The national geophysical data center bathymetric program     

Maureen R. Kenny  Kurt E. Brown 《Marine Geodesy》2013,36(2-3):165-175

The National Geophysical Data Center's (NGDC's) mission is data management in the broadest sense, playing a role in the nation's research into the environment and providing data to a wide group of users. NGDC also operates components of the International Council of Scientific Unions (ICSU) World Data Center A. The Marine Geology and Geophysics Division of NGDC handles bathymetric data acquisition, manipulation, archival, and dissemination and operates the International Hydrographic Organization Data Center for Digital Bathymetry. Four major data bases have been developed to manage the large volume of data received: the Global Marine Geophysical Data Base (geophysical data acquired in a time series); the NOAA National Ocean Service Hydrographic Data Base; the International Hydrographic Data Base (contains bathymetric data, other than NOS surveys, with no time‐tagging); and the Multibeam Bathymetric Data Base. In addition, gridded data sets such as ETOPO5 are available from NGDC. Bathymetric data are acquired by NGDC through data exchange, funded and contract programs, processing of long‐term data holdings, data digitization from hardcopy sources, and national and international linkages. NGDC personnel participate nationally and internationally on numerous committees associated with studies of the seafloor including charting and bathymetric needs.  相似文献   

Observations of X/M asteroids across multiple wavelengths     

Maureen E. Ockert-Bell  Beth Ellen Clark  Michael K. Shepard  Andrew S. Rivkin  Cristina A. Thomas  S.J. Bus 《Icarus》2008,195(1):206-219

We have conducted a radar-driven observational campaign of main-belt asteroids (MBAs) focused on X/M class asteroids using the Arecibo radar and NASA Infrared Telescope Facilities (IRTF). M-type asteroids have been identified as metallic, enstatite chondrites and/or heavily altered carbonaceous chondrites [Bell, J.F., Davis, D., Hartmann, W.K., Gaffey, M.J., 1989. In: Binzel, R.P., Gehrels, T., Matthews, M.S. (Eds.), Asteroids II. Univ. of Arizona Press, Tucson, pp. 921-948; Gaffey, M.J., McCord, T.B., 1979. In: Gehrels, T., Matthews, M.S. (Eds.), Asteroids. Univ. of Arizona Press, Tucson, pp. 688-723; Vilas, F., 1994. Icarus 111, 456-467]. Radar wavelength observations can determine whether an asteroid is metallic and provide information about the porosity and regolith depth. Near-infrared observations can help determine the grain size, porosity and composition of an object. Concurrent observations with these tools can give us a wealth of information about an object. Our objectives for this observation program were to (a) determine if there are any consistent relationships between spectra in the near-infrared wavelengths and radar signatures and (b) look for rotationally resolved relationships between asteroid radar properties and near-infrared spectral properties. This paper describes preliminary results of an ongoing survey of near-infrared observations of M-type asteroids and is a companion paper to radar observations reported by Shepard [Shepard, M.K., and 19 colleagues, 2008a. Icarus 195, 184-205]. In the analysis of 16 asteroid near-infrared spectra and nine radar measurements, we find a trend indicating a correlation between continuum slope from 1.7 to 2.45 μm and radar albedo—an asteroid with a steep continuum slope also has a bright radar albedo, which suggests a significant metal content. This may provide a means to use near-IR observations to predict the most likely metallic candidates for radar studies.  相似文献   

Facilitating Co-Production of Transdisciplinary Knowledge for Sustainability: Working with Canadian Biosphere Reserve Practitioners     

Maureen G. Reed  Paivi Abernethy 《社会与自然资源》2018,31(1):39-56

Sustainability scientists argue that diverse knowledge holders should work together in social learning processes to co-produce knowledge in support of sustainability. Yet, how to co-produce such knowledge remains unexplored. A multi-year, national knowledge sharing partnership among Canadian biosphere reserve practitioners, academic researchers and policy advisors revealed that a skilled facilitator was necessary for successful knowledge co-production. We draw attention to the multiple barriers to learning and knowledge co-production, and to the skills required of the facilitator to address them. The facilitator helped draw together local and formalized western knowledge systems (weaving) and diffuse innovations across local sites (out-scaling) and between local sites and the broader program network (up-scaling). Our experience reveals that simply bringing parties together will not generate transformative change for sustainability. Rather, multi-lateral facilitators are needed to ensure deliberate and managed interventions and to institutionalize learning across a diverse collective.  相似文献   

