@article{fdi:010075662,
  title = {{A}ssessment of time of emergence of anthropogenic deoxygenation and warming : insights from a {CESM} simulation from 850 to 2100 {CE}},
  author = {{H}ameau, {A}. and {M}ignot, {J}uliette and {J}oos, {F}.},
  editor = {},
  language = {{ENG}},
  abstract = {{M}arine deoxygenation and anthropogenic ocean warming are observed and projected to intensify in the future. {T}hese changes potentially impact the functions and services of marine ecosystems. {A} key question is whether marine ecosystems are already or will soon be exposed to environmental conditions not experienced during the last millennium. {U}sing a forced simulation with the {C}ommunity {E}arth {S}ystem {M}odel ({CESM}) over the period 850 to 2100, we find that anthropogenic deoxygenation and warming in the thermocline exceeded natural variability in, respectively, 60% and 90% of total ocean area. {C}ontrol simulations are typically used to estimate the pre-industrial variability level. {H}owever, the natural variability of oxygen ({O}-2) and temperature ({T}) inferred from the last millennium period is systematically larger than the internal variability simulated in the corresponding control simulation. {T}his renders natural variability from control simulations to be biased towards low estimates. {H}ere, natural variability is assessed from the last millennium period (850-1800 {CE}), thus considering the response to forcing from explosive volcanic eruptions, solar irradiance and greenhouse gases in addition to internal, chaotic variability. {R}esults suggest that in the tropical thermocline, where biological and solubility-driven {O}-2 changes counteract each other, anthropogenic changes in apparent oxygen utilisation ({AOU}) and in {O}-2 solubility ({O}-2; sol) are detectable earlier than {O}-2 changes. {B}oth natural variability and change in {AOU} are predominantly driven by variations in circulation with a smaller role for productivity. {B}y the end of the 21st century, ventilation becomes more vigorous in the tropical thermocline, whereas ideal age in deep waters increases by more than 200 years relative to the pre-industrial period. {D}ifferent methodological choices are compared and the time for an anthropogenic signal to emerge ({T}o{E}) is earlier in many thermocline regions when using variability from a shorter period, from the control simulation or estimates from the industrial period instead of the variability from the last millennium. {O}ur results highlight that published methods may lead to deviations in {T}o{E} estimates, calling for a careful quantification of variability. {T}hey also highlight that realised anthropogenic change exceeds natural variations in many regions.},
  keywords = {{MONDE}},
  booktitle = {},
  journal = {{B}iogeosciences},
  volume = {16},
  numero = {8},
  pages = {1755--1780},
  ISSN = {1726-4170},
  year = {2019},
  DOI = {10.5194/bg-16-1755-2019},
  URL = {https://www.documentation.ird.fr/hor/fdi:010075662},
}