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We used a dynamic mixed layer model to determine carbon export by the oxygen mass balance method from a time series of O-2/Ar, N-2/Ar and Ne measurements collected at station ALOHA near Hawaii from July 2000 to June 2001. The inert gas measurements constrain the flux of oxygen into the mixed layer from small, collapsing bubbles (injection) to be greater than or equal to the flux from larger bubbles (exchange), with mean estimates of the ratio in the range of 1-2. We also show that monthly observations of temperature and inert gases cannot constrain the rate of diapycnal mixing at this location, because of uncertainties in air-sea heat flux estimates and bubble dynamics. Organic carbon export from the mixed layer calculated from our dataset was 1.1 +/- 0.5 mol C m(-2) yr(-1), with most of the error deriving from uncertainties in the parameterization of diffusive gas exchange with wind speed. Our estimates of carbon export from the zone beneath the mixed layer but still in the euphotic zone ranged from 0 to 0.6 mol C m(-2) yr(-1) as the rate of background diapycnal mixing was increased from 0. 1 to 1.0 cm(2) s(-1). We conclude that the oxygen mass balance method has errors of about a factor of two in areas similar to the subtropical North Pacific, with the main uncertainties deriving from mixing rates and the parameterization of diffusive gas exchange.

We describe an analytical method with improved precision for measuring the concentration of neon dissolved in water. Measurements were calibrated by isotope dilution, with addition of a Ne-22 spike directly to the evacuated sample flask prior to water collection. The use of glass flasks for water sampling, with flushing of air from the system by CO2, greatly reduced the chance of contamination. Dissolved gases were extracted from the water sample by equilibration with a headspace and cryogenically processed to remove interferences. The Ne-22/Ne-20 ratio was then measured on a quadrupole mass spectrometer operated in static mode. Mass fractionation by the system was accounted for by frequent analyses of the Ne-22/Ne-20 ratio in air. We routinely obtained precisions of +/-0.13% based on the standard deviation of duplicate field samples. Accuracy of the method, in the form of possible systematic offsets that could skew all the data, was assessed to be +/-0.18%, excluding a possible +/-0.2% error in the estimate of the Ne concentration of air. (C) 2004 Elsevier B.V. All rights reserved.

Large discrepancies in published neon and nitrogen solubility data limit the interpretation of oceanic measurements of these gases. We present new solubility measurements for neon, nitrogen and argon in distilled water and seawater, over a temperature range of 1-30 degreesC. Water was equilibrated with air at measured temperatures, salinities and pressures. Dissolved Ne concentrations were then determined by isotope dilution using a quadrupole mass spectrometer. Ratios of O2/N2/Ar were measured on a stable isotope ratio mass spectrometer, from which absolute N2 and Ar concentrations were calculated using published O2 solubilities. We propose new equations, fitted to the data, for the equilibrium concentrations of Ne, N2 and Ar with estimated errors of 0.30%, 0.14% and 0.13%, respectively. The Ar results matched those of most previous researchers within 0.4%. However, the Ne and N2 results were greater by 1% or more than those of Weiss (1971,1970). (C) 2004 Elsevier Ltd. All rights reserved.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2010.06.001 Byline: Steven Emerson, Charles Stump Keywords: Net community production; Oxygen mass balance; Subarctic pacific; In situ measurements Abstract: Net community biological production in the euphotic zone of the ocean fuels organic matter and oxygen export from the upper ocean, which has a large influence on the atmospheric pressure of carbon dioxide and is the driving force for metabolite distributions in the sea. We determine the net annual biological oxygen production in the mixed layer of the northeast subarctic Pacific Ocean from in situ O.sub.2 and N.sub.2 measurements. Temperature, salinity, total gas pressure and O.sub.2 were measured every 3h for 9 months in 2007 at about 3m depth on a surface mooring at Station P (50[degrees]N, 145[degrees]W). The concentration of nitrogen gas, N.sub.2, determined from separate total gas pressure and pO.sub.2 measurements, was used as an inert tracer of the physical processes that induce gas departure from thermodynamic equilibrium with the atmosphere. We use a simple model of the ocean's mixed layer along with the nitrogen concentration to constrain the importance of bubbles, gas exchange and horizontal advection, which are then used in the oxygen mass balance to derive net biological oxygen production. The mixed-layer oxygen mass balance is dominated by exchange with the atmosphere, and we determine a mean summertime oxygen production of 24mmolO.sub.2 m.sup.-2 d.sup.-1. The annual pattern in the difference between the supersaturation of oxygen and nitrogen in the surface waters reveals very little net oxygen production during the winter at this location. The calculated annual net community production (NCP) of carbon from this new method, 2.5molm.sup.-2 yr.sup.-1, agrees to within its error of aboutx40% with previous determinations at this location from oxygen mass balance, NO.sub.3.sup.- draw down and.sup.234Th measurements. This value is either indistinguishable from or lower than annual NCP measurements in the subtropical North Pacific, indicating that there is no experimental evidence for differences in annual NCP between the subarctic and subtropical North Pacific Ocean. Author Affiliation: School of Oceanography, University of Washington, P.O. 355351, Seattle, WA 98195, USA Article History: Received 18 December 2009; Revised 10 June 2010; Accepted 13 June 2010

A conductivity temperature depth and oxygen sensor and a gas tension device were used to obtain data for remotely determining net production of biological oxygen in the Pacific Ocean's euphotic zone. While this method is useful, the oxygen sensor's drift makes frequent calibration necessary.

We developed a method to measure picogram quantities of vanadium in calcite and seawater by isotope dilution (ID) inductively coupled plasma mass spectrometry using electrothermal vaporization (ETV) to introduce the sample into the plasma. A 50V isotope spike enriched to 44 atom % was equilibrated with samples, followed by chemical purification by cation exchange chromatography. Samples were introduced into the ETV unit with a Pd modifier and heated to 1000 [degrees] C. This quantitatively eliminates the [ClO.sup.+] isobaric interference with V at m/z 51 for solutions up to 0.5 N HCl. The procedural blank was 0.27 pg of V. Corrections for 50Ti and 50Cr, which interfere with the 50V signal, were made by measurement of 49Ti and 53Cr. These isobaric interferences and variable ArC levels were the limiting sources of error in the ID measurement and diminished the detection limit to 6 pg of V. The detection limit for nonisotope dilution applications was 0.3 pg of V. Measurement precision on the Same sample of dissolved calcite over the course of one run was [+ or -]3% (1[Sigma]). Accuracy was confirmed by determination of V standards in CaC[O.sub.3] and by comparative measurement with ID thermal ionization mass spectrometry and graphite furnace atomic absorption spectroscopy.

A study of the distributions of nitrates and Apparent Oxygen Utilization in the upper subtropical North Pacific Ocean shows a layer just below the 1% light level and above the density of sigma theta 25.6 with negative performed nitrate values which may be due to respiration of nitrogen-poor dissolved organic matter from the ocean surface with possible nitrate uptake. The results suggest that the processes creating the negative nitrate feature may alter the metabolite stoichiometry in upper subtropical Pacific Ocean.

Biological productivity, determined from oxygen mass balance and incubation experiments, is time independent. The flux of metabolic products from the surface ocean is crucial to the carbon dioxide concentration in the atmosphere and the global ecosystem. Experiments conducted in the mixed layer of the subarctic Pacific Ocean show the chemical mass balance and incubation measurements.

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