Cloud vertical distribution from radiosonde,remote sensing,and model simulations     

Jinqiang Zhang  Zhanqing Li  Hongbin Chen  Hyelim Yoo  Maureen Cribb 《Climate Dynamics》2014,43(3-4):1129-1140

Knowledge of cloud vertical structure is important for meteorological and climate studies due to the impact of clouds on both the Earth’s radiation budget and atmospheric adiabatic heating. Yet it is among the most difficult quantities to observe. In this study, we develop a long-term (10 years) radiosonde-based cloud profile product over the Southern Great Plains and along with ground-based and space-borne remote sensing products, use it to evaluate cloud layer distributions simulated by the National Centers for Environmental Prediction global forecast system (GFS) model. The primary objective of this study is to identify advantages and limitations associated with different cloud layer detection methods and model simulations. Cloud occurrence frequencies are evaluated on monthly, annual, and seasonal scales. Cloud vertical distributions from all datasets are bimodal with a lower peak located in the boundary layer and an upper peak located in the high troposphere. In general, radiosonde low-level cloud retrievals bear close resemblance to the ground-based remote sensing product in terms of their variability and gross spatial patterns. The ground-based remote sensing approach tends to underestimate high clouds relative to the radiosonde-based estimation and satellite products which tend to underestimate low clouds. As such, caution must be exercised to use any single product. Overall, the GFS model simulates less low-level and more high-level clouds than observations. In terms of total cloud cover, GFS model simulations agree fairly well with the ground-based remote sensing product. A large wet bias is revealed in GFS-simulated relative humidity fields at high levels in the atmosphere.  相似文献   

Strontium isotope identification of water mixing and recharge sources in a river system (Oder River,central Europe): A quantitative approach          下载免费PDF全文

Mateusz Zieliński  Jolanta Dopieralska  Zdzislaw Belka  Aleksandra Walczak  Marcin Siepak  Michał Jakubowicz 《水文研究》2018,32(16):2597-2611

This study uses Sr isotope composition (⁸⁷Sr/⁸⁶Sr) and Sr content of waters of the Oder, one of the largest rivers in central Europe, to fingerprint natural and anthropogenic contributions to its Sr budget and to evaluate water mixing processes in its hydrological system. It also demonstrates a simple method of quantifying natural and anthropogenic Sr inputs in the watershed. The method has potential for environmental and archaeological research because past Sr geochemistry of river water can easily be reconstructed. For the first time, a catchment‐scale impact of anthropogenic sources on the Sr budget of a middle‐size river is shown in a quantitative way. The water of the Oder is characterized by a relatively uniform Sr isotope composition, from 0.7100 to 0.7108, contrasting with strong variations in Sr concentration, from 0.25 to 1.27 mg/L. There is a general seasonal trend in variability, with waters becoming more radiogenic and dilute with respect to the Sr in the spring time. This Sr systematics differs significantly from the Sr budgets of the majority of the Oder tributaries that exhibit more radiogenic composition and systematically lower Sr concentrations. A mixing scenario in the Oder involves Sr contribution from four principal water sources: (a) shallow ground waters with Sr derived from near‐surface weathering of silicates, (b) moderately radiogenic mine waters from the Upper Silesian Coal Basin, (c) unradiogenic mine waters from the Permian sequence of the copper district, and (d) unradiogenic ground waters from shallow‐seated Palaeogene, Neogene, and Mesozoic aquifers. The Sr budget of the Oder is primarily controlled by inputs of dissolved Sr from anthropogenic sources, which overprint the natural background, controlled by geology. Thus, about 47.5% of Sr originates from agriculture, industrial, and municipal additions, 31.5% from mine water inputs, and only 21% from natural sources, that is, rock weathering and atmospheric precipitation. Reconstruction of the past Sr chemistry of the Oder reveals that its present‐day Sr isotope composition is temporary and significantly different from that of the preindustrial times.  相似文献   

Late Holocene inter-annual temperature variability reconstructed from the δ18O of archaeological Ostrea angasi shells     

S. Tynan  B. Opdyke  A. Dutton  M. Walczak 《Australian Journal of Earth Sciences》2017,64(6):779-791

Two multi-year oxygen isotope (δ¹⁸O) records were obtained from archaeological Ostrea angasi shells, confirming the potential of this species to provide valuable environmental records for the late Holocene period in southeastern Australia. High-resolution δ¹⁸O_shell samples from the O. angasi clearly display a seasonal variability, offering insight into past climate conditions in a region where such information is presently limited.

