Hypsometry of ocean basin provinces

Menard, H. W.; Smith, Sheila A.

doi:10.1029/jz071i018p04305

Cited by 342 publications

(199 citation statements)

References 9 publications

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“…[48][49][50]. When conservatively scaled to depths below ~4000m (i.e., ~50% of modern seafloor area 51 ), these rates yield overall sulphur fluxes between ~7 -50 x 10 10 molS y -1 . Note that the upper end of this range is greater than estimates of the modern volcanic sulphur flux.…”

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confidence: 99%

Long-term sedimentary recycling of rare sulphur isotope anomalies

Reinhard

Planavsky

Lyons

2013

Nature

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Sulphur Isotope Database:An extensive sulphur isotope database was used in the construction of Main Text Figure 1. These data were compiled from primary references 1-37 , although in some cases age constraints for certain units were obtained from other sources [38][39][40][41] or estimated. For Main Text Figure 1b, we calculated the cumulative average ∆ 33 S value for all samples up to each year of publication. The average values reported here thus include some contribution from sulphate minerals. However, the overwhelming majority of the data are sulphide mineral phases, and given that most sulphate data are characterized by negative ∆ 33 S values their inclusion will largely attenuate the pattern emphasized here, rendering our argument conservative. Furthermore, the overall effect of their inclusion is quite small (Fig. S1a,b). We also examined the effect of filtering data from analyses made via secondary ion mass spectrometry (SIMS) and analyses of macroscopic pyrite textures, which are not likely to be representative of bulk weathering crust, but again note that the basic pattern remains unchanged (Fig. S1a,b).The mean ∆ 33 S values shown in Fig. 1 are presented as unweighted averages. We consider this approach qualitatively justified, in that the database is composed largely of fine-grained siliciclastic sedimentary rocks that are relatively organic carbon and sulphur rich. Such rocks will not only be, on average, the most sulphur-enriched phases of the crust, but they will also likely hold the majority of the weathering sulphur reservoir at Earth's surface. Nonetheless, it is important to consider the possibility that there is a bias related to systematic relationships between the sulphur content of sedimentary rocks and their ∆ 33 S value. For this purpose, we compiled the available sulphur concentration data for the units within the isotope database and performed concentration-weighted statistical analyses.There does not appear to be any systematic relationship between rare sulphur isotope composition and sulphur content within the database (Fig. S2a). In addition, the cumulative unweighted average is nearly indistinguishable from the concentration-weighted average within this subset of the database (Fig. S2a,b). When the evolution of the overall ∆ 33 S value of the database is concentration-weighted, it shows a generally similar pattern through time to that of the overall mean values (Fig. S2b). Indeed, the mean ∆ 33 S value when weighted by concentration is more positive than the unweighted mean for a given population from the database. We stress the caveat that many of the published rare sulphur isotope datasets do not contain sulphur concentration data, so unfortunately this analysis cannot be performed on the entire database. However, the coupled isotope and concentration data represent well over 500 samples that range in sulphur content over three orders of magnitude. These considerations lead us to conclude that the pattern expressed in the overall mean ∆ 33 S values through time is robust and is ...

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confidence: 99%

Long-term sedimentary recycling of rare sulphur isotope anomalies

Reinhard

Planavsky

Lyons

2013

Nature

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“…6A). Annual production of biologically labile photoproducts by 10Њ-latitude bands was estimated from the cross product of the calculated depthintegrated fluxes (extrapolating cloud cover data to 85Њ latitude) and the latitudinal distribution of the coastal ocean, as calculated from data in Levitus (1982) (assuming 27.1 ϫ 10 6 km 2 of coastal ocean; Menard and Smith 1966) (Fig. 6A).…”

Section: Comparison Of Quantum Yield Spectra Among Classes Of Dom Phomentioning

confidence: 99%

Determination of apparent quantum yield spectra for the formation of biologically labile photoproducts

Miller

Moran

Sheldon

et al. 2002

Limnology & Oceanography

142

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Quantum yield spectra for the photochemical formation of biologically labile photoproducts from dissolved organic matter (DOM) have not been available previously, although they would greatly facilitate attempts to model photoproduct formation rates across latitudinal, seasonal, and depth-related changes in spectral irradiance. Apparent quantum yield spectra were calculated for two coastal environments from the southeastern United States using postirradiation bacterial respiration as a measure of total labile photoproduct formation and a cutoff filter method to model spectral dependence. As has been the case for previously studied classes of DOM photoproducts (i.e., dissolved inorganic carbon, CO, and H 2 O 2 ), ultraviolet (UV)-B irradiance was significantly more efficient at forming labile photoproducts (i.e., compounds readily assimilated by marine bacterioplankton) than UV-A and visible irradiance. Calculations of DOM photoproduct formation in southeastern U.S. coastal surface waters indicate a formation ratio for biologically labile photoproducts : CO of 13 : 1. The slope of a natural log plot of the apparent quantum yield spectrum obtained for biologically labile photoproducts was similar to that for CO (0.028 nm Ϫ1 vs. 0.034 nm Ϫ1 ). Modeled kinetic rates therefore indicate that the production ratio of these photoproduct classes is approximately maintained despite variations in the solar spectrum that occur with depth in a water column or distance from shore. Application of the apparent quantum yield to coastal regions worldwide predicts an annual formation rate of biologically labile photoproducts in coastal waters of 206 ϫ 10 12 g C.Exposure of marine dissolved organic matter (DOM) to natural sunlight modifies the chemical structure of DOM and produces a suite of organic and inorganic photoproducts that can affect biological productivity (Kieber et al. 1989), oceanic carbon cycling (Mopper et al. 1991;Miller and Zepp 1995), atmospheric flux of CO and CO 2 (Miller and Zepp 1995;Gao and Zepp 1998;Erickson et al. 2000), and many other processes. Although significant progress has been made in identifying DOM photoproducts and documenting

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“…Table 3. The mean depth of the Paofic Ocean is taken to be 4200 m [43]. The ocean margin volume fraction (fro) is assumed to be 0.…”

Section: °Bementioning

confidence: 99%

“…For the purpose of comparing 1°Be scavenging rates at different sites in the ocean, Be/Th ratios should, therefore, be normalized to a constant water depth. The mean depth of 4200 m of the Pacific [43] was chosen against which the Be/Th ratios were normalized:…”

Section: Intensified Scavenging Of 231pa and L°be In Ocean Marginsmentioning

confidence: 99%