HR: 0800h
AN: PP21A-1365    [Abstracts]
TI: An Ice Core Melter System for Continuous Major and Trace Chemical Analyses of a New Mt. Logan Summit Ice Core
AU: * Osterberg, E C
EM: erich.osterberg@umit.maine.edu
AF: Climate Change Institute, University of Maine, Bryand Global Sciences Building, Orono, ME 04469 United States
AU: Handley, M J
EM: handley@maine.edu
AF: Climate Change Institute, University of Maine, Bryand Global Sciences Building, Orono, ME 04469 United States
AU: Sneed, S D
EM: sharon.sneed@maine.edu
AF: Climate Change Institute, University of Maine, Bryand Global Sciences Building, Orono, ME 04469 United States
AU: Mayewski, P A
EM: paul.mayewski@maine.edu
AF: Climate Change Institute, University of Maine, Bryand Global Sciences Building, Orono, ME 04469 United States
AU: Kreutz, K J
EM: karl.kreutz@maine.edu
AF: Climate Change Institute, University of Maine, Bryand Global Sciences Building, Orono, ME 04469 United States
AU: Fisher, D A
EM: fisher@nrn1.nrcan.gc.ca
AF: Geological Survey of Canada, 601 Booth St., Ottawa, On K1A 0E8 Canada
AB: The ice core melter system at the University of Maine Climate Change Institute has been recently modified and updated to allow high-resolution ($<$1-2 cm ice/sample), continuous and coregistered sampling of ice cores, most notably the 2001 Mt. Logan summit ice core (187 m to bedrock), for analyses of 34 trace elements (Sr, Cd, Sb, Cs, Ba, Pb, Bi, U, As, Al, S, Ca, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, REE suite) by inductively coupled plasma mass spectrometry (ICP-MS), 8 major ions (Na$^{+}$, Ca$^{2+}$, Mg$^{2+}$, K$^{+}$, Cl$^{-}$, SO$_{4}$$^{2-}$, NO$_{3}$$^{-}$, MSA) by ion chromatography (IC), stable water isotopes ($\delta$$^{18}$O, $\delta$D, {\it d}) and volcanic tephra. The UMaine continuous melter (UMCoM) system is housed in a dedicated clean room with HEPA filtered air. Standard clean room procedures are employed during melting. A Wagenbach-style continuous melter system has been modified to include a pure Nickel melthead that can be easily dismantled for thorough cleaning. The system allows melting of both ice and firn without wicking of the meltwater into unmelted core. Contrary to ice core melter systems in which the meltwater is directly channeled to online instruments for continuous flow analyses, the UMCoM system collects discrete samples for each chemical analysis under ultraclean conditions. Meltwater from the pristine innermost section of the ice core is split between one fraction collector that accumulates ICP-MS samples in acid pre-cleaned polypropylene vials under a class-100 HEPA clean bench, and a second fraction collector that accumulates IC samples. A third fraction collector accumulates isotope and tephra samples from the potentially contaminated outer portion of the core. This method is advantageous because an archive of each sample remains for subsequent analyses (including trace element isotope ratios), and ICP-MS analytes are scanned for longer intervals and in replicate. Method detection limits, calculated from de-ionized water blanks passed through the entire UMCoM system, are below 10% of average Mt. Logan values. A strong correlation (R$^{2}$$>$0.9) between Ca and S concentrations measured on different fractions of the same sample by IC and ICP-MS validates sample coregistration. Preliminary analyses of data from the 2001 Mt. Logan summit ice core confirm subannual resolution sampling and annual scale variability of major and trace elements. Accumulation rate models and isotope data suggest that annual resolution will be possible to 1000-2000 y.b.p., with multi-annual to centennial resolution for the remainder of the Holocene and possibly including the last deglaciation. Dust proxy elements, including REEs, strongly co-vary in time-series and reveal concentration ratio fluctuations interpreted as source region changes. Volcanic eruptions are characterized by elevated concentrations of S, SO$_{4}$$^{2-}$, Cu, Sb, Zn and other trace elements. Concentrations of potential anthropogenic contaminants are also discussed.
DE: 3344 Paleoclimatology
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0365 Troposphere--composition and chemistry
DE: 0394 Instruments and techniques
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting