Articles | Volume 21, issue 4
https://doi.org/10.5194/os-21-1549-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/os-21-1549-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
29 Jul 2025
Research article |
| 29 Jul 2025
| 29 Jul 2025
The Southern Ocean Time Series: a climatological view of hydrography, biogeochemistry, phytoplankton community composition, and carbon export in the Subantarctic Zone
Elizabeth H. Shadwick
CORRESPONDING AUTHOR
CSIRO Environment, Hobart, TAS, Australia
Australian Antarctic Program Partnership, Hobart, TAS, Australia
Cathryn A. Wynn-Edwards
CSIRO Environment, Hobart, TAS, Australia
Australian Antarctic Program Partnership, Hobart, TAS, Australia
Ruth S. Eriksen
CSIRO Environment, Hobart, TAS, Australia
Australian Antarctic Program Partnership, Hobart, TAS, Australia
CSIRO National Collections and Marine Infrastructure, Hobart, TAS, Australia
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia
Peter Jansen
CSIRO National Collections and Marine Infrastructure, Hobart, TAS, Australia
Xiang Yang
Australian Antarctic Program Partnership, Hobart, TAS, Australia
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia
Gemma Woodward
Australian Antarctic Program Partnership, Hobart, TAS, Australia
Diana Davies
Australian Antarctic Program Partnership, Hobart, TAS, Australia
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Pearse J. Buchanan, P. Jyoteeshkumar Reddy, Richard J. Matear, Matthew A. Chamberlain, Tyler Rohr, Dougal Squire, and Elizabeth H. Shadwick
Biogeosciences, 22, 5349–5385, https://doi.org/10.5194/bg-22-5349-2025, https://doi.org/10.5194/bg-22-5349-2025, 2025
Short summary
Short summary
We calibrate a new version of the World Ocean Model of Biogeochemistry and Trophic dynamics (WOMBAT-lite) using a surrogate machine learning approach. A Gaussian process surrogate trained on 512 simulations emulated tens of thousands, enabling global sensitivity analysis and Bayesian optimization of 26 parameters. We constrain 13 key parameters, improving fit to 8 datasets (chlorophyll a, air–sea CO₂ fluxes, nutrient limitation), and provide an optimal set for community use.
Pearse J. Buchanan, P. Jyoteeshkumar Reddy, Richard J. Matear, Matthew A. Chamberlain, Tyler Rohr, Dougal Squire, and Elizabeth H. Shadwick
Biogeosciences, 22, 5349–5385, https://doi.org/10.5194/bg-22-5349-2025, https://doi.org/10.5194/bg-22-5349-2025, 2025
Short summary
Short summary
We calibrate a new version of the World Ocean Model of Biogeochemistry and Trophic dynamics (WOMBAT-lite) using a surrogate machine learning approach. A Gaussian process surrogate trained on 512 simulations emulated tens of thousands, enabling global sensitivity analysis and Bayesian optimization of 26 parameters. We constrain 13 key parameters, improving fit to 8 datasets (chlorophyll a, air–sea CO₂ fluxes, nutrient limitation), and provide an optimal set for community use.
Cited articles
Ardhuin, F., Molero, B., Bohé, A., Nouguier, F., Collard, F., Houghton, I., Hay, A., and Legresy, B.: Phase resolved swells across ocean basins in SWOT altimetry data: revealing centimetre scale wave heights including coastal reflection, Geophys. Res. Lett., 51, e2024GL109658, https://doi.org/10.1029/2024GL109658, 2024. a
Bates, N. R., Astor, Y. M., Church, M. J., Currie, K., Dore, J. E., González-Dávila, M., Lorenzoni, L., Muller-Karger, F., Olafsson, J., and Santana-Casiano, J. M.: A time-series view of changing ocean chemistry due to ocean uptake of anthropogenic CO2 and ocean acidification, Oceanography, 27, 126–141, https://doi.org/10.5670/oceanog.2014.16, 2014. a, b, c
Beaufort, L., Probert, I., de Garidel-Thoron, T., Bendif, E. M., Ruiz-Pino, D., Metzl, N., Goyet, C., Buchet, N., Coupel, P., Grelaud, M., Rost, B., Rickaby, R. E. M., and de Vargas, C.: Sensitivity of coccolithophores to carbonate chemistry and ocean acidification, Nature, 476, 80–83, https://doi.org/10.1038/nature10295, 2011. a
Behrenfeld, M. J. and Falkowski, P. G.: Photosynthetic rates derived from satellite-based chlorophyll concentration, Limnol. Oceanogr., 42, 1–20, 1997. a
Bohé, A., Chen, A., Chen, C., Dubois, P., Fore, A., Molero, B., Peral, E., Raynal, M., Stiles, B., Ardhuin, F., Hay, A., Legresy, B., Lenain, L., and Villas Bôas, A. B.: Measuring Significant Wave Height Fields in Two Dimensions at Kilometric Scales With SWOT, IEEE T. Geosci. Remote, 63, 1–19, https://doi.org/10.1109/TGRS.2025.3551605, 2025. a
Bowie, A. R., Lannuzel, D., Remenyi, T. A., Wagener, T., Lam, P. J., Boyd, P. W., Guieu, C., Townsend, A. T., and Trull, T. W.: Biogeochemical iron budgets of the Southern Ocean south of Australia: decoupling of iron and nutrient cycles in the subantarctic zone by the summertime supply, Global Biogeochem. Cy., 23, GB4034, https://doi.org/10.1029/2009GB003500, 2009. a
Boyd, P. W. and Trull, T. W.: Understanding the export of biogenic particles in oceanic waters: Is there consensus?, Prog. Oceanogr., 72, 276–312, https://doi.org/10.1016/j.pocean.2006.10.007, 2007. a
Boyd, P. W., Claustre, H., Levy, M., Siegel, D. A., and Weber, T.: Multi-faceted particle pumps drive carbon sequestration in the ocean, Nature, 568, 327–335, https://doi.org/10.1038/s41586-019-1098-2, 2019. a
Boyd, P. W., Antoine, D., Baldry, K., Cornec, M., Ellwood, M., Halfter, S., Lacour, L., Latour, P., Strzepek, R. F., Trull, T. W., and Rohr, T.: Controls on polar Southern Ocean deep chlorophyll maxima: viewpoints from multiple observational platforms, Global Biogeochem. Cy., 38, e2023GB008033, https://doi.org/10.1029/2023GB008033, 2024. a
Britten, G. L., Wakamatsu, L., and Primeau, F. W.: The temperature-ballast hypothesis explains carbon export efficiency observations in the Southern Ocean, Geophys. Res. Lett., 44, 1831–1838, https://doi.org/10.1002/2016GL072378, 2006. a
Brix, H., Currie, K. I., and Fletcher, S. E. M.: Seasonal variability of the carbon cycle in subantarctic surface water in the South West Pacific, Global Biogeochem. Cy., 27, 200–211, https://doi.org/10.1002/gbc.20023, 2013. a
Closset, I., Cardinal, D., Bray, S. G., Thil, F., Djouraev, I., Rigual-Hernández, A. S., and Trull', T. W.: Seasonal variations, origin, and fate of settling diatoms in the Southern Ocean tracked by silicon isotope records in deep sediment traps, Global Biogeochem. Cy., 29, 1495–1510, https://doi.org/10.1002/2015GB005180, 2015. a
Conte, M., Pedrosa-Pamies, R., Weber, J., and Johnson, R.: The climatology of the deep particle flux in the oligotrophic western North Atlantic gyre, 1978–2022, Prog. Oceanogr., p. 103433, https://doi.org/10.1016/j.pocean.2025.103433, 2025. a
Couespel, D., Lévy, M., and Bopp, L.: Oceanic primary production decline halved in eddy-resolving simulations of global warming, Biogeosciences, 18, 4321–4349, https://doi.org/10.5194/bg-18-4321-2021, 2021. a
Cresswell, G.: Currents of the continental shelf and upper slope of Tasmania, Papers and Proceedings of the Royal Society of Tasmania, 133, 21–30, https://doi.org/10.26749/rstpp.133.3.21, 2000. a
Currie, K. I., Reid, M. R., and Hunter, K. A.: Interannual variability of carbon dioxide drawdown by subantarctic surface waters near New Zealand, Biogeochemistry, 107, 23–34, https://doi.org/10.1007/s10533-009-9355-3, 2011. a
Davies, D. M., Jansen, P., and Trull, T. W.: Southern Ocean Time Series (SOTS) Quality Assessment and Control Report Remote Access Sampler Sample Analysis. Macronutrient analysis. Version 1.0, Tech. rep., CSIRO, Hobart, Australia, https://doi.org/10.26198/5e156a63a8f75, 2020. a, b
Dickson, A. G.: Standard potential of the reaction:
Dickson, A. G., Sabine, C. L., and Christian, J. R. (Eds.): Guide to Best Practices for Ocean CO2 Measurement, PICES Special Publication 3, ISBN 1-897176-07-4, 2007. a
Duke, P. J., Hamme, R. C., Ianson, D., Landschützer, P., Ahmed, M. M. M., Swart, N. C., and Covert, P. A.: Estimating marine carbon uptake in the northeast Pacific using a neural network approach, Biogeosciences, 20, 3919–3941, https://doi.org/10.5194/bg-20-3919-2023, 2023. a, b
Eriksen, R. S., Trull, T. W., Davies, D., Jansen, P., Davidson, A. T., Westwood, K., and van den Enden, R.: Seasonal succession of phytoplankton community structure from autonomous sampling at the Australian Southern Ocean Time Series (SOTS) observatory, Mar. Ecol. Prog. Ser., 589, 13–31, https://doi.org/10.3354/meps12420, 2018. a, b, c
Eriksen, R. S., Davies, D. M., Wynn-Edwards, C. A., and Trull, T. W.: Southern Ocean Time Series (SOTS) Quality Assessment and Control Report Remote Access Sampler Sample Analysis. Phytoplankton analysis. Version 1.0, Tech. rep., CSIRO, Hobart, Australia, https://doi.org/10.26198/5f115475407b3, 2020. a, b, c, d
Fassbender, A. J., Savine, C. L., and Cronin, M. F.: Net community production and calcification from 7 years of NOAA Station Papa Mooring measurements, Global Biogeochem. Cy., 30, 250–267, https://doi.org/10.1002/2015GB005205, 2016. a, b
Gnanadesikan, A., Russell, J. L., and Fanrong Zeng: How does ocean ventilation change under global warming?, Ocean Sci., 3, 43–53, https://doi.org/10.5194/os-3-43-2007, 2007. a
Henson, S. A., Sanders, R., and Madsen, E.: Global patterns in efficiency of particulate organic carbon export and transfer to the deep ocean: export and transfer efficiency, Global Biogeochem. Cy., 26, GB1028, https://doi.org/10.1029/2011GB004099, 2012. a
Herraiz-Borreguero, L. and Rintoul, S. R.: Subantarctic Mode Water variability influenced by mesoscale eddies south of Tasmania, J. Geophys. Res., 115, C4, https://doi.org/10.1029/2008jc005146, 2010. a, b
Herraiz-Borreguero, L. and Rintoul, S. R.: Regional circulation and its impact on upper ocean variability south of Tasmania (Australia), Deep-Sea Res. Pt. II, 58, 2071–2081, 2011. a
Honda, M. C., Imai, K., Nojiri, Y., Hoshi, F., Sugawara, T., and Kusakabe, M.: The biological pump in the northwestern North Pacific based on fluxes and major components of particulate matter obtained by sediment-trap experiments (1997–2000), Deep-Sea Res. Pt. II, 49, 5595–5625, https://doi.org/10.1016/S0967-0645(02)00201-1, 2002. a
Imai, K., Nojiri, Y., Tsurushima, N., and Saino, T.: Time series of seasonal variation of primary productivity at station KNOT (44°N, 155°E) in the sub-arctic western North Pacific, Deep-Sea Res. Pt. II, 49, 5395–5408, 2002. a
Ishii, M., Kosugi, N., Sasano, D., Saito, S., Midorikawa, T., and Inoue, H. Y.: Ocean acidification off the south coast of Japan: a result from time series observations of CO2 parameters from 1994 to 2008, J. Geophys. Res., 116, C06022, https://doi.org/10.1029/2010JC006831, 2011. a
Jansen, P., Shadwick, E. H., and Trull, T. W.: Southern Ocean Time Series (SOTS): Multi-year Gridded Product Version 1.1, Tech. rep., CSIRO, Hobart, Australia, https://doi.org/10.26198/ae20-8c83, 2022a. a
Jansen, P., Shadwick, E. H., and Trull, T. W.: Southern Ocean Time Series (SOTS) Quality Assessment and Control Report Salinity Records Version 2.0, Tech. rep., CSIRO, Hobart, Australia, https://doi.org/10.26198/rv8y-2q14, 2022b. a
Jansen, P., Shadwick, E. H., and Trull, T. W.: Southern Ocean Time Series (SOTS) Quality Assessment and Control Report Temperature Records Version 2.0, Tech. rep., CSIRO, Hobart, Australia, https://doi.org/10.26198/gfgr-fq47, 2022c. a, b
Jansen, P., Wynn-Edwards, C. A., Shadwick, E. H., and Trull, T. W.: Southern Ocean Time Series (SOTS) Quality Assessment and Control Report Oxygen Records Version 1.0, Tech. rep., CSIRO, Hobart, Australia, https://doi.org/10.26198/1te4-jq81, 2023. a
King, A. L. and Howard, W. R.: Planktonic foraminiferal flux seasonality in Subantarctic sediment traps: a test for paleoclimate reconstructions, Paleoceanography, 18, 1019, https://doi.org/10.1029/2002PA000839 2003. a, b
Koelling, J., Atamanchuk, D., Karstensen, J., Handmann, P., and Wallace, D. W. R.: Oxygen export to the deep ocean following Labrador Sea Water formation, Biogeosciences, 19, 437–454, https://doi.org/10.5194/bg-19-437-2022, 2022. a
Latour, P., Strzepek, R. F., Wuttig, K., van der Merwe, P., Bach, L. T., Eggins, S., Boyd, P. W., Ellwood, M. J., Pinfold, T. L., and Bowie, A. R.: Seasonality of phytoplankton growth limitation by iron and manganese in subantarctic waters, Elementa: Science of the Anthropocene, 11, 00022, https://doi.org/10.1525/elementa.2023.00022, 2023. a
Lee, K., Kim, T.-W., Byrne, R. H., Millero, F. J., Feely, R. A., and Liu, Y.-M.: The universal ratio of boron to chlorinity for the North Pacific and North Atlantic Oceans, Geochim. Cosmochim. Ac., 74, 1801–1811, https://doi.org/10.1016/j.gca.2009.12.027, 2000. a
Lewis, E. and Wallace, D. W. R.: Program Developed for CO2 Systems Calculations, ORNL/CDIAC 105, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory US Department of Energy, Oak Ridge, Tennessee, https://doi.org/10.2172/639712, 1998. a
Lueker, T. J., Dickson, A. G., and Keeling, C. D.: Ocean pCO2 calculated from dissolved inorganic carbon, alkalinity, and equations for K1 and K2: validation based on laboratory measurements of CO2 in gas and seawater at equilibrium, Mar. Chem., 70, 105–119, https://doi.org/10.1016/S0304-4203(00)00022-0, 2000. a
McCartney, K., Witkowski, J., Jordan, R., Daugbjerg, N., Malinverno, E., van Wezel, R., Kano, H., Abe, K., Scott, F., Schweizer, M., Young, J., Hallegraeff, G., and Shiozawa, A.: Fine structure of silicoflagellate double skeletons, Mar. Micropaleontol., 113, 10–19, https://doi.org/10.1016/j.marmicro.2014.08.006, 2024. a
McClish, S., Bushinsky, S., Briggs, N., and Douglas, C.: Seasonal re-entrainment of respired organic matter decouples Southern Ocean surface production and annual net community production, ESS Open Archive, February 04, 2025, https://doi.org/10.22541/essoar.173867523.39087309/v1, 2025. a
McKinley, G. A., Takahashi, T., Buitenhuis, E., Chai, F., Christian, J. R., Doney, S. C., Jiang, M.-S., Lindsay, K., Moore, J. K., Quéré, C. L., Lima, I., Murtugudde, R., Shi, L., and Wetzel, P.: North Pacific carbon cycle response to climate variability on seasonal to decadal timescales, J. Geophys. Res., 111, C07S06, https://doi.org/10.1029/2005JC003173, 2009. a
Mortenson, E., Lenton, A., Shadwick, E. H., Ttrull, T. W., Chamberlain, M., and Zhang, X.: Divergent trajectories of ocean warming and acidification, Environ. Res. Lett., 16, 124063, https://doi.org/10.1088/1748-9326/ac3d57, 2021. a
Moy, A. D., Howard, W., Bray, S. G., and Trull, T.: Reduced calcification in modern Southern Ocean planktonic foraminifera, Nat. Geosci., 2, 276–280, https://doi.org/10.1038/NGEO460, 2009. a, b, c
Ono, H., Kosugi, N., Toyama, K., Tsujino, H., Kojima, A., Enyo, K., Iida, Y., Nakano, T., and Ishii, M.: Acceleration of ocean acidification in the Western North Pacific, Geophys. Res. Lett., 46, 13161–13169, https://doi.org/10.1029/2019GL085121, 2019. a, b
Pardo, P. C., Tilbrook, B., van Ooijen, E., Passmore, A., Neill, C., Jansen, P., Sutton, A. J., and Trull, T. W.: Surface ocean carbon dioxide variability in South Pacific boundary currents and Subantarctic waters, Nat. Sci. Rep.-UK, 9, 7592, https://doi.org/10.1038/s41598-019-44109-2, 2019. a, b, c, d, e
Parslow, J. S., Boyd, P. W., Rintoul, S. R., and Griffiths, F. B.: A persistent sub-surface chlorophyll maximum in the Polar Frontal Zone south of Australia: seasonal progression and implications for phytoplankton-light-nutrient interactions, J. Geophys. Res., 106, 31543–31557, https://doi.org/10.1029/2000jc000322, 2001. a
Perez, F. F. and Fraga, F.: Association constant of fluoride and hydrogen ions in seawater, Mar. Chem., 21, 161–168, https://doi.org/10.1016/0304-4203(87)90036-3, 1987. a
Rapizo, H., Babanin, A. V., Schulz, E., Hemer, M. A., and Durrant, T. H.: Observation of wind-waves from a moored buoy in the Southern Ocean, Ocean Dynam., 65, 1275–1288, https://doi.org/10.1007/s10236-015-0873-3, 2015. a
Rees, C., Pender, L., Sherrin, K., Schwanger, C., Hughes, P., Tibben, S., Marouchos, A., and Rayner, M.: Methods for reproducible shipboard SFA nutrient measurement using RMNS and automated data processing, Limnol. Oceanogr. Methods, 17, 25–41, https://doi.org/10.1002/lom3.10294, 2019. a
Ridgway, K. R.: Long-term trend and decadal variability of the southward penetration of the East Australian Current, Geopys. Res. Lett., 34, L13613, https://doi.org/10.1029/2007GL030393 2007. a
Riebesell, U., Zondervan, I., Rost, B., Tortell, P. D., Zeebe, R. E., and Morel, F. M. M.: Reduced calcification of marine plankton in response to increased atmospheric CO2, Nature, 407, 364–367, https://doi.org/10.1038/35030078, 2000. a
Rigual-Hernández, A. S., Trull, T. W., Bray, S. G., and Armand, L.: The fate of diatom valves in the Subantarctic and Polar Frontal Zones of the Southern Ocean: sediment trap versus surface sediment assemblages, Palaeogeogr. Palaeocl., 457, 129–143, https://doi.org/10.1016/j.palaeo.2016.06.004, 2016. a
Rigual Hernández, A. S., Flores, J. A., Sierro, F. J., Fuertes, M. A., Cros, L., and Trull, T. W.: Coccolithophore populations and their contribution to carbonate export during an annual cycle in the Australian sector of the Antarctic zone, Biogeosciences, 15, 1843–1862, https://doi.org/10.5194/bg-15-1843-2018, 2018. a
Rigual-Hernández, A. S., Trull, T., Flores, J. A., Nodder, S., Eriksen, R., Davies, D., Hallegraeff, G. M., Sierro, F. J., Patil, S. M., Cortina, A., Ballegeer, A. M., Northcote, L. C., Abrantes, F., and Rufino, M. M.: Full annual monitoring of Subantarctic Emiliania huxleyi populations reveals highly calcified morphotypes in high-CO2 winter conditions, Sci. Rep.-UK, 10, 1–14, https://doi.org/10.1038/s41598-020-59375-8, 2020a. a, b, c, d, e, f
Rigual Hernández, A. S., Trull, T. W., Nodder, S. D., Flores, J. A., Bostock, H., Abrantes, F., Eriksen, R. S., Sierro, F. J., Davies, D. M., Ballegeer, A.-M., Fuertes, M. A., and Northcote, L. C.: Coccolithophore biodiversity controls carbonate export in the Southern Ocean, Biogeosciences, 17, 245–263, https://doi.org/10.5194/bg-17-245-2020, 2020b. a, b, c, d
Rigual-Hernández, A. S., Langer, G., Sierro, F. J., Bostock, H., Sanchez-Santos, J. M., Nodder, D. D., Trull, T. W., Ballegeer, A. M., Moy, A. D., Eriksen, R., Makowka, L., Bejard, T. M., Rigal-Munoz, F. H., Hernandez-Marin, A., Zorita-Viota, M., and Flores, J. A.: Reduction in size of the calcifying phytoplankton Calcidiscus leptoporus to environmental changes between the Holocene and modern Subantarctic Southern Ocean, Frontiers in Marine Science, 10, 1–14, https://doi.org/10.3389/fmars.2023.1159884, 2023. a
Rigual-Hernández, A., Sánchez-Santos, J., Eriksen, R., Moy, A., Sierro, F., Flores, J., Abrantes, F., Bostock, H., Nodder, S., González-Lanchas, A., and Trull, T.: Limited variability in the phytoplankton Emiliania huxleyi since the pre-industrial era in the Subantarctic Southern Ocean, Anthropocene, 31, 100254, https://doi.org/10.1016/j.ancene.2020.100254, 2020. a
Rintoul, S. R. and Bullister, J. L.: A late winter hydrographic section from Tasmania to Antarctica, Deep-Sea Res. Pt. I, 46, 1417–1454, https://doi.org/10.1016/S0967-0637(99)00013-8, 1999. a
Rintoul, S. R. and England, M. H.: Ekman transport dominates local air–sea fluxes in driving variability of Subantarctic mode water, J. Phys. Oceanogr., 32, 1308–1321, https://doi.org/10.1175/1520-0485(2002)032<1308:ETDLAS>2.0.CO;2, 2002. a
Roemmich, D. and Gilson, J.: The 2004–2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program, Prog. Oceanogr., 82, 81–100, https://doi.org/10.1016/j.pocean.2009.03.004, 2009. a
Sabine, C. L., Feely, R. A., Gruber, N., Key, R. M., Lee, K., Bullister, J. L., Wanninkhof, R., Wong, C. S., Wallace, D. W. R., Tilbrook, B., Millero, F. J., Peng, T.-H., Kozyr, A., Ono, T., and Rios, A. F.: The oceanic sink for anthropogenic CO2, Science, 305, 367–371, 2004. a
Sarmiento, J. L., Gruber, N., Brzezinski, M. A., and Dunner, J. P.: High-latitude control of thermocline nutrients and low latitude biological productivity, Nature, 427, 56–60, https://doi.org/10.1038/nature02204, 2004. a
Sathyendranath, S., Brewin, R. J., Brockmann, C., Brotas, V., Calton, B., Chuprin, A., Cipollini, P., Couto, A. B., Dingle, J., Doerffer, R., Donlon, C., Dowell, M., Farman, A., Grant, M., Groom, S., Horseman, A., Jackson, T., Krasemann, H., Lavender, S., Martinez-Vicente, V., Mazeran, C., Mélin, F., Moore, T. S., Müller, D., Regner, P., Roy, S., Steele, C. J., Steinmetz, F., Swinton, J., Taberner, M., Thompson, A., Valente, A., Zühlke, M., Brando, V. E., Feng, H., Feldman, G., Franz, B. A., Frouin, R., Gould, R. W., Hooker, S. B., Kahru, M., Kratzer, S., Mitchell, B. G., Muller-Karger, F. E., Sosik, H. M., Voss, K. J., Werdell, J., and Platt, T.: An ocean-colour time series for use in climate studies: the experience of the Ocean-Colour Climate Change Initiative (OC-CCI), Sensors, 19, 4285, https://doi.org/10.3390/s19194285, 2019. a
Schallenberg, C., Jansen, P., and Trull, T. W.: Southern Ocean Time Series (SOTS) Quality Assessment and Control Report Wetlabs FLNTUS instruments Version 2.0, Tech. rep., CSIRO, Hobart, Australia, https://doi.org/10.26198/5c4a932ca8ae4, 2017. a
Schallenberg, C., Harley, J. W., Jansen, P., Davies, D. M., and Trull, T. W.: Multi-year observations of fluorescence and backscatter at the Southern Ocean Time Series (SOTS) shed light on two distinct seasonal bio-optical regimes, Frontiers in Marine Science, 6, 1–19, https://doi.org/10.3389/fmars.2019.00595, 2019. a, b
Schallenberg, C., Strzepek, R. F., Schuback, N., Clementson, L. A., Boyd, P. W., and Trull, T. W.: Diel quenching of Southern Ocean phytoplankton fluorescence is related to iron limitation, Biogeosciences, 17, 793–812, https://doi.org/10.5194/bg-17-793-2020, 2020. a
Sedwick, P. N., DiTullio, G. R., Hutchins, D. A., Boyd, P. W., Griffiths, F. B., Crossley, A. C., Trull, T. W., and Queguiner, B.: Limitation of algal growth by iron deficiency in the Australian Subantarctic region, Geophys. Res. Lett., 26, 2865–2868, 1999. a
Shadwick, E. H., Trull, T. W., Tilbrook, B., Sutton, A. J., Schulz, E., and Sabine, C. L.: Seasonality of biological and physical controls on surface ocean CO2 from hourly observations at the Southern Ocean Time Series site south of Australia, Global Biogeochem. Cy., 29, 1–16, https://doi.org/10.1002/2014GB004906, 2015. a, b, c, d, e, f, g, h, i, j, k, l, m, n
Shadwick, E. H., Davies, D. M., Jansen, P., and Trull, T. W.: Southern Ocean Time Series (SOTS) Quality Assessment and Control Report Remote Access Sampler: Total Alkalinity and Total Dissolved Inorganic Carbon Analyses, 2009–2018. Version 1.0, Tech. rep., CSIRO, Hobart, Australia, https://doi.org/10.26198/5f3f23c8b51d6, 2020. a, b
Shadwick, E. H., Rigual-Hernández, A., Eriksen, R., Jansen, P., Davis, D., Wynn-Edwards, C., Sutton, A., Schallenberg, C., Schulz, E., and Trull, T. W.: Changes in Southern Ocean biogeochemistry and the potential impact on pH-sensitive planktonic organisms, Oceanography, 34, 14–15, https://doi.org/10.5670/oceanog.2021.supplement.02-06, 2021. a, b
Shadwick, E. H., Wynn-Edwards, C. A., Davies, D. M., Jansen, P., Bray, S. G., Eriksen, R., and Trull, T. W.: Southern Ocean Time Series (SOTS) Datasets, Australian Ocean Data Network [data set], https://portal.aodn.org.au/ (last access: 22 July 2025), 2025. a
Sharp, J. D., Pierrot, D., Humphreys, M. P., Epitalon, J.-M., Orr, J. C., Lewis, E. R., and Wallace, D. W. R.: CO2SYSv3 for MATLAB (Version 3.2.1), Tech. rep., Zenodo [code], https://doi.org/10.5281/zenodo.7552554, 2023. a
Sun, Y., Wynn-Edwards, C. A., Trull, T. W., and Ellwood, M. J.: The role of Acantharia in Southern Ocean strontium cycling and carbon export: insights from dissolved strontium concentrations and seasonal flux patterns, Global Biogeochem. Cy., 38, e2024GB008227, https://doi.org/10.1029/2024GB008227, 2024. a
Sutton, A. J., Sabine, C. L., Maenner-Jones, S., Lawrence-Slavas, N., Meinig, C., Feely, R. A., Mathis, J. T., Musielewicz, S., Bott, R., McLain, P. D., Fought, H. J., and Kozyr, A.: A high-frequency atmospheric and seawater pCO2 data set from 14 open-ocean sites using a moored autonomous system, Earth Syst. Sci. Data, 6, 353–366, https://doi.org/10.5194/essd-6-353-2014, 2014. a, b
Sutton, A. J., Wanninkhof, R., Sabine, C., Feely, R., Cronin, M. F., and Weller, R. A.: Variability and trends in surface seawater pCO2 and CO2 flux in the Pacific Ocean, Geophys. Res. Lett., 44, 5627–5636, https://doi.org/10.1002/2017GL073814, 2017. a, b, c
Sutton, A. J., Feely, R. A., Maenner-Jones, S., Musielwicz, S., Osborne, J., Dietrich, C., Monacci, N., Cross, J., Bott, R., Kozyr, A., Andersson, A. J., Bates, N. R., Cai, W.-J., Cronin, M. F., De Carlo, E. H., Hales, B., Howden, S. D., Lee, C. M., Manzello, D. P., McPhaden, M. J., Meléndez, M., Mickett, J. B., Newton, J. A., Noakes, S. E., Noh, J. H., Olafsdottir, S. R., Salisbury, J. E., Send, U., Trull, T. W., Vandemark, D. C., and Weller, R. A.: Autonomous seawater pCO2 and pH time series from 40 surface buoys and the emergence of anthropogenic trends, Earth Syst. Sci. Data, 11, 421–439, https://doi.org/10.5194/essd-11-421-2019, 2019. a
Sutton, A. J., Battisti, R., Carter, B., Evans, W., Newton, J., Alin, S., Bates, N. R., Cai, W.-J., Currie, K., Feely, R. A., Sabine, C., Tanhua, T., Tilbrook, B., and Wanninkhof, R.: Advancing best practices for assessing trends of ocean acidification time series, Frontiers in Marine Science, 9, 1045667, https://doi.org/10.3389/fmars.2022.1045667, 2022. a
Takahashi, T., Sutherland, S. C., Wanninkhof, R., Sweeney, C., Feely, R. A., Chipman, D. W., Hales, B., Friederich, G., Chavez, F., Sabine, C., Watson, A., Bakker, D. C., Schuster, U., Metzl, N., Yoshikawa-Inoue, H., Ishii, M., Midorikawa, T., Nojiri, Y., Körtzinger, A., Steinhoff, T., Hoppema, M., Olafsson, J., Arnarson, T. S., Tilbrook, B., Johannessen, T., Olsen, A., Bellerby, R., Wong, C., Delille, B., Bates, N., and de Baar, H. J.: Climatological mean and decadal changes in surface ocean pCO2, and net sea-air CO2 flux over the global oceans, Deep-Sea Res. Pt. II, 56, 554–577, 2009. a
Tamsitt, V., Cerovecki, I., Josey, S. A., Gille, S. T., and Schulz, E.: Mooring observations of air–sea heat fluxes in two subantarctic mode water formation regions, J. Climate, 33, 2757–2777, https://doi.org/10.1175/JCLI-D-19-0653.1, 2020. a, b
Thompson, A. F., Dove, L. A., Flint, E., Lacour, L., and Boyd, P. W.: Interactions between multiple physical particle injection pumps in the Southern Ocean, Global Biogeochem. Cy., 38, e2024GB008122, https://doi.org/10.1029/2024GB008122, 2024. a
Timothy, D., Wong, C., Barwell-Clarke, J., Page, J., White, L., and Macdonald, R.: Climatology of sediment flux and composition in the subarctic Northeast Pacific Ocean with biogeochemical implications, Prog. Oceanogr., 116, 95–129, https://doi.org/10.1016/j.pocean.2013.06.017, 2013. a
Traill, C. D., Weiss, J., Wynn-Edwards, C., Perron, M. M. G., Chase, Z., and Bowie, A. R.: Lithogenic particle flux to the subantarctic Southern Ocean: a multi-tracer estimate using sediment trap samples, Global Biogeochem. Cy., 36, e2022GB007391, https://doi.org/10.1029/2022GB007391, 2022. a, b
Traill, C. D., Conde-Pardo, P., Rohr, T., van der Merwe, P., Townsend, A. T., Latour, P., Gault-Ringold, M., Wuttig, K., Corkill, M., Holmes, T. M., Warner, M. J., Shadwick, E., and Bowie, A. R.: Mechanistic constraints on the drivers of Southern Ocean meridional iron distributions between Tasmania and Antarctica, Global Biogeochem. Cy., 38, e2023GB007856, https://doi.org/10.1029/2023GB007856, 2024. a
Trull, T. W., Jansen, P., Schulz, E., Weeding, B., Davies, D. M., and Bray, S. G.: Autonomous multi-trophic observations of productivity and export at the Australian Southern Ocean Time Series (SOTS) reveal sequential mechanisms of physical-biological coupling, Frontiers in Marine Science, 6, 525, https://doi.org/10.3389/fmars.2019.00525, 2019. a, b, c, d, e, f, g, h, i
van der Merwe, P., Trull, T. W., Goodwin, T., Jansen, P., and Bowie, A.: The autonomous clean environmental (ACE) sampler: a trace-metal clean seawater sampler suitable for open-ocean time-series applications, Limnol. Oceanogr. Methods, 17, 490–504, https://doi.org/10.1002/lom3.10327, 2011. a
van Heuven, S., Pierrot, D., Rae, J., Lewis, E., and Wallace, D.: CO2SYS v 1.1, MATLAB program developed for CO2 system calculations. ORNL/CDIAC-105b, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. DoE, Oak Ridge, TN, 2011. a
Wakita, M., Watanabe, S., Murata, A., Tsurushima, N., and Honda, M.: Decadal change of dissolved inorganic carbon in the subarctic western North Pacific Ocean, Tellus B, 62, 608–620, https://doi.org/10.1111/j.1600-0889.2010.00476.x, 2010. a, b, c
Westberry, T., Behrenfeld, M. J., Siegel, D. A., and Boss, E.: Carbon-based primary productivity modelling with vertically resolved photoacclimation, Global Biogeochem. Cy., 22, GB2024, https://doi.org/10.1029/2007GB003078, 2008. a
Wilks, J. V. and Armand, L. K.: Diversity and taxonomic identification of Shionodiscus spp. in the Australian sector of the Subantarctic Zone, Diatom Res., 32, 295–307, 2017. a
Wilks, J. V., Rigual-Hernández, A. S., Trull, T. W., Bray, S. G., Flores, J.-A., and Armand, L. K.: Biogeochemical flux and phytoplankton succession: a year-long sediment trap record in the Australian sector of the Subantarctic Zone, Deep-Sea Res. Pt. I, 121, 143–159, 2017. a
Wong, C. S. and Matear, R. J.: Sporadic silicate limitation of phytoplankton productivity in the subarctic NE Pacific, Deep-Sea Res. Pt. II, 46, 2539–2555, 1999. a
Wynn-Edwards, C. A., Davies, D. M., Jansen, P., Shadwick, E. H., and Trull, T. W.: Southern Ocean Time Series. SOTS Annual Reports: 2018/2019, Report 1. Overview. Version 1.0, Tech. rep., CSIRO, Hobart, Australia, https://doi.org/10.26198/r9ny-r549, 2020a (data available at: https://catalogue-imos.aodn.org.au/geonetwork/srv/eng/catalog.search#/metadata/afc166ce-6b34-44d9-b64c-8bb10fd43a07, last access: 22 July 2025). a
Wynn-Edwards, C. A., Davies, D. M., Shadwick, E. H., and Trull, T. W.: Southern Ocean Time Series. SOTS Quality assessment and control report. Sediment trap particle fluxes Version 1.0., Tech. rep., CSIRO, Hobart, Australia, https://doi.org/10.26198/5dfad21358a8d, 2020b. a, b
Wynn-Edwards, C. A., Shadwick, E. H., Davies, D. M., Bray, S. G., Jansen, P., Trinh, R., and Trull, T. W.: Particle fluxes at the Australian Southern Ocean Time Series (SOTS) achieve organic carbon sequestration at rates close to the global median, are dominated by biogenic carbonates, and show no temporal trends over 20-years, Front. Earth Sci., 8, 329, https://doi.org/10.3389/feart.2020.00329, 2020c. a, b, c, d, e, f
Wynn-Edwards, C. A., Shadwick, E. H., Jansen, P., Schallenberg, C., Maurer, T. L., and Sutton, A. J.: Subantarctic pCO2 estimated from a biogeochemical float: comparison with moored observations reinforces the importance of spatial and temporal variability, Frontiers in Marine Science, 10, 1231953, https://doi.org/10.3389/fmars.2023.1231953, 2023. a
Yang, X., Wynn-Edwards, C. A., Strutton, P., and Shadwick, E. H.: Carbon export in the subantarctic zone revealed by multi-year observations from biogeochemical-Argo floats and sediment traps, Global Biogeochem. Cy., 38, e2024GB008135, https://doi.org/10.1029/2024GB008135, 2024b. a, b, c
Short summary
The Southern Ocean Time Series acquires observations in subantarctic waters south of Australia. We present the seasonality in hydrography, biogeochemistry, phytoplankton community composition, and particulate organic and inorganic carbon export to the deep sea using observations collected between 1997 and 2022. We also review recent research underpinned by these observations and emphasize the value of long time series for understanding ocean processes and responses to a changing climate.
The Southern Ocean Time Series acquires observations in subantarctic waters south of Australia....
