The first two years of SeaWiFS (Sea viewing Wide Field of view Sensor) data (1997–1999) are used to document the variability of large-scale surface chlorophyll patterns within the coastal region along the full latitudinal extent of each of the four major global eastern boundary currents; the California, Humboldt, Benguela and Canary Currents. Seasonal chlorophyll patterns are compared to coincident seasonal cycles of Ekman transport calculated from satellite scatterometer data. In all four regions, maximum chlorophyll concentrations are generally temporally and latitudinally coincident with the seasonal maximum in upwelling (offshore Ekman transport) over most of their latitudinal range, but exceptions are documented. Interannual differences are evident in each region, most notably in the two Pacific regions where the 1997–1998 chlorophyll seasonality was affected by El Niño conditions. Significant differences between previously published chlorophyll seasonality deduced from the relatively sparse coverage of the Coastal Zone Color Scanner (CZCS) and the more complete coverage of SeaWiFS in both Southern Hemisphere regions are evident.

During the recent GasEx‐2001 cruise in the Equatorial Pacific aboard the NOAA ship Ronald H. Brown, carbon measurements were made in the region of 3°S, 125°W. Continuous surface water fCO2 measurements were conducted onboard in both underway and discrete analysis modes. During the 15‐day experiment, surface water fCO2 values averaged 473 ± 2 μatm, providing a constant condition of supersaturation and flux of CO2 from the ocean to the atmosphere. The relationship of gas transfer with wind speed developed in this study is used along with regional estimates of air‐water fCO2 differences to determine CO2 fluxes in the equatorial Pacific. The regional fCO2 fields are estimated from algorithms developed from previous measurements collected on the Ronald H. Brown and Ka'imimoana over the past 10 years between 5°N and 10°S, 90°W and 165°E. Using the W. McGillis et al. gas transfer‐wind speed relationship, we estimate an average flux of 1.5 ± 0.4 mol C m−2 yr−1 for the study region, with a six‐fold difference in the regional efflux of CO2 between the strong El Niño events of 1986–1987 and 1997–1998 and the La Niña events of 1996 and 1999–2001 (i.e., 0.1 to 0.56 Pg C yr−1). The combined effects of uncertainties in the gas transfer velocity and wind fields lead to average difference of 27% between the lowest and highest estimates of the CO2 flux from the region. In contrast, the uncertainties in the fCO2‐SST relationships give an average difference of about 35% between the lowest and highest estimates of the CO2 flux.

High productivity (maxima ∼3gCm−2day−1) of the Eastern Boundary Currents (EBCs), i.e. the California, Peru-Humboldt, Canary and Benguela Currents, is driven by a combination of local forcing and large-scale circulation. The characteristics of the deep water brought to the surface by upwelling favorable winds depend on the large-scale circulation patterns. Here we use a new hydrographic and nutrient climatology together with satellite measurements of the wind vector, sea-surface temperature (SST), chlorophyll concentration, and primary production modeled from ocean color to quantify the meridional and seasonal patterns of upwelling dynamics and biological response. The unprecedented combination of data sets allows us to describe objectively the variability for small regions within each current and to characterize the governing factors for biological production. The temporal and spatial environmental variability was due in most regions to large-scale circulation, alone or in combination with offshore transport (local forcing). The observed meridional and seasonal patterns of biomass and primary production were most highly correlated to components representing large-scale circulation. The biomass sustained by a given nutrient concentration in the Atlantic EBCs was twice as large as that of the Pacific EBCs. This apparent greater efficiency may be due to availability of iron, physical retention, or differences in planktonic community structure.

A numerical model is used to quantify the pathways of carbon flow through the planktonic ecosystem from 1996 through 1998 at 9.5°S off the coast of Peru. The objective was to evaluate the response of the planktonic ecosystem to the forcing associated with normal conditions in 1996, the 1997–1998 El Niño, and the La Niña which began in June of 1998. During El Niño, the depth of the upper layer increased, temperature increased, and the nitrate concentration in the source water for upwelling was reduced. La Niña forcing was the opposite. The simulated phytoplankton biomass, carbon uptake, vertical export, and food available for higher trophic levels were reduced during the El Niño period compared to normal conditions. Phytoplankton biomass and uptake were slightly less during La Niña than in 1996, though carbon export and advective loss were significantly enhanced. A series of numerical experiments were run to determine whether the upwelling rate, source water characteristics, depth of the upper layer, or phytoplankton size composition of the source water was the primary forcing factor for the planktonic community. Although all factors contributed to the magnitude of the simulated response, the primary determinant for El Niño conditions was the concentration of new nitrogen in the upwelling source water, followed by depth of the upper layer and upwelling rate. The depth of the upper layer was the dominant forcing term for La Niña, followed by upwelling rate and temperature of the source water.

Seasonal climatologies of upper-ocean hydrographic properties and nutrients are presented for four different major coastal upwelling centers: the California, Peru-Humboldt, Canary, and Benguela regions. The climatologies are built from historical hydrographic data primarily to serve as a tool for comparative studies of productivity variations and nutrient fluxes in the near-coastal zone. Care was taken to ensure that quantities were interpolated vertically to, and averaged horizontally on, approximately neutral surfaces to constrain averaging among only those water masses that would naturally mix easily. Rather than rely on potential density surfaces that are not coincident with neutral surfaces in regions with large vertical excursions of isopycnals, the neutral surfaces were properly approximated through the use of specific volume anomaly (δ) surfaces, and were spaced closely in the vertical (approximately 0.1 σ-unit apart). Horizontal averaging to a 1/6° spatial grid was accomplished via the application of bicubic splines under tension, and provided sufficient spatial resolution for resolving upwelling patterns near the coastline. Seasonal mean nutrient-to-nutrient relationships also were constructed as another diagnostic tool for inter-regional comparisons, and are consistent with expected Redfield ratios. A consistent, high-resolution climatology is now publicly available as a tool for local and comparative studies of four different upwelling zones.

Results of a single‐blind round‐robin comparison of satellite primary productivity algorithms are presented. The goal of the round‐robin exercise was to determine the accuracy of the algorithms in predicting depth‐integrated primary production from information amenable to remote sensing. Twelve algorithms, developed by 10 teams, were evaluated by comparing their ability to estimate depth‐integrated daily production (IP, mg C m−2) at 89 stations in geographically diverse provinces. Algorithms were furnished information about the surface chlorophyll concentration, temperature, photosynthetic available radiation, latitude, longitude, and day of the year. Algorithm results were then compared with IP estimates derived from 14C uptake measurements at the same stations. Estimates from the best‐performing algorithms were generally within a factor of 2 of the 14C‐derived estimates. Many algorithms had systematic biases that can possibly be eliminated by reparameterizing underlying relationships. The performance of the algorithms and degree of correlation with each other were independent of the algorithms’ complexity.

We present the evolution of oceanographic conditions off the western coast of South America between 1996 and 1999, including the cold periods of 1996 and 1998–1999 and the 1997–1998 El Niño, using satellite observations of sea level, winds, sea surface temperature (SST), and chlorophyll concentration. Following a period of cold SST and low sea levels in 1996, both were anomalously high between March 1997 and May 1998. The anomalies were greatest between 5°S and 15°S, although they extended beyond 40°S. Two distinct peaks in sea level and SST occurred in June–July 1997 and December 1997 to January 1998, separated by a relaxation period (August–November) of weaker anomalies. Satellite winds were upwelling favorable throughout the time period for most of the region and in fact increased between November 1997 and March 1998 between 5°S and 25°S. Satellite‐derived chlorophyll concentrations are available for November 1996 to June 1997 (Ocean Color and Temperature Sensor (OCTS)) and then from October 1997 to present (Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS)). Near‐surface chlorophyll concentrations fell from May to June 1997 and from December 1997 to March 1998. The decrease was more pronounced in northern Chile than off the coast of Peru or central Chile and was stronger for larger cross‐shelf averaging bins since nearshore concentrations remained relatively high.

The evolution of oceanographic conditions in the upwelling region off northern Chile (18°–24°S) between 1996 and 1998 (including the 1997–1998 El Niño) is presented using hydrographic measurements acquired on quarterly cruises of the Chilean Fisheries Institute, with sea surface temperature (SST), sea level, and wind speeds from Arica (18.5°S), Iquique (20.5°S), and Antofagasta (23.5°S) and a time series of vertical temperature profiles off Iquique. Spatial patterns of sea surface temperature and salinity from May 1996 to March 1997 followed a normal seasonal progression, though conditions were anomalously cool and fresh. Starting in March 1997, positive anomalies in sea level and sea surface temperature propagated along the South American coast to 37°S. Maximum sea level anomalies occurred in two peaks in May–July 1997 and October 1997 to February 1998, separated by a relaxation period. Maximum anomalies (2°C and 0.1 practical salinity units (psu)) extended to 400 m in December 1997 within 50 km of the coast. March 1998 presented the largest surface anomalies (>4°C and 0.6 psu). Strong poleward flow (20–35 cm s−1) occurred to 400 m or deeper during both sea level maxima and weaker (10 cm s−1) equatorward flow followed each peak. By May 1998, SST had returned to the climatological mean, and flow was equatorward next to the coast. However, offshore salinity remained anomalously high owing to a tongue of subtropical water extending southeast along the Peruvian coast. Conditions off northern Chile returned to normal between August and December 1998. The timing of the anomalies suggests a connection to equatorial waves. The progression of the 1997–1998 El Niño was very similar to that of 1982–1983, though with different timing with respect to seasons.

Time series of satellite measurements are used to describe patterns of surface temperature and chlorophyll associated with the 1996 cold La Niña phase and the 1997–1998 warm El Niño phase of the El Niño‐Southern Oscillation cycle in the upwelling region off northern Chile. Surface temperature data are available through the entire study period. Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) data first became available in September 1997 during a relaxation in El Niño conditions identified by in situ hydrographic data. Over the time period of coincident satellite data, chlorophyll patterns closely track surface temperature patterns. Increases both in nearshore chlorophyll concentration and in cross‐shelf extension of elevated concentrations are associated with decreased coastal temperatures during both the relaxation in El Niño conditions in September‐November 1997 and the recovery from El Niño conditions after March 1998. Between these two periods during austral summer (December 1997 to March 1998) and maximum El Niño temperature anomalies, temperature patterns normally associated with upwelling were absent and chlorophyll concentrations were minimal. Cross‐shelf chlorophyll distributions appear to be modulated by surface temperature frontal zones and are positively correlated with a satellite‐derived upwelling index. Frontal zone patterns and the upwelling index in 1996 imply an austral summer nearshore chlorophyll maximum, consistent with SeaWiFS data from 1998–1999, after the El Niño. SeaWiFS retrievals in the data set used here are higher than in situ measurements by a factor of 2–4; however, consistency in the offset suggests relative patterns are valid.

This study provides a satellite-based estimate of potential primary production in the four Eastern Boundary Currents (EBCs), i.e. the California, Humboldt, Canary, and Benguela currents, from the first 24 months of the Sea-Viewing Wide Field of View Sensor, SeaWiFS. Within each EBC, production was estimated for the area of high chlorophyll concentration (>1mgm−3) or active area, which is likely to determine the production that can be utilized by higher trophic levels. Primary production decreased with latitude within each EBC while the extent of the active area was related to the magnitude of offshore transport. The most productive EBC was the Benguela Current (0.37GtCyr−1), followed by the Canary (0.33GtCyr−1), Humboldt (0.20GtCyr−1), and California (0.04GtCyr−1) Currents. Interannual differences between 1997, 1998, and 1999 were largest for 1997 (measured by the Ocean Color Temperature Scanner, OCTS), which may be due primarily to the different sensor and algorithm. The Humboldt Current was more productive, and the Canary much less, during 1997 than in the two following years. The El Niño of 1997–1998 led to smaller annual production in 1998 in the Pacific EBCs. The upper bound of sustainable fish yield was estimated assuming a food chain of 2.6 links and an average trophic efficiency of 10%. The resulting values are 4–150 times larger than the observed fish catch from 1990 through 1997. Actual catch data in the Benguela Current were 20 times smaller than in the Humboldt Current. The most likely explanations for the differences in potential and observed fish catch are related to differing trophic structure and spatial accessibility in different EBCs. If the estimated yield is an upper bound that will be decreased to 10% or 20% by environmental accessibility, the small pelagic fishery in all four EBCs is likely to be food-limited.

The North Atlantic east of the Grand Banks presents a thermal front from 40° to 50°N between the warm North Atlantic Current (NAC) and the cold Labrador Current. Here we use the trajectories of 84 isopycnal RAFOS floats deployed on the 27.2 and 27.5 σT surface in 1993–1995 and 218 surface drifters deployed by the International Ice Patrol and the Institut für Meereskunde (Kiel, Germany) between 1978 and 1993 to understand the pathways of the NAC. The mean flow pattern, kinetic energy, directional stability, and most probable path through 1° by 1° boxes are derived for each of the three surfaces. Speed and kinetic energy decrease with depth, although directional stability is comparable at all levels. The axis of the NAC, which follows the 4000 m isobath along the western boundary, is described by mean kinetic energy (MKE) values surpassing 100 cm2 s−2 at the surface or 50 cm2 s−2 on the float surfaces and correspond to regions with directional stabilities in excess of 60%. Maximum values of eddy kinetic energy are found just offshore of the maximum MKE associated with the NAC main pathway and decrease rapidly to the east. Two cyclonic meanders are identified at 44°N, 45°W near the Newfoundland Seamounts and at 46°N, 42°W near Flemish Cap. The main difference between the patterns derived for the surface drifters and floats was the greater eastward extent of the cyclonic trough at 44°N and intensity of the Mann Eddy (42°N, 44°W) during the float sampling period (1993–1995).

This study aims to identify the controlling processes of phytoplankton distributions in the Alboran Sea (western Mediterranean Sea). A three‐dimensional primitive equation model, the Navy Layered Ocean Model, forced by satellite‐measured winds from the European Remote Sensing satellites (ERS‐1 and 2) and the NASA scatterometer (NSCAT), is used to examine circulation from January 1996 to December 1998 and to simulate the distribution of passive tracers within the basin. We discuss the impact of the basin circulation on the observed patterns of chlorophyll observed by the Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) and the Ocean Color and Temperature Scanner (OCTS). The upper layer is fertilized with nutrients which are transported by the western anticyclonic gyre from the coastal upwelling sites in the northwest. Nutrients are supplied also by eddy‐induced upwelling in the periphery of the gyre path (found to be 20 to 60% of the supply due to advection in the present simulations). Circulation controls the supply of nutrients and the observed phytoplankton biomass in the upper layer during the nonbloom months (late spring, summer, and early fall). During the bloom regime, seasonal destratification is the dominant fertilizing process for the entire basin.

The first three years of SeaWiFS data (1997–2000) provide the most complete quantification to date of chlorophyll seasonal variability along the full latitudinal extent of the four major eastern boundary currents (EBCs). Comparisons to previously published chlorophyll seasonal climatologies deduced from the relatively sparse coverage provided by the Coastal Zone Color Scanner (CZCS) show significant differences in both southern hemisphere EBCs, while northern hemisphere regions are qualitatively similar. Comparisons between chlorophyll and cross‐shelf Ekman transport seasonal cycles, calculated from coincident satellite scatterometer data, show seasonal maxima have similar phases over most of the California Current, at higher (>32°S) latitudes in the Peru‐Chile and Benguela Currents (>30°S) and at lowest latitudes (< 20°N) in the Canary Current. Latitudinal zones within which phases diverge are indicative of alternate and/or more distant forcing.

A size-based ecosystem model was modified to include periodic upwelling events and used to evaluate the effect of episodic nutrient supply on the standing stock, carbon uptake, and carbon flow into mesozooplankton grazing and sinking flux in a coastal upwelling regime. Two ecosystem configurations were compared: a single food chain made up of net phytoplankton and mesozoo- plankton (one autotroph and one heterotroph, A1H1), and three interconnected food chains plus bacteria (three autotrophs and four heterotrophs, A3H4). The carbon pathways in the A1H1 simu- lations were under stronger physical control than those of the A3H4 runs, where the small size classes are not affected by frequent upwelling events. In the more complex food web simulations, the microbial pathway determines the total carbon uptake and grazing rates, and regenerated nitrogen accounts for more than half of the total primary production for periods of 20 days or longer between events. By contrast, new production, export of carbon through sinking and mesozooplankton grazing are more important in the A1H1 simulations. In the A3H4 simulations, the turnover time scale of the autotroph biomass increases as the period between upwelling events increases, because of the larger contribution of slow-growing net phytoplankton. The upwelling period was characterized for three upwelling sites from the alongshore wind speed measured by the NASA Scatterometer (NSCAT) and the corresponding model output compared with literature data. This validation exercise for three upwelling sites and a downstream embayment suggests that standing stock, carbon uptake and size fractionation were best supported by the A3H4 simulations, while the simulated sinking fluxes are not distinguishable in the two configurations.

The circulation and upwelling processes that control the phytoplankton distribution in the Alboran Sea (western Mediterranean) are examined from a climatological perspective for the first time. To characterize the annual cycle of the near‐surface phytoplankton patterns, we analyze the monthly distributions of pigments from the Coastal Zone Color Scanner (CZCS). Two regimes occur: a fall‐to‐winter bloom (November–March) and a non‐bloom period (May–September). These regimes differentiate the basin from other parts of the western Mediterranean, where a significant spring bloom occurs. The newest ocean color data sets available today from the Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) and the Ocean Color and Temperature Scanner (OCTS) fall within this annual progression. The combined interaction of seasonal stratification, coastal and gyre‐induced upwelling, and horizontal advection control the near‐surface pigment distribution in Alboran, while light availability does not determine the seasonal cycle of pigments.

The properties measured by isopycnal floats can be compiled to provide hydrographic information about the sampled surfaces. The height and temperature of two specific volume anomaly surfaces reported by 84 RAFOS floats deployed in the North Atlantic Current (NAC' region are compared here with the climatological hydrographic database. The mean pathway of the NAC and other prominent features of the region are similar in float‐derived and climatological surfaces. The most striking difference between floats and climatology, an extended trough in the NAC path at 44°N in the float‐derived surface, reflects the sampling time scales. The baroclinic transport of the NAC estimated from RAFOS floats using the observed climatological relationship between the potential energy anomaly and the height of the specific volume anomaly surfaces was 42 Sv at 42°N and 24 Sv at 47°N, in reasonable agreement with climatological estimates.