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Supercooled Southern Ocean Waters

Haumann, F. Alexander and Moorman, Ruth and Riser, Stephen C. and Smedsrud, Lars H. and Maksym, Ted and Wong, Annie P. S. and Wilson, Earle A. and Drucker, Robert and Talley, Lynne D. and Johnson, Kenneth S. and Key, Robert M. and Sarmiento, Jorge L. (2020) Supercooled Southern Ocean Waters. Geophysical Research Letters, 47 (20). Art. No. e2020GL090242. ISSN 0094-8276.

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In cold polar waters, temperatures sometimes drop below the freezing point, a process referred to as supercooling. However, observational challenges in polar regions limit our understanding of the spatial and temporal extent of this phenomenon. We here provide observational evidence that supercooled waters are much more widespread in the seasonally ice‐covered Southern Ocean than previously reported. In 5.8% of all analyzed hydrographic profiles south of 55°S, we find temperatures below the surface freezing point (“potential” supercooling), and half of these have temperatures below the local freezing point (“in situ” supercooling). Their occurrence doubles when neglecting measurement uncertainties. We attribute deep coastal‐ocean supercooling to melting of Antarctic ice shelves and surface‐induced supercooling in the seasonal sea‐ice region to wintertime sea‐ice formation. The latter supercooling type can extend down to the permanent pycnocline due to convective sinking plumes—an important mechanism for vertical tracer transport and water‐mass structure in the polar ocean.

Item Type:Article
Related URLs:
URLURL TypeDescription ItemData ItemData ItemData ItemData ItemData
http://www.argo.ucsd.eduRelated ItemInternational Argo Program
http://argo.jcommops.orgRelated ItemInternational Argo Program
Haumann, F. Alexander0000-0002-8218-977X
Moorman, Ruth0000-0001-5054-1559
Riser, Stephen C.0000-0002-8593-312X
Smedsrud, Lars H.0000-0001-7391-0740
Maksym, Ted0000-0003-3164-1882
Wong, Annie P. S.0000-0003-3305-1640
Wilson, Earle A.0000-0003-2329-5115
Talley, Lynne D.0000-0003-1574-729X
Johnson, Kenneth S.0000-0001-5513-5584
Sarmiento, Jorge L.0000-0001-5219-2604
Additional Information:© 2020 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Issue Online: 22 October 2020; Version of Record online: 22 October 2020; Accepted manuscript online: 09 October 2020; Manuscript accepted: 26 September 2020; Manuscript revised: 23 September 2020; Manuscript received: 07 August 2020. F. A. H. was supported by the Swiss National Science Foundation (SNSF; Schweizerischer Nationalfonds zur Förderung der wissenschaftlichen Forschung) grant numbers P2EZP2_175162 and P400P2_186681. This work was supported by the National Science Foundation (NSF) Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) Project under the NSF Award PLR‐1425989. R. M. would like to thank the National Oceanic and Atmospheric Administration (NOAA) GFDL for mentorship and computational support. S. R. was also supported by the U.S. Argo grant and NOAA grant NA15OAR4320063 to the University of Washington. L. H. S. thanks the Fulbright Foundation for the U.S.‐Norway Arctic Chair grant. We are deeply thankful to the large number of scientists, technicians, and funding agencies contributing to these databases, being responsible for the collection and quality control of the high‐quality data that form the basis of this work. We thank Josh Plant for his initial notification on very low temperatures observed in some of the float profiles. We would also like to thank the students, teachers, and schools who are participating in the SOCCOM Adopt‐a‐Float program. Four of the floats used in this study were adopted and have a clear signal of supercooling. These participants are listed in Table S1. Data Availability Statement: All data used in this study are openly available in these repositories and cited in the references (,,,, and Argo data were collected and made freely available by the International Argo Program and the national programs that contribute to it ( and The Argo Program is part of the Global Ocean Observing System. The marine mammal data were collected and made freely available by the International MEOP Consortium and the national programs that contribute to it ( Ship‐based CTD data were made freely available by World Ocean Database 2018 and the national programs that contributed to it.
Funding AgencyGrant Number
Swiss National Science Foundation (SNSF)P2EZP2_175162
Swiss National Science Foundation (SNSF)P400P2_186681
National Oceanic and Atmospheric Administration (NOAA)NA15OAR4320063
Fulbright FoundationUNSPECIFIED
Subject Keywords:Southern Ocean; supercooling; sea ice; ice shelf; observations; convection
Issue or Number:20
Record Number:CaltechAUTHORS:20201012-163632248
Persistent URL:
Official Citation:Haumann, F. A., Moorman, R., Riser, S. C., Smedsrud, L. H., Maksym, T., Wong, A. P. S., et al. (2020). Supercooled Southern Ocean waters. Geophysical Research Letters, 47, e2020GL090242.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106006
Deposited By: George Porter
Deposited On:13 Oct 2020 17:11
Last Modified:29 Oct 2020 18:02

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