Benthic carbon mineralization on a global scale

Abstract

[1] In this study we present a global distribution pattern and budget of the minimum flux of particulate organic carbon to the sea floor (J POCa ). The estimations are based on regionally specific correlations between the diffusive oxygen flux across the sedimentwater interface, the total organic carbon content in surface sediments, and the oxygen concentration in bottom waters. For this, we modified the principal equation of Cai and Reimers [1995] as a basic monod reaction rate, applied within 11 regions where in situ measurements of diffusive oxygen uptake exist. By application of the resulting transfer functions to other regions with similar sedimentary conditions and areal interpolation, we calculated a minimum global budget of particulate organic carbon that actually reaches the sea floor of $0.5 GtC yr À1 (>1000 m water depth (wd)), whereas approximately 0.002-0.12 GtC yr À1 is buried in the sediments (0.01-0.4% of surface primary production). Despite the fact that our global budget is in good agreement with previous studies, we found conspicuous differences among the distribution patterns of primary production, calculations based on particle trap collections of the POC flux, and J POCa of this study. These deviations, especially located at the southeastern and southwestern Atlantic Ocean, the Greenland and Norwegian Sea and the entire equatorial Pacific Ocean, strongly indicate a considerable influence of lateral particle transport on the vertical link between surface waters and underlying sediments. This observation is supported by sediment trap data. Furthermore, local differences in the availability and quality of the organic matter as well as different transport mechanisms through the water column are discussed.

Swept under the carpet: organic matter burial decreases global ocean biogeochemical model sensitivity to remineralization length scale

“…In general, the model scenarios reflect the very high benthic remineralization rates observed along the coasts, and predict very low remineralization in the subtropical gyres. For the Northern Hemisphere the simulated low subtropical values are supported only by the few observations by Seiter et al (2005). However, in the South Pacific, Fischer et al (2009) observed some sites with rather high benthic fluxes, which are not simulated by the model.…”

“…Benthic and riverine fluxes in all models increase with decreasing flux exponent (= increasing particle sinking speed). The strength of burial has only little influence on particle flux in 2000 m, but global burial and therefore riverine input is higher in models with strong burial (BUR and DUNNE), The panels also denote the RMSE of the modeled vs. observed benthic remineralization (data set by Seiter et al, 2005), and the number of data points sampled (upper numbers: without Arabian Sea data, lower numbers: total data set). while benthic remineralization is higher in the model with weak burial (WBUR).…”

“…We therefore define detritus remineralization vertically integrated over the deepest model box as an (upper) model estimate of benthic remineralization per sea-floor area. Figure 9 shows simulated benthic remineralization of model BUR, together with observations as compiled by Seiter et al (2005, we use a data set provided by Christian Hensen). The data set is supplemented by observations of Fischer et al (2009) taken in the South Pacific, an area which otherwise would be only sparsely represented in the observations.…”

A transfer function for the prediction of gas hydrate inventories in marine sediments

“…In a second and more detailed parameter analysis the effect of POCar and GHSZ was analysed in a number of runs of the standardised numerical model by covering a wider range of natural variations of these parameters than in typical continental margin environments: GHSZ from 100 to 2000 m (Dickens, 2001) (Seiter et al, 2005). The GHSZ was varied by changing the thermal gradient from 10 to 65 • /km, the seafloor temperature from 1 to 6 • C, and the water depth from 500 to 6000 m. In order to identify possible interdependencies between POCar and GHSZ, crosswise variations were calculated.…”

Baseline biogeochemical data from Australia's continental margin links seabed sediments to water column characteristics

“…The percentage TN (%TN) of seabed sediment ranges from ,0.03 to 1.2% (Burdige, 2007). These concentrations are controlled by OM supply to the sea floor, degradation rates, mineral interactions and dilution from inorganic phases (Seiter et al 2005). TOC (and TN) concentrations are usually inversely correlated with grain size (Mayer 1994 (Hedges and Keil 1995).…”