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A common strategy for calculating the direction and rate of carbon dioxide gas (CO2) exchange between the ocean and atmosphere relies on knowledge of the partial pressure of CO2 in surface seawater (pCO2(sw)), a quantity that is frequently observed by autonomous sensors on ships and moored buoys, albeit with significant spatial and temporal gaps. Here we present a monthly gridded data product of pCO2(sw) at 0.25∘ latitude by 0.25∘ longitude resolution in the northeastern Pacific Ocean, centered on the California Current System (CCS) and spanning all months from January 1998 to December 2020. The data product (RFR-CCS; Sharp et al., 2022; https://doi.org/10.5281/zenodo.5523389) was created using observations from the most recent (2021) version of the Surface Ocean CO2 Atlas (Bakker et al., 2016). These observations were fit against a variety of collocated and contemporaneous satellite- and model-derived surface variables using a random forest regression (RFR) model. We validate RFR-CCS in multiple ways, including direct comparisons with observations from sensors on moored buoys, and find that the data product effectively captures seasonal pCO2(sw) cycles at nearshore sites. This result is notable because global gridded pCO2(sw) products do not capture local variability effectively in this region, suggesting that RFR-CCS is a better option than regional extractions from global products to represent pCO2(sw) in the CCS over the last 2 decades. Lessons learned from the construction of RFR-CCS provide insight into how global pCO2(sw) products could effectively characterize seasonal variability in nearshore coastal environments. We briefly review the physical and biological processes – acting across a variety of spatial and temporal scales – that are responsible for the latitudinal and nearshore-to-offshore pCO2(sw) gradients seen in the RFR-CCS reconstruction of pCO2(sw). RFR-CCS will be valuable for the validation of high-resolution models, the attribution of spatiotemporal carbonate system variability to physical and biological drivers, and the quantification of multiyear trends and interannual variability of ocean acidification.

We introduce three new Empirical Seawater Property Estimation Routines (ESPERs) capable of predicting seawater phosphate, nitrate, silicate, oxygen, total titration seawater alkalinity, total hydrogen scale pH (pHT), and total dissolved inorganic carbon (DIC) from up to 16 combinations of seawater property measurements. The routines generate estimates from neural networks (ESPER_NN), locally interpolated regressions (ESPER_LIR), or both (ESPER_Mixed). They require a salinity value and coordinate information, and benefit from additional seawater measurements if available. These routines are intended for seawater property measurement quality control and quality assessment, generating estimates for calculations that require approximate values, original science, and producing biogeochemical property context from a data set. Relative to earlier LIR routines, the updates expand their functionality, including new estimated properties and combinations of predictors, a larger training data product including new cruises from the 2020 Global Data Analysis Project data product release, and the implementation of a first-principles approach for quantifying the impacts of anthropogenic carbon on DIC and pHT. We show that the new routines perform at least as well as existing routines, and, in some cases, outperform existing approaches, even when limited to the same training data. Given that additional training data has been incorporated into these updated routines, these updates should be considered an improvement over earlier versions. The routines are intended for all ocean depths for the interval from 1980 to ~2030 c.e., and we caution against using the routines to directly quantify surface ocean seasonality or make more distant predictions of DIC or pHT., 1,823

Over a decade ago, oceanographers began installing oxygen sensors on Argo floats to be deployed throughout the world ocean with the express objective of better constraining trends and variability in the ocean’s inventory of oxygen. Until now, measurements from these Argo-mounted oxygen sensors have been mainly used for localized process studies on air–sea oxygen exchange, biological pump efficiency, upper ocean primary production, and oxygen minimum zone dynamics. Here we present a four-dimensional gridded product of ocean interior oxygen, derived via machine learning algorithms trained on dissolved oxygen observations from Argo-mounted sensors and discrete measurements from ship-based surveys, and applied to temperature and salinity fields constructed from the global Argo array. The data product is called GOBAI-O2 for Gridded Ocean Biogeochemistry from Artificial Intelligence – Oxygen (Sharp et al., 2022; https://doi.org/10.25921/z72m-yz67; last access: 30 Aug. 2022); it covers 86 % of the global ocean area on a 1° latitude by 1° longitude grid, spans the years 2004–2021 with monthly resolution, and extends from the ocean surface to two kilometers in depth on 58 levels. Two machine learning algorithms — random forest regressions and feed-forward neural networks — are used in the development of GOBAI-O2, and the performance of those algorithms is assessed using real observations and Earth system model output. GOBAI-O2 is evaluated through comparisons to the World Ocean Atlas and to direct observations from large-scale hydrographic research cruises. Finally, potential uses for GOBAI-O2 are demonstrated by presenting average oxygen fields on isobaric and isopycnal surfaces, average oxygen fields across vertical–meridional sections, climatological cycles of oxygen averaged over different pressure intervals, and a globally integrated oxygen inventory time series.

To investigate changes in ocean structure during the spring transition and responses of biological activity, two BGC-Argo floats equipped with oxygen, fluorescence (to estimate chlorophyll a concentration – Chl a), backscatter (to estimate particulate organic carbon concentration – [POC]), and nitrate sensors conducted daily vertical profiles of the water column from a depth of 2000 m to the sea surface in the western North Pacific from January to April of 2018. Data for calibrating each sensor were obtained via shipboard sampling that occurred when the floats were deployed and recovered. During the float-deployment periods, repeated meteorological disturbances passed over the study area and caused the mixed layer to deepen. After deep-mixing events, the upper layer restratified and nitrate concentrations decreased while Chl a and POC concentrations increased, suggesting that spring mixing events promote primary productivity through the temporary alleviation of nutrient and light limitation. At the end of March, POC accumulation rates and nitrate decrease rates within the euphotic zone (0–70 m) were the largest of the four events observed, ranging from +84 to +210 mmol C m−2 d−1 and –28 to –49 mmol N m−2 d−1, respectively. The subsurface consumption rate of oxygen (i.e., the degradation rate of organic matter) after the fourth event (the end of March) was estimated to be –0.62 micromol O2 kg−1 d−1. At depths of 300–400 m (below the mixed layer), the POC concentrations increased slightly throughout the observation period. The POC flux at a depth of 300 m was estimated to be 1.1 mmol C m−2 d−1. Our float observation has made it possible to observed biogeochemical parameters, which previously could only be estimated by shipboard observation and experiments, in the field and in real time.

To calculate the direction and rate of carbon dioxide gas (CO2) exchange between the ocean and atmosphere, it is critical to know the partial pressure of CO2 in surface seawater (pCO2(sw)). Over the last decade, a variety of data products of global monthly pCO2(sw) have been produced, primarily for the open ocean on 1° latitude by 1° longitude grids. More recently, monthly products of pCO2(sw) that are more finely spatially resolved in the coastal ocean have been made available. A remaining challenge in the development of pCO2(sw) products is the robust characterization of seasonal variability, especially in nearshore coastal environments. Here we present a monthly data product of pCO2(sw) at 0.25° latitude by 0.25° longitude resolution in the Northeast Pacific Ocean, centered around the California Current System (CCS). The data product (RFR-CCS; Sharp et al., 2021; https://doi.org/10.5281/zenodo.5523389) was created using the most recent (2021) version of the Surface Ocean CO2 Atlas (Bakker et al., 2016) from which pCO2(sw) observations were extracted and fit against a variety of satellite- and model-derived surface variables using a random forest regression (RFR) model. We validate RFR-CCS in multiple ways, including direct comparisons with observations from moored autonomous surface platforms, and find that the data product effectively captures seasonal pCO2(sw) cycles at nearshore mooring sites. This result is notable because alternative global products for the coastal ocean do not capture local variability effectively in this region. We briefly review the physical and biological processes — acting across a variety of spatial and temporal scales — that are responsible for the latitudinal and nearshore-to-offshore pCO2(sw) gradients seen in RFR-CCS reconstructions of pCO2(sw).

International audience; The goal of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) field campaign is to develop a predictive understanding of the export, fate, and carbon cycle impacts of global ocean net primary production. To accomplish this goal, observations of export flux pathways, plankton community composition, food web processes, and optical, physical, and biogeochemical (BGC) properties are needed over a range of ecosystem states. Here we introduce the first EXPORTS field deployment to Ocean Station Papa in the Northeast Pacific Ocean during summer of 2018, providing context for other papers in this special collection. The experiment was conducted with two ships: a Process Ship, focused on ecological rates, BGC fluxes, temporal changes in food web, and BGC and optical properties, that followed an instrumented Lagrangian float; and a Survey Ship that sampled BGC and optical properties in spatial patterns around the Process Ship. An array of autonomous underwater assets provided measurements over a range of spatial and temporal scales, and partnering programs and remote sensing observations provided additional observational context. The oceanographic setting was typical of late-summer conditions at Ocean Station Papa: a shallow mixed layer, strong vertical and weak horizontal gradients in hydrographic properties, sluggish sub-inertial currents, elevated macronutrient concentrations and low phytoplankton abundances. Although nutrient concentrations were consistent with previous observations, mixed layer chlorophyll was lower than typically observed, resulting in a deeper euphotic zone. Analyses of surface layer temperature and salinity found three distinct surface water types, allowing for diagnosis of whether observed changes were spatial or temporal. The 2018 EXPORTS field deployment is among the most comprehensive biological pump studies ever conducted. A second deployment to the North Atlantic Ocean occurred in spring 2021, which will be followed by focused work on data synthesis and modeling using the entire EXPORTS data set.

Two Argo floats equipped with oxygen, chlorophyll (Chl), backscatter, and nitrate sensors conducted daily vertical profiles of the water column from a depth of 2000 m to the sea surface in the western North Pacific from January to April of 2018. Data for calibrating each sensor were obtained via shipboard sampling that occurred when the floats were deployed and recovered. Float backscatter observations were converted to particulate organic carbon (POC) concentrations using an empirical relationship derived from contemporaneous float profiles of backscatter and shipboard observations of suspended organic carbon particles. During the float deployment periods, repeated meteorological disturbances (storms) passed over the study area and caused the mixed layer to deepen. During these events, nitrate was entrained from deeper layers into the surface mixed layer, while Chl and POC in the surface mixed layer were redistributed into deeper layers. After the storms, the upper layer gradually restratified, nitrate concentrations in the surface layer decreased, and Chl and POC concentrations increased. When the floats observed the same water mass, the net community production within the euphotic layer (0–70 m), determined from the increases in POC, was 126–664 mg C m−2 d−1 (10.5–55.3 mmol C m−2 d−1) close to the values reported from a nearby area. The C/N ratio of the increase in POC and the decrease in nitrate was closed to the Redfield ratio, which indicates that the sensors were able to observe the net biochemical processes in this area despite the relatively low concentrations of nitrate and POC. To determine the fate of particles transported from the surface ocean to the twilight layer, the ratio of oxygen consumption and nitrate regeneration rates were compared. This O2/N ratio approached the Redfield ratio when the floats followed the same water mass continuously, but the consumption rate of POC was significantly lower than what would be expected based on the oxygen consumption and nitrate release rates. This suggests that dissolved organic carbon was the main substrate for the respiration in the twilight layer.

The number and quality of ocean pH measurements have increased substantially over the past few decades such that trends, variability, and spatial patterns of change are now being evaluated. However, comparing pH changes across domains with different initial pH values can be misleading because a pH change reflects a relative change in the hydrogen ion concentration ([H+], expressed in mol kg−1) rather than an absolute change in [H+]. We recommend that [H+] be used in addition to pH when describing such changes and provide three examples illustrating why.

Syntheses of carbonate chemistry spatial patterns are important for predicting ocean acidification impacts, but are lacking in coastal oceans. Here, we show that along the North American Atlantic and Gulf coasts the meridional distributions of dissolved inorganic carbon (DIC) and carbonate mineral saturation state (Ω) are controlled by partial equilibrium with the atmosphere resulting in relatively low DIC and high Ω in warm southern waters and the opposite in cold northern waters. However, pH and the partial pressure of CO2 (pCO2) do not exhibit a simple spatial pattern and are controlled by local physical and net biological processes which impede equilibrium with the atmosphere. Along the Pacific coast, upwelling brings subsurface waters with low Ω and pH to the surface where net biological production works to raise their values. Different temperature sensitivities of carbonate properties and different timescales of influencing processes lead to contrasting property distributions within and among margins., Anthropogenic CO2 is acidifying the ocean, but knowledge of the carbonate properties underlying these dynamics in coastal oceans is lacking. Here, the authors reveal spatial distribution patterns and variability in carbonate chemistry along North America’s coasts.

International audience; A positive marine chemistry‐climate feedback was originally proposed by Revelle and Suess (1957, https://doi.org/10.3402/tellusa.v9i1.9075), whereby the invasion flux of anthropogenic carbon into the ocean serves to inhibit future marine CO2 uptake through reductions to the buffering capacity of surface seawater. Here we use an ocean circulation‐carbon cycle model to identify an upper limit on the impact of reemergence of anthropogenic carbon into the ocean's mixed layer on the cumulative airborne fraction of CO2 in the atmosphere. We find under an RCP8.5 emissions pathway (with steady circulation) that the cumulative airborne fraction of CO2 has a sevenfold reduction by 2100 when the CO2 buffering capacity of surface seawater is maintained at preindustrial levels. Our results indicate that the effect of reemergence of anthropogenic carbon into the mixed layer on the buffering capacity of CO2 amplifies the transient climate sensitivity of the Earth system.

It has become clear that anthropogenic carbon invasion into the surface ocean drives changes in the seasonal cycles of carbon dioxide partial pressure (pCO(2)) and pH. However, it is not yet known whether the resulting sea-air CO2 fluxes are symmetric in their seasonal expression. Here we consider a novel application of observational constraints and modeling inferences to test the hypothesis that changes in the ocean's Revelle factor facilitate a seasonally asymmetric response in pCO(2) and the sea-air CO2 flux. We use an analytical framework that builds on observed sea surface pCO(2) variability for the modern era and incorporates transient dissolved inorganic carbon concentrations from an Earth system model. Our findings reveal asymmetric amplification of pCO(2) and pH seasonal cycles by a factor of two (or more) above preindustrial levels under Representative Concentration Pathway 8.5. These changes are significantly larger than observed modes of interannual variability and are relevant to climate feedbacks associated with Revelle factor perturbations. Notably, this response occurs in the absence of changes to the seasonal cycle amplitudes of dissolved inorganic carbon, total alkalinity, salinity, and temperature, indicating that significant alteration of surface pCO(2) can occur without modifying the physical or biological ocean state. This result challenges the historical paradigm that if the same amount of carbon and nutrients is entrained and subsequently exported, there is no impact on anthropogenic carbon uptake. Anticipation of seasonal asymmetries in the sea surface pCO(2) and CO2 flux response to ocean carbon uptake over the 21st century may have important implications for carbon cycle feedbacks. Plain Language Summary The ocean uptake of human released carbon dioxide (CO2) is causing the natural seasonal swings in seawater CO2 to grow over time. Using observations and numerical models, we conduct a theoretical experiment to see how the surface ocean may respond to continued carbon additions under business-as-usual future atmospheric CO2 concentrations. We find that between 1861 and 2100, the chemical properties of CO2 in seawater cause the seasonal CO2 maximum to grow by more than the seasonal CO2 minimum. As a result, the rate of summer surface ocean CO2 growth is different than winter, requiring year-round observations to accurately measure the overall annual ocean carbon absorption. Additionally, these seasonal CO2 changes affect how much carbon is lost from the ocean during high-CO2 periods relative to how much carbon is gained from the atmosphere during low-CO2 periods, creating a trend in the average ocean carbon absorption over years to decades that must be considered in the interpretation of marine carbon cycle observations and numerical models. These findings are important as they have implications for future rates of climate change and ocean acidification.

Fingerprinting ocean acidification (OA) in US West Coast waters is extremely challenging due to the large magnitude of natural carbonate chemistry variations common to these regions. Additionally, quantifying a change requires information about the initial conditions, which is not readily available in most coastal systems. In an effort to address this issue, we have collated high-quality publicly available data to characterize the modern seasonal carbonate chemistry variability in marine surface waters of the US Pacific Northwest. Underway ship data from version 4 of the Surface Ocean CO2 Atlas, discrete observations from various sampling platforms, and sustained measurements from regional moorings were incorporated to provide ∼  100 000 inorganic carbon observations from which modern seasonal cycles were estimated. Underway ship and discrete observations were merged and gridded to a 0.1°  ×  0.1° scale. Eight unique regions were identified and seasonal cycles from grid cells within each region were averaged. Data from nine surface moorings were also compiled and used to develop robust estimates of mean seasonal cycles for comparison with the eight regions. This manuscript describes our methodology and the resulting mean seasonal cycles for multiple OA metrics in an effort to provide a large-scale environmental context for ongoing research, adaptation, and management efforts throughout the US Pacific Northwest. Major findings include the identification of unique chemical characteristics across the study domain. There is a clear increase in the ratio of dissolved inorganic carbon (DIC) to total alkalinity (TA) and in the seasonal cycle amplitude of carbonate system parameters when moving from the open ocean North Pacific into the Salish Sea. Due to the logarithmic nature of the pH scale (pH  =  −log10[H+], where [H+] is the hydrogen ion concentration), lower annual mean pH values (associated with elevated DIC  :  TA ratios) coupled with larger magnitude seasonal pH cycles results in seasonal [H+] ranges that are ∼  27 times larger in Hood Canal than in the neighboring North Pacific open ocean. Organisms living in the Salish Sea are thus exposed to much larger seasonal acidity changes than those living in nearby open ocean waters. Additionally, our findings suggest that lower buffering capacities in the Salish Sea make these waters less efficient at absorbing anthropogenic carbon than open ocean waters at the same latitude.All data used in this analysis are publically available at the following websites: Surface Ocean CO2 Atlas version 4 coastal data, https://doi.pangaea.de/10.1594/PANGAEA.866856 (Bakker et al., 2016a);National Oceanic and Atmospheric Administration (NOAA) West Coast Ocean Acidification cruise data, https://doi.org/10.3334/CDIAC/otg.CLIVAR_NACP_West_Coast_Cruise_2007 (Feely and Sabine, 2013); https://doi.org/10.7289/V5JQ0XZ1 (Feely et al., 2015b); https://data.nodc.noaa.gov/cgi-bin/iso?id=gov.noaa.nodc:0157445 (Feely et al., 2016a); https://doi.org/10.7289/V5C53HXP (Feely et al., 2015a);University of Washington (UW) and Washington Ocean Acidification Center cruise data, https://doi.org/10.5281/zenodo.1184657 (Fassbender et al., 2018);Washington State Department of Ecology seaplane data, https://doi.org/10.5281/zenodo.1184657 (Fassbender et al., 2018);NOAA Moored Autonomous pCO2 (MAPCO2) buoy data, https://doi.org/10.3334/CDIAC/OTG.TSM_LAPUSH_125W_48N (Sutton et al., 2012); https://doi.org/10.3334/CDIAC/OTG.TSM_WA_125W_47N (Sutton et al., 2013); https://doi.org/10.3334/CDIAC/OTG.TSM_DABOB_122W_478N (Sutton et al., 2014a); https://doi.org/10.3334/CDIAC/OTG.TSM_TWANOH_123W_47N (Sutton et al., 2016a);UW Oceanic Remote Chemical/Optical Analyzer buoy data, https://doi.org/10.5281/zenodo.1184657 (Fassbender et al., 2018);NOAA Pacific Coast Ocean Observing System cruise data, https://doi.org/10.5281/zenodo.1184657 (Fassbender et al., 2018).

Inorganic carbon chemistry data from the surface and subsurface waters of the West Coast of North America have been compared with similar data from the northern Gulf of Mexico to demonstrate how future changes in CO2 emissions will affect chemical changes in coastal waters affected by respiration-induced hypoxia ([O2] ≤ ~ 60 µmol kg−1). In surface waters, the percentage change in the carbon parameters due to increasing CO2 emissions are very similar for both regions even though the absolute decrease in aragonite saturation is much higher in the warmer waters of the Gulf of Mexico. However, in subsurface waters the changes are enhanced due to differences in the initial oxygen concentration and the changes in the buffer capacity (i.e., increasing Revelle Factor) with increasing respiration from the oxidation of organic matter, with the largest impacts on pH and CO2 partial pressure (pCO2) occurring in the colder West Coast waters. As anthropogenic CO2 concentrations begin to build up in subsurface waters, increased atmospheric CO2 will expose organisms to hypercapnic conditions (pCO2 >1000 µatm) within subsurface depths. Since the maintenance of the extracellular pH appears as the first line of defense against external stresses, many biological response studies have been focused on pCO2-induced hypercapnia. The extent of subsurface exposure will occur sooner and be more widespread in colder waters due to their capacity to hold more dissolved oxygen and the accompanying weaker acid-base buffer capacity. Under present conditions, organisms in the West Coast are exposed to hypercapnic conditions when oxygen concentrations are near 100 µmol kg−1 but will experience hypercapnia at oxygen concentrations of 260 µmol kg−1 by year 2100 under the highest elevated-CO2 conditions. Hypercapnia does not occur at present in the Gulf of Mexico but will occur at oxygen concentrations of 170 µmol kg−1 by the end of the century under similar conditions. The aragonite saturation horizon is currently above the hypoxic zone in the West Coast. With increasing atmospheric CO2, it is expected to shoal up close to surface waters under the IPCC Representative Concentration Pathway (RCP) 8.5 in West Coast waters, while aragonite saturation state will exhibit steeper gradients in the Gulf of Mexico. This study demonstrates how different biological thresholds (e.g., hypoxia, CaCO3 undersaturation, hypercapnia) will vary asymmetrically because of local initial conditions that are affected differently with increasing atmospheric CO2. The direction of change in amplitude of hypercapnia will be similar in both ecosystems, exposing both biological communities from the West Coast and Gulf of Mexico to intensification of stressful conditions. However, the region of lower Revelle factors (i.e., the Gulf of Mexico), currently provides an adequate refuge habitat that might no longer be the case under the most severe RCP scenarios.

Surface ocean carbon chemistry is changing rapidly. Partial pressures of carbon dioxide gas (pCO2) are rising, pH levels are declining, and the ocean's buffer capacity is eroding. Regional differences in short-term pH trends primarily have been attributed to physical and biological processes; however, heterogeneous seawater carbonate chemistry may also be playing an important role. Here we use Surface Ocean CO2 Atlas (SOCAT) Version 4 data to develop 12-month gridded climatologies of carbonate system variables and explore the coherent spatial patterns of ocean acidification and attenuation in the ocean carbon sink caused by rising atmospheric pCO2. High-latitude regions exhibit the highest pH and buffer capacity sensitivities to pCO2 increases, while the equatorial Pacific is uniquely insensitive due to a newly defined aqueous CO2 concentration effect. Importantly, dissimilar regional pH trends do not necessarily equate to dissimilar acidity ([H+]) trends, indicating that [H+] is a more useful metric of acidification.

Seven years of data from the NOAA Kuroshio Extension Observatory (KEO) surface mooring, located in the North Pacific Ocean carbon sink region, were used to evaluate drivers of mixed-layer carbon cycling. A time-dependent mass balance approach relying on two carbon tracers was used to diagnostically evaluate how surface ocean processes influence mixed-layer carbon concentrations over the annual cycle. Results indicate that the annual physical carbon input is predominantly balanced by biological carbon uptake during the intense spring bloom. Net annual gas exchange that adds carbon to the mixed layer and the opposing influence of net precipitation that dilutes carbon concentrations make up smaller contributions to the annual mixed-layer carbon budget. Decomposing the biological term into annual net community production (aNCP) and calcium carbonate production (aCaCO3) yields 7 ± 3 mol C m−2 yr−1 aNCP and 0.5 ± 0.3 mol C m−2 yr−1 aCaCO3, giving an annually integrated particulate inorganic carbon to particulate organic carbon production ratio of 0.07 ± 0.05, as a lower limit. Although we find that vertical physical processes dominate carbon input to the mixed layer at KEO, it remains unclear how horizontal features, such as eddies, influence carbon production and export by altering nutrient supply as well as the depth of winter ventilation. Further research evaluating linkages between Kuroshio Extension jet instabilities, eddy activity, and nutrient supply mechanisms is needed to adequately characterize the drivers and sensitivities of carbon cycling near KEO.

Advances in technology and modeling capabilities are driving a surge in progress in our understanding of how ocean ecosystems mix and mingle on medium to small scales.

Evidence of ocean acidification (OA) throughout the global ocean has galvanized some coastal communities to evaluate carbonate chemistry variations closer to home. An impediment to doing this effectively is that, often, only one carbonate system parameter is measured at a time, while two are required to fully constrain the inorganic carbon chemistry of seawater. In order to leverage the abundant single-carbonate-parameter datasets in Washington State for more rigorous OA research, we have characterized an empirical relationship between total alkalinity (TA) and salinity (TA = 47.7 × S + 647; 1σ = ±17 μmol kg−1) for regional surface waters (≤25 m) that is robust in the salinity range from 20 to 35 for all seasons. The relationship was evaluated using 5 years of 3-h contemporaneous observations of salinity, carbon dioxide partial pressure (pCO2), and pH from a surface mooring on the outer coast of Washington. In situ pCO2 observations and salinity-based estimates of TA were used to calculate pH for comparison with in situ pH measurements. On average, the calculated pH values were 0.02 units lower than the measured pH values across multiple pH sensor deployments and showed extremely high fidelity in tracking the measured high-frequency pH variations. Our results indicate that the TA-salinity relationship will be a useful tool for expanding single-carbonate-parameter datasets in Washington State and quality controlling dual pCO2-pH time series.

Correlations between aragonite saturation state (ΩAr) and calcification have been identified in many laboratory manipulation experiments aiming to assess biological responses to ocean acidification (OA). These relationships have been used with projections of ΩAr under continued OA to evaluate potential impacts on marine calcifiers. Recent work suggests, however, that calcification in some species may be controlled by the ratio of bicarbonate to hydrogen ion, or the substrate-to-inhibitor ratio (SIR), rather than ΩAr. SIR and ΩAr are not always positively correlated in the natural environment, which means that ΩAr can be a poor indicator of the calcifying environment when ΩAr->1. Highly variable carbonate chemistry in the coastal zone challenges our ability to monitor fluctuations in ΩAr, SIR, and the ΩAr-SIR relationship making it difficult to assess biological OA exposures and vulnerability. Careful consideration of natural variability throughout ocean environments is required to accurately determine the influence of OA on biological calcification.

Seven years of near-continuous observations from the Ocean Station Papa (OSP) surface mooring were used to evaluate drivers of marine carbon cycling in the eastern subarctic Pacific. Processes contributing to mixed layer carbon inventory changes throughout each deployment year were quantitatively assessed using a time-dependent mass balance approach in which total alkalinity and dissolved inorganic carbon were used as tracers. By using two mixed layer carbon tracers, it was possible to isolate the influences of net community production (NCP) and calcification. Our results indicate that the annual NCP at OSP is 2 ± 1 mol C m−2 yr−1 and the annual calcification is 0.3 ± 0.3 mol C m−2 yr−1. Piecing together evidence for potentially significant dissolved organic carbon cycling in this region, we estimate a particulate inorganic carbon to particulate organic carbon ratio between 0.15 and 0.25. This is at least double the global average, adding to the growing evidence that calcifying organisms play an important role in carbon export at this location. These results, coupled with significant seasonality in the NCP, suggest that carbon cycling near OSP may be more complex than previously thought and highlight the importance of continuous observations for robust assessments of biogeochemical cycling.

Fingerprinting ocean acidification (OA) in U.S. West Coast waters is extremely challenging due to the large magnitude of natural carbonate chemistry variations common to these regions. Additionally, quantifying a change requires information about the initial conditions, which is not readily available in most coastal systems. In an effort to address this issue, we have collated high-quality, publicly-available data to characterize the modern seasonal carbonate chemistry variability in marine surface waters of the Pacific Northwest. Underway ship data from Version 4 of the Surface Ocean CO2 Atlas, discrete observations from various sampling platforms, and sustained measurements from regional moorings were incorporated to provide ~ 100,000 inorganic carbon observations from which modern seasonal cycles were estimated. Underway ship and discrete observations were merged and gridded to a 0.1° × 0.1° scale. Eight unique regions were identified and seasonal cycles from grid cells within each region were averaged. Data from nine surface moorings were also compiled and used to develop robust estimates of mean seasonal cycles for comparison with the eight regions. This manuscript describes our methodology and the resulting mean seasonal cycles for multiple OA metrics in an effort to provide large-scale, environmental context for ongoing research, adaptation, and management efforts throughout the Pacific Northwest. Major findings include the identification of unique chemical characteristics across the study domain. There is a clear increase in the ratio of dissolved inorganic carbon (DIC) to total alkalinity (TA) and in the seasonal cycle amplitude of carbonate system parameters when moving from the open ocean North Pacific into the Salish Sea. Due to the logarithmic nature of the pH scale (pH = −log10[H+], where [H+] is the hydrogen ion concentration), lower annual mean pH values (associated with elevated DIC : TA) coupled with larger magnitude seasonal pH cycles results in seasonal [H+] ranges that are ~ 27 times larger in Hood Canal than in the neighboring North Pacific open ocean. Organisms living in the Salish Sea are thus exposed to much larger seasonal acidity changes than those living in nearby open ocean waters. Additionally, our findings suggest that lower buffering capacities in the Salish Sea make these waters less efficient at absorbing anthropogenic carbon than open ocean waters at the same latitude. All data used in this analysis are publically available at the following websites: • Surface Ocean CO2 Atlas Version 4 coastal data, doi:10.1594/PANGAEA.866856; • National Oceanic and Atmospheric Administration (NOAA) West Coast Ocean Acidification cruise data, doi:10.3334/CDIAC/otg.CLIVAR_NACP_West_Coast_Cruise_2007; doi:10.3334/CDIAC/OTG.COAST_WCOA2011; doi:10.3334/CDIAC/OTG.COAST_WCOA2012; doi:10.7289/V5C53HXP; • University of Washington (UW) and Washington Ocean Acidification Center cruise data, doi:10.5281/zenodo.1184657; • Washington State Department of Ecology seaplane data, 10.5281/zenodo.1184657; • NOAA Moored Autonomous pCO2 (MAPCO2) Buoy data, doi:10.3334/CDIAC/OTG.TSM_LAPUSH_125W_48N; doi:10.3334/CDIAC/OTG.TSM_WA_125W_47N; doi:10.3334/CDIAC/OTG.TSM_DABOB_122W_478N; doi:10.3334/CDIAC/OTG.TSM_TWANOH_123W_47N; • UW Oceanic Remote Chemical/Optical Analyzer Buoy data, doi:10.5281/zenodo.1184657; • NOAA Pacific Coast Ocean Observing System cruise data, doi:10.5281/zenodo.1184657.

Ocean carbon monitoring efforts have increased dramatically in the past few decades in response to the need for better marine carbon cycle characterization. Autonomous pH and carbon dioxide (CO2) sensors capable of yearlong deployments are now commercially available; however, due to their strong covariance, this is the least desirable pair of carbonate system parameters to measure for high-quality, in situ, carbon-cycle studies. To expand the number of tools available for autonomous carbonate system observations, we have developed a robust surface ocean dissolved inorganic carbon (DIC) sensor capable of extended (year) field deployments with a laboratory determined uncertainty of ±5 μmol kg(-1). Results from the first two field tests of this prototype sensor indicate that measurements of DIC are ∼90% more accurate than estimates of DIC calculated from contemporaneous and collocated measurements of pH and CO2. The improved accuracy from directly measuring DIC gives rise to new opportunities for quantitative, autonomous carbon-cycle studies.

Sabine, C. L. et al., As a response to public demand for a well-documented, quality controlled, publically available, global surface ocean carbon dioxide (CO2) data set, the international marine carbon science community developed the Surface Ocean CO2 Atlas (SOCAT). The first SOCAT product is a collection of 6.3 million quality controlled surface CO2 data from the global oceans and coastal seas, spanning four decades (1968–2007). The SOCAT gridded data presented here is the second data product to come from the SOCAT project. Recognizing that some groups may have trouble working with millions of measurements, the SOCAT gridded product was generated to provide a robust, regularly spaced CO2 fugacity (fCO2) product with minimal spatial and temporal interpolation, which should be easier to work with for many applications. Gridded SOCAT is rich with information that has not been fully explored yet (e.g., regional differences in the seasonal cycles), but also contains biases and limitations that the user needs to recognize and address (e.g., local influences on values in some coastal regions)., SOCAT is promoted by IOCCP, the Sur- face Ocean Lower Atmosphere Study, and the Integrated Marine Biogeochemistry and Ecosystem Research program. Douglas Wallace (Dalhousie University, Canada and former SOLAS chair) has strongly encouraged SOCAT. Support has been received from the University of Bergen (Norway), the Bjerknes Centre for Cli- mate Research (Norway), the National Oceanic and Atmospheric Administration (United States), the University of Washington (United States), Oak Ridge National Laboratory (United States), the University of East Anglia (United Kingdom), PANGAEA – Data Publisher for Earth & Environmental data (Germany), the Alfred Wegener Institute for Polar and Marine Research (Ger- many), the Centre National de la Recherche Scientifique (France), the CarboOcean (Norway, GOCE 511176-1) and CarboChange (Norway, FP7 264879) projects of the European Union, the US National Science Foundation (United States, OCE-1068958), the international Scientific Committee on Oceanic Research (SCOR, United States, OCE-0938349), and the UK Ocean Acidification Research Programme (NE / H017046 / 1; funded by the Natural Environment Research Council, the Department for Energy and Climate Change and the Department for Environment, Food and Rural A ff airs). Support for SOCAT meetings has been received from IOCCP, IMBER, the European Cooperation in Science and Technology (COST) Action 735 (United Kingdom), Geomar (Germany), the National Institute for Environmental Studies (Japan), and the Commonwealth Scientific and Industrial Research Organisation (Australia).

As climate-science graduate students at the University of Washington, we had the opportunity to engage in a political process focused on implementing legislation to reduce greenhouse gas emissions in Washington State. Our insights gained from this rare, first-hand, experience may be particularly relevant to other climate scientists. We argue that inflexible research goals within the United States climate-science community limit the relevance of the knowledge our community creates. The mismatch between climate-science research and the information needs of policy makers, while widely acknowledged in certain domains, has yet to be fully appreciated within many earth science disciplines. Broadening the climate-science training of graduate students to include education on the uses of climate information outside of academic settings would both inform and motivate new research directions, and engender validation of non-traditional research within disciplinary cultures.

Coastal upwelling events in the California Current System can transport subsurface waters with high levels of carbon dioxide (CO 2 ) to the sea surface near shore. As these waters age and are advected offshore, CO 2 levels decrease dramatically, falling well below the atmospheric concentration beyond the continental shelf break. In May 2007 we observed an upwelling event off the coast of northern California. During the upwelling event subsurface respiration along the upwelling path added ∼35 μmol kg −1 of dissolved inorganic carbon (DIC) to the water as it transited toward shore causing the waters to become undersaturated with respect to Aragonite. Within the mixed layer, p CO 2 levels were reduced by the biological uptake of DIC (up to 70%), gas exchange (up to 44%), and the addition of total alkalinity through CaCO 3 dissolution in the undersaturated waters (up to 23%). The percentage contribution of each of these processes was dependent on distance from shore. At the time of measurement, a phytoplankton bloom was just beginning to develop over the continental shelf. A box model was used to project the evolution of the water chemistry as the bloom developed. The biological utilization of available nitrate resulted in a DIC decrease of ∼200 μmol kg −1 , sea surface p CO 2 near ∼200 ppm, and an aragonite saturation state of ∼3. These results suggest that respiration processes along the upwelling path generally increase the acidification of the waters that are being upwelled, but once the waters reach the surface biological productivity and gas exchange reduce that acidification over time.

19 páginas, 6 tablas, 4 figuras.-- B. Pfeil ... et al.-- Proyecto Carbochange.-- Distribuido bajo licencia Creative Commons, A well-documented, publicly available, global data set of surface ocean carbon dioxide (CO2) parameters has been called for by international groups for nearly two decades. The Surface Ocean CO2 Atlas (SOCAT) project was initiated by the international marine carbon science community in 2007 with the aim of providing a comprehensive, publicly available, regularly updated, global data set of marine surface CO2, which had been subject to quality control (QC). Many additional CO2 data, not yet made public via the Carbon Dioxide Information Analysis Center (CDIAC), were retrieved from data originators, public websites and other data centres. All data were put in a uniform format following a strict protocol. Quality control was carried out according to clearly defined criteria. Regional specialists performed the quality control, using state-of-the-art web-based tools, specially developed for accomplishing this global team effort. SOCAT version 1.5 was made public in September 2011 and holds 6.3 million quality controlled surface CO2 data points from the global oceans and coastal seas, spanning four decades (1968–2007). Three types of data products are available: individual cruise files, a merged complete data set and gridded products. With the rapid expansion of marine CO2 data collection and the importance of quantifying net global oceanic CO2 uptake and its changes, sustained data synthesis and data access are priorities., Bjerknes Centre for Climate Research, University of Bergen, Uni Research (Norway), US National Oceanic and Atmospheric Administration, University of Washington, Oak Ridge National Laboratory (US), University of East Anglia (UEA, UK), PANGAEA