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Landrum, LL, Gammon RH, Feely RA, Murphy PP, Kelly KC, Cosca CE, Weiss RF.  1996.  North Pacific Ocean CO2 disequilibrium for spring through summer, 1985-1989. Journal of Geophysical Research-Oceans. 101:28539-28555.   10.1029/96jc02100   AbstractWebsite

Extensive measurements of CO2 fugacity in the North Pacific surface ocean and overlying atmosphere during the years 1985-1989 are synthesized and interpreted to yield a basin-wide estimate of Delta fCO(2). The observations, taken from February through early September, suggest that the subtropical and subarctic North Pacific is a small sink for atmospheric CO2 (0.07 to 0.2 Gton C (half year)(-1) for the region north of 15 degrees N). Objective analysis techniques are used to estimate uncertainty fields resulting from constructing basin-wide contours of oceanic fCO(2) on the basis of individual cruise transects. The uncertainties are significant and imply that future sampling programs need to recognize that estimating oceanic uptake of anthropogenic CO2 from ship-transect observations of oceanic fCO(2) alone will require very extensive sampling.

Mensch, M, Bayer R, Bullister JL, Schlosser P, Weiss RF.  1996.  The Distribution of Tritium and CFCs in the Weddell Sea during the mid-1980s. Progress in Oceanography. 38:377-415.   10.1016/s0079-6611(97)00007-4   AbstractWebsite

Transient tracer data (tritium, CFC11 and CFC12) from the southern, central and northwestern Weddell Sea collected during Polarstern cruises ANT III-3, ANT V-2/3/4 and during Andenes cruise NARE 85 are presented and discussed in the context of hydrographic observations. A kinematic, time-dependent, multi-box model is used to estimate mean residence times and formation rates of several water masses observed in the Weddell Sea. Ice Shelf Water is marked by higher tritium and lower CFC concentrations compared to surface waters. The tracer signature of Ice Shelf Water can only be explained by assuming that its source water mass, Western Shelf Water, has characteristics different from those of surface waters. Using the transient nature of tritium and the CFCs, the mean residence time of Western Shelf Water on the shelf is estimated to be approximately 5 years. Ice Shelf Water is renewed on a time scale of about 14 years from Western Shelf Water by interaction of this water mass with glacial ice underneath the FilchnerRonne Ice shelf. The Ice Shelf Water signature can be traced across the sill of the Filchner Depression and down the continental slope of the southern Weddell Sea. On the continental slope, new Weddell Sea Bottom Water is formed by entrainment of Weddell Deep Water and Weddell Sea Deep Water into the Ice Shelf Water plume. In the northwestern Weddell Sea, new Weddell Sea Bottom Water is observed in two narrow, deep boundary currents flowing along the base of the continental slope. Classically defined Weddeil Sea Bottom Water (theta <= 0.7 degrees C) and Weddell Sea Deep Water (-0.7 degrees C <= theta <= 0 degrees C) are ventilated from the deeper of these boundary currents by lateral spreading and mixing. Model-based estimates yield a total formation rate of 3.5Sv for new Weddell Sea Bottom Water (theta = -1.0 degrees C) and a formation rate of at least 11Sv for Antarctic Bottom Water (theta = -0.5 degrees C). (C) 1997 Elsevier Science Ltd

Prinn, RG, Weiss RF, Miller BR, Huang J, Alyea FN, Cunnold DM, Fraser PJ, Hartley DE, Simmonds PG.  1995.  Atmospheric trends and lifetime of CH3CCI3 and global OH concentrations . Science. 269:187-192.   10.1126/science.269.5221.187   AbstractWebsite

Determination of the atmospheric concentrations and lifetime of trichloroethane (CH3CCl3) is very important in the context of global change. This halocarbon is involved in depletion of ozone, and the hydroxyl radical (OH) concentrations determined from its lifetime provide estimates of the lifetimes of most other hydrogen-containing gases involved in the ozone layer and climate. Global measurements of trichloroethane indicate rising concentrations before and declining concentrations after late 1991. The lifetime of CH3CCl3 in the total atmosphere is 4.8 +/- 0.3 years, which is substantially lower than previously estimated. The deduced hydroxyl radical concentration, which measures the atmosphere's oxidizing capability, shows little change from 1978 to 1994.

Nevison, CD, Weiss RF, Erickson DJ.  1995.  Global oceanic emissions of nitrous oxide. Journal of Geophysical Research-Oceans. 100:15809-15820.   10.1029/95jc00684   AbstractWebsite

The global N2O flux from the ocean to the atmosphere is calculated based on more than 60,000 expedition measurements of the N2O anomaly in surface water. The expedition data are extrapolated globally and coupled to daily air-sea gas transfer coefficients modeled at 2.8 degrees x 2.8 degrees resolution to estimate a global ocean source of about 4 (1.2-6.8) Tg N yr(-1). The wide range of uncertainty in the source estimate arises mainly from uncertainties in the air-sea gas transfer coefficients and in the global extrapolation of the summertime-biased surface N2O data set. The strongest source is predicted from the 40-60 degrees S latitude band. Strong emissions also are predicted from the northern Pacific Ocean, the equatorial upwelling zone, and coastal upwelling zones occurring predominantly in the tropical northern hemisphere. High apparent oxygen utilization (AOU) at 100 m below the mixed layer is found to be correlated positively both to N2O production at depth and to the surface N2O anomaly. On the basis of these correlations, the expedition data are partitioned into two subsets associated with high and low AOU at depth. The zonally averaged monthly means in each subset are extrapolated to produce two latitude-by-month matrices in which monthly surface N2O is expressed as the deviation from the annual mean. Both matrices contain large uncertainties. The low-AOU matrix, which mainly includes surface N2O data from the North Atlantic and the subtropical gyres, suggests many regions with positive summer deviations and negative winter deviations, consistent with a seasonal cycle predominantly driven by seasonal heating and cooling of the surface ocean. The high-AOU subset, which includes the regions most important to the global N2O ocean source, suggests some regions with positive winter deviations and negative summer deviations, consistent with a seasonal cycle predominantly driven by wintertime mixing of surface water with N2O-rich deep water. Coupled seasonal changes in gas transfer coefficients and surface N2O in these important source regions could strongly influence the global ocean source.

Wisegarver, DP, Bullister JL, Van Woy FA, Menzia FA, Weiss RF.  1995.  Chlorofluorocarbon measurements in the Southwestern Pacific during the CGC-90 expedition. :98., Seattle, Washington: United States Department of Commerce, National Oceanic and Atmospheric Administration, Environmental Research Laboratories Abstract
Penkett, SA, Butler JH, Kurylo MJ, Reeves CE, Rodriguez JM, Singh H, Toohey D, Weiss R.  1995.  Methyl bromide. Scientific assessment of ozone depletion: 1994 (World Meterological Organization, Global Ozone Research and Monitoring Report). ( World Meteorological O, Ed.).:26., Geneva, Switzerland; Nairobi, Kenya; Washington, DC, USA: World Meteorological Organization Abstract
Cunnold, DM, Fraser PJ, Weiss RF, Prinn RG, Simmonds PG, Miller BR, Alyea FN, Crawford AJ.  1994.  Global trends and annual releases of CCl3F and CCl2F2 estimated from ALE/GAGE and other measurements from July 1978 to June 1991. Journal of Geophysical Research-Atmospheres. 99:1107-1126.   10.1029/93jd02715   AbstractWebsite

Thirteen years of Atmospheric Lifetime Experiment/Global Atmospheric Gases Experiment CCl3F and CCl2F2 measurements at five remote, surface, globally distributed sites are analyzed. Comparisons are made against shipboard measurements by the Scripps Institution of Oceanography group and archived air samples collected at Cape Grim, Tasmania, since 1978. CCl3F in the lower troposphere was increasing at an average rate of 9.2 ppt/yr over the period July 1978 to June 1988. CCl2F2 was increasing at an average 17.3 ppt/yr in the lower troposphere over the same period. However, between July 1988 and June 1991 the increases of CCl3F and CCl2F2 in this region have averaged just 7.0 ppt/yr and 15.7 ppt/yr, respectively. The rate of increase has been decreasing 2.4 ppt/yr and 2.9 ppt/yr(2) over this 3-year period. Based on a recent scenario of the global releases of these compounds and using the new calibration scale SIO 1993, the equilibrium lifetimes are estimated to be 44(-10)(+17) and 180(_81)(+820) years for CCl3F and CCl2F2, respectively. Using these lifetime estimates and a two-dimensional model, it is estimated that global releases of these two chlorofluorocarbons in 1990 were 249+/-28 x 10(6) kg for CCl3F and 366+/-30 x 10(6) kg for CCl2F2. It is also estimated that combined releases of these chlorofluorocarbons in 1990 were 21+/-5% less than those in 1986.

Reverdin, G, Weiss RF, Jenkins WJ.  1993.  Ventilation of the Atlantic Ocean equatorial thermocline. Journal of Geophysical Research-Oceans. 98:16289-16310.   10.1029/93jc00976   AbstractWebsite

The ventilation of the lower equatorial Atlantic thermocline (100 m to 400 m) is investigated from the distributions of salinity, oxygen, the chlorofluoromethanes F-11 and F-12, tritium, and the excess helium 3; 1983 data suggest a correlation on isopycnal surfaces between oxygen, chlorofluoromethanes and to a lesser extent, with the apparent ages derived from F-11/F-12 and helium 3/tritium. The apparent ages increase with depth from 10 years on sigma(THETA)=26.5 to over 15 years near 400 m. The tracers are largely undersaturated with respect to the surface concentrations corresponding to the apparent ages. We investigate the ventilation processes responsible for these distributions with simple circulation models, where water from the subtropical gyres reaches isopycnally the equatorial thermocline. The few model parameters are determined by fitting the simulations to the chlorofluoromethane distributions in 1983. The sensitivity of these parameters to expected errors on the past surface concentrations and to vertical mixing is comparable and can result in an error of more than 20% in the model parameters. In 1983, model [H-3] and [He-3]* are too large, in particular when no diapycnal mixing is modeled, but the differences could have arisen from errors on past surface concentrations. During the 1980s, die model overestimates the increase in chlorofluoromethanes, in particular F-12. The fitted model inflow from the southern subtropical gyre between 110 m and 400 m is 14 x 10(6) m3 s-1, in the range of expected transports by the western boundary current near Brazil. The model oxygen utilization rate is on the order of 12 mmol kg-1 yr-1 at 100 m and 5 mmol kg-1 yr-1 at 400 m (below sigma(theta)=27.1).

Edmond, JM, Stallard RF, Craig H, Craig V, Weiss RF, Coulter GW.  1993.  Nutrient chemistry of the water column of Lake Tanganyika. Limnology and Oceanography. 38:725-738. AbstractWebsite

Lake Tanganyika shows permanent thermal stratification with deep-water temperatures that have been stable over the period of observation (since 1939). The lake is anoxic below approximately 150-m depth. In general the nutrients show Redfield behavior save in the deep waters of the northern basin where large excesses of phosphate and ammonia are present. Bacterial disproportionation of organic material probably plays an important role in producing these excesses. Inorganic desorption from fluvial detritus is also a possible source of excess phosphate in deep waters. The oxic-anoxic boundary at approximately 150 m is a sink for all forms of fixed nitrogen. Thus the nutrient budget of the lake probably involves fixation of nitrogen in the surface layer in addition to substantial inputs from rainfall and runoff, with the phosphate supplied by vertical mixing. Because these processes are in approximate balance under present conditions, the productivity of the lake must be very sensitive to changes in climatic forcing.

Weiss, RF.  1993.  South Atlantic Ventilation Experiment : SIO chlorofluorocarbon measurements. Scripps Institution of Oceanography Reference Series. :466., La Jolla, CA: Scripps Institution of Oceanography, University of California, San Diego Abstract
Warner, MJ, Weiss RF.  1992.  Chlorofluoromethanes in South Atlantic Antarctic Intermediate Water. Deep-Sea Research Part a-Oceanographic Research Papers. 39:2053-2075.   10.1016/0198-0149(92)90013-j   AbstractWebsite

Distributions of the dissolved atmospheric chlorofluoromethanes (CFMs) F-11 and F-12 in the South Atlantic Ocean are used to study the ventilation and circulation of Antarctic Intermediate Water (AAIW). CFM distributions on an isopycnal surface representative of AAIW are consistent with recently ventilated water entering the subtropical gyre in the southwestern Atlantic and then being advected anticyclonically around this gyre. The westward-flowing northern limb of the gyre apparently divides near the coast of South America with some water flowing southward to recirculate in the gyre, and the balance flowing northward along the coast of Brazil. At the equator this northward current divides again with one branch going eastward along the equator and the other continuing into the Northern Hemisphere. In the eastern tropical Atlantic, the CFM concentrations on this isopycnal surface in the cyclonic gyre are extremely low between the subtropical gyre and the equatorial tongue. Along the prime meridian, the F-11 and F-12 concentrations on the 27.2 sigma(theta) isopycnal surface between the mixed layer outcrop and the northern edge of the subtropical gyre are fitted to a one-dimensional advection-diffusion model. This model assumes that the CFMs enter the subtropical gyre solely by northward diffusion from the mixed layer outcrop to the southern edge of the subtropical gyre, and that their distributions within the gyre are controlled by both advective and diffusive processes. Velocity and eddy diffusion coefficients are calculated from a least-squares fit to the data. These values are then used to calculate a mean oxygen consumption rate which is consistent with rates calculated using models of other time-dependent geochemical tracers.

Gordon, AL, Weiss RF, Smethie WM, Warner MJ.  1992.  Thermocline and intermediate water communication between the south Atlantic and Indian oceans. Journal of Geophysical Research-Oceans. 97:7223-7240.   10.1029/92jc00485   AbstractWebsite

A conductivity-temperature-depth and tracer chemistry section in the southeast South Atlantic in December 1989 and January 1990 presents strong evidence that there is a significant interocean exchange of thermocline and intermediate water between the South Atlantic and Indian oceans. Eastward flowing water at 10-degrees-W composed of South Atlantic Central (thermocline) Water is too enriched with chlorofluoromethanes 11 and 12 and oxygen to be the sole source of similar theta-S water within the northward flowing Benguela Current. About two thirds of the Benguela Current thermocline transport is drawn from the Indian Ocean; the rest is South Atlantic water that has folded into the Benguela Current in association with the Agulhas eddy-shedding process. South Atlantic Central water passes in the Indian Ocean by a route to the south of the Agulhas Return Current. The South Atlantic water loops back to the Atlantic within the Indian Ocean, perhaps mostly within the Agulhas recirculation cell of the southwest Indian Ocean. Linkage of Atlantic and Indian Ocean water diminishes with increasing depth; it extends through the lower thermocline into the Antarctic Intermediate Water (AAIW) (about 50% is derived from the Indian Ocean) but not into the deep water. While much of the interocean exchange remains on an approximate horizontal "isopycnal" plane, as much as 10 x 10(6) m3 s-1 of Indian Ocean water within the 25 x 10(6) m3 s-1 Benguela Current, mostly derived from the lower thermocline and AAIW, may balance deeper Atlantic export of North Atlantic Deep Water (NADW). The addition of salt water from the evaporative Indian Ocean into the South Atlantic Ocean thermocline and AAIW levels may precondition the Atlantic for NADW formation. While AAIW seems to be the chief feed for NADW, the bulk of it enters the subtropical South Atlantic, spiked with Indian Ocean salt, within the Benguela Current rather than along the western boundary of the South Atlantic.

Keir, RS, Michel RL, Weiss RF.  1992.  Ocean mixing versus gas-exchange in Antarctic Shelf Waters near 150°E. Deep-Sea Research Part a-Oceanographic Research Papers. 39:97-119. AbstractWebsite

In February 1985, chlorofluoromethanes (CFMs), tritium and radiocarbon were measured in Antarctic continental shelf waters near 150-degrees-E. These distributions are used to evaluate (1) the transport of Warm Deep Water (WDW) and Antarctic Surface Water onto the shelf, and (2) the gas exchange rates across the sea surface. The time varying response of these tracers to atmospheric forcing is simulated with a box model of the water masses in this region. In the model, horizontal mixing of surface waters strongly affects the shelf radiocarbon level, but the CFMs and tritium are not affected. The observed low tritium concentrations (< 0.2 TU) in the shelf waters provide a lower limit to the transport of tritium deficient Warm Deep Water into the region, which is equivalent to a vertical flux of about 75 m y-1. This implies a maximum residence time of WDW in the basin of about 8 years. The transport of subsurface water out of the basin at the shelf break is estimated to be approximately 0.2 to 0.4 x 10(6) m3 s-1. The average annual CFM piston velocity for gas exchange is estimated to be about 200 m y-1.

Weiss, RF, Van Woy FA, Salameh PK.  1992.  Surface water and atmospheric carbon dioxide and nitrous oxide observations by shipboard automated gas chromatography : results from expeditions between 1977 and 1990. Scripps Institution of Oceanography Reference Series. :144., La Jolla, Calif.: Scripps Institution of Oceanography, University of California, San Diego Abstract
Falkner, KK, Measures CI, Herbelin SE, Edmond JM, Weiss RF.  1991.  The major and minor element geochemistry of Lake Baikal. Limnology and Oceanography. 36:413-423. AbstractWebsite

A comprehensive, joint Soviet-American study of the chemistry of Lake Baikal, the world's deepest (1,632 m) lake, was carried out in July 1988. In this paper, we report the major, minor, and preliminary trace element concentrations for three profiles obtained at or near the deepest and central part of the three major basins of the lake. With the exception of Ba, the distributions of major and minor elements were homogeneous, displaying no variations greater than analytical uncertainties. Average concentrations in mu-mol kg-1 (1 SD) are titration alkalinity = 1,093(6), SO42- = 57.4(1.3), Cl = 12.3(0.7), Ca = 402(7), Mg = 126(1), Na = 155(4), and K = 24.1(1.0); and in nmol kg-1 are Sr = 1,350(30), Li = 296(12), Ba = 74.7(2.6), Rb = 7.10(0.23), and U = 1.77(0.12). Excluding K and Cl, these values compare favorably with previously published results. Although some hydrothermal activity is known to occur within the lake, it does not appear to significantly affect major ion cycling. The residence times of the major ions are 330 yr or the same as that of water in the basin and so are controlled predominantly by their riverine fluxes. There is not yet enough information to assess whether hydrothermal processes affect minor element cycles. Ba concentrations decrease with depth, showing abrupt decreases near the bottom at two stations. It appears to undergo some form of uptake at the sediments, but further study is required to discern the processes governing Ba distribution.

Weiss, RF, Carmack EC, Koropalov VM.  1991.  Deep-water renewal and biological production in Lake Baikal. Nature. 349:665-669.   10.1038/349665a0   AbstractWebsite

The physics of mixing in deep temperate lakes is strongly constrained by the existence of a temperature of maximum density for fresh water, and by the pressure dependence of that temperature. The world's deepest lake is well suited to the study of such deep-water renewal processes, and also to the determination of the rate of renewal using time-dependent chemical tracers. The mean rates of biological recycling of oxygen, carbon and nutrients for the entire lake can then also be determined.

Whitworth, T, Nowlin WD, Pillsbury RD, Moore MI, Weiss RF.  1991.  Observations of the Antarctic Circumpolar Current and deep boundary current in the southwest Atlantic. Journal of Geophysical Research-Oceans. 96:15105-15118.   10.1029/91jc01319   AbstractWebsite

Fourteen-month velocity and temperature records from an array of 14 moorings north and west of the Falkland Plateau and supporting hydrographic and tracer data reveal a narrow boundary current that carries dense Antarctic waters. The current flows west along the northern flank of the Falkland Plateau with mean speeds of more than 10 cm s-1 at 5000 m and more than 30 cm s-1 at 2500 m. The westward flow extends from the bottom to at least 1000 m, but the upper portion of the current is a branch of the Antarctic Circumpolar Current (ACC) following the only deepwater route between the Scotia Sea and the Argentine Basin. Waters colder than 0.2-degrees-C are too cold to be associated with the ACC at Drake Passage and must ultimately derive from the Weddell Sea as part of the deep thermohaline circulation. The westward transport of water colder than 0.2-degrees-C is 8.2 x 10(6) m3 s-1. In the mean the bottom boundary current is similar to that predicted by the Stommel-Arons model, but considerable variability is introduced by the meandering of the overlying ACC. Chlorofluorocarbon data suggest that new Antarctic water from the Georgia Basin enters the Argentine Basin via the deep boundary current, which passes beneath the ACC; some new water is also advected east after being entrained in the ACC. Most of the water in the deep boundary current is recirculated water that has been in residence in the Argentine Basin for some time. Water colder than -0.2-degrees-C is relatively new to the basin and comprises about 2.5 x 10(6) m3 s-1 of the westward flow of the boundary current.

Carmack, EC, Weiss RF.  1991.  Convection in Lake Baikal: an example of thermobaric instability. Deep Convection and Deep Water Formation in the Oceans. ( Chu PC, Gascard JC, Eds.).:215-228., Burlington: Elsevier Abstract

This book contains articles presenting current knowledge about the formation and renewal of deep waters in the ocean. These articles were presented at an international workshop at the Naval Postgraduate School in Monterey in March 1990.

Weiss, RF.  1991.  Transient tracers in the ocean, tropical Atlantic study: chlorofluorocarbon measurements. Scripps Institution of Oceanography Reference Series. :159., San Diego; La Jolla: University of California ; Scripps Institution of Oceanography Abstract
Weiss, RF.  1990.  Ajax expedition chlorofluorocarbon measurements. Scripps Institution of Oceanography Reference Series. 90-6:190., La Jolla, CA: University of California, San Diego, Scripps Institution of Oceanography Abstract
Bender, M, Jahnke R, Weiss R, Martin W, Heggie DT, Orchardo J, Sowers T.  1989.  Organic carbon oxidation and benthic nitrogen and silica dynamics in San Clemente Basin, a continental borderland site. Geochimica Et Cosmochimica Acta. 53:685-697.   10.1016/0016-7037(89)90011-2   AbstractWebsite

Organic carbon oxidation rates in San Clemente Basin were determined by benthic chamber experiments using the Bottom Lander, along with studies of pore water chemistry. Non-steady-state diagenetic models are developed for interpreting concentration-time data from the benthic chamber experiments. O2, NO3−, and SO42− are all important oxidants for organic carbon at our study site. Regenerated fixed nitrogen was consumed by NO3− reduction. There is a flux of NO3− into the sediments, and the benthic flux of NH4+ is undetectable. The total rate at which fixed nitrogen is removed from the oceans at this site is about twice the flux of PON to the sea floor. SiO2 fluxes calculated from interfacial pore water gradients are in satisfactory agreement with those determined using the Lander. Most silica dissolution must therefore occur within the sediments, although interstitial profiles show that little dissolution occurs below 1 cm depth.

Weiss, RF, Price BA.  1989.  Dead Sea gas solubilities. Earth and Planetary Science Letters. 92:7-10.   10.1016/0012-821x(89)90016-2   AbstractWebsite

The solubilities of helium and argon have been measured in Dead Sea brine. A simple model is presented whereby the solubilities of these and other gases in Dead Sea water as functions of temperature and salinity may be closely approximated from existing equations for the solubilities of these gases in pure water and seawater. The salting out per unit mass of Dead Sea salt exceeds that of sea salt by about 9%. The Bunsen solubility coefficients of a number of selected gases in the Dead Sea are about 15–25% of their values in pure water. Parametric equations are given for calculating the equilibrium concentrations of dissolved atmospheric gases in the Dead Sea.

Bullister, JL, Weiss RF.  1988.  Determination of CCl3F and CCl2F2 in seawater and air. Deep-Sea Research Part a-Oceanographic Research Papers. 35:839-853.   10.1016/0198-0149(88)90033-7   AbstractWebsite

An improved analytical technique has been developed for the rapid and accurate shipboard measurement of two anthropogenically produced chlorofluorocarbons (CFCs), CCl3F (F-11) and CCl2F2 (F-12) in air and seawater. Gas samples (dry air or standard) are injected into a stream of purified gas and then concentrated in a low temperature trap. Seawater samples collected in oceanographic Niskin bottles are transferred into glass syringes for storage until analysis. An aliquot of approximately 30 cm3 of seawater is introduced into a glass stripping chamber where the dissolved gases are purged with purified gas, and the evolved CFCs are concentrated in the same cold trap. The trap is subsequently isolated and heated, and the CFCs are automatically transferred by a stream of carrier gas into a precolumn and then a chromatographic separating column. The CCl3F and CCl2F2 peaks are detected by an electron capture detector (ECD) and their areas are integrated digitally. CFC amounts are calculated using fitted calibration curves, generated by injection of various multiple aliquots of gas standard containing known concentrations of CFCs. Preliminary concentration values for these compounds are printed at the completion of each analysis. Total analysis time for air and water samples is < 10 min, allowing detailed vertical profiles of the concentrations of these compounds in the water column and concentrations in the overlying atmosphere to be determined within a few hours of the completion of a hydrographic station. Typical relative standard deviations for analyses of CCl3F and CCl2F2 in near-surface seawater containing equilibrium levels of these compounds are approximately 1%. Limits of detection for both compounds in 30 cm3 seawater samples are about 0.005 × 10−12 mol kg−1.

Fine, RA, Warner MJ, Weiss RF.  1988.  Water mass modification at the Agulhas retroflection: chlorofluoromethane studies. Deep-Sea Research Part a-Oceanographic Research Papers. 35:311-332.   10.1016/0198-0149(88)90013-1   AbstractWebsite

Chlorofluoromethane (CFM) and hydrographic data from the 1983 Agulhas Retroflection cruise are used to show the importance of the region in ventilating thermocline and Intermediate Waters of the southwest Indian ocean gyre. Generally South Atlantic waters are more recently ventilated by at least two years than those of the South Indian Ocean, probably because the latter are farther downstream from the source regions near the South Atlantic subantarctic sector. A two-component mixing model shows that the outflow from the Agulhas Retroflection (14-4°C) was composed of South Indian water and at least 23% South Atlantic water. However, at the density of Indian sector Subantarctic Mode Water the inflow into the Agulhas Retroflection was well preserved in the outflow, and the South Atlantic and Indian waters appear to be ventilated by different water masses. In addition, strong interleaving was found throughout the survey area (between 14 and 4°C), characterized by correlations of negative salinity anomalies with high CFM concentrations. At the density of Antarctic Intermediate Water (AAIW) there was interleaving of both low salinity water and higher salinity Red Sea Water. Using estimates of past atmospheric ratios of two CFMs, we calculate that AAIW within the retroflection was 50–75% diluted by mixing with CFM-free water since leaving the source region. Results from the two-component mixing model, which show substantial contributions of South Atlantic water in the outflow, suggest that the return flow for the 10 Sv leakage of Indian Ocean water via the Agulhas Current into the South Atlantic [Gordon (1985) Science, 227, 1030–1033; Gordonet al. (1987) Deep-Sea Research, 34, 565–600] is occurring at thermocline and intermediate depths. A combination of active mixing in this region and similarity in the ventilation processes may be the reason that the South Atlantic and Indian thermoclines are coincident in temperature and salinity space (between 15 and 7°C) as noted by Gordon.

Somayajulu, BLK, Rengarajan R, Lal D, Weiss RF, Craig H.  1987.  GEOSECS Atlantic 32Si profiles. Earth and Planetary Science Letters. 85:329-342.   10.1016/0012-821x(87)90131-2   AbstractWebsite

Measurements of five cosmogenic32Si vertical profiles in Atlantic waters (27°N to 60°S) are presented. The amounts of dissolved SiO2 extracted range from 2 to 54 g; the amounts of water from which SiO2 was extracted range between 540 kg and 270, 000 kg. In additon, SiO2 recovered from four surface particulate composites (64°N to 61°S) were also analyzed for32Si.32Si measurements were made by milking and counting the daughter activity, 32P. The net32P activities range from 0.7 to 6.8 cph; typical errors in measurements of the32P activities are 20–30%.The32Si concentrations vary from 0.6 dpm/106 kg of water in the North Atlantic surface waters to 235 dpm/106 kg at 400 m depth in the circumpolar waters. The vertical profiles of32Si at the five Atlantic stations approximately follow the Si profiles but the depth gradients are different. This would be expected also considering the in-situ release mechanisms due to dissolution and advection/diffusion from the bottom waters. Except for the circumpolar station 89, where the Si and32Si profiles show the effect of marked vertical mixing (nearly depth independent profiles), the profiles show the following features: (1) specific activities of32Si (32Si/SiO2 ratios) are lowest at intermediate depths, and (2) on an average the surface specific activities are higher, by 2–4 times, than the bottom water values. These data are consistent with generation of the highest specific activity32Si waters at the surface, where Si concentrations are lowest and precipitation adds cosmogenic32Si scavenged from the troposphere. Rapid removal of biogenic silica to the water-sediment interface, without much dissolution during transit, leads to the second regime of high32Si specific activities.The32Si inventories in the water column in the latitude belt 27°N-27°S are in the range (1–1.4) × 10−2 dpm32Si/cm2, which is consistent with the expected fallout of cosmogenic32Si. However, the32Si column inventories south of 40°S are higher by a factor of ∼ 5–7, whereas the corresponding Si inventories increase by only a factor of 3. This excess32Si in the Southern Ocean cannot be explained by direct fallout from the stratosphere or by melting of Antarctic snow and ice. Instead, this excess is maintained primarily by the southward deep-water transport of32Si dissolved from sinking particulates.