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Comments on the role of marine sediment burial as a repository for anthropogenic CO 2
Author(s) -
Berner Robert A.
Publication year - 1992
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/91gb02990
Subject(s) - continental shelf , oceanography , sediment , continental margin , upwelling , total organic carbon , geology , biogeochemical cycle , pelagic zone , pelagic sediment , organic matter , estuary , biogeochemistry , environmental science , paleontology , ecology , biology , tectonics
In a recent letter to this journal, Smith and Mackenzie [1991] emphasized the role of near‐shore environments, such as bays and estuaries, as being the principal locus for the enhanced burial of organic matter due to anthropogenically derived nutrient inputs to the oceans. I commend them for this because of the relative lack of attention given to near‐shore environments by much of the biogeochemical and ocanographic community. It is along continental margins and not in the pelagic ocean where most organic matter, as well as most sediment, is buried. From an extensive review of the sediment literature I have shown [Berner, 1982] that principal organic carbonburial on a global basis occurs in deltas and other continental margin environments. (A large proportion of the organic C may be of terrestrial origin.) Although the average carbon content of the surficial portions of deltaic and continental shelf muds is only about 0.75%C, the large mass of sediment carrying this small carbon percentage adds up to a very large burial rate. The riverine flux of suspended sediment to the oceans has been estimated [e.g., Milliman and Meade, 1983; Milliman and Syvitski, 1992] to be between 12,000 and 25,000 Tg (10 2 grams) per year, and most of this sediment is deposited at present on or near the continental shelves. At 0.75 % C this amounts to anannual carbon burial rate of 90–190 Tg C. Burial rates in other environments such as offshore upwelling zones of high productivity or the vast pelagic realms of the oceans do not come close to matching these rates. If one is to look for a locus for the burial of excess carbon from fossil fuel burning and deforestation, the place to look is near the continents.