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Recent recovery of Antarctic Bottom Water formation in the Ross Sea driven by climate anomalies

Nature Geoscience volume 13, pages 780–786 (2020)Cite this article

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Abstract

Antarctic Bottom Water (AABW) supplies the lower limb of the global overturning circulation, ventilates the abyssal ocean and sequesters heat and carbon on multidecadal to millennial timescales. AABW originates on the Antarctic continental shelf, where strong winter cooling and brine released during sea ice formation produce Dense Shelf Water, which sinks to the deep ocean. The salinity, density and volume of AABW have decreased over the last 50 years, with the most marked changes observed in the Ross Sea. These changes have been attributed to increased melting of the Antarctic Ice Sheet. Here we use in situ observations to document a recovery in the salinity, density and thickness (that is, depth range) of AABW formed in the Ross Sea, with properties in 2018–2019 similar to those observed in the 1990s. The recovery was caused by increased sea ice formation on the continental shelf. Increased sea ice formation was triggered by anomalous wind forcing associated with the unusual combination of positive Southern Annular Mode and extreme El Niño conditions between 2015 and 2018. Our study highlights the sensitivity of AABW formation to remote forcing and shows that climate anomalies can drive episodic increases in local sea ice formation that counter the tendency for increased ice-sheet melt to reduce AABW formation.

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Fig. 1: Recovery of AABW formed in the Ross Sea.
Fig. 2: Link between DSW salinity, sea ice production and import.
Fig. 3: Sea ice changes in the Ross Sea.
Fig. 4: Interannual variability of winds and sea ice in the western Amundsen Sea.
Fig. 5: Anomalous climate forcing between 2015 and 2018.
Fig. 6: Schematic illustrating the physical mechanisms driving enhanced AABW formation in the Ross Sea.

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Data availability

Oceanographic data were collected and made publicly available by the International Global Ship-based Hydrographic Investigations Program (http://www.go-ship.org/), by the National Oceanic and Atmospheric Administration (NOAA) (https://www.nodc.noaa.gov), by the International Argo Program and the national programmes that contribute to it (http://www.argodatamgt.org; http://www.argo.ucsd.edu; http://argo.jcommops.org), by the Italian National Antarctic Research Programme (http://morsea.uniparthenope.it) and during Nathaniel B. Palmer expeditions in 2013 and 2018 as part of TRACERS (https://doi.org/10.1594/IEDA/320068) and CICLOPS (https://www.bco-dmo.org/dataset/783911). Atmospheric data are provided by the ECMWF ERA5 reanalysis (https://go.nature.com/2J6PvuY). The National Snow and Ice Data Center provides the satellite-derived data used in this study: sea ice concentration and brightness temperature (https://nsidc.org/data/G02202/versions/3; https://nsidc.org/data/AU_SI12/versions/1; https://nsidc.org/data/smmr_ssmi) and sea ice motion (https://nsidc.org/data/NSIDC-0116/versions/4).

Climate indices are provided by the British Antarctic Survey (SAM: https://legacy.bas.ac.uk/met/gjma/sam.html) and by the National Centre for Atmospheric Research (SOI: https://go.nature.com/2Tz3TOJ).

Code availability

MATLAB scripts used for the analyses described in this study can be obtained from the corresponding author on reasonable request.

References

  1. Orsi, A. H., Johnson, G. C. & Bullister, J. L. Circulation, mixing, and production of Antarctic bottom water. Prog. Oceanogr. 43, 55–109 (1999).

    Google Scholar 

  2. Lumpkin, R. & Speer, K. Global ocean meridional overturning. J. Phys. Oceanogr. 37, 2550–2562 (2007).

    Google Scholar 

  3. Johnson, G. C. Quantifying Antarctic Bottom Water and North Atlantic Deep Water volumes. J. Geophys. Res. 113, C05027 (2008).

    Google Scholar 

  4. de Lavergne, C., Madec, G., Roquet, F., Holmes, R. & McDougall, T. Abyssal ocean overturning shaped by seafloor distribution. Nature 551, 181–186 (2017).

    Google Scholar 

  5. Sigman, D. M. & Boyle, E. A. Glacial/interglacial variations in atmospheric carbon dioxide. Nature 407, 859–869 (2000).

    Google Scholar 

  6. Ferrari, R. et al. Antarctic sea ice control on ocean circulation in present and glacial climates. Proc. Natl Acad. Sci. USA 111, 8753–8758 (2014).

    Google Scholar 

  7. Nihashi, S. & Ohshima, K. I. Circumpolar mapping of Antarctic coastal polynyas and landfast sea ice: relationship and variability. J. Clim. 28, 3650–3670 (2015).

    Google Scholar 

  8. Rintoul, S. R. Rapid freshening of Antarctic Bottom Water formed in the Indian and Pacific oceans. Geophys. Res. Lett. 34, L06606 (2007).

    Google Scholar 

  9. Jacobs, S. S. & Giulivi, C. F. Large multidecadal salinity trends near the Pacific–Antarctic continental margin. J. Clim. 23, 4508–4524 (2010).

    Google Scholar 

  10. Purkey, S. G. & Johnson, G. C. Antarctic bottom water warming and freshening: contributions to sea level rise, ocean freshwater budgets, and global heat gain. J. Clim. 26, 6105–6122 (2013).

    Google Scholar 

  11. Menezes, V. V., Macdonald, A. M. & Schatzman, C. Accelerated freshening of Antarctic Bottom Water over the last decade in the Southern Indian Ocean. Sci. Adv. 3, e1601426 (2017).

  12. Gordon, A. L., Orsi, A., Muench, R. & Visbeck, M. Western Ross Sea continental slope gravity currents. Deep Sea Res. II 56, 796–817 (2009).

    Google Scholar 

  13. Shimada, K., Aoki, S., Ohshima, K. I. & Rintoul, S. R. Influence of Ross Sea Bottom Water changes on the warming and freshening of the Antarctic Bottom Water in the Australian–Antarctic Basin. Ocean Sci. 8, 419–432 (2012).

    Google Scholar 

  14. Orsi, A. H. & Wiederwohl, C. L. A recount of Ross Sea waters. Deep Sea Res. II 56, 778–795 (2009).

    Google Scholar 

  15. Jendersie, S., Williams, M. J., Langhorne, P. J. & Robertson, R. The density‐driven winter intensification of the Ross Sea circulation. J. Geophys. Res. Oceans 123, 7702–7724 (2018).

    Google Scholar 

  16. Nakayama, Y., Timmermann, R., Rodehacke, C. B., Schröder, M. & Hellmer, H. H. Modeling the spreading of glacial meltwater from the Amundsen and Bellingshausen Seas. Geophys. Res. Lett. 41, 7942–7949 (2014).

    Google Scholar 

  17. Castagno, P. et al. Rebound of shelf water salinity in the Ross Sea. Nat. Commun. 10, 5441 (2019).

    Google Scholar 

  18. van Wijk, E. M. & Rintoul, S. R. Freshening drives contraction of Antarctic Bottom Water in the Australian Antarctic Basin. Geophys. Res. Lett. 41, 1657–1664 (2014).

    Google Scholar 

  19. Gordon, A. L., Huber, B. A. & Busecke, J. Bottom water export from the western Ross Sea, 2007 through 2010. Geophys. Res. Lett. 42, 5387–5394 (2015).

    Google Scholar 

  20. Budillon, G., Castagno, P., Aliani, S., Spezie, G. & Padman, L. Thermohaline variability and Antarctic Bottom Water formation at the Ross Sea shelf break. Deep Sea Res. I 58, 1002–1018 (2011).

    Google Scholar 

  21. Tamura, T., Ohshima, K. I., Nihashi, S. & Hasumi, H. Estimation of surface heat/salt fluxes associated with sea ice growth/melt in the southern ocean. SOLA 7, 17–20 (2011).

    Google Scholar 

  22. Tamura, T., Ohshima, K. I., Fraser, A. D. & Williams, G. D. Sea ice production variability in Antarctic coastal polynyas. J. Geophys. Res. 121, 2967–2979 (2016).

    Google Scholar 

  23. Holland, P. R. & Kimura, N. Observed concentration budgets of Arctic and Antarctic sea ice. J. Clim. 29, 5241–5249 (2016).

    Google Scholar 

  24. Comiso, J. C., Kwok, R., Martin, S. & Gordon, A. L. Variability and trends in sea ice extent and ice production in the Ross Sea. J. Geophys. Res. 116, C04021 (2011).

    Google Scholar 

  25. Drucker, R., Martin, S. & Kwok, R. Sea ice production and export from coastal polynyas in the Weddell and Ross Seas. Geophys. Res. Lett. 38, L17502 (2011).

    Google Scholar 

  26. Kwok, R., Pang, S. S. & Kacimi, S. Sea ice drift in the Southern Ocean: regional patterns, variability, and trends. Elem. Sci. Anth. 5, 32 (2017).

    Google Scholar 

  27. Porter, D. F. et al. Evolution of the seasonal surface mixed layer of the Ross Sea, Antarctica, observed with autonomous profiling floats. J. Geophys. Res. Oceans 124, 4934–4953 (2019).

    Google Scholar 

  28. Rignot, E. et al. Four decades of Antarctic ice sheet mass balance from 1979–2017. Proc. Natl Acad. Sci. USA 116, 1095–1103 (2019).

    Google Scholar 

  29. Nicholls, K. W. & Østerhus, S. Interannual variability and ventilation timescales in the ocean cavity beneath Filchner–Ronne Ice Shelf, Antarctica. J. Geophys. Res. 109, C04014 (2004).

    Google Scholar 

  30. Holland, P. R. The seasonality of Antarctic sea ice trends. Geophys. Res. Lett. 41, 4230–4237 (2014).

    Google Scholar 

  31. Fogt, R. L., Bromwich, D. H. & Hines, K. M. Understanding the SAM influence on the South Pacific ENSO teleconnection. Clim. Dyn. 36, 1555–1576 (2011).

    Google Scholar 

  32. Gordon, A. L., Huber, B., McKee, D. & Visbeck, M. A seasonal cycle in the export of bottom water from the Weddell Sea. Nat. Geosci. 3, 551–556 (2010).

    Google Scholar 

  33. McKee, D. C., Yuan, X., Gordon, A. L., Huber, B. A. & Dong, Z. Climate impact on interannual variability of Weddell Sea Bottom Water. J. Geophys. Res. 116, C05020 (2011).

    Google Scholar 

  34. Abrahamsen, E. P. et al. Stabilization of dense Antarctic water supply to the Atlantic Ocean overturning circulation. Nat. Clim. Change 9, 742–746 (2019).

    Google Scholar 

  35. Fyfe, J. C., Saenko, O. A., Zickfeld, K., Eby, M. & Weaver, A. J. The role of poleward-intensifying winds on Southern Ocean warming. J. Clim. 20, 5391–5400 (2007).

    Google Scholar 

  36. Sigmond, M., Reader, M. C., Fyfe, J. C. & Gillett, N. P. Drivers of past and future Southern Ocean change: stratospheric ozone verses greenhouse gas impact. Geophys. Res. Lett. 38, L12601 (2011).

    Google Scholar 

  37. Cai, W. et al. Increasing frequency of extreme El Niño events due to greenhouse warming. Nat. Clim. Change 4, 111–116 (2014).

    Google Scholar 

  38. Lim, E. et al. Continuation of tropical Pacific Ocean temperature trend may weaken extreme El Niño and its linkage to the Southern Annular Mode. Sci. Rep. 9, 17044 (2019).

    Google Scholar 

  39. Lago, V. & England, M. H. Projected slowdown of Antarctic Bottom Water formation in response to amplified meltwater contributions. J. Clim. 32, 6319–6335 (2019).

    Google Scholar 

  40. Silvano, A. et al. Freshening by glacial meltwater enhances melting of ice shelves and reduces formation of Antarctic Bottom Water. Sci. Adv. 4, eaap9467 (2018).

    Google Scholar 

  41. Heuzé, C., Heywood, K. J., Stevens, D. P. & Ridley, J. K. Southern Ocean bottom water characteristics in CMIP5 models. Geophys. Res. Lett. 40, 1409–1414 (2013).

    Google Scholar 

  42. Arndt, J. E. et al. The International Bathymetric Chart of the Southern Ocean (IBCSO) Version 1.0—a new bathymetric compilation covering circum-Antarctic waters. Geophys. Res. Lett. 40, 3111–3117 (2013).

    Google Scholar 

  43. Boyer, T. P. et al. World Ocean Database 2013 NOAA Atlas NESDIS No. 72 (eds Levitus, S. & Mishonov, A.) 209 (NOAA, 2013); https://doi.org/10.7289/V5NZ85MT

  44. Johnson, G. C. & Orsi, A. H. Southwest Pacific Ocean water-mass changes between 1968/69 and 1990/91. J. Clim. 10, 306–316 (1997).

    Google Scholar 

  45. Roemmich, D. et al. Deep SOLO: a full-depth profiling float for the Argo Program. J. Atmos. Ocean. Technol. 36, 1967–1981 (2019).

    Google Scholar 

  46. McDougall, T. J. & Barker, P. M. Getting Started with TEOS-10 and the Gibbs Seawater (GSW) Oceanographic Toolbox (SCOR/IAPSO WG127, 2011).

  47. Hersbach, H. & Dee, D. ERA5 reanalysis is in production. ECMWF Newsletter No. 147 https://go.nature.com/31Oo0gl(2016).

  48. Meier, W. N., et al. NOAA/NSIDC Climate Data Record of Passive Microwave Sea Ice Concentration Version 3 (National Snow and Ice Data Center, 2017).

  49. Meier, W. N., Markus, T. & Comiso, J. C. AMSR-E/AMSR2 Unified L3 Daily 12.5 km Brightness Temperatures, Sea Ice Concentration, Motion & Snow Depth Polar Grids Version 1 (National Snow and Ice Data Center, 2018).

  50. Tschudi, M., Meier, W. N., Stewart, J. S., Fowler, C. & Maslanik, J. Polar Pathfinder Daily 25 km EASE-Grid Sea Ice Motion Vectors Version 4 (National Snow and Ice Data Center, 2019).

  51. Kimura, N. Sea ice motion in response to surface wind and ocean current in the Southern Ocean. J. Meteorol. Soc. Jpn 82, 1223–1231 (2004).

    Google Scholar 

  52. Kwok, R. Ross Sea ice motion, area flux, and deformation. J. Clim. 18, 3759–3776 (2005).

    Google Scholar 

  53. Lytle, V. I. & Ackley, S. F. Heat flux through sea ice in the western Weddell Sea: convective and conductive processes. J. Geophys. Res. 101, 8853–8868 (1996).

    Google Scholar 

  54. Lytle, V. I. et al. Ice formation in the Mertz Glacier Polynya, East Antarctica, during winter. Ann. Glaciol. 33, 368–372 (2001).

    Google Scholar 

  55. Marshall, G. J. Trends in the Southern Annular Mode from observations and reanalyses. J. Clim. 16, 4134–4143 (2003).

    Google Scholar 

  56. Dinniman, M. S., Klinck, J. M., Hofmann, E. E. & Smith, W. O. Effects of projected changes in wind, atmospheric temperature, and freshwater inflow on the Ross Sea. J. Clim. 31, 1619–1635 (2018).

    Google Scholar 

  57. Shepherd, A. et al. Mass balance of the Antarctic Ice Sheet from 1992 to 2017. Nature 556, 219–222 (2018).

    Google Scholar 

  58. Jenkins, A. et al. West Antarctic Ice Sheet retreat in the Amundsen Sea driven by decadal oceanic variability. Nat. Geosci. 11, 733–738 (2018).

    Google Scholar 

  59. Holland, P. R. et al. West Antarctic ice loss influenced by internal climate variability and anthropogenic forcing. Nat. Geosci. 12, 718–724 (2019).

    Google Scholar 

  60. Paolo, F. S. et al. Response of Pacific-sector Antarctic ice shelves to the El Niño/Southern Oscillation. Nat. Geosci. 11, 121–126 (2018).

    Google Scholar 

  61. Stern, A. A., Adcroft, A. & Sergienko, O. The effects of Antarctic iceberg calving-size distribution in a global climate model. J. Geophys. Res. Oceans 121, 5773–5788 (2016).

    Google Scholar 

  62. Merino, N. et al. Antarctic icebergs melt over the Southern Ocean: climatology and impact on sea ice. Ocean Model. 104, 99–110 (2016).

