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The δ 18 O of dissolved O 2 as a tracer of mixing and respiration in the mesopelagic ocean
Author(s) -
Levine Naomi Marcil,
Bender Michael L.,
Doney Scott C.
Publication year - 2009
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 - 10.1029/2007gb003162
Subject(s) - isopycnal , mesopelagic zone , photic zone , isotopes of oxygen , respiration , oxygen , stable isotope ratio , tracer , oxygen minimum zone , oceanography , oxygen 18 , chemistry , geology , pelagic zone , upwelling , phytoplankton , nutrient , botany , biology , physics , organic chemistry , quantum mechanics , nuclear physics , nuclear chemistry
The isotopic composition of dissolved oxygen in the mesopelagic ocean is a unique tracer of respiration and transport. New δ 18 O of O 2 data from the tropical South Atlantic oxygen minimum zone are presented and compared to global δ 18 O data. The δ 18 O variability in oxygen poor waters is attributed to differences in physical and biogeochemical processes. Simple respiration‐transport models show that both isopycnal diffusion and advection must be properly considered when interpreting oxygen isotope signatures along an isopycnal surface. We estimate rates of respiration and oxygen isotope fractionation for the study region using a two‐dimensional (2‐D) isopycnal and 1‐D diapycnal model. Estimated respiration rates are consistent with previous studies. However, to account for observed δ 18 O values at low [O 2 ], model solutions need to invoke either very low [O 2 ] that have not been observed in the South Atlantic or an isotope effect that is lower than values measured in the laboratory or euphotic zone.