The oxygen isotope record in O. angasi reflects a combined temperature–salinity signal. Observations of δ¹⁸O_shell data from modern specimens are used as a point of reference to assist in decoupling these two influences, with the two archaeological samples compared with the δ¹⁸O_shell profile of four modern O. angasi. Assuming similar paleo- δ¹⁸O_water values at the collection sites, data from these archaeological shells present a record of temperatures during the period of their growth that are consistently lower than modern day, with mean annual temperatures ～2°C cooler.  相似文献   

Seasonal variations in the production and consumption of amino acids by coastal microplankton     

Maureen D. Keller  Timothy H. Mague  Marguerite Badenhausen  Hilary E. Glover 《Estuarine, Coastal and Shelf Science》1982,15(3):301-315

A seasonal study on coastal microplankton was conducted in surface waters near Boothbay Harbor, Maine. Phytoplankton biomass, particulate production and extracellular organic release were examined in conjunction with microheterotrophic biomass and the uptake and respiration of amino acids. In situ dissolved free amino acid (DFAA) concentrations were also determined. Several phytoplankton blooms occurred throughout the year, in mid-summer, late autumn and in mid-winter. Heterotrophic activity and biomass paralleled phytoplankton extracellular release more closely than either phytoplankton particulate production or biomass. DFAA concentrations were not wholly dependent on extracellular release. Heterotrophic uptake did not appear to be dependent on DFAA concentrations but rather on rates of production of DOC by phytoplankton.  相似文献   

Last interglacial beetle fauna from New Zealand     

Maureen J Marra 《Quaternary Research》2003,59(1):122-131

Fossil beetles from two last interglacial lake deposits from southern Wairarapa, central New Zealand are provisionally ascribed to marine oxygen isotope stages (MIS) 5a-e. Both assemblages represent ecological successions from lake margins to forest. The lower sample (MIS 5e) is characterized by species found today in northern New Zealand. These species, including Lorelus crassicornis, ‘Dasytes’ laticeps, Cryptobius nitidius, ‘Stenomalium’ sulcithorax, Psilocnaeia nana, and Microbrontes lineatus, represent a southward displacement from modern distributions by up to 700 km. Climate reconstruction indicates that temperatures at the time of deposition were 1.6-2.5°C warmer in the summer (January) and 2.3-3.2°C warmer in the winter (July) than at present. These results match local and regional pollen and phytolith findings of warmer, wetter conditions at the thermal maximum of the last interglaciation. In contrast, the upper sample is characterized by species that have widespread modern-day distributions. This indicates that modern conditions were attained later in MIS5, after the MIS 5e thermal maximum.  相似文献   

Carbon Stores, Sinks, and Sources in Forests of Northwestern Russia: Can We Reconcile Forest Inventories with Remote Sensing Results?     

Olga N. Krankina  Mark E. Harmon  Warren B. Cohen  Doug R. Oetter  Zyrina Olga  Maureen V. Duane 《Climatic change》2004,67(2):257-272

Forest inventories and remote sensing are the two principal data sources used to estimate carbon (C) stocks and fluxes for large forest regions. National governments have historically relied on forest inventories for assessments but developments in remote sensing technology provide additional opportunities for operational C monitoring. The estimate of total C stock in live forest biomass modeled from Landsat imagery for the St. Petersburg region was consistent with estimates derived from forest inventory data for the early 1990s (272 and 269 TgC, respectively). The estimates of mean C sink in live forest biomass also agreed well (0.36 and 0.34 Mg C ha^–1 yr^–1). Virtually all forest lands were accumulating C in live biomass, however when the net change in total ecosystem C stock was considered, 19% of the forest area were a net source of C. The average net C sink in total ecosystem biomass is quite weak (0.08 MgC ha^–1 yr^–1 and could be reversed by minor increases in harvest rates or a small decline in biomass growth rates.  相似文献   

Streetvending in Peruvian Cities: The Spatio-Temporal Behavior of Ambulantes*     

Maureen Hays-Mitchell 《The Professional geographer》1994,46(4):425-438

Informal trade is a historically rooted and empirically important livelihood in Andean America. This paper examines the spatial dimensions of informal commerce by documenting and analyzing the locational patterns and preferences of streetvendors and the locational constraints imposed on their activities in six Peruvian cities. The interplay of streetvendor needs and municipal exigencies is found to determine the spatio-temporal behavior of streetvendors. A fundamental shift in municipal policy to a more pragmatic attitude toward streetvending is noted.  相似文献