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Prahl, Frederick G

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Works: 6 works in 6 publications in 1 language and 6 library holdings
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Publications about Frederick G Prahl
Publications by Frederick G Prahl
Most widely held works by Frederick G Prahl
Stable isotope ratios of foraminifera and sea surface temperature estimation of sediment core W2804A-14, supplementary data to: Jasper, John P; Hayes, John M; Mix, Alan C; Prahl, Frederick G (1994): Photosynthetic fractionation of 13C and concentrations of dissolved CO2 in the central equatorial Pacific during the last 255,000 years. Paleoceanography, 9(6), 781-798 by John P Jasper( Computer File )
in English and held by 1 library worldwide
Carbon isotopically based estimates of CO2 levels have been generated from a record of the photosynthetic fractionation of 13C (epsilon p) in a central equatorial Pacific sediment core that spans the last 255 ka. Contents of 13C in phytoplanktonic biomass were determined by analysis of C37 alkadienones. These compounds are exclusive products of Prymnesiophyte algae which at present grow most abundantly at depths of 70-90 m in the central equatorial Pacific. A record of the isotopic compostion of dissolved CO2 was constructed from isotopic analyses of the planktonic foraminifera Neogloboquadrina dutertrei, which calcifies at 70-90 m in the same region. Values of epsilon p, derived by comparison of the organic and inorganic delta values, were transformed to yield concentrations of dissolved CO2 (c e) based on a new, site-specific calibration of the relationship between epsilon p and c e. The calibration was based on reassessment of existing epsilon p versus c e data, which support a physiologically based model in which epsilon p is inversely related to c e. Values of PCO2, the partial pressure of CO2 that would be in equilibrium with the estimated concentrations of dissolved CO2, were calculated using Henry's law and the temperature determined from the alkenone-unsaturation index UK 37. Uncertainties in these values arise mainly from uncertainties about the appropriateness (particularly over time) of the site-specific relationship between epsilon p and 1/c e. These are discussed in detail and it is concluded that the observed record of epsilon p most probably reflects significant variations in Delta pCO2, the ocean-atmosphere disequilibrium, which appears to have ranged from 110 ?atm during glacial intervals (ocean > atmosphere) to 60 ?atm during interglacials. Fluxes of CO2 to the atmosphere would thus have been significantly larger during glacial intervals. If this were characteristic of large areas of the equatorial Pacific, then greater glacial sinks for the equatorially evaded CO2 must have existed elsewhere. Statistical analysis of air-sea pCO2 differences and other parameters revealed significant (p < 0.01) inverse correlations of Delta pCO2 with sea surface temperature and with the mass accumulation rate of opal. The former suggests response to the strength of upwelling, the latter may indicate either drawdown of CO2 by siliceous phytoplankton or variation of [CO2]/[Si(OH)4] ratios in upwelling waters
Sedimentology and stable isotope ratios of the northwest Pacific, supplementary data to: Lyle, Mitchell W; Zahn, Rainer; Prahl, Frederick G; Dymond, Jack R; Collier, Robert W; Pisias, Nicklas G; Suess, Erwin (1992): Paleoproductivity and carbon burial across the California current: the multitracer transect 42?N. Paleoceanography, 7(3), 251-272 by Mitchell W Lyle( Computer File )
in English and held by 1 library worldwide
The Multitracers Experiment studied a transect of water column, sediment trap, and sediment data taken across the California Current to develop quantitative methods for hindcasting paleoproductivity. The experiment used three sediment trap moorings located 120 km, 270 km, and 630 km from shore at the Oregon/California border in North America. We report here about the sedimentation and burial of particulate organic carbon (Corg) and CaCO3. In order to observe how the integrated CaCO3 and Corg burial across the transect has changed since the last glacial maximum, we have correlated core from the three sites using time scales constrained by both radiocarbon and oxygen isotopes. By comparing surface sediments to a two-and-a-half year sediment trap record, we have also defined the modern preservation rates for many of the labile sedimentary materials. Our analysis of the Corg data indicates that significant amounts (20-40%) of the total Corg being buried today in surface sediments is terrestrial. At the last glacial maximum, the terrestrial Corg fraction within 300 km of the coast was about twice as large. Such large fluxes of terrestrial Corg obscure the marine Corg record, which can be interpreted as productivity. When we corrected for the terrestrial organic matter, we found that the mass accumulation rate of marine Corg roughly doubled from the glacial maximum to the present. Because preservation rates of organic carbon are high in the high sedimentation rate cores, corrections for degradation are straightforward and we can be confident that organic carbon rain rate (new productivity) also doubled. As confirmation, the highest burial fluxes of other biogenic components (opal and Ba) also occur in the Holocene. Productivity off Oregon has thus increased dramatically since the last glacial maximum. CaCO3 fluxes also changed radically through the deglaciation; however, they are linked not to CaCO3 production but rather to changes in deepwater carbonate chemistry between 18 Ka and now
Final report : organic wastes in high energy neareshore [sic] oceanic ecosystems : fates and effects by J. J Gonor( Book )
1 edition published in 1988 in English and held by 1 library worldwide
Bulk geochemical and lipid biomarker data for sediment core W8402A-14, supplementary data to: Prahl, Frederick G; Muehlhausen, LA; Lyle, Mitchell W (1989): An organic Geochemical Assessment of Oceanographic conditions at manop site C over the Past 26,000 Years. Paleoceanography, 4(5), 495-510 by Frederick G Prahl( Computer File )
