1,721,032 research outputs found
Recommended from our members
Detection of El Nino and decade time scale variations of sea surface temperature from banded coral records: implications for the carbon dioxide cycle.
Full text linkStable oxygen isotope ratios from annually banded corals are correlated with historical records of sea surface temperature in the central and eastern tropical Pacific ocean. El Nino events between 1929 and 1976 are detected using this method, but there are discrepancies between the records of El Ninos from corals and those determined using historical hydrographic and meteorologic data. The average annual description of delta 18O during El Nino events is greater at the Galapagos Island sites (0.45per mille) than at the Fanning and Canton Island sites in the mid-Pacific (0.20-0.30per mille and less than 0.2per mille, respectively). Of prime importance is evidence of decade time scale variability of sea surface temperature (SST) in the tropical Pacific. In particular, annually averaged SST appears to have been 0.5o-1oC higher in the eastern tropical Pacific during the 1930's than during subsequent years. A significant net flux of CO2 from the surface ocean to the atmosphere is envisioned during these periods of higher SST.-Autho
Detection of El Nino and decade time scale variations of sea surface temperature from banded coral records: implications for the carbon dioxide cycle.
No full text
Lipid-like material as the source of the uncharacterized organic carbon in the ocean?
No full textThe composition and formation mechanisms of the uncharacterized fraction of oceanic particulate organic carbon (POC) are not well understood. We isolated biologically important compound classes and the acid-insoluble fraction, a proxy of the uncharacterized fraction, from sinking POC in the deep Northeast Pacific and measured carbon isotope ratios to constrain the source(s) of the uncharacterized fraction. Stable carbon and radiocarbon isotope signatures of the acid-insoluble fraction were similar to those of the lipid fraction, implying that the acid-insoluble fraction might be composed of selectively accumulated lipid-like macromolecules.X1155sciescopu
Blank correction for Delta C-14 measurements in organic compound classes of oceanic particulate matter
No full textContaminant carbon (blank carbon) was studied for its impact on the carbon isotope measurements (Delta C-14 and delta C-13) of 3 organic compound classes of oceanic particulate organic matter. Two methods of blank correction and associated uncertainties were studied. First, the carbon blanks were quantified manometrically and the isotope ratios of the blank carbon were measured directly. Second, the isotope ratios of the blank carbon were estimated using the standard dilution method from the difference in Delta C-14 values between unprocessed and processed standards. The 2 methods agreed within the uncertainties. The standard deviations of numerous Delta C-14 measurements made on processed standard compounds were comparable to those of real samples. Blank correction using the standard dilution method is much less sensitive to the error in determination of blank carbon mass than is correction using the directly measured mass and Delta C-14 values of the blank carbon. The standard dilution method is recommended for correcting Delta C-14 analyses of small samples that involve incorporation of a significant amount of blank carbon.X1119sciescopu
Carbon isotope ratios of organic compound fractions in oceanic suspended particles
No full textTo study cycling of organic fractions in the ocean, relative abundances and radio- and stable-carbon isotope measurements of total lipid extract, acid-soluble, and acid-insoluble fractions of suspended particulate organic carbon (POC) were made. Changes in relative abundances occurred mostly in the upper 1000 m of the water column, with a decrease in total lipid extract and the acid-soluble fraction and an increase in the acid-insoluble fraction with increasing depth. We found lower Delta(14)C values for total lipid extract and the acid-insoluble fraction than for the acid-soluble fraction, which is consistent with the previous suggestion of incorporation of dissolved organic carbon and/or resuspended sediment to POC (Druffel and Williams, 1990; Sherrell et al., 1998). The Delta(14)C values of these fractions in a given organic carbon pool must be understood in terms of acquisition of (14)C-depleted carbon from other carbon pools in addition to aging within the reservoir.X1113sciescopu
- …
