The role of the Southern Ocean in sea-level change

Dr Zhang

Project leader: Dr Xuebin Zhang (CSIRO)

Staff, students and associates: Prof Xianyao Chen (OUC); Prof John Church (UNSW); Prof Mat King (UTAS); Dr Yuehua (Veronica) Li (UNSW); Dr Kewei Lyu (CSIRO); Dr Steven Phipps (UTAS); Dr Christopher Watson (UTAS); Miss Jinping Wang (Ocean University of China PhD Student); Mr Jingwei Zhang (UTAS PhD Student).

[Music plays and animation waves appear moving up from the bottom of the screen and text appears above: The Centre for Southern Hemisphere Oceans Research]

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Xuebin Zhang: This project is going to address some scientific questions related to the sea level change such as the ocean heat uptake and redistribution in the Southern Ocean, and the contribution of the Antarctic ice sheet to the sea level change

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and regional distribution of sea level and associated underlying dynamic process in the Southern Ocean.

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Oh yeah, it’s a very important question to understand the sea level rise because in the past like two or three decades the research community already made very good progress in understanding and project in sea level changes but a significant gap still exists and the decision maker and the end user, they want much better information than what we can deliver right now.

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The Southern Ocean is one of the few key areas where the heat is up, particularly in the ocean, and secondly warming in the Southern Ocean is critical for the dynamic response of the Antarctic ice sheet.

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I hope through this project we can achieve better understanding and the projecting of the sea level rise, so this information can be used for better mitigation and habitation planning for sea level rise.

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Dr Xuebin Zhang introduces the Southern Ocean sea level change project

Latest news

Predicting Tropical Pacific decadal climate variability and change

1 October 2021

Tropical Pacific decadal climate variability and change (TPDV) affects the global climate system, extreme weather events, agricultural production, streamflow, marine and terrestrial ecosystems, and biodiversity. Although major international efforts are underway to provide decadal climate predictions, there is still a great deal of uncertainty. A review article by Power et al. (Including Cai, W., Zhang, X., and Wang, G.) (2021), published in Science, critically synthesises what is known and not known about the characteristics and causes of TPDV, and the accuracy to which it can be simulated and predicted. The article concludes with recommendations to improve our understanding of and ability to predict TPDV.

Read the review article at this link.

Projected ocean warming constrained by the ocean observational record

14 September, 2021

An accurate estimate of global ocean warming is critical in tracking the Earth’s energy imbalance and assessing the status of current and future climate change. In a paper published in Nature Climate Change, CSHOR researchers, Drs Lyu and Zhang and Prof Church, report that improved ocean observations in the past 15 years can be used to reduce uncertainties in climate model projections of 21st century ocean warming.

Further detail, including a link to the publication, Dr Lyu’s interview, and an article in The Conversation, is available here.

Link to CSHOR science seminar project presentation, July 2021

Reconciling global mean and regional sea level change in projections and observations

15 February 2021

A study led by Ocean University of China and CSHOR student, Jinping Wang, and published in Nature Communications, finds climate model projections of sea level rise in the early 21st century are in good agreement with sea level data recorded in the corresponding period. Read more at this link.

Prof John Church Elected to the AGU Fellows Class of 2020

18 November 2020

Prof John Church was elected to the AGU Fellows Class of 2020 for his exceptional contribution to the American Geophysical Union’s (AGU’s) Earth and space sciences community. Dr Church is a Professor at UNSW’s Climate Change Research Centre (CCRC), and collaborates with CSHOR’s Southern Ocean and sea-level change.

Project objectives

Sea-level rise is an important climate change research topic. Global mean sea level (GMSL) has been rising according to tide gauge and satellite altimetry observations, and is projected to continue to rise, with a likely range between 0.28 m and 0.98 m by 2100. A larger rise could occur if there is a significantly larger contribution from changes in Antarctic dynamics. Over 100 million people live within a metre of current high tide mark, thus are highly likely to be affected by sea-level rise. Several processes can affect GMSL, including ocean thermal expansion, mass loss of glaciers and ice caps, the Antarctic Ice Sheet and the Greenland Ice Sheet, and changes in the land-water storage.

The Southern Ocean is a key area for improving projections of ocean heat content and sea-level change because: it is one of the key areas where heat enters the ocean, resulting in heat storage in the upper ocean and in the abyssal layers, and contributing to ocean thermal expansion; and a warming ocean is critical to the dynamic response of the Antarctic ice sheet.

Key objectives of the project are to:

  1. Quantify the amount of heat entering the Southern Ocean and associated sea-level change.
  2. Separate the impact of wind-induced vs Antarctic freshwater-induced ocean responses, and natural versus anthropogenic forcing in sea level and ocean dynamics in the SO;
  3. Examine the robustness of the dipole structure of sea-level change (centred at ~50oS) in coarse resolution models to the impacts of meso-scale eddies by comparing coarse-resolution and eddy-resolving model results, and analyse whether there are distinct responses to strengthening vs shifting of westerly winds.
  4. Refine sea-level projections based on updated observations and projections of the Antarctica Ice Sheet contribution, together with other sea level contributions.

To achieve above objectives, we will use available observations, Climate Model Intercomparison Project (CMIP) models, and an eddy-resolving (1/10o) global ocean model. For the projection of Ice Sheet contribution, we will use either stand-alone or coupled ice sheet modelling from the Ice Sheet Model Intercomparison for CMIP6.

Publications

Albrecht, F., O. Pizarro, A. Montecinos and X. Zhang (2019). Understanding Sea Level Change in the South Pacific during the late 20th and early 21st Century. Journal of Geophysical Research: Oceans, 124. https://doi.org/10.1029/2018JC014828.

Carson, M., Lyu, K., Richter, K., Becker, M., Domingues, C. M., Han, W., & Zanna, L. (2019). Climate Model Uncertainty and Trend Detection in Regional Sea Level Projections: A Review. Surveys in Geophysics. https://doi.org/10.1007/s10712-019-09559-3.

Chen, X. Y., Zhang, X. B., Church, J. A., Watson, C. S., King, M. A., Monselesan, D., Legrésy, B., & Harig, C. (2017). The increasing rate of global mean sea-level rise during 1993-2014. Nature Climate Change, 7(7), 492-497. http://www.nature.com/articles/nclimate3325.

Gregory, J., et al. (2019). Concepts and Terminology for Sea Level: Mean, Variability and Change, Both Local and Global. Surveys in Geophysics. https://doi.org/10.1007/s10712-019-09525-z.

Grose, M., S. Narsey, F. Delage, A. Dowdy, M. Bador, G. Boschat, C. Chung, J. Kajtar, S. Rauniyar, M. Freund, K. Lyu, H. Rashid, X. Zhang, S. Wales, C. Trenham, N. Holbrook, T. Cowan, L. Alexander, J. Arblaster and S. Power (2020). Insights from CMIP6 for Australia’s future climate. Earth’s Future, 8, e2019EF001469. https://doi.org/10.1029/2019EF001469.

Han, W., Stammer, D., Thompson, P., Ezer, T., Palanisamy, H., Zhang, X., . . . Yuan, D. (2019). Impacts of Basin-Scale Climate Modes on Coastal Sea Level: a Review. Surveys in Geophysics. https://doi.org/10.1007/s10712-019-09562-8.

Hayashida, H., R.J. Matear, P. G. Strutton and X. Zhang (2020). Insights into projected changes in marine heatwaves from a high-resolution ocean circulation model. Nature Communications, 11, 4352. https://doi.org/10.1038/s41467-020-18241-x .

Irving, D., W. Hobbs, J. Church, and J. Zika (2020). A Mass and Energy Conservation Analysis of Drift in the CMIP6 Ensemble.2020. Journal of Climate, online release. https://doi.org/10.1175/JCLI-D-20-0281.1.

Jin, Y., X. Zhang, J. A. Church and X. Bao (2021). Projected sea-level changes in the marginal seas near China based on dynamical downscaling. Journal of Climate, https://doi.org/10.1175/JCLI-D-20-0796.1.

