Global Ocean Sediment Composition and Burial Flux in the Deep Sea

Quantitative knowledge about the burial of sedimentary components at the seafloor has wide-ranging implications in ocean science, from global climate to continental weathering. The use of 230Th-normalized fluxes reduces uncertainties that many prior studies faced by accounting for the effects of sediment redistribution by bottom currents and minimizing the impact of age model uncertainty. Here we employ a recently compiled global data set of 230Th-normalized fluxes with an updated database of seafloor surface sediment composition to derive atlases of the deep-sea burial flux of calcium carbonate, biogenic opal, total organic carbon (TOC), nonbiogenic material, iron, mercury, and excess barium (Baxs). The spatial patterns of major component burial are mainly consistent with prior work, but the new quantitative estimates allow evaluations of deep-sea budgets. Our integrated deep-sea burial fluxes are 136 Tg C/yr CaCO3, 153 Tg Si/yr opal, 20Tg C/yr TOC, 220 Mg Hg/yr, and 2.6 Tg Baxs/yr. This opal flux is roughly a factor of 2 increase over previous estimates, with important implications for the global Si cycle. Sedimentary Fe fluxes reflect a mixture of sources including lithogenic material, hydrothermal inputs and authigenic phases. The fluxes of some commonly used paleo-productivity proxies (TOC, biogenic opal, and Baxs) are not well-correlated geographically with satellite-based productivity estimates. Our new compilation of sedimentary fluxes provides detailed regional and global information, which will help refine the understanding of sediment preservation

Compositions of suspended matter in the North (Severnaya) Dvina River mouth area in summer periods of 2001-2005

Quantitative distribution and grain size composition of suspended particulate matter (SPM) in the marginal filter of the North (Severnaya) Dvina River during summer low water periods of 2001-2005 were analyzed in water on board immediately after sampling (without preliminary treatment) using a Coulter counter. This analysis revealed main regularities in transformation of grain size spectra at successive salinity steps of the marginal filter, as well as boundaries between these steps based on data obtained by direct complex studies of SPM dispersion. It is established that water salinity is the main factor that controls changes in grain size distribution and composition of suspended matter in the marginal filter. Concentrations of <0.01 mm size fraction and salinity demonstrate negative correlations between each other. It is shown that areas characterized by mass development of phytoplankton are located along the outer boundary of the marginal filter (at the biological step), where salinity reaches 23-24 psu. Contents of particulate forms of some chemical (lithogenic) elements and organic carbon indicating genetic composition of SPM and their relations with grain size composition of SPM are studied