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Sensitivity Of Spruce/Moss Boreal Forest Carbon Balance To Seasonal Anomalies In Weather, Steve Frolking
Sensitivity Of Spruce/Moss Boreal Forest Carbon Balance To Seasonal Anomalies In Weather, Steve Frolking
Earth Sciences
A process-oriented, daily time step model of a spruce/moss boreal ecosystem simulated 1994 and 1995 productivity for a Boreal Ecosystem-Atmosphere Study site near Thompson, Manitoba. Simulated black spruce net primary productivity (NPP) was 139 g C m−2 in 1994 and 112 in 1995; feathermoss NPP was 13.0 g C m−2 in 1994 and 9.7 in 1995; decomposition was 126 g C m−2 in 1994 and 130 in 1995; net ecosystem productivity (NEP) was an uptake of 26.3 g C m−2 in 1994 and 2.5 in 1995. A very dry period for the first half of the …
Distributions Of Beryllium 7 And Lead 2109, And Soluble Aerosol-Associated Ionic Species Over The Western Pacific: Pem West B, February-March 1994, Jack E. Dibb, R. Talbot, Barry Lefer, Eric Scheuer, G L. Gregory, E V. Browell, J D. Bradshaw, S T. Sandholm, H B. Singh
Distributions Of Beryllium 7 And Lead 2109, And Soluble Aerosol-Associated Ionic Species Over The Western Pacific: Pem West B, February-March 1994, Jack E. Dibb, R. Talbot, Barry Lefer, Eric Scheuer, G L. Gregory, E V. Browell, J D. Bradshaw, S T. Sandholm, H B. Singh
Earth Sciences
Aerosol sampling for the determination of the concentrations of soluble ionic species and the natural radionuclides 7Be and 210Pb was conducted from the NASA DC-8 over the western Pacific as part of GTE/PEM-West B during February-March 1994. Concentrations of most soluble ionic species in the free troposphere were higher in samples collected on flights originating from Hong Kong and Japan than those collected further east over the open ocean. In both regions the measured concentrations were higher than those found during PEM-West A (fall 1991). Activities of 210Pb, a tracer of air masses influenced by sources on …
Chemical Characteristics Of Continental Outflow From Asia To The Troposphere Over The Western Pacific Ocean During February-March 1994: Results From Pem-West B, R. Talbot, Jack E. Dibb, Barry Lefer, J D. Bradshaw, S T. Sandholm, D R. Blake, N J. Blake, G W. Sachse, J E. Collins Jr, B J. Heikes, J T. Merrill, G L. Gregory, B E. Anderson, H B. Singh, D C. Thornton, A R. Bandy, R F. Pueschel
Chemical Characteristics Of Continental Outflow From Asia To The Troposphere Over The Western Pacific Ocean During February-March 1994: Results From Pem-West B, R. Talbot, Jack E. Dibb, Barry Lefer, J D. Bradshaw, S T. Sandholm, D R. Blake, N J. Blake, G W. Sachse, J E. Collins Jr, B J. Heikes, J T. Merrill, G L. Gregory, B E. Anderson, H B. Singh, D C. Thornton, A R. Bandy, R F. Pueschel
Earth Sciences
We present here the chemical composition of outflow from the Asian continent to the atmosphere over the western Pacific basin during the Pacific Exploratory Mission-West (PEM-West B) in February–March 1994. Comprehensive measurements of important tropospheric trace gases and aerosol particulate matter were performed from the NASA DC-8 airborne laboratory. Backward 5 day isentropic trajectories were used to partition the outflow from two major source regions: continental north (>20°N) and continental south (<20°N). Air parcels that had not passed over continental areas for the previous 5 days were classified as originating from an aged marine source. The trajectories and the chemistry together indicated that there was extensive rapid outflow of air parcels at altitudes below 5 km, while aged marine air was rarely encountered and only at <20°N latitude. The outflow at low altitudes had enhancements in common industrial solvent vapors such as C2Cl4, CH3CCl3, and C6H6, intermixed with the combustion emission products C2H2, C …
Comparisons Of Trace Constituents From Ground Stations And The Dc-8 Aircraft During Pem-West B, Richard Arimoto, R A. Duce, J M. Prospero, D L. Savoie, R. Talbot, Jack E. Dibb, B J. Heikes, B J. Ray, N F. Lewis, U Tomza
Comparisons Of Trace Constituents From Ground Stations And The Dc-8 Aircraft During Pem-West B, Richard Arimoto, R A. Duce, J M. Prospero, D L. Savoie, R. Talbot, Jack E. Dibb, B J. Heikes, B J. Ray, N F. Lewis, U Tomza
Earth Sciences
Chemical data from ground stations in Asia and the North Pacific are compared with data from the DC-8 aircraft collected during the Pacific Exploratory Measurements in the Western Pacific Ocean (PEM-West B) mission. Ground station sampling took place on Hong Kong, Taiwan, Okinawa, and Cheju; and at three Pacific islands, Shemya, Midway, and Oahu. Aircraft samples were collected during 19 flights, most over the western North Pacific. Aluminum was used as an indicator of mineral aerosol, and even though the aircraft did sample Asian dust, strong dust storms were not encountered. The frequency distribution for non-sea-salt sulfate (nss SO4 …
