DOI: 10.5061/dryad.mpg4f4r61
title: Southern Ocean's circulation impact on the marine carbon cycle

description: In the context of past and present climate change, the Southern Ocean (SO)
 has been identified as a crucial region modulating the concentration of
 atmospheric CO2. The sustained upwelling of carbon-rich deep waters and
 inefficient nutrient utilisation at the surface of SO leads to an
 outgassing of natural CO2, while anthropogenic CO2 is entrained to depth
 during the formation of Antarctic Bottom water (AABW), Antarctic
 intermediate water (AAIW) and sub-Antarctic mode water (SAMW). Changes to
 the SO circulation resulting from both dynamic and buoyancy forcing can
 alter the rate of upwelling as well as formation and subsequent transport
 of AABW, AAIW and SAMW, thus impacting the air-sea CO2 exchange in SO.
 Models of all complexity robustly show that stronger southern hemispheric
 (SH) westerlies enhance the SO upwelling, thus leading to stronger natural
 CO2 outgassing, with a sensitivity of ∼0.13 GtC/yr for a 10% increase in
 SH westerly windstress. While the impact of changes in the position of the
 SH westerly winds was previously unclear, recent simulations with
 high-resolution ocean/sea-ice/carbon cycle models show that a poleward
 shift of the SH westerlies also enhances natural CO2 outgassing with a
 sensitivity of ∼0.08GtC/yr for a 5• poleward shift. While enhanced AABW
 transport reduces deep ocean natural DIC concentration and increases
 surface natural DIC concentration, it acts on a centennial timescale.
 Future work should better constrain both the natural and anthropogenic
 carbon cycle response to changes in AABW and the compound impacts of
 dynamic and buoyancy changes on the SO marine carbon cycle.
description: This data present the outputs of several numerical
 experiments:  global eddy-rich model
 (ACCESS-OM2-01, 0.1deg resolution, 75 vertical levels) forced by the
 55-year Japanese Reanalysis for driving oceans (JRA55-do) (Tsujino et al.,
 2018) over the period 1958 to 2021.  global model
 (ACCESS-OM2, 1deg resolution, 50 vertical levels) forced by the 55-year
 Japanese Reanalysis for driving oceans (JRA55-do) (Tsujino et al., 2018)
 over the period 1958 to 2021. sensitivity experiments
 performed with the  (ACCESS-OM2-01, 0.25deg resolution, 50 vertical
 levels) in which the SH near surface wind speeds are abruptly modified.
 The zonally uniform and temporally steady perturbations are applied to the
 CORE-NYF 6-hourly wind field between 25S and 70S with smoothing within 5
 degree latitude of the perturbation boundaries. The perturbations include
 i) a 20% increase, ii) a 20% increase, iii) 4 degree poleward shift, iv) a
 16% decrease in windstress between 32S and 65S, and iv) a 4 degree
 equatorward shift of the SH westerly windstress. The first four idealized
 experiments are integrated for 42 years, while the last one is run for 125
 years. Sensitivity experiment performed with the
  Earth system model of intermediate complexity LOVECLIM under constant
 pre-industrial condition: stronger AABW transport for 1000 yrs generated
 by increased surface salinity (-0.15 Sv, Menviel et al., 2015).
description: # Southern Ocean's circulation impact on the marine carbon cycle
 [https://doi.org/10.5061/dryad.mpg4f4r61](https://doi.org/10.5061/dryad.mpg4f4r61) The data contains: 1\) The relationship between SH westerly windstress and natural CO2 flux in experiments performed with the: -ACCESS-OM2 (ACCESS-OM2-SOflux.txt) \- ACCESS-OM2-01 (ACCESS-OM2-01-SOflux.txt) \- ACCESS-OM2-025 (ACCESS-OM2-025-SOfluxStrength.txt and ACCESS-OM2-025-SOfluxPosition.txt) 2\) Zonally averaged DIC concentration (mmol/m3) and remineralized DIC anomalies (mmol/m3) for experiments performed with the ACCESS-OM2-025 (Menviel et al., 2018): DIC-PI-CTR.nc: dcw = DIC in an experiment with poleward intensified SH westerlies, dcc = DIC in the control run, dcorg = Remineralized DIC anomalies for the experiment with poleward intensified SH westerlies compared to the control run 3\) Zonally averaged DIC concentration (mmol/m3) and remineralized DIC anomalies (mmol/m3) for experiments performed with LOVECLIM (Menviel et al., 2015): DICano-SOs-LOVECLIM.nc dcs = DIC in an experiment with stronger AABW dcc = DIC in the control run, dcorg = Remineralized DIC anomalies for the experiment with stronger AABW compared to the control run