Thermodynamics of sea ice phase composition revisited

Martin Vancoppenolle (Lead Author), Gurvan Madec, Max Thomas, Trevor J. McDougall

Research output: Contribution to journalArticle

5 Citations (Scopus)
14 Downloads (Pure)

Abstract

Pure ice, brine and solid minerals are the main contributors to sea ice mass. Constitutional changes with salinity and temperature exert a fundamental control on sea ice physical, chemical, and biological properties. However, current estimation methods and model representations of the sea ice phase composition suffer from two limitations—in a context of poorly quantified uncertainties. First, salt minerals are neglected. Second, formulations are inconsistent with international standards, in particular with the International Thermodynamic Equation of Seawater (TEOS-10). To address these issues, we revisit the thermodynamics of the sea ice phase composition by confronting observations, theory, and the usual computation methods. We find remarkable agreement between observations and the Gibbs-Pitzer theory as implemented in FREZCHEM, both for brine salinity (RMSE=1.9g/kg) and liquid H2O mass fraction(RMSE=8.6g/kg). On this basis, we propose expanded sea ice phase composition equations including minerals, expressed in terms of International Temperature Scale 1990 temperature and absolute salinity,and valid down to the eutectic temperature (−36.2◦C). These equations precisely reproduce FREZCHEM,outcompeting currently used calculation techniques. We also suggest a modification of the TEOS-10seawater Gibbs function giving a liquidus curve consistent with observations down to the eutectic temperature without changing TEOS-10 inside its original validity range.
Original languageEnglish
Pages (from-to)615-634
Number of pages20
JournalJournal of Geophysical Research - Oceans
Volume124
Issue number1
Early online date28 Dec 2018
DOIs
Publication statusPublished - Jan 2019

Keywords

  • Sea ice
  • Thermodynamics
  • phase
  • minerals

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