in English and held by 1 library worldwide
Eleven sediment samples taken downcore and representing the past 26 kyr of deposition at MANOP site C (0?57.2?N, 138?57.3?W) were analyzed for lipid biomarker composition. Biomarkers of both terrestrial and marine sources of organic carbon were identified. In general, concentration profiles for these biomarkers and for total organic carbon (TOC) displayed three common stratigraphic features in the time series: (1) a maximum within the surface sediment mixed layer (<=4 ka); (2) a broad minimum extending throughout the interglacial deposit; and (3) a deep, pronounced maximum within the glacial deposit. Using the biomarker records, a simple binary mixing model is described that assesses the proportion of terrestrial to marine TOC in these sediments. Best estimates from this model suggest that 20% of the TOC is land-derived, introduced by long-range eolian transport, and the remainder is derived from marine productivity. The direct correlation between the records for terrestrial and marine TOC with depth in this core fits an interpretation that primary productivity at site C has been controlled by wind-driven upwelling at least over the last glacial/interglacial cycle. The biomarker records place the greatest wind strength and highest primary productivity within the time frame of 18 to 22 kyr B.P. Diagenetic effects limit our ability to ascertain directly from the biomarker records the absolute magnitude that different types of primary productivity have changed at this ocean location over the past 26 kyr
Sea surface temperature reconstruction of sediment profile W8709A-8, supplementary data to: Prahl, Frederick G; Pisias, Nicklas G; Sparrow, Margaret A; Sabin, Anne (1995): Assessment of sea-surface temperature at 42?N in the California Current over the last 30,000 years. Paleoceanography, 10(4), 763-774 by Frederick G Prahl( Computer File )
in English and held by 1 library worldwide
Assessment of changes in surface ocean conditions, in particular, sea-surface temperature (SST), is essential to understand long-term changes in climate especially in regions where continental climate is strongly influenced by oceanographic processes. To evaluate changes in SST in the northeast Pacific, we have analyzed long-chain alkenones of prymnesiophyte origin at 38 depths in a piston and associated trigger core collected beneath the contemporary core of the California Current System at 42?N, 270 km off the coast of Oregon/California. The samples span 30,000 years of deposition at this location. Unsaturation patterns (UK'37) in the alkenone series display a statistically significant difference (p <<0.001) between interglacial (0.44 ? 0.02, n = 11) and glacial (0.29 ? 0.04, n = 20) intervals of the cores. Detailed examination of other compositional features of the C37, C38, C39 alkenone series and a related C36 alkenoate series measured downcore suggests the published UK'37 - temperature calibration (UK'37 = 0.034 * T + 0.039 ) , defined for cultures of a strain of Emiliania huxleyi isolated from the subarctic Pacific, provides best estimates of winter SST at our study site. This inference is purely statistical and does not imply, however, that the phytoplankton source of these biomarkers is most productive in winter or at the ocean surface. The temperature record for UK'37 implies (1) an 4?C shift occurred in winter SST from 7.5 ? 1.1?C at the last glacial maximum to 11.7 ? 0.7?C in the present interglacial period, and (2) this warming trend was confined to the time frame 14-10 Ka within the glacial to interglacial transition period. These conclusions are corroborated entirely by results from an independent SST transformation of radiolarian species assemblage data obtained from the same core materials
Alkenone UK37 measured in the upper water column at pump stations CariacoTrench, Peru and Vertex, supplementary data to: Prahl, Frederick G; Wakeham, Stuart (1987): Calibration of unsaturation patterns in long-chain ketone compositions for paleotemperature assessment. Nature, 330(6146), 367-369 by Frederick G Prahl( Computer File )
in English and held by 1 library worldwide
A series of long-chain (C37, C38, C39), primarily di and tri-unsaturated methyl and ethyl ketones, first identified in sediments from Walvis Ridge off West Africa and from Black Sea (de Leeuw et al., 1979), has been found in marine sediments throughout the world (Brassell et al., 1986 doi:10.1038/320129a0). The marine coccolithophorid Emiliania huxleyi and members of the class Prymnesiophyceae are now the recognized sources of these compounds (Volkman et al., 1979; Marlowe, et al., 1984). Experiments with laboratory cultures of algae showed the degree of unsaturation in the ketone seris biosynthesized depends on growth temperature (Brassell et al., 1986; Marlowe, 1984), a physiological respons observed for classical membrane lipids (vanDeenen et al., 1972). Brassell and co-workers (Brassell et al., 198; Brassell et al., 1986b) thus proposed that systematic fluctuations in the unsaturation of these alkenones noted down-core in sediments from the Kane Gap region of the north-east tropical Atlantic Ocean and correlated with glacial-interglacial cycles provide an organic geochemical measure of past sea-surface water temperatures. Using laboratory cultures of E. huxleyi, we have calibrated changes in the unsaturation pattern of the long-chain ketone series versus growth temperature. The calibration curve is linear and accurtely predicts unsuturation patterns observed in natural particulate materials collected from oceanic waters of known temperature. We present evidence supporting the proposed paleotemperature hypothesis (Brassell et al., 1986, Brassel et al., 1986b) and suggesting absolute 'sea-surface temperatures' for a given oceanic location can be estimated from an analysis of long-chain ketone compositions preserved in glacial and interglacial horizons of deep-sea sediment cores
 
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English (6)
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