King, M. A., and C. S. Watson (2020). Antarctic Surface Mass Balance: natural variability, noise and detecting new trends. Geophysical Research Letters, 47, e2020GL087493. https://doi.org/10.1029/2020GL087493.

Li, Z., N. J. Holbrook, X. Zhang, E. C. J. Oliver, and E. A. Cougnon (2020). Remote Forcing of Tasman Sea Marine Heatwaves. Journal of Climate, 33(12), 5337–5354. https://doi.org/10.1175/JCLI-D-19-0641.1.

Li, S., W. Liu, K. Lyu and X. Zhang (2021). The effects of stratospheric ozone depletion on Southern Ocean heat uptake and storage. Climate Dynamics, https://doi.org/10.1007/s00382-021-05803-y.

Liu, W., M. I. Hegglin, R. Checa-Garcia, S. Li, N. P. Gillett, K. Lyu, X. Zhang and N. C. Swart (2022). Disentangling the impacts of stratospheric ozone depletion and tropospheric ozone increases on Southern Ocean warming. Nature Climate Change, 12, 365–372, https://doi.org/10.1038/s41558-022-01320-w.

Lyu, K., X. Zhang, J. A. Church and Q. Wu (2020). Processes responsible for the Southern Hemisphere ocean heat uptake and redistribution under anthropogenic warming, Journal of Climate, 33(9), 3787-3807. https://doi.org/10.1175/JCLI-D-19-0478.1.

Lyu, K., X. Zhang, and J. A. Church (2020). Regional Dynamic Sea Level Simulated in the CMIP5 and CMIP6 Models: Mean Biases, Future Projections, and Their Linkages. Journal of Climate, 33(15), 6377–6398. https://doi.org/10.1175/JCLI-D-19-1029.1.

Lyu, K., Zhang, X. & Church, J.A. (2021). Projected ocean warming constrained by the ocean observational record. Nature Climate Change. https://doi.org/10.1038/s41558-021-01151-1.

Meyssignac,  Benoit, Tim Boyer, Zhongxiang Zhao, Maria Z Hakuba, Felix W Landerer, Detlef Stammer, Armin Köhl, Seiji Kato, Tristan L’Ecuyer, Michael Ablain, John Patrick Abraham, Alejandro Blazquez, Anny Cazenave, John A Church, Rebecca Cowley, Lijing Cheng, Catia Domingues, Donata Giglio, Viktor Gouretski, Masayoshi Ishii, Gregory C Johnson, Rachel E Killick, David Legler, William Llovel, John Lyman, Matthew Dudley Palmer, Steve Piotrowicz, Sarah Purkey, Dean Roemmich, Rémy Roca, Abhishek Savita, Karina von Schuckmann, Sabrina Speich, Graeme Stephens, Gongjie G Wang, Susan Elisabeth Wijffels, Nathalie Zilberman (2019). Measuring Global Ocean Heat Content to estimate the Earth Energy Imbalance. Frontiers in Marine Science, 6(432). https://doi.org/10.3389/fmars.2019.00432.

Mortenson, E., A. Lenton, E. Shadwick, T. Trull, M. Chamberlain and X. Zhang, 2021. Divergent trajectories of ocean warming and acidification, Environmental Research Letters, in press, https://doi.org/10.1088/1748-9326/ac3d57.

Phipps, S. J., Roberts, J. L., and King, M. A. (2021). An iterative process for efficient optimisation of parameters in geoscientific models: a demonstration using the Parallel Ice Sheet Model (PISM) version 0.7.3, Geoscientific Model Development, https://doi.org/10.5194/gmd-2020-382.

Ponte, R. M., Carson, M., Cirano, M., Domingues, C. M., Jevrejeva, S., Marcos, M., . . . Zhang, X. (2019). Towards Comprehensive Observing and Modeling Systems for Monitoring and Predicting Regional to Coastal Sea Level. Frontiers in Marine Science, 6(437). https://www.frontiersin.org/article/10.3389/fmars.2019.00437.

Power. S., Lengaigne, M., Capotondi, A. et al. (Including Cai, W., Zhang, X. and Wang G.) (2021). Decadal climate variability in the tropical Pacific: Characteristics, causes, predictability, and prospects. Science 374 (6563), eaay9165. https://doi.org/10.1126/science.aay9165.

Richter, K., Benoit, M., Aimée, B. A. S., Angélique, M., John, A. C., Xavier, F., . . . Nicolas, C. (2020). Detecting a forced signal in satellite-era sea-level change. Environmental Research Letters. https://iopscience.iop.org/article/10.1088/1748-9326/ab986e.

Savita, A., C. M. Domingues, T. Boyer, V. Gouretski, M. Ishii, G. C. Johnson, J. M. Lyman, J. K. Willis, S. J. Marsland, W. Hobbs, J. A. Church, D. P. Monselesan, P. Dobrohotoff, R. Cowley and S. E. Wijffels (2021). Quantifying spread in spatio-temporal changes of upper-ocean heat content estimates: an internationally coordinated comparison. Journal of Climate. https://doi.org/10.1175/JCLI-D-20-0603.1.

Sohail, T., D. B. Irving, J. D. Zika, R. M. Holmes and J. A. Church (2021). Fifty year trends in global ocean heat content traced to surface heat fluxes in the sub-polar ocean. Geophysical Research Letters, 48, e2020GL091439, https://doi.org/10.1029/2020GL091439.

Sohail, T., J. D. Zika, D. B. Irving, and J. A. Church (2022). Observed poleward freshwater transport since 1970. Nature, 602, 617-622, https://doi.org/10.1038/s41586-021-04370-w.

Stammer , D., van de Wal, R. S. W., Nicholls, R. J., Church, J. A., Le Cozannet, G., Lowe, J. A., et al. (2019). Framework for high‐end estimates of sea level rise for stakeholder applications. Earth’s Future, 7, 923–938. https://doi.org/10.1029/2019EF001163.

Todd, A., L. Zanna, M. Couldrey, J. Gregory, Q. Wu, J. Church, R. Farneti, R. Navarro-Labastida, K. Lyu, O. Saenko, D.Yang and X. Zhang (2020). Ocean-only FAFMIP: understanding regional patterns of ocean heat content and dynamic sea level change. Journal of Advances in Modelling Earth Systems, 12(8).  https://doi.org/10.1029/2019MS002027.

Van de Wal, R.S.W., X. Zhang, S. Minobe, S. Jevrejeva, R.E.M. Riva, C. Little, K. Richter and M. Palmer (2019). Uncertainties in Long‑Term Twenty‑First Century Process‑Based Coastal Sea‑Level Projections. Surveys in Geophysics, 40, 1655-1671. https://doi.org/10.1007/s10712-019-09575-3.

Wang, J., Church, J. A., Zhang, X., Gregory, J. M., Zanna, L., & Chen, X. (2021). Evaluation of the local sea-level budget at tide gauges since 1958. Geophysical Research Letters, 48, e2021GL094502. https://doi.org/10.1029/2021GL094502.

Wang, J., Church, J.A., Zhang, X. Chen, X. (2021). Reconciling global mean and regional sea level change in projections and observations. Nature Communications, 12, 990. https://doi.org/10.1038/s41467-021-21265-6.

Wang, L., Lyu, K., Zhuang, W., Zhang, W., Makarim, S., & Yan, X. H. (2021). Recent shift in the warming of the southern oceans modulated by decadal climate variability. Geophysical Research Letters, 48, e2020GL090889. https://doi.org/10.1029/2020GL090889.

Wu, Q., X. Zhang, J. A. Church, and J. Hu (2019). ENSO-related Global Ocean Heat Content Variations, Journal of Climate, 32, 45-68. https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-17-0861.1.

Wu, Q., X. Zhang, J.A. Church, J. Hu, J. Gregory (2021). Evolving patterns of sterodynamic sea-level rise under mitigation scenarios and insights from linear system theory. Climate Dynamics, https://doi.org/10.1007/s00382-021-05727-7.