Publication Date:
2022-05-26
Description:
© The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 115 (2016): 63–73, doi:10.1016/j.dsr.2016.05.010.
Description:
Remineralization of organic matter in the mesopelagic zone (ca. 150–700 m) is a
key controlling factor of carbon export to the deep ocean. By using a tracer conservation model applied to climatological data of oxygen, dissolved inorganic carbon (DIC) and
nitrate, we computed mesopelagic respiration at the ESTOC (European Station for Time-
Series in the Ocean, Canary Islands) site, located in the Eastern boundary region of the
North Atlantic subtropical gyre. The tracer conservation model included vertical Ekman
advection, geostrophic horizontal transport and vertical diffusion, and the biological remineralization terms were diagnosed by assuming steady state. Three different approaches
were used to compute reference velocities used for the calculation of geostrophic velocities and flux divergences: a no-motion level at 3000 m, surface geostrophic velocities
computed from the averaged absolute dynamic topography field, and surface velocities
optimized from the temperature model. Mesopelagic respiration rates computed from the
model were 2.8–8.9molO2 m2 y=1, 2.0–3.1mol Cm2 y=1 and 0.6–1.0molNm2 y=1, consistent with remineralization processes occurring close to Redfield stoichiometry. Model
estimates were in close agreement with respiratory activity, derived from electron transport
system (ETS) measurements collected in the same region at the end of the winter bloom
period (3.61 ± 0.48molO2 m=2 y=1). According to ETS estimates, 50% of the respiration
in the upper 1000 m took place below 150 m. Model results showed that oxygen, DIC and
nitrate budgets were dominated by lateral advection, pointing to horizontal transport as the
main source of organic carbon fuelling the heterotrophic respiration activity in this region.
Description:
Funding for this study was provided by the Xunta de Galicia under the research project VARITROP (09MDS001312PR, PI B. Mouriño-Carballido) and by the Ministerio de Educación y
Cultura under the research project MESOPELAGIC (MAR97-1036, PI S. Hernández-León).
B. Fernández-Castro acknowledges the receipt of FPU grant from the Spanish government
(AP2010-5594).
Description:
2017-05-26
Keywords:
Mesopelagic respiration
;
Tracer conservation model
;
Horizontal advection
;
North Atlantic subtropical gyre
;
ESTOC
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
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