The effect of composition on the density of Indian Ocean waters

Frank J Millero, Jason Waters, Ryan Woosley, Fen Huang, Mareva Chanson

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The conductivity and density was measured on samples collected in the Indian Ocean during the I9 Climate Variability and Predictability (CLIVAR) cruise. The relative densities ρ-ρ0 were compared to those determined from the equation of state of seawater. The excess densities Δρ=ρMeasCalc ranged from 0 in surface waters to 0.025 kg m-3 in deep waters due to additions of nutrients and carbonates. The values Δρ were found to be a linear function of the increases of TA, TCO2, Si(OH)4 and NO3 in the deep waters (σ=0.004-0.005 kg m-3). The correlations with changes in Si(OH)4 gave the best estimates since the concentrations do not have a large effect on the conductivity. By combining the Indian and earlier Pacific measurements (N=249), we have103Δρ/kg m-3=0.12+104ΔSi(OH)4(σ=0.0041 kg m-3). These results indicate that the effect of changes in the composition of seawater for most of the world oceans can be estimated from the combined results in the Pacific and Indian oceans. The excess densities can also be accounted for by determining the change in the absolute salinity of seawater, defined as SA=S+ΔS, where S is the conductivity salinity and ΔS is equal to the mass of added nutrients and carbonates. SA can then be used in the equation of state to calculate the density (σ=0.0041×10-6 kg m-3). Measurements made on artificial seawater (S=35) agree with the values determined from the equations of state, indicating that the dissolved organic compounds in seawater do not affect the conductivity to density relationships for real seawater. We recommended either SA or ΔSi(OH)4 be used to estimate the changes in the density of seawater due to the addition of nutrients and carbonates to ocean waters.

Original languageEnglish (US)
Pages (from-to)460-470
Number of pages11
JournalDeep-Sea Research Part I: Oceanographic Research Papers
Volume55
Issue number4
DOIs
StatePublished - Apr 2008

Fingerprint

Indian Ocean
seawater
conductivity
equation of state
carbonates
water
carbonate
nutrient
deep water
nutrients
salinity
ocean
effect
organic compounds
organic compound
Pacific Ocean
surface water
oceans
climate

Keywords

  • Absolute salinity
  • Excess density
  • Indian Ocean

ASJC Scopus subject areas

  • Aquatic Science
  • Geology
  • Oceanography

Cite this

The effect of composition on the density of Indian Ocean waters. / Millero, Frank J; Waters, Jason; Woosley, Ryan; Huang, Fen; Chanson, Mareva.

In: Deep-Sea Research Part I: Oceanographic Research Papers, Vol. 55, No. 4, 04.2008, p. 460-470.

Research output: Contribution to journalArticle

Millero, Frank J ; Waters, Jason ; Woosley, Ryan ; Huang, Fen ; Chanson, Mareva. / The effect of composition on the density of Indian Ocean waters. In: Deep-Sea Research Part I: Oceanographic Research Papers. 2008 ; Vol. 55, No. 4. pp. 460-470.
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