Abstract
The conductivities and densities were measured on 331 samples collected in the South Pacific Ocean during the P18 CLIVAR (Climate Variability and Predictability) cruise. The relative densities (ρ - ρ0) were compared to those determined from the equation of state of seawater. The excess densities (Δρ = ρMeas - ρCalc) ranged from ± 0.003 kg m- 3 in surface waters to 0.015 kg m- 3 in deep waters due to additions of nutrients and carbonates. The values of Δρ were found to be a linear function of the increases of ΔNTA, ΔSi(OH)4 and ΔNO3 in the deep waters (σ = 0.002 to 0.005 kg m- 3). The best correlations of Δρ with changes in concentration of ΔSi(OH)4 are (N = 331) given byΔ ρ / kg m- 3 = - 1.7 · 10- 3 + 9.4 · 10- 5 Δ Si (OH)4 (σ = 0.0043 kg m- 3) . Correlation of the South Pacific data with earlier measurements made in the North Pacific and Indian oceans (N = 596) are given byΔ ρ / (kg m- 3) = - 1.7 · 10- 3 + 9.44 · 10- 5 Δ Si (OH)4 (σ = 0.0043 kg m- 3) . The excess densities can also be accounted for by determining the change in the absolute salinity (SA) of seawater. The values of ΔS have been estimated fromΔ S = 50 Δ NTA + 68 Δ SiO2 + 63 Δ HNO3 + 82 Δ H3 PO4 . The values of Δρ/kg m- 3 calculated from the estimated values of SA agreed with the measured densities with a standard error of ± 0.004 kg m- 3. Values of SA determined from density measurements also show a correlation with ΔSi(OH)4. The Indian and South Pacific values have been fitted to (σ = 0.0044)Δ S = - 2.4 · 10- 3 + 1.06 · 10- 4 Δ Si (OH)4 . An error of ± 0.0044 g kg- 1 in SA is equivalent to and error of ± 0.003 kg m- 3 in the density (which is the precision of the density measurements).
Original language | English (US) |
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Pages (from-to) | 56-62 |
Number of pages | 7 |
Journal | Marine Chemistry |
Volume | 114 |
Issue number | 1-2 |
DOIs | |
State | Published - Apr 20 2009 |
Keywords
- Absolute salinity
- Excess density
- South Pacific Ocean
ASJC Scopus subject areas
- Oceanography
- Chemistry(all)
- Environmental Chemistry
- Water Science and Technology