@article{fdi:010082163,
  title = {{V}ariability of dissolved oxygen in the bottom layer of the {S}outhern {S}enegalese shelf},
  author = {{T}all, {A}. {W}. and {M}achu, {E}ric and {E}chevin, {V}. and {C}apet, {X}. and {P}ietri, {A}. and {C}orrea, {K}. and {S}all, {S}. {M}. and {L}azar, {A}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he observation station "{M}elax" was deployed in 2015 on the wide and shallow south {S}enegalese shelf to study the ocean dynamics, air-sea interactions, and dissolved oxygen ({DO}) cycle. {D}ata from {F}ebruary 2015 to {A}ugust 2016 were used to study the main physical processes affecting the variability of {DO} in the bottom layer (similar to 30 m depth) on time scales ranging from tidal to seasonal. {B}etween {N}ovember and {M}ay, wind-driven upwelling provides phytoplankton enrichment of the surface layers and brings cold, salty, and depleted {DO} on the shelf. {W}ater properties at {M}elax vary depending on the source waters located at the shelf edge. {T}he {DO} concentration changes between the shelf edge and {M}elax are broadly consistent with the inferred respiration rates estimated in previous studies. {I}n contrast, the monsoon season ({J}uly-{O}ctober) is characterized by weak westerly winds and northward currents. {B}ottom waters are warmer, fresher, and more oxygenated. {T}he slower circulation in this period allows a stronger decoupling between the water properties of the waters observed at {M}elax and those of the source waters. {S}tratification strengthening near the bottom layer inhibits vertical mixing and induces strong high-frequency variability in properties caused by internal tide-generated waves. {I}ntense upwelling events can deepen the mixed layer and intermittently transform the bottom layer waters (locally or remotely). {R}elaxation events associated with current reversals significantly modify their properties. {C}oastal trapped waves constitute a distant forcing that can act year-round, impacting both shelf waters and source regions. {P}lain {L}anguage {S}ummary {G}lobal warming and extra nutrient loads from agriculture and waste-waters reduce the oxygen content in the ocean. {I}ncidentally, oxygen-depleted waters are encountered with increased frequency oceanwide and this trend is more pronounced in coastal environments. {T}emperature and oxygen impact the metabolism of marine organisms and their variations can be major sources of (natural or anthropogenic) stresses. {W}e used here measurements made at a fixed monitoring buoy ({M}elax) located over the southern {S}enegalese mid-shelf (35 m depth) to study the variability of bottom oxygen (the surface being well oxygenated). {I}ts seasonality is constrained by the circulation and the wind regime. {T}hey induce the transport of deep, colder, saltier, and less oxygenated waters from the shelf break onto the shelf during the upwelling season compared to the monsoon season. {T}he properties of water masses on the shelf thus depend on those of the water masses drawn from the open ocean through the shelf break which can be modified by many processes acting over a wide range of scales from days to seasons and longer. {O}n the shelf, respiration of organic matter reduces oxygen whereas diurnal wind variability and internal tides oxygenate bottom layers when the water column is stratified.},
  keywords = {{SENEGAL} ; {ATLANTIQUE}},
  booktitle = {},
  journal = {{J}ournal of {G}eophysical {R}esearch : {O}ceans},
  volume = {126},
  numero = {5},
  pages = {e2020{JC}016854 [27 p.]},
  ISSN = {2169-9275},
  year = {2021},
  DOI = {10.1029/2020jc016854},
  URL = {https://www.documentation.ird.fr/hor/fdi:010082163},
}