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Articles 1 - 14 of 14
Full-Text Articles in Entire DC Network
Beryllium In Granulite-Facies Pegmatites In Archean Napier Complex, Antarctica, Edward S. Grew
Beryllium In Granulite-Facies Pegmatites In Archean Napier Complex, Antarctica, Edward S. Grew
University of Maine Office of Research Administration: Grant Reports
This award, provided by the Office of Polar Programs of the National Science Foundation, supports participation of a researcher from the University of Maine in an expedition of the Japanese Antarctic Research Expedition (JARE) to study beryllium enriched minerals in Enderby Land. Beryllium is a rare element in crustal rocks and enrichments are especially unusual in granulite-facies (high temperature and pressure, and relatively dry conditions) metamorphic rocks. This project focuses on unique beryllium-enriched pegmatites in the Archean ultra-high temperature (up to 1000 degrees C) granulite-facies Napier Complex in eastern Casey Bay, Enderby Land, East Antarctica. The primary objective is to …
Powre: High-Resolution Chronology Of Millennial-Scale Lake-Level Fluctuations In The Dry Valleys (Antarctica) From Uranium-Thorium And Radiocarbon Dating, Brenda L. Hall
University of Maine Office of Research Administration: Grant Reports
The Professional Opportunities for Women in Research and Engineering (POWRE) program affords new research and educational enhancement opportunities for women scientists. This project, which addresses the fundamental problem of the cause of millennial-scale climate change, contains components specifically designed to increase the educational and research skills of the principal investigator. She will learn the following new information/skills: 1) thermal ionization mass spectrometry (TIMS) uranium/thorium (U/TH) dating with Dr. G. Henderson at Lamont-Doherty Earth Observatory (LDEO) and Oxford University, 2) millennial-scale climate change with Drs. W. Broecker and G. Bond, LDEO, and with Drs. D. Oppo and L. Keigwin, Woods Hole …
Response Of A First-Order Stream In Maine To Short-Term In-Stream Acidification, Stephen A. Norton, Rota Wagai, Tomas Navratil, James M. Kaste, Frederick A. Rissberger
Response Of A First-Order Stream In Maine To Short-Term In-Stream Acidification, Stephen A. Norton, Rota Wagai, Tomas Navratil, James M. Kaste, Frederick A. Rissberger
Earth Science Faculty Scholarship
An experimental short-term acidification with HCl at a first-order stream in central Maine, USA was used to study processes controlling the changes in stream chemistry and to assess the ability of stream substrate to buffer pH. The streambed exerted a strong buffering capacity against pH change by ion exchange during the 6-hour acidification. Streambed substrates had substantial cation and anion exchange capacity in the pH range of 4.1 to 6.5. The ion exchange for cations and SO42- were rapid and reversible. The speed of release of cations from stream substrates was Na1+ > Ca2+ > Mg2+ > Aln+ > Be2+, perhaps relating to charge …
The Effect Of Spatial And Temporal Accumulation Rate Variability In West Antarctica On Soluble Ion Deposition, K. J. Kreutz, Paul Andrew Mayewski, L. D. Meeker, M. S. Twickler, S. I. Whitlow
The Effect Of Spatial And Temporal Accumulation Rate Variability In West Antarctica On Soluble Ion Deposition, K. J. Kreutz, Paul Andrew Mayewski, L. D. Meeker, M. S. Twickler, S. I. Whitlow
Earth Science Faculty Scholarship
Annually‐dated snowpit and ice core records from two areas of West Antarctica are used to investigate spatial accumulation patterns and to evaluate temporal accumulation rate/glaciochemical concentration and flux relationships. Mean accumulation rate gradients in Marie Byrd Land (11–23 gcm−2yr−1 over 150 km, decreasing to the south) and Siple Dome (10–18 gcm−2yr−1 over 60 km, decreasing to the south) are consistent for at least the last several decades, and demonstrate the influence of the offshore quasi‐permanent Amundsen Sea low pressure system on moisture flux into the region. Local and regional‐scale topography in both regions appears …
Does Elevated Nitrogen And Sulfur Deposition Lead To Net Base Cation Losses In Northern New England Forest Soils?, Ivan J. Fernandez, Stephen A. Norton, Jeffrey Kahl, Lindsey E. Rustad
Does Elevated Nitrogen And Sulfur Deposition Lead To Net Base Cation Losses In Northern New England Forest Soils?, Ivan J. Fernandez, Stephen A. Norton, Jeffrey Kahl, Lindsey E. Rustad
University of Maine Office of Research Administration: Grant Reports
The aims of this research are to continue treatment and monitoring of a paired watershed experiment at Bear Brook in northern Maine, with an emphasis on changes in soil base cations, particularly calcium. Base cation depletion is well-recognised as a potential problem in soils that have been subjected to acidic N deposition but few data exist from well-controlled, long-term experiments. The Bear Brook watershed has been periodically treated with ammonium sulfate since the fall of 1989 and is believed to be approaching N saturation. Since 1993 the relationship between base cations and strong acid anions has changed, such that labile …
Sea Level Pressure Variability In The Amundsen Sea Region Inferred From A West Antarctic Glaciochemical Record, K. J. Kreutz, Paul Andrew Mayewski, I. I. Pittalwala, L. D. Meeker, M. S. Twickler, S. I. Whitlow
Sea Level Pressure Variability In The Amundsen Sea Region Inferred From A West Antarctic Glaciochemical Record, K. J. Kreutz, Paul Andrew Mayewski, I. I. Pittalwala, L. D. Meeker, M. S. Twickler, S. I. Whitlow
Earth Science Faculty Scholarship
Using European Center for Medium-Range Weather Forecasts (ECMWF) numerical operational analyses, sea ice extent records, and station pressure data, we investigate the influence of sea level pressure variability in the Amundsen Sea region on a West Antarctic (Siple Dome) glaciochemical record. Empirical orthogonal function analysis of the high-resolution Siple Dome multivariate ice core chemical time series record (SDEOF1) documents lower tropospheric transport of sea-salt aerosols to the site. During 1985–1994 the SDEOF1 record of high (low) aerosol transport corresponds to anomalously low (high) sea level pressure (SLP) in the Amundsen Sea region. Spatial correlation patterns between ECMWF monthly SLP fields …
Derived Quantities: A Coupled Dynamic/Thermodynamic Ice Sheet Model, James L. Fastook
Derived Quantities: A Coupled Dynamic/Thermodynamic Ice Sheet Model, James L. Fastook
University of Maine Office of Research Administration: Grant Reports
This award is for support for a program of research involving the use of inverse modeling to derive information from the measured configuration of an ice sheet to yield important information about the conditions both at the bed and within the ice column. It is proposed to convert a column-averaged model to a column- integrated model that accounts explicitly for internal thermodynamics and variations of material properties that depend on this internal temperature field. An existing finite-element 3- D temperature solver will be coupled with an existing finite- element map-plane continuity solver. The result will allow more detailed analysis of …
Calculating Basal Thermal Zones Beneath The Antarctic Ice Sheet, Ellen Wilch, Terence J. Huges
Calculating Basal Thermal Zones Beneath The Antarctic Ice Sheet, Ellen Wilch, Terence J. Huges
Earth Science Faculty Scholarship
A procedure is presented for using a simple flowline model to calculate the fraction of the bed that is thawed beneath present-day ice sheets, and therefore for mapping thawed, frozen, melting and freezing basal thermal zones. The procedure is based on the proposition, easily demonstrated, that variations in surface slope along ice flowlines are due primarily to variations in bed topography and ice-bed coupling, where ice-bed coupling for sheet flow is represented by the basal thawed fraction. This procedure is then applied to the central flowlines of flow bands on the Antarctic ice sheet where accumulation rates, surface elevations and …
Glacier Calving: A Numerical Model Of Forces In The Calving-Speed/Water-Depth Relation, Brian Hanson, Roger Hooke
Glacier Calving: A Numerical Model Of Forces In The Calving-Speed/Water-Depth Relation, Brian Hanson, Roger Hooke
Earth Science Faculty Scholarship
Empirical data suggest that the race of calving of grounded glaciers terminating in water is directly proportional to the water depth. Important controls on calving may be the extent to which a calving face tends to become oversteepened by differential flow within the ice and the extent to which bending moments promote extrusion and bottom crevassing at the base of a calving face. Numerical modelling suggests that the tendency to become oversteepened increases roughly linearly with water depth. In addition, extending longitudinal deviatoric stresses at the base of a calving face increase with water depth. These processes provide a possible …
Sliding Of Ice Past An Obstacle At Engabreen, Norway, Denis Cohen, Roger Hooke, Neal R. Iverson, Jack Kohler
Sliding Of Ice Past An Obstacle At Engabreen, Norway, Denis Cohen, Roger Hooke, Neal R. Iverson, Jack Kohler
Earth Science Faculty Scholarship
At Engabreen, Norway, an instrumented panel containing a decimetric obstacle was mounted flush With the bed surface beneath 210 m of ice. Simultaneous measurements of normal and shear stresses, ice velocity and temperature were obtained as dirty basal ice flowed past the obstacle. Our measurements were broadly consistent with ice thickness, flow conditions and bedrock topography near the site of the experiment. Ice speed 0.45 m above the bed was about 130 mm d(-1), much less than the surface velocity of 800 mm d(-1) Average normal stress on the panel was 1.0-1.6 MPa, smaller than the expected ice overburden pressure. …
Evidence For Recent Climate Change From Ice Cores In The Central Himalaya, Qin Dahe, Paul Andrew Mayewski, Cameron P. Wake, Kang Shichang, Ren Jiawen, Hou Shugui, Yao Tandong, Yang Qinzhao, Jin Zhefan, Mi Desheng
Evidence For Recent Climate Change From Ice Cores In The Central Himalaya, Qin Dahe, Paul Andrew Mayewski, Cameron P. Wake, Kang Shichang, Ren Jiawen, Hou Shugui, Yao Tandong, Yang Qinzhao, Jin Zhefan, Mi Desheng
Earth Science Faculty Scholarship
Comparison of the terminus locations of Rongbuk Glacier, Mount Everest, measured in 1966 and 1997 shows that in the past 30 years the glacier has retreated 170-270 m, equivalent to a retreat speed of 5.5-8.7 m a−1. During summer 1997, a 15 m firn core was recovered from Dasuopu glacier (28°23′N, 85°44′E; 7000 m a.s.l.) on the northwest margin of Xixabangma Feng, Xizang (Tibet). The seasonal variations of δ18O values in the core indicate that monsoon signals are clearly recorded in the glacier. δ18O values are controlled by the amount effect in the monsoon …
The Miraflores El Nino Disaster: Convergent Catastrophes And Prehistoric Agrarian Change In Southern Peru, Dennis R. Satterlee, Michael E. Moseley, David K. Keefer, Jorge E. Tapia A.
The Miraflores El Nino Disaster: Convergent Catastrophes And Prehistoric Agrarian Change In Southern Peru, Dennis R. Satterlee, Michael E. Moseley, David K. Keefer, Jorge E. Tapia A.
Andean Past
No abstract provided.
The Puzolana Obsidian Source: Locating The Geologic Source Of Ayacucho Type Obsidian, Richard L. Burger, Michael D. Glascock
The Puzolana Obsidian Source: Locating The Geologic Source Of Ayacucho Type Obsidian, Richard L. Burger, Michael D. Glascock
Andean Past
No abstract provided.
Monsoon And Dust Signals Recorded In Dasuopu Glacier, Tibetan Plateau, Kang Shichang, Cameron P. Wake, Qin Dahe, Paul Andrew Mayewski, Yao Tandong
Monsoon And Dust Signals Recorded In Dasuopu Glacier, Tibetan Plateau, Kang Shichang, Cameron P. Wake, Qin Dahe, Paul Andrew Mayewski, Yao Tandong
Earth Science Faculty Scholarship
During summer 1997, a 15m firn core was recovered from Dasuopu glacier (28°23'N, 85° 44' E; 7000 m a.s.l.) on the northwest margin of Xixabangma Feng in the central Himalaya. Oxygen isotope values and concentrations of Ca2+, Mg2+, NH4+, SO42- and NO3- were measured over the 10 years of snow accumulation captured in the firn core. The seasonal variations of δ18O values and major-ion concentrations in the Dasuopu core indicated that summer monsoon and dust signals are clearly recorded in Dasuopu glacier. Annual variations in the δ …