West Basin Research Articles

Full cost or “sustainability cost” pricing in irrigated agriculture. Charging for water can be effective, but is it sufficient?

AbstractIn France, the water management issue is no longer a matter of developing stakeholder participation or transferring state competence to user associations. But, as for other countries with a significant irrigated agriculture, two socio‐economic questions need to be answered: (i) How to ensure the sustainability of investments by raising the price of water without discouraging economic development? (ii) How to share water between users when resources are scarce?Answering these questions brings up the two basic principles of good water management for sustainable development: as it consumes more than 70% of the available water of low flow periods, irrigated agriculture must respect the other uses by limiting its demand to the allocated volume; as it involves large and long‐term public investments, irrigated agriculture must at least bear the “sustainability cost” of the irrigation schemes including the upstream water resources. Such a general answer is of course largely case‐specific and should be adjusted to each institutional framework. In France today, the Sociétés d'Aménagement Régional (SARs) are currently applying these principles. This paper will address both socio‐economic questions stated above, with a specific discussion on the case of a water‐stressed basin in the south west of France where a specific step‐pricing and quota system has been set up in order to regulate the demand. It is argued that “full cost pricing of water services”, as recommended in the World Water Vision (The Hague 2000), is not practical in the short term and, if pursued, could lead to very undesirable results. As a conclusion, two recommendations are proposed with a view to developing best practices in charging for water. Copyright © 2002 John Wiley & Sons, Ltd.

Effects of ultraviolet radiation on rates and size distribution of primary production by Lake Erie phytoplankton

The impact of natural solar ultraviolet radiation (UVR), particularly UVB (297–320 nm), on phytoplankton primary production in Lake Erie was investigated during the spring and summer of 1997. Radiocarbon incorporation and size-selective filtration was used to trace total production and its distribution among particulate and dissolved pools. On average, 1-h exposures produced half the UVB-dependent inhibition of total production realized in 8-h exposures, indicating rapid kinetics of photoinhibition. Cumulative UVB-dependent photoinhibition averaged 36% in 8-h simulated surface exposures. The efficiency of photoinhibition was greater for N-deficient than N-replete communities, but was not related to phytoplankton light history, P limitation, or the dominant genera. The proportion of recently fixed carbon occurring in the dissolved pool after 8-h exposures was significantly greater in higher-UVB treatments, whereas the share in picoplankton (<2 µm) was significantly lower. Significant UVB-dependent inhibition of total production was limited on average to relatively severe exposures, but the rapid kinetics of inhibition and the apparent effects on the allocation of carbon suggest it may be important to the lake's food web. Differences in optical properties and thermal stratification patterns suggested that the relatively turbid west basin was potentially more susceptible to UVR photoinhibition than the more transparent east or central basins.

Morphology and Late Quaternary sedimentation in the Gulf of Oman Basin

The morphology of the Gulf of Oman Basin, a 3,400 m deep oceanic basin between Oman and southern Pakistan and southern Iran, ranges from a convergent margin (Makran margin) along the north side, a passive type (Oman margin) along the south side, translation types along the basin's west (Zendan Fault-Oman Line) and east (Murray Ridge) sides and a narrow continental rise and a wide abyssal plain in the centre of the basin. Sediment input into the basin during the Late Quaternary has been mainly from the north as a result of the uplift of the Coast Makran Mountains in the Late Miocene-Pliocene. Today most of this detritrus is deposited on the shelf and upper continental slope and perched basins behind the fold/fault ridges on the lower slope. The presence of fans and channels on the continental rise on the north side of the basin indicate, however, that continental derived debris was, and possibly is, being transported to the deep-sea by turbidity currents via gaps in the ridges on the lower slope. In addition to land derived terrigenous sediments, the basin deposits also contain biogenic (organic matter and calcium carbonate), eolian detritus and hydrates and authigenic carbonates from the tectonic dewatering of the Makran accretionary wedge. The eolian sediment is carried into the Gulf of Oman Basin from Arabia and the Mesopotamia Valley by the northwesterly Shamal winds. This type of detritus was particularly abundant during the glacial arid periods 21,000–20,000 and 11,000 (Younger Dryas) years ago when exposure of the Persian (Arabian) Gulf increased the area of dust entrainment and shifted the position of the source of the eolian sediments closer to the basin.

ABSTRACT: Organic Carbon-Sulfur Relations in Lacustrine Shales of the West African Basins: Implications for Paleoclimate and Source Rock Potential

ABSTRACT: Organic Carbon-Sulfur Relations in Lacustrine Shales of the West African Basins: Implications for Paleoclimate and Source Rock Potential

Trends of sea level rise in the South China Sea during the 1990s: An altimetry result

Using 7 years of TOPEX/POSEIDON satellite altimetry data, we have identified a general trend of sea level rising in the South China Sea between January 1993 and December 1999. The estimated bulk rising rate of the entire basin is -1 cm/a. The rise of sea level appears to be spatially non-homogeneous, which shows a highest rate of 2.7 cm/a in the deep basin west of Luzon and generally low (even negative) rates over the shallow continental shelves. It is believed that the observed rapid rising of sea level is a regional phenomenon and is mainly caused by warming of the upper layer of the South China Sea, which showed a bulk warming rate of 0.15℃/a in the same period. It is also suggested that the observed rising trend is mainly a decadal signal, which is possibly associated with decadal variation of the Pacific warm pool region.

Submarine evidence for large-scale debris avalanches in the Lesser Antilles Arc

Results from a recent marine geophysical survey demonstrate the importance of the process of flank collapse in the growth and evolution of volcanoes along an island arc. The Aguadomar cruise, aboard the French R/V L’Atalante, surveyed the flanks of the Lesser Antilles Arc between the islands of Montserrat and St. Lucia. Analysis of the data shows that flank collapse events occurred on active volcanoes all along the arc and resulted in debris avalanches, some of them being of large magnitude. The debris avalanche deposits display hummocky topography on the swath bathymetry, speckled pattern on backscatter images, hyperbolic facies on 3.5 kHz echosounder data and chaotic units on air gun seismic profiles. They extend from horseshoe-shaped structures previously identified on the subaerial part of the volcanoes. In the southern part of the arc, large-scale debris avalanche deposits were identified on the floor of the Grenada Basin west of active volcanoes on Dominica, Martinique and St. Lucia. The extent of debris avalanche deposits off Dominica is about 3500 km 2. The debris avalanches have resulted from major flank collapse events which may be mainly controlled by the large-scale structure of the island arc and the presence of the deep Grenada Basin. In the northern part of the arc, several debris avalanche deposits were also identified around the island of Montserrat. With smaller extent (20–120 km 2), they are present on the east, south and west submarine flanks of Soufriere Hills volcano which has been erupting since July 1995. Flank collapse is thus a recurrent process in the recent history of this volcano. The marine data are also relevant for a discussion of the transport mechanisms of debris avalanches on the seafloor surrounding a volcanic island arc.

Mesoscale characteristics

The spatial length, time, and propagation characteristics of the ocean mesoscale variability are examined throughout the globe. Sea surface height (SSH) variations from a combination of the Geosat Exact Repeat Mission, ERS‐1, ERS‐2, and TOPEX/Poseidon altimeter satellites are used to compute the observed covariance of the mesoscale. The mesoscale is defined as the residual SSH after removing a filtered large‐scale SSH having length scales greater than 750 km zonally and 250 km meridionally. From the observed binned covariance function, an objective analysis computes characteristics of the climatological mesoscale variability. Westward propagation is dominant throughout the globe. The Antarctic Circumpolar Current appears to affect the zonal propagation, as the propagation direction is eastward throughout this current. Length scales and propagation speeds generally decrease away from the equator and are slightly larger in the west basin areas than in the east basin areas. Zonal propagation speeds are roughly in agreement with speeds based on linear quasi‐geostrophic dynamics. The eddy field diverges from the equator and converges at 15° in the Northern and Southern Hemispheres. Requirements for synoptic mesoscale observation are examined.

Early Cretaceous Paleomagnetic Results From The Haiyuan Area And Their Tectonic Implications

AbstractA paleomagnetic study was carried out at 13 sites of lower Cretaceous red beds in the Haiyuan area, south west of Ninxia‐Hui autonomons region. A high‐temperature component was isolated using thermal demagnetization, which passed positive reversal test at 95% confidence level. The preliminary magnetic stratigraphic sequence from Liwaxia and Heshangpu formations, showing normal and reversal polarities changes, seems comparable with the lower Cretaceous magnetic time scale. We therefore suggest that the high‐temperature component probably represents the primary magnetization. The characteristic remanent magnetization direction after tilt correction is D = 12.7° , I = 50.2° , α95 = 6.3° . The corresponding paleopole lies at 78.2°N, 218.0°E (dp = 5.7° , dm = 8.4° ). Compared with the lower Cretaceous poles from the Ordos basin in west of North China Block, we conclude that the Haiyuan area has neither northward motion nor rotation with respect to the stable Ordos basin since lower Cretaceous time. The result indicates that along the southeastern section of the Haiyuan fault zone there is no large‐scale left‐slip movement, and that the effect of India and Eurasia collision has been diminished in the Haiyuan area.

Water quality assessment for indirect potable reuse: a new methodology for controlling trace organic compounds at the West Basin Water Recycling Plant (California, USA)

The West Basin Water Recycling plant (California; USA) was built to increase the region's water resource availability. The plant influent is produced at Los Angeles Hyperion wastewater treatment plant and is treated through two parallel treatment processes depending on the end use: (1) Title 22 water for industrial and urban use, and (2) barrier treatment for groundwater recharge. A new methodology was applied to monitor the fate of base neutral compounds in the water barrier treatment train. The methodology included large sample volumes coupled with integrated chromatographic analysis (ICA). Data indicated a 25% increase in concentration of base neutral compounds after RO pretreatment, followed by a 70% removal efficiency after RO. The increase in concentration after RO pretreatment appears to be linked to the use of lime clarification.

CASE STUDY: Management of Wastewater Recycle Streams at the West Basin Water Recycling Plant

CASE STUDY: Management of Wastewater Recycle Streams at the West Basin Water Recycling Plant

Thermally driven porosity reduction: impact on basin subsidence

Abstract At temperatures higher than c. 80°C, thermally driven, isochemical diagenetic porosity loss in siliciclastic sediments leads to a thinning of the sediment column. This process, termed thermochemical compaction, results in surface subsidence and generation of sediment accommodation space. The diagenetic reactions driving thermochemical compaction will operate regardless of the initial mechanism of basin formation and in addition to any externally controlled processes causing continued subsidence. Thermochemical subsidence rates are an inverse function of geothermal gradients. The total rates of subsidence at the surface, including isostatic and mechanical compaction effects, may reach several tens of metres per million years, and may have been important in driving Tertiary subsidence in basins west of Ireland. Unlike the exponentially decaying subsidence caused by tectonic thinning and rifting of the crust, thermochemical basin subsidence is a self-regulated intrabasinal process, which proceeds at a relatively high constant rate over geological time. If not arrested by extrabasinal or tectonic events, the overall effect can ultimately result in sediment metamorphism and granitization.

Geochemistry of the Yandal belt metavolcanic rocks, Eastern Goldfields Province, Western Australia

Archaean felsic metavolcanic rocks occur throughout the Yandal belt in the north of the Eastern Goldfields of Western Australia where they are most abundant in the higher parts of the stratigraphy. With the exception of the Spring Well Sequence at the southern end of the belt, these rocks are typically dacites showing geochemical affinities with Archaean high‐Al trondhjemite‐tonalite‐dacite (TTD) suites. They have high Sr, Al2O3, and (La/Yb)N; low Y, Nb, Zr and heavy rare‐earth elements (HREE); and lack a significant Eu anomaly. In contrast, broadly coeval mafic volcanic rocks have flat REE patterns and trace‐element compositions more typical of modern backarc basin basalts. The Spring Well Sequence is readily distinguished lithologically and geochemically from the remainder of the Yandal belt. Spring Well basaltic andesites are geochemically similar to modern calc‐alkaline arc magmas, i.e. negative Nb–Ta anomalies and enrichment of both large‐ion lithophile elements (LILE) and light rare‐earth elements (LREE). Andesites and rhyolites, both abundant in the Spring Well Sequence, have elevated LILE relative to high field strength elements, and moderate to strong negative Nb, Ta, Sr and Ti anomalies. Rhyolites have low Sr/Y and relatively flat REE patterns ((La/Yb)N = 4.2–5.0). The chemistry and lithostratigraphic associations of the Yandal belt, with the exception of the Spring Well area, suggest a similarity with the Kalgoorlie Terrane, which is supported by published geochronological data. In contrast, the abundance of rhyolite, distinctive calc‐alkaline chemistry and ca2690 Ma age of the Spring Well Sequence suggests a possible association with ca2692 Ma bimodal calc‐alkaline arc‐rift sequence at Teutonic Bore and similar rocks at Melita and Jeedamya, 150 km south of Spring Well. The abundance of TTD dacite and tholeiitic basalt throughout the Yandal belt suggests magma generation from both decompression partial melting of mantle peridotite to produce backarc tholeiitic magma, and partial melting of subducted oceanic lithosphere to produce high‐Al dacite‐tonalite magma. Based on field relationships of the lithological associations, spatial geochemical patterns and published geochronological data, a shallow, west‐dipping subduction model is postulated for the Yandal belt. In this model, widespread tholeiitic basalt and TTD dacite volcanic sequences are thought to have formed in a backarc basin west of a predominantly submerged continental margin volcanic arc. The dominance of dacite in the upper stratigraphy of the Yandal belt could indicate the development of a secondary volcanic ridge or arc in this basin. The Spring Well Sequence is interpreted to occupy the northern preserved portion of the primary arc, remnants of which now extend south through Teutonic Bore to the Melita and Jeedamya volcanic centres. South of Spring Well, volcanic sequences become distinctly bimodal with basalt and high silica rhyolite suggesting an increasing influence of arc extension toward the south.

Arsenic content and groundwater geochemistry of the San Antonio-El Triunfo, Carrizal and Los Planes aquifers in southernmost Baja California, Mexico

The San Antonio-El Triunfo mining district, located at a mountainous region 45 km south-east of La Paz, Baja California, has been worked since the late 1700s. Mine waste material produced during 200 years of mineral extraction area poses a risk of local groundwater pollution and eventually, regional pollution to the Carrizal (west basin) and the Los Planes (east basin) aquifers. There are different types of deposits in the mining area. These are dominated by epithermal veins, in which arsenopyrite is an important component. Carrillo and Drever (1998a) concluded that, even though the amount of mine waste is relatively small in comparison to the large scale area, significant As in groundwater derived from the mine waste piles is found locally in the groundwater. This paper shows the results of geochemical analyses of groundwater samples from the San Antonio-El Triunfo area and the Carrizal and Los Planes aquifers during several years of monitoring (1993–1997). The highest values of total dissolved solids (TDS) and As are in the mineralized area where the mining operations occurred (∼1500 ppm TDS and 0.41 ppm As). The lowest concentrations of TDS and As are, in general, away from the mineralized area (∼500 ppm TDS and 0.01 ppm As). Sulfate and bicarbonate (alkalinity) are, in general, high near the mineralized area and low away from it. The arsenic concentrations vary seasonally, especially after the heavy summer thunderstorms. Geochemical modeling (MINTEQA2 and NETPATH) and analysis of the regional geochemical evolution of the groundwater from the mining area towards the aquifer of Los Planes shows that the most likely hydrochemical processes include: dilution, precipitation of calcite, and adsorption of As onto surfaces of iron oxyhydroxides (ferrihydrite). These processes act as natural controls to the extent and amount of As pollution in the Carrizal and Los Planes aquifers.

IRON TRANSPORT AND RETENTION IN OCHRE-RICH WATERCOURSES

Mineral Resources EngineeringVol. 09, No. 03, pp. 357-375 (2000) No AccessIRON TRANSPORT AND RETENTION IN OCHRE-RICH WATERCOURSESMICHAEL J. CARLILE and A. WILLIAM L. DUDENEYMICHAEL J. CARLILEDepartment of Biology, Imperial College, Silwood Park, Ascot SL5 7PY, UK Search for more papers by this author and A. WILLIAM L. DUDENEYT. H. Huxley School for the Environment, Earth Sciences and Engineering, Imperial College, London SW7 2BP, UK Search for more papers by this author https://doi.org/10.1142/S0950609800000251Cited by:1 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail AbstractFerrous and ferric iron concentrations were determined over two years in an ochre-rich watercourse originating from ferruginous strata in the Bagshot Sands, some 40 km to the west of London. The watercourse comprised a bog, 3 km stream and 200 years old wetland/lake system. The data were used to interpret iron transport and retention characteristics of this system and, by comparison and inference, of analogous systems contaminated by iron from other environmental and post-industrial processes. Assessments were made of the effectiveness and longevity of the wetland/lake system as a sediment trap and of the likely ageing behaviour, if left unattended, of modern constructed wetlands treating similar ferruginous discharges from abandoned coal mines. FiguresReferencesRelatedDetailsCited By 1Spatial and temporal relationships between Eocene sand horizons and iron contamination in stream water in the Thames Basin west of London, UKJ.J. Barrott, A.W.L. Dudeney and P.J. Mason16 August 2013 | Geochemistry: Exploration, Environment, Analysis, Vol. 14, No. 1 Recommended Vol. 09, No. 03 Metrics History PDF download

Overview to water recycling in California: success stories

Provides a summary of recycled water use in California, illustrating the evolution of its application from individual projects for nearby users, to city‐wide and district programs. Presents three detailed case studies of recent water recycling projects: the West Basin Water Recycling project in Los Angeles County, the South Bay Water Recycling project in Santa Clara County, and several projects in Marin County. Barriers to recycled water projects include the cost, institutional barriers that separate water supply and wastewater functions, slow regulatory response in permitting, recognizing new technology and expended uses, and educating stakeholders. From the case studies, common elements to successful implementation demonstrate the importance of working with numerous stakeholders throughout the process and addressing their concerns, creating new institutional partnerships, educating stakeholders to bring actors together, market services, and engender support, acquiring financial assistance and providing incentives and, finally, relying on large volume users to support a more cost‐effective design.

Dynamically Active Areas in the South China Sea Detected from TOPEX/POSEIDON Satellite Altimeter Data

TOPEX/POSEIDON (T/P) altimeter measurements from December 1992 to April 1998 were processed to study the sea surface height (SSH) variation in the South China Sea (SCS). Patterns of variance of the SSH deviations from the four-year (1993–1996) mean show that there are three high-variation areas in the deep basin. The first is at the northern basin west of Luzon Island (16°–18° N, 117°–119° E), the second is at the center of the SCS (14°–16° N, 113.5°–114.5° E), and the third is off the central Vietnam coast (12°–13° N, 110°–112° E). From empirical orthogonal function (EOF) analysis, we found that the variations of these three active areas are dominated by annual cycles, but out of phase. The first two areas have the highest SSH in June and the lowest SSH in December. The third one off the Vietnam coast has the highest SSH in February and the lowest SSH in August. The EOF analysis also reveals that the variation of SSH in the SCS has a response to El Niño events.

Application of aerated biofilters for production of high quality water for industrial reuse in West Basin

The results of 5 years operation of 8 full-scale up-flow aerated Biofor® biofilters, installed at the West Basin Recycling Plant treatment plant (California), demonstrated the efficiency and reliability of this technology in the production of high quality ammonia free water for industrial reuse as cooling water in oil refineries. High nitrification rates up to 0.75 kg d−1 m−3 (0.047 lb d−1 ft−3) were obtained atwater velocities of 6.7 m h−1 (867.5 gpm). The hydraulic retention time in the biofilters was short without any negative consequences on the process. During all five years of operation, all Biofor® units demonstrated very reliable performances with 100% ammonia removal efficiency and very low residual suspended solids concentration of about 4.0 mg TSS L−1.

Quantitative inferences of past hypolimnetic anoxia and nutrient levels from a Canadan Precambrian Shield lake

Paleolimnological analyses were used to infer limnological changes during the past ~ 300 yrs in the west basin of Peninsula Lake, a small (853 ha) Precambrian Shield lake in Ontario, Canada, that has been subjected to moderate cultural disturbances (forest clearance, cottage and resort development). This study represents a pioneering attempt to use sedimentary chironomid assemblages and weighted-averaging models to quantify past hypolimnetic anoxia (expressed as the anoxic factor, AF). Impacts of forest clearance and human land-use on deepwater oxygen availability and surface water quality were assessed by comparing chironomid-inferred AF and diatom-inferred total phosphorus concentration ([TP]) to changes in terrestrial pollen and historical data. This study also discusses the ability of chironomids to quantitatively infer changes in AF.Pre-disturbance chironomid assemblages were stable and dominated by taxa indicative of oxygen-rich hypolimnetic conditions (e.g., Protanypus, Heterotrissocladius, Micropsectra type), while diatoms indicated oligotrophic lake status (diatom inferred [TP] = 5-7 μg·l-1). Chironomids characteristic of lower oxygen availability (e.g., Chironomus, Procladius) increased following land-clearance, road construction, establishment of a grist mill and lakeshore development beginning ca. 1870. Increased abundances of Tanytarsus s. lat., a multigeneric group of mainly littoral chironomids, since 1900, indicated that littoral chironomids may have comprised a greater proportion of fossil assemblages during periods of eutrophication and prolonged anoxia. Abundances of meso-eutrophic diatom taxa (e.g., Fragilaria crotonensis, Asterionella formosa, Aulacoseira ambigua, A. subarctica) increased concurrent with European settlement (ca. 1870) and diatom-inferred [TP] doubled (~ 6-12 μg·l-1), further indicating that naturally-oligotrophic Precambrian Shield lakes were extremely sensitive to initial land-clearance activities.Recent increases in oligotrophic diatom taxa (e.g., Cyclotella stelligera) indicate a shift to more oligotrophic conditions since ca. mid-1960s, with greatest changes since ca. 1980. The chironomids Heterotrissocladius and Micropsectra type also increased at this time suggesting greater deepwater oxygen availability. These recent water-quality improvements, possibly in response to enhanced nutrient removal from detergents and sewage, climate-related reductions in external phosphorus loads, and catchment (but not lake) acidification and reforestation, suggest that habitat for commercially-valuable cold-water fishes has improved in recent decades despite greater recreational lake-use.Paleolimnological assessment of trophic status changes in Peninsula Lake using fossil diatom and chironomid assemblages were in good agreement. Diatom inferences of [TP] and chironomid inferences of AF both suggest that Peninsula Lake was historically oligotrophic, became oligo-mesotrophic after European settlement, and returned to oligotrophy in recent yrs. Chironomid inferences of [TP] consistently underestimated the trophic status of Peninsula Lake, possibly due to its relatively large hypolimnion. These results suggest that AF represents a useful tool for quantitatively reconstructing the past trophic status of deeper, stratified lakes.

Geochemistry of organic-rich Cretaceous and Jurassic mudstones in the West Lewis and West Flannan basins, Offshore north-west Scotland: Implications for source rock presence in the north-east Rockall Trough

The West Lewis and West Flannan basins serve as important calibration sites for understanding the source rock distribution and quality in the north-eastern part of the Rockall Trough. In the West Lewis Basin, two shallow boreholes penetrated organic-rich, oil-prone Bathonian mudstones which were deposited in a fresh to brackish water environment. These mudstones will generate oils rich in paraffins upon maturation. Organic-rich, oil-prone Ryazanian mudstones were discovered in both the West Lewis and West Flannan basins. They are offshore marine mudstones with a predominance of algal organic matter, akin to the Kimmeridge Clay in the North Sea and basins west of Shetland. The Bathonian mudstones will generate their hydrocarbon products at higher temperatures than the Ryazanian mudstones. The presence of lower Cretaceous and middle Jurassic oil-prone mudstones in basins on the Hebrides Shelf is intriguing and suggests that similar source rocks may be present along the north-eastern margin of the Rockall Trough.

Circulation and volume flux of the North Atlantic using synoptic hydrographic data in a Bernoulli inverse

A new formulation of the Bernoulli inverse is used to determine the circulation and flux of the North Atlantic from synoptic CTD observations. The inverse assumes that the compressible Bernoulli function, modified potential temperature and salinity are conserved on streamlines in steady, geostrophic, hydrostatic, mass and density conserving flow. Crossings between CTD stations in the distribution of modified potential temperature versus salinity define a set of streamlines. The Bernoulli function is conserved along streamlines and the difference in the Bernoulli function at each crossing is related to the contribution of the unknown sea-surface height (SSH) to the Bernoulli function. These crossings form a set of overdetermined simultaneous linear equations which we solve using a singular value decomposition. A covariance matrix of the SSH solution gives a good estimate of the SSH solution error. From the SSH we calculate a barotropic reference velocity which is added to the baroclinic velocity from the observed density distribution giving the total geostrophic velocity. The inverse is tested using output from the Ocean Circulation and Climate Advanced Model (OCCAM) where the SSH is known a priori: the mean SSH error is 2.2 cm, corresponding to a velocity error of ~1 cm/s for stations separated by 300 km. Inverses of the CTD data have a significantly smaller mean SSH error of 1.2 cm which corresponds to a velocity error of ~0.5 cm/s. Solutions are sensitive to the inclusion of deep crossings which result from observational error as a consequence of small meridional salinity gradients in North Atlantic Deep Water. The inverse is better than a classical dynamic height analysis of the data, by which we mean that the variance of the inverse circulation at depth is greater than the error variance. In the upper ocean (shallower than ?2 = 36.873 which is the top of the Labrador Sea Water) the North Atlantic Current and west wind drift transport 35 ± 4 Sv eastward between 39N and 54N. In the eastern North Atlantic the North Atlantic Current turns northward, west of 20W, with a flux of 14 ± 3 Sv into the Iceland Basin west of the Rockall-Hatton Plateau. The depth-integrated flux of the subpolar gyre in the Irminger Basin is 16 ± 6 Sv fed equally from sources in the western North Atlantic and from flow which crosses the Reykjanes Ridge east to west from the eastern North Atlantic. The circulation at the depth of the Labrador Sea Water is a mid-depth minimum and is generally dominated by error estimates. However, the flux west to east across the Mid-Atlantic Ridge is 3 ± 2 Sv. A simple estimate of the mean flushing time of the Labrador Sea Water layer in the eastern North Atlantic is ~16 years. At depth, over the Porcupine Abyssal Plain the inverse puts in place a basin scale cyclonic circulation and we note agreement with mean circulation rates of 1 to 2 cm/s derived from current meters.