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The influence of air‐sea exchange on the isotopic composition of oceanic carbon: Observations and modeling
Author(s) -
LynchStieglitz Jean,
Stocker Thomas F.,
Broecker Wallace S.,
Fairbanks Richard G.
Publication year - 1995
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 - 10.1029/95gb02574
Subject(s) - ocean gyre , atmosphere (unit) , oceanography , carbon cycle , carbon fibers , environmental science , dissolved organic carbon , deep sea , equator , surface water , atmospheric sciences , geology , subtropics , latitude , meteorology , ecology , physics , materials science , geodesy , ecosystem , environmental engineering , composite number , composite material , biology
Although the carbon isotopic composition of ocean waters after they leave the surface ocean is determined by biological cycling, air‐sea exchange affects the carbon isotopic composition of surface waters in two ways. The equilibrium fractionation between oceanic and atmospheric carbon increases with decreasing temperature. In Southern Ocean Surface Waters this isotopic equilibration enriches δ 13 C relative to the δ 13 C expected from uptake and release of carbon by biological processes alone. Similarly, surface waters in the subtropical gyres are depleted in δ 13 C due to extensive air‐sea exchange at warm temperatures. Countering the tendency toward isotopic equilibration with the atmosphere (a relatively slow process), are the effects of the equilibration of CO 2 itself (a much faster process). In regions where there is a net transfer of isotopically light CO 2 from the ocean to the atmosphere (e.g., the equator) surface waters become enriched in 13 C, whereas in regions where isotopically light CO 2 is entering the ocean (e.g., the North Atlantic) surface waters become depleted in 13 C. A compilation of high quality oceanic δ 13 C measurements along with experiments performed using a zonally averaged three‐basin dynamic ocean model are used to explore these processes.