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The distributions and temporal shifts of transient tracer fields in the ocean should theoretically facilitate an understanding of ocean ventilation processes on different timescales although this is not often realized in reality. An approach is to concurrently analyze distributions of multiple tracers to enhance data resolution and to expand independent observational factors for model formulation. A set of concurrent tritium, excess 3He, and chlorofluorocarbon measurements from a meridional section in the eastern North Atlantic is used to test the suggestion.

The distributions of chlorofluorocarbon-11 (CFC-11) and CFC-12 which were measured as part of a hydrographic section of the eastern North Atlantic between Icelandand the equator during Jul-Aug 1988 were presented. CFCs are used as transient tracers to study large-scale ocean circulation. The ventilation time-scales andwater mass pathways in the eastern basin of the North Atlantic were illustratedbased on CFC distribution data in conjunction with hydrographic data taken during the study cruise.

The dynamics of the planktonic ecosystem in the coastal upwelling zone within the California Current System is studied using a three-dimensional (3-D), eddy-resolving circulation model coupled to an ecosystem/biogeochemistry model. Results reveal that the model is capable of replicating many of the large-scale, time-averaged features of the coastal upwelling system.

Coastal water clarity varies at high temporal and spatial scales due to weather, climate, and human activity along coastlines. Systematic observations are crucial to assessing the impact of water clarity change on aquatic habitats. In this study, Secchi disk depths (Z SD) from Boston Harbor, Buzzards Bay, Cape Cod Bay, and Narragansett Bay water quality monitoring organizations were compiled to validate Z SD derived from Landsat 8 (L8) imagery, and to generate high spatial resolution Z SD maps. From 58 L8 images, acceptable agreement was found between in situ and L8 Z SD in Buzzards Bay (N = 42, RMSE = 0.96 m, MAPD = 28%), Cape Cod Bay (N = 11, RMSE = 0.62 m, MAPD = 10%), and Narragansett Bay (N = 8, RMSE = 0.59 m, MAPD = 26%). This work demonstrates the value of merging in situ Z SD with high spatial resolution remote sensing estimates for improved coastal water quality monitoring. • Robust comparison of high spatial satellite imagery with coastal water clarity measurements • Good agreement between same day in situ and satellite water clarity matchups • Variability in water clarity captured with satellite imagery [ABSTRACT FROM AUTHOR]

Abstract: We quantify the mechanisms governing interannual variability in the global, upper-ocean inorganic carbon system using a hindcast simulation (1979–2004) of an ecosystem-biogeochemistry model forced with time-evolving atmospheric physics and dust deposition. We analyze the variability of three key, interrelated metrics—air–sea CO2 flux, surface-water carbon dioxide partial pressure pCO2, and upper-ocean dissolved inorganic carbon (DIC) inventory—presenting for each metric global spatial maps of the root mean square (rms) of anomalies from a model monthly climatology. The contribution of specific driving factors is diagnosed using Taylor expansions and linear regression analysis. The major regions of variability occur in the Southern Ocean, tropical Indo-Pacific, and Northern Hemisphere temperate and subpolar latitudes. Ocean circulation is the dominant factor driving variability over most of the ocean, modulating surface dissolved inorganic carbon that in turn alters surface-water pCO2 and air–sea CO2 flux variability (global integrated anomaly rms of 0.34PgCyr−1). Biological export and thermal solubility effects partially damp circulation-driven pCO2 variability in the tropics, while in the subtropics, thermal solubility contributes positively to surface-water pCO2 and air–sea CO2 flux variability. Gas transfer and net freshwater inputs induce variability in the air–sea CO2 flux in some specific regions. A component of air–sea CO2 flux variability (global integrated anomaly rms of 0.14PgCyr−1) arises from variations in biological export production induced by variations in atmospheric iron deposition downwind of dust source regions. Beginning in the mid-1990s, reduced global dust deposition generates increased air–sea CO2 outgassing in the Southern Ocean, consistent with trends derived from atmospheric CO2 inversions. [Copyright &y& Elsevier]

Abstract: Improved sampling technologies, international observing networks, and data synthesis efforts are providing an unprecedented view of the global patterns and decadal variability of surface-ocean partial pressure of carbon dioxide (pCO2) and air–sea CO2 flux. A new observational synthesis for surface-ocean pCO2 leads to a global ocean net CO2 sink of −1.8PgCyr−1 (±0.7); continental margins and estuaries together act as a small net source (∼0.15PgCyr−1). New results on decadal trends indicate recent decreases in efficiency of the ocean to absorb CO2 in the Southern Ocean, North Atlantic, and Equatorial Pacific. Although we do not yet have an estimate of the trend in the global oceanic sink of CO2, the existing observations may help explain temporal variations in the fraction of anthropogenic CO2 emissions that remain in the atmosphere (airborne fraction). Major vulnerabilities in the future behavior of the ocean-carbon–climate system include the effects of ocean warming, enhanced vertical stratification, strengthening and poleward contraction of westerly winds in the Southern Ocean, and shifts in the biological pump and ecosystem functioning. To address issues of both ocean-carbon variability and vulnerability, a sustained surface-ocean-carbon-observing system needs to be established with improved global spatial coverage and internationally coordinated data synthesis activities. [Copyright &y& Elsevier]

Abstract: A decade-long Synthesis and Modeling Project (SMP) was conducted as the final element of the US Joint Global Ocean Flux Study (JGOFS). The SMP goal was to synthesize knowledge gained from field studies into a set of models that reflect our current understanding of the oceanic carbon cycle. Specific, innovative aspects of the project included the close partnership among scientists conducting field, laboratory, remote sensing, and numerical research and the strong emphasis on data management and web-based, public release of models and data products. Several recurrent science themes arose across the SMP effort including: the development of a new generation of ocean ecosystem and biogeochemistry models that include iron limitation, flexible elemental composition, size structure, geochemical functional groups, and particle composition; the application of inverse models and data assimilation techniques to marine food-web data; the creation of whole-ocean synthesis products from the JGOFS global CO2 survey and other studies; and the analysis and modeling of ecosystem and biogeochemical responses to climate and CO2 system perturbations on time-scales ranging from seasonal and inter-annual variability to anthropogenic climate warming and longer. [Copyright &y& Elsevier]

Presents a study which examined the iron cycling and nutrient-limitation patterns in surface waters of the world ocean. Use of a global marine ecosystem mixed-layer model to examine phytoplankton growth rates; Methodology; Results and discussion.

Presents a study which developed a global marine ecosystem model. Integration of field data collected as part of the Joint Global Ocean Flux Study program; Methods; Results and discussion.

Focuses on the Synthesis and Modeling Project (SMP) of the United States Joint Global Ocean Flux Study program on marine biogeochemistry and ocean carbon cycle. Objectives of the SMP; Theoretical background on marine biogeochemistry; Results of some SMP research projects.

Abstract: The US Joint Global Ocean Flux Study (JGOFS) database management system is an online, oceanographic database assembled from the research activities of the US JGOFS field and Synthesis and Modeling Program (SMP). It is based on modern, object-oriented programming, with a web-based user interface (http://usjgofs.whoi.edu/jg/dir/jgofs) that gives all users, regardless of the computer platform being used, equal access to the data and metadata. It is populated with an extensive set of biogeochemical data from the US JGOFS community along with the attendant metadata. This article summarizes the lessons learned that may serve as a primer for future oceanographic and earth science research programs. Good data management requires devoted resources, about 5–10% of the total cost of the program. A data management office should be established at the initiation of the program, conventions for standard methods, names, and units need to be established before the field program begins, and an agreed-to list of metadata must be collected systematically along with the data. Open and accessible data management depends upon investigators agreeing to share their data with each other, leading to more rapid scientific discovery. Data management should support data distribution and archival; interactions between the data managers and the principal investigators make the database a living database. Innovative use of commercial products in information technology can save time and money in scientific database management. Technology allows access to the database to be transparent in location and intuitive in use. Finally, the most important investments in data management are the people hired. [Copyright &y& Elsevier]

Presents a study on how mesoscale variability impacts the large-scale patterns and magnitudes of biogeochemical fluxes in the North Atlantic ocean. Characterization of the physical eddy environment; Measures of time/space variability; Models used in studying the effect of hydrodynamical mesoscale processes on planktonic ecosystems of the North Atlantic ocean; Quantification of mesoscale variability's role on plankton dynamics.

Abstract: The uptake of atmospheric carbon dioxide (CO2) into the mid-latitudes of the North Atlantic Ocean through the production of wintertime Sub-Tropical Mode Water (STMW) also known as Eighteen Degree Water (EDW) is poorly quantified and constrained. Nonetheless, it has been proposed that the EDW could serve as an important short-term sink of anthropogenic CO2. The objective of the present investigation was to determine sea–air CO2 gas exchange rates and seawater CO2 dynamics during wintertime formation of EDW in the North Atlantic Ocean. During 2006 and 2007, several research cruises were undertaken as part of the CLIMODE project across the northwest Atlantic Ocean with the intent to study the pre-conditioning, formation, and the evolution of EDW. Sea–air CO2 exchange rates were calculated based on measurements of atmospheric pCO2, surface seawater pCO2 and wind speed with positive values denoting a net flux from the surface ocean to the atmosphere. Average sea–air CO2 flux calculated along cruise tracks in the formation region equaled −18±6mmol CO2 m−2 d−1 and −14±9mmol CO2 m−2 d−1 in January of 2006 and March of 2007, respectively. Average sea–air CO2 flux in newly formed outcropping EDW in February and March of 2007 equaled −28±10mmol CO2 m−2 d−1. These estimates exceeded previous flux estimates in this region by 40–185%. The magnitude of CO2 flux was mainly controlled by the observed variability in wind speed and ΔpCO2 with smaller changes owing to variability in sea surface temperature. Small but statistically significant difference (4.1±2.6μmolkg−1) in dissolved inorganic carbon (DIC) was observed in two occurrences of newly formed EDW in February and March of 2007. This difference was explained either by differences in the relative contribution from different water masses involved in the initial formation process of EDW or temporal changes owing to sea–air CO2 exchange (∼25%) and vertical and/or lateral mixing (∼75%) with water masses high in DIC from the cold side of the Gulf Stream and/or from below the permanent thermocline. Based on the present estimate of sea–air CO2 flux in newly formed EDW and a formation rate of 9.3Svy (Sverdrup year=106 m3 s−1 flow sustained for 1 year), CO2 uptake by newly formed EDW may constitute 3–6% of the total North Atlantic CO2 sink. However, advection of surface waters that carry an elevated burden of anthropogenic CO2 that are transported to the formation region and transformed to mode water may contribute additional CO2 to the total net uptake and sequestration of anthropogenic CO2 to the ocean interior. [Copyright &y& Elsevier]

Abstract: Detection and attribution of hydrographic and biogeochemical changes in the deep ocean are challenging due to the small magnitude of their signals and to limitations in the accuracy of available data. However, there are indications that anthropogenic and climate change signals are starting to manifest at depth. The deep ocean below 2000m comprises about 50% of the total ocean volume, and changes in the deep ocean should be followed over time to accurately assess the partitioning of anthropogenic carbon dioxide (CO2) between the ocean, terrestrial biosphere, and atmosphere. Here we determine the changes in the interior deep-water inorganic carbon content by a novel means that uses the partial pressure of CO2 measured at 20°C, pCO2(20), along three meridional transects in the Atlantic and Pacific oceans. These changes are measured on decadal time scales using observations from the World Ocean Circulation Experiment (WOCE)/World Hydrographic Program (WHP) of the 1980s and 1990s and the CLIVAR/CO2 Repeat Hydrography Program of the past decade. The pCO2(20) values show a consistent increase in deep water over the time period. Changes in total dissolved inorganic carbon (DIC) content in the deep interior are not significant or consistent, as most of the signal is below the level of analytical uncertainty. Using an approximate relationship between pCO2(20) and DIC change, we infer DIC changes that are at the margin of detectability. However, when integrated on the basin scale, the increases range from 8–40% of the total specific water column changes over the past several decades. Patterns in chlorofluorocarbons (CFCs), along with output from an ocean model, suggest that the changes in pCO2(20) and DIC are of anthropogenic origin. [Copyright &y& Elsevier]

Abstract: Significant effort has been invested in understanding the role of iron in marine ecosystems over the past few decades. What began as shipboard amendment experiments quickly grew into a succession of in situ, mesoscale ocean iron fertilization (OIF) experiments carried out in all three high nutrient low chlorophyll (HNLC) regions of the world ocean. Dedicated process studies have also looked at regions of the ocean that are seasonally exposed to iron-replete conditions as natural OIF experiments. However, one problem common to many OIF experiments is determination of biological response beyond the duration of the experiment (typically<1 month). Satellite-derived products have been used to address this shortcoming with some success, but thus far, have been limited snapshots of a single parameter, chlorophyll. Here, we investigate phytoplankton responses to OIF in both purposeful and naturally iron enriched systems using estimates of chlorophyll (Chl), phytoplankton carbon biomass (Cphyto), their ratio (Chl:Cphyto) and two fluorescence indices, fluorescence per unit chlorophyll (FLH:Chl) and the chlorophyll fluorescence efficiency (ϕ f ). These quantities allow partitioning of the biological response to OIF into that due to changes in biomass and that due to phytoplankton physiology. We find that relative increases in Chl (∼10–20x) following OIF far exceed increases in Cphyto (<4–5x), suggesting that a significant fraction of the observed Chl increase is associated with physiological adjustment to increased growth rates, photoacclimation, and floristic shifts in the phytoplankton community. Further, a consistent pattern of decreased satellite fluorescence efficiency (FLH:Chl or ϕ f ) following OIF is observed that is in agreement with current understanding of phytoplankton physiological responses to relief from iron stress. The current study extends our ability to retrieve phytoplankton physiology from space-based sensors, strengthens the link between satellite fluorescence and iron availability, and shows that satellite ocean color analyses provide a unique tool for monitoring OIF experiments. [Copyright &y& Elsevier]

Abstract: In this paper, we review the state of the art and major challenges in current efforts to incorporate biogeochemical functional groups into models that can be applied on basin-wide and global scales, with an emphasis on models that might ultimately be used to predict how biogeochemical cycles in the ocean will respond to global warming. We define the term “biogeochemical functional group” to refer to groups of organisms that mediate specific chemical reactions in the ocean. Thus, according to this definition, “functional groups” have no phylogenetic meaning—these are composed of many different species with common biogeochemical functions. Substantial progress has been made in the last decade toward quantifying the rates of these various functions and understanding the factors that control them. For some of these groups, we have developed fairly sophisticated models that incorporate this understanding, e.g. for diazotrophs (e.g. Trichodesmium), silica producers (diatoms) and calcifiers (e.g. coccolithophorids and specifically Emiliania huxleyi). However, current representations of nitrogen fixation and calcification are incomplete, i.e., based primarily upon models of Trichodesmium and E. huxleyi, respectively, and many important functional groups have not yet been considered in open-ocean biogeochemical models. Progress has been made over the last decade in efforts to simulate dimethylsulfide (DMS) production and cycling (i.e., by dinoflagellates and prymnesiophytes) and denitrification, but these efforts are still in their infancy, and many significant problems remain. One obvious gap is that virtually all functional group modeling efforts have focused on autotrophic microbes, while higher trophic levels have been completely ignored. It appears that in some cases (e.g., calcification), incorporating higher trophic levels may be essential not only for representing a particular biogeochemical reaction, but also for modeling export. Another serious problem is our tendency to model the organisms for which we have the most validation data (e.g., E. huxleyi and Trichodesmium) even when they may represent only a fraction of the biogeochemical functional group we are trying to represent. When we step back and look at the paleo-oceanographic record, it suggests that oxygen concentrations have played a central role in the evolution and emergence of many of the key functional groups that influence biogeochemical cycles in the present-day ocean. However, more subtle effects are likely to be important over the next century like changes in silicate supply or turbulence that can influence the relative success of diatoms versus dinoflagellates, coccolithophorids and diazotrophs. In general, inferences drawn from the paleo-oceanographic record and theoretical work suggest that global warming will tend to favor the latter because it will give rise to increased stratification. However, decreases in pH and Fe supply could adversely impact coccolithophorids and diazotrophs in the future. It may be necessary to include explicit dynamic representations of nitrogen fixation, denitrification, silicification and calcification in our models if our goal is predicting the oceanic carbon cycle in the future, because these processes appear to play a very significant role in the carbon cycle of the present-day ocean and they are sensitive to climate change. Observations and models suggest that it may also be necessary to include the DMS cycle to predict future climate, though the effects are still highly uncertain. We have learned a tremendous amount about the distributions and biogeochemical impact of bacteria in the ocean in recent years, yet this improved understanding has not yet been incorporated into many of our models. All of these considerations lead us toward the development of increasingly complex models. However, recent quantitative model intercomparison studies suggest that continuing to add complexity and more functional groups to our ecosystem models may lead to decreases in predictive ability if the models are not properly constrained with available data. We also caution that capturing the present-day variability tells us little about how well a particular model can predict the future. If our goal is to develop models that can be used to predict how the oceans will respond to global warming, then we need to make more rigorous assessments of predictive skill using the available data. [Copyright &y& Elsevier]