Large-Scale Distributions Of Tropospheric Nitric, Formic, And Acetic Acids Over The Western Pacific Basin During Wintertime, R. Talbot, Jack E. Dibb, Barry Lefer, Eric Scheuer, J D. Bradshaw, S T. Sandholm, S Smyth, D R. Blake, N J. Blake, G W. Sachse, J E. Collins Jr, G L. Gregory
Large-Scale Distributions Of Tropospheric Nitric, Formic, And Acetic Acids Over The Western Pacific Basin During Wintertime, R. Talbot, Jack E. Dibb, Barry Lefer, Eric Scheuer, J D. Bradshaw, S T. Sandholm, S Smyth, D R. Blake, N J. Blake, G W. Sachse, J E. Collins Jr, G L. Gregory
Earth Sciences
We report here measurements of the acidic gases nitric (HNO3), formic (HCOOH), and acetic (CH3COOH) over the western Pacific basin during the February-March 1994 Pacific Exploratory Mission-West (PEM-West B). These data were obtained aboard the NASA DC-8 research aircraft as it flew missions in the altitude range of 0.3–12.5 km over equatorial regions near Guam and then further westward encompassing the entire Pacific Rim arc. Aged marine air over the equatorial Pacific generally exhibited mixing ratios of acidic gases <100 parts per trillion by volume (pptv). Near the Asian continent, discrete plumes encountered below 6 km altitude contained up to 8 parts per billion by volume (ppbv) HNO3 and 10 ppbv HCOOH and CH3COOH. Overall there was a general correlation between mixing …
Transport Of Sulfur Dioxide From The Asian Pacific Rim To The North Pacific Troposphere, D C. Thornton, A R. Bandy, Byrin W. Blomquist, R. Talbot, Jack E. Dibb
Transport Of Sulfur Dioxide From The Asian Pacific Rim To The North Pacific Troposphere, D C. Thornton, A R. Bandy, Byrin W. Blomquist, R. Talbot, Jack E. Dibb
Earth Sciences
The NASA Pacific Exploratory Mission over the Western Pacific Ocean (PEM-West B) field experiment provided an opportunity to study sulfur dioxide (SO2) in the troposphere over the western Pacific Ocean from the tropics to 60°N during February–March 1993. The large suite of chemical and physical measurements yielded a complex matrix in which to understand the distribution of sulfur dioxide over the western Pacific region. In contrast to the late summer period of Pacific Exploratory Mission-West A (PEM-West A) (1991) over this same area, SO2showed little increase with altitude, and concentrations were much lower in the free …
Assessment Of The Record Of The 1982 El Chichón Eruption As Preserved In Greenland Snow, Gregory A. Zielinski, Jack E. Dibb, Qinzhao Yang, Paul A. Mayewski, Sallie I. Whitlow, Mark S. Twickler, Mark S. Germani
Assessment Of The Record Of The 1982 El Chichón Eruption As Preserved In Greenland Snow, Gregory A. Zielinski, Jack E. Dibb, Qinzhao Yang, Paul A. Mayewski, Sallie I. Whitlow, Mark S. Twickler, Mark S. Germani
Earth Sciences
Variability in the SO4 2- and Cl- time series for the 1980s from 12 shallow snow pits across the Greenland ice sheet is used to evaluate the record of the 1982 El Chichón eruption and the potential for recording a moderate northern equatorial eruption in a single Greenland ice core. Composition of volcanic glass found in spring 1983 snow in one of the pits in the Summit region matches that from El Chichón glass, thereby verifying the deposition of material from the eruption. High Na+ and Cl- concentrations in this same layer probably represent deposition of the reaction products of …
Temporal And Spatial Variability Of Snow Accumulation In Central Greenland, H Kuhns, C Davidson, Jack E. Dibb, C Stearns, M H. Bergin, J L. Jaffrezo
Temporal And Spatial Variability Of Snow Accumulation In Central Greenland, H Kuhns, C Davidson, Jack E. Dibb, C Stearns, M H. Bergin, J L. Jaffrezo
Earth Sciences
Snow accumulation records from central Greenland are explored to improve the understanding of the accumulation signal in Greenland ice core records. Results from a “forest” of 100 bamboo poles and automated accumulation monitors in the vicinity of Summit as well as shallow cores collected in the Summit and Crete areas are presented. Based on these accumulation data, a regression has been calculated to quantify the signal-to-noise variance ratio of ice core accumulation signals on a variety of temporal (1 week to 2 years) and spatial (20 m to 200 km) scales. Results are consistent with data obtained from year-round automated …
Air-Snow Exchange Investigations At Summit, Greenland: An Overview, Jack E. Dibb, J L. Jaffrezo
Air-Snow Exchange Investigations At Summit, Greenland: An Overview, Jack E. Dibb, J L. Jaffrezo
Earth Sciences
The Greenland Ice Sheet Project 2 (GISP2) and Greenland Ice Core Project (GRIP) deep drilling programs at Summit, Greenland included support (both logistical and scientific) of extensive investigation of atmospheric transport and air-snow exchange processes of gases and particles relevant to the interpretation of the ice-core records. Much of the sampling for the air-snow exchange investigations was conducted at a unique solar-powered camp 30 km southwest of the GISP2 drill camp (even further from the GRIP camp) and was characterized by a high degree of international collaboration and cooperation. The wide range of expertise and analytical capabilities of the 20-plus …
Equilibration Of The Terrestrial Water, Nitrogen, And Carbon Cycles, David S. Schimel, Rob Braswell, W J. Parton
Equilibration Of The Terrestrial Water, Nitrogen, And Carbon Cycles, David S. Schimel, Rob Braswell, W J. Parton
Earth Sciences
Recent advances in biologically based ecosystem models of the coupled terrestrial, hydrological, carbon, and nutrient cycles have provided new perspectives on the terrestrial biosphere’s behavior globally, over a range of time scales. We used the terrestrial ecosystem model Century to examine relationships between carbon, nitrogen, and water dynamics. The model, run to a quasi-steady-state, shows strong correlations between carbon, water, and nitrogen fluxes that lead to equilibration of wateryenergy and nitrogen limitation of net primary productivity. This occurs because as the water flux increases, the potentials for carbon uptake (photosynthesis), and inputs and losses of nitrogen, all increase. As the …
Variations In The Predicted Spatial Distribution Of Atmospheric Nitrogen Deposition And Their Impact On Carbon Uptake By Terrestrial Ecosystems, Elisabeth A. Holland, Rob Braswell, Jean-Francois Lamarque, Alan R. Townsend, James Sulzman, Jean-Francois Muller, Frank Dentener, Guy Brasseur, H Levy Ii, Joyce E. Penner, Geert-Jan Roelofs
Variations In The Predicted Spatial Distribution Of Atmospheric Nitrogen Deposition And Their Impact On Carbon Uptake By Terrestrial Ecosystems, Elisabeth A. Holland, Rob Braswell, Jean-Francois Lamarque, Alan R. Townsend, James Sulzman, Jean-Francois Muller, Frank Dentener, Guy Brasseur, H Levy Ii, Joyce E. Penner, Geert-Jan Roelofs
Earth Sciences
Widespread mobilization of nitrogen into the atmosphere from industry, agriculture, and biomass burning and its subsequent deposition have the potential to alleviate nitrogen limitation of productivity in terrestrial ecosystems, and may contribute to enhanced terrestrial carbon uptake. To evaluate the importance of the spatial distribution of nitrogen deposition for carbon uptake and to better quantify its magnitude and uncertainty NOy-N deposition fields from five different three-dimensional chemical models, GCTM, GRANTOUR, IMAGES, MOGUNTIA, and ECHAM were used to drive NDEP, a perturbation model of terrestrial carbon uptake. Differences in atmospheric sources of NOx-N, transport, resolution, and representation …
Continental Scale Variability In Ecosystem Processes: Models, Data, And The Role Of Disturbance, David S. Schimel, Rob Braswell
Continental Scale Variability In Ecosystem Processes: Models, Data, And The Role Of Disturbance, David S. Schimel, Rob Braswell
Earth Sciences
Management of ecosystems at large regional or continental scales and determination of the vulnerability of ecosystems to large-scale changes in climate or atmospheric chemistry require understanding how ecosystem processes are governed at large spatial scales. A collaborative project, the Vegetation and Ecosystem Modeling and Analysis Project (VEMAP), addressed modeling of multiple resource limitation at the scale of the conterminous United States, and the responses of ecosystems to environmental change. In this paper, we evaluate the model-generated patterns of spatial variability within and between ecosystems using Century, TEM, and Biome-BGC, and the relationships between modeled water balance, nutrients, and carbon dynamics. …
A 200-Year 210pb Record From Greenland, Jack E. Dibb, Henrick B. Clausen
A 200-Year 210pb Record From Greenland, Jack E. Dibb, Henrick B. Clausen
Earth Sciences
A continuous profile of 210Pb activity extending back to 1766 has been developed for a firn/ice core collected at Site D in central Greenland in 1984. Unexpectedly high activities of 210Pb were found at the base of this core (0.032 pCi kg−1 in samples more than 200 years old), calling into question the common assumption that supported 210Pb can be neglected when constructing chronologies in glacial snow and ice. It is problematic to assert that all of the 210Pb measured at depth should be attributed to the supported fraction, given previous estimates of dust loading …