    Google Scholar 

  63. Rackow, T. et al. Simulation of small to giant Antarctic iceberg evolution: differential impact on climatology estimates. J. Geophys. Res. Oceans 122, 3170–3190 (2017).

    Google Scholar 

  64. Castagno, P., Falco, P., Dinniman, M. S., Spezie, G. & Budillon, G. Temporal variability of the circumpolar deep water inflow onto the Ross Sea continental shelf. J. Mar. Syst. 166, 37–49 (2017).

    Google Scholar 

  65. Worby, A. P. et al. Thickness distribution of Antarctic sea ice. J. Geophys. Res. 113, C05S92 (2008).

    Google Scholar 

Download references

Acknowledgements

This research was supported by the Centre for Southern Hemisphere Oceans Research (CSHOR), a partnership between the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Qingdao National Laboratory for Marine Science, as well as the Antarctic Climate and Ecosystems Cooperative Research Centre, the Australian Antarctic Program Partnership and the Earth Systems and Climate Change Hub of the Australian Government’s National Environmental Science Program. A.S., P.R.H. and A.C.N.G. acknowledge funding from NERC (grant number NE/SO11994/1). F.A.H. was supported by SNSF grant numbers P2EZP2_175162 and P400P2_186681 and NSF grant number PLR-1425989.

Author information

Authors and Affiliations

  1. Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, UK

    Alessandro Silvano & Alberto C. Naveira Garabato

  2. CSIRO Oceans & Atmosphere, Hobart, Tasmania, Australia

    Alessandro Silvano, Annie Foppert & Stephen R. Rintoul

  3. Centre for Southern Hemisphere Oceans Research, Hobart, Tasmania, Australia

    Alessandro Silvano, Annie Foppert & Stephen R. Rintoul

  4. Australian Antarctic Program Partnership, University of Tasmania, Hobart, Tasmania, Australia

    Annie Foppert & Stephen R. Rintoul

  5. British Antarctic Survey, Cambridge, UK

    Paul R. Holland & F. Alexander Haumann

  6. National Institute of Polar Research, Tachikawa, Japan

    Takeshi Tamura

  7. SOKENDAI, Graduate University for Advanced Studies, Tachikawa, Japan

    Takeshi Tamura

  8. Atmosphere and Ocean Research Institute, The University of Tokyo, Tokyo, Japan

    Noriaki Kimura

  9. Department of Sciences and Technologies, Parthenope University, Naples, Italy

    Pasquale Castagno, Pierpaolo Falco & Giorgio Budillon

  10. Consorzio Nazionale Interuniversitario per le Scienze del Mare, Rome, Italy

    Pierpaolo Falco & Giorgio Budillon

  11. Atmospheric and Oceanic Sciences, Princeton University, Princeton, NJ, USA

    F. Alexander Haumann

  12. Woods Hole Oceanographic Institution, Woods Hole, MA, USA

    Alison M. Macdonald

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  1. Alessandro Silvano
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Contributions

A.S. and S.R.R. conceived the study. A.S., A.F. and S.R.R. analysed the oceanographic data. S.R.R., P.C., P.F., G.B. and A.M.M. collected part of the oceanographic data used in this study. A.S., P.R.H., T.T. and N.K. analysed the sea ice and atmospheric data. F.A.H. and A.C.N.G. provided essential insight in the interpretation of the observations. A.S. wrote the manuscript with input from all the coauthors.

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Correspondence to Alessandro Silvano.

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Extended data

Extended Data Fig. 1 Easterly winds at the shelf break of the western Ross Sea.

Following Gordon et al.19, winds are obtained by rotating the coordinate system clockwise by 40° to follow shelf break isobaths and are spatially averaged in the box 70S°-75°S, 175°E-175°W. Monthly data are in black while data temporally averaged between February and April are in red. The ‘Feb-Apr winds’ are shown because the strongest wind-driven export of DSW from the western Ross Sea continental shelf occurs in these months19.

Extended Data Fig. 2 Salinification of dense waters on the eastern Ross Sea continental shelf.

a, Time series of absolute salinity (g kg-1) collected by a profiling float (WMO: 5904150) between late 2013 and early 2017 (map in c). b, same as a for conservative temperature (°C). d, e same a, b for another profiling float (WMO: 5904152) between late 2013 and early 2018. f, Time series of salinity averaged in the bottom 200 m of the water column for water cooler than -1.85 °C for float 5904150 (red) and 5904152 (black).

Extended Data Fig. 3 Link between DSW salinity and sea ice production.

a, Yearly sea ice formation (km 3) over the entire Ross Sea continental shelf (solid black), Ross Ice Shelf (red) and Terra Nova Bay (blue) polynyas. Polynyas are defined as areas where yearly sea ice formation is larger than 5 m (see Fig. 3). Solid green is DSW absolute salinity (g kg-1) in Terra Nova Bay17. b, Same as a for anomalies. c, Correlation between DSW salinity and yearly sea ice formation (colors the same as a, dashed black line represents the 99% confidence interval). Sea ice production leads DSW salinity.

Extended Data Fig. 4 Sea ice motion and fluxes.

Winter climatology of a, winds (m s-1) from ERA5, b, sea ice motion (m s-1) from Pathfinder and c, sea ice motion from the Kimura dataset. d, Winter sea ice area inflow (105 km2) into the southern Ross Sea through the meridional transect shown in red in a. Estimates are obtained using the wind-approximation for sea ice motion and CDR for sea ice concentration (green), Pathfinder for sea ice motion and CDR for sea ice concentration (blue), and the Kimura dataset for sea ice motion and AMSR-E/AMSR2 for sea ice concentration (red). The three estimates agree reasonably well with each other. e, Winter sea ice area flux through a transect that encloses the Ross Sea continental shelf (green line in a). The dashed (dotted) lines indicate sea ice flowing into (out of) the Ross Sea continental shelf. The net (solid) is a proxy for how much sea ice forms on the continental shelf. Note how the wind approximation fails in representing the export, but it well captures the inflow.

Extended Data Fig. 5 Link between sea ice formation and import.

a, In blue is the yearly (November to October) anomaly of sea ice area (105 km2) imported from the Amundsen Sea into the Ross Sea between 1992 and 2018, calculated across the gate shown in red in Extended Data Fig. 4a. Note that the y-axis is reversed. Overlaid in black is the yearly (March to October) anomaly of sea ice production (km3) over the Ross Sea continental shelf (as shown in Extended Data Fig. 3b). b, Summer (November to February) anomaly of imported sea ice area and early winter (March to May) sea ice production anomaly. c, Winter (March to October) anomaly of imported sea ice area and sea ice production anomaly in late winter (June to October). Correlations between time series shown in each panel are in red.

Extended Data Fig. 6 Ross Sea continental shelf spatial averages.

a, Southerly winds (m s-1). Monthly data are in black, while values temporally averaged over summer and winter months are in red and blue, respectively. b, Surface air temperature (°C). Black and red lines as in a. c, Sea ice area (105 km2) lost on the Ross Sea continental shelf due to sea ice melting (see sea ice concentration budget in the Methods). The values are obtained from the time integration of the residual term between November and February, further integrated over the continental shelf. Only negative values (which in summer is mostly due to melting) are included in the calculation.

Extended Data Fig. 7 Winter climate indices.

Anomalies of SAM (black) and SOI (red) during winter.

Extended Data Fig. 8 Wind multiple regression analysis.

As Fig. 5 but including the multiple regression of SOI and SAM onto winds, instead of showing geostrophic winds derived by the mean sea level pressure.

Extended Data Fig. 9 Sea ice concentration budget.

a (b) Winter climatology of the divergence (residual) term of the sea ice concentration budget (see Methods). Values indicate sea ice concentration change over the winter season associated with divergence/residual term. Positive values indicate a source of sea ice (that is more divergence is negative, while more sea ice formation is positive). c (d) Anomalies of the divergence (residual) term temporally averaged between 2015 and 2018. Climatologies are calculated using all available years (that is 2003-2010 and 2013-2018). Here anomalies are the deviations from the climatologies. Overlaid in a (c) are vectors representing the winter climatology (2015-2018 anomaly) of sea ice drift (‘Kimura’23).

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Silvano, A., Foppert, A., Rintoul, S.R. et al. Recent recovery of Antarctic Bottom Water formation in the Ross Sea driven by climate anomalies. Nat. Geosci. 13, 780–786 (2020). https://doi.org/10.1038/s41561-020-00655-3

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