal Oscillation (PDO). The velocity and competence of the meltwater plume increased in the period 1987-1992, likely associated with the numerous ENSO events that resulted in higher winter precipitation. Hubbard Glacier summer sediment thickness data follow a similar temporal trend as the Alsek River discharge hydrograph, the only currently glacierized basin gaged by the USGS in the region, suggesting that the two drainage basins respond similarly to regional climate forcing. Cross-correlation time-series of Alsek River discharge with temperature and precipitation data from the weather station at Yakutat, AK show that summers with higher mean temperatures correlate with increased discharge and to a lesser extent with the amount of precipitation accumulated during the preceding winter. Two 17-m-long jumbo cores from Muir Inlet contain up to 75 years of complete melt-season deposits and associated spring-neap packages. Multi-taper method and singular spectrum analysis spectral estimation techniques were used to calculate statistically significant periodicity in both the melt season deposit thicknesses and spring-neap package thicknesses for each core. Periodicity in melt season deposit thickness shows that both cores contain significant ENSO signals and that one core (EW0408 60JC) contains significant PDO signals. This research has shown that high-resolution records of fjord sedimentation from tidewater glaciers may be a reliable proxy for past magnitude, duration, and temporal distribution of annual meltwater discharge into Alaskan glacial fjords, thus adding to the climate change record in a sensitive area.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1655 Water cycles (1836)
DE: 1833 Hydroclimatology
DE: 4934 Insolation forcing
DE: 9355 Pacific Ocean
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting