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A multiparameter mixing approach, ‘MIX’, for determining oceanic anthropogenic CO2 was used to reconstruct the industrial-era change in the 13C/12C of dissolved inorganic carbon (δ13C of DIC) along the 1992 165°E WOCE P13N section in the North Pacific Ocean. The back-calculation approach was tested against a known anthropogenic tracer, chlorofluorocarbon-11 (CFC-11), and also by reconstructing an ocean general circulation model's (OGCM) anthropogenic δ13C change. MIX proved accurate to ±10% against measured CFC-11, but only to ±∼25% reconstructing the OGCM's δ13C change from 1992 model output. The OGCM's CFC distribution was also poorly reconstructed using MIX, indicating that this test suffers from limitations in the OGCM's representation of water masses in the ocean. The MIX industrial-era near-surface (200 m) δ13C change reconstructed from the WOCE P13N data ranged from −0.8‰ in the subtropics (15–30°N), to −0.6‰ in the tropics (10°N), and −0.4 to −0.2‰ north of 40°N. Depth-integrated changes along 165°E were −400‰·m to −500‰·m at low latitudes, and were smaller (−200‰·m) north of 40°N. The MIX North Pacific δ13C change is consistent with the global anthropogenic CO2 inventory of 118 ± 17 Pg from ΔC*. [ABSTRACT FROM AUTHOR]

The spatiotemporal variability of upper ocean inorganic carbon parameters and air-sea CO2 exchange in the Indian Ocean was examined using inorganic carbon data collected as part of the World Ocean Circulation Experiment (WOCE) cruises in 1995. Multiple linear regression methods were used to interpolate and extrapolate the temporally and geographically limited inorganic carbon data set to the entire Indian Ocean basin using other climatological hydrographic and biogeochemical data. The spatiotemporal distributions of total carbon dioxide (TCO2), alkalinity, and seawater pCO2 were evaluated for the Indian Ocean and regions of interest including the Arabian Sea, Bay of Bengal, and 10°N-35°S zones. The Indian Ocean was a net source of CO2 to the atmosphere, and a net sea-to-air CO2 flux of +237 ± 132 Tg C yr-1 (+0.24 Pg C yr-1) was estimated. Regionally, the Arabian Sea, Bay of Bengal, and 10°N-10°S zones were perennial sources of CO2 to the atmosphere. In the 10°S-35°S zone, the CO2 sink or source status of the surface ocean shifts seasonally, although the region is a net oceanic sink of atmospheric CO2. [ABSTRACT FROM AUTHOR]

Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends continue, key marine organisms—such as corals and some plankton—will have difficulty maintaining their external calcium carbonate skeletons. Here we use 13 models of the ocean–carbon cycle to assess calcium carbonate saturation under the IS92a ‘business-as-usual’ scenario for future emissions of anthropogenic carbon dioxide. In our projections, Southern Ocean surface waters will begin to become undersaturated with respect to aragonite, a metastable form of calcium carbonate, by the year 2050. By 2100, this undersaturation could extend throughout the entire Southern Ocean and into the subarctic Pacific Ocean. When live pteropods were exposed to our predicted level of undersaturation during a two-day shipboard experiment, their aragonite shells showed notable dissolution. Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously. [ABSTRACT FROM AUTHOR]

Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer-based separation technique, we estimate a global oceanic anthropogenic carbon dioxide (CO[sub 2]) sink for the period from 1800 to 1994 of 118 ± 19 petagrams of carbon. The oceanic sink accounts for ∼48% of the total fossil-fuel and cement-manufacturing emissions, implying that the terrestrial biosphere was a net source of CO[sub 2] to the atmosphere of about 39 ± 28 petagrams of carbon for this period. The current fraction of total anthropogenic CO[sub 2] emissions stored in the ocean appears to be about one-third of the long-term potential. [ABSTRACT FROM AUTHOR]

Rising atmospheric carbon dioxide (CO[sub 2]) concentrations over the past two centuries have led to greater CO[sub 2] uptake by the oceans. This acidification process has changed the saturation state of the oceans with respect to calcium carbonate (CaCO[sub 3]) particles. Here we estimate the in situ CaCO[sub 3] dissolution rates for the global oceans from total alkalinity and chlorofluorocarbon data, and we also discuss the future impacts of anthropogenic CO[sub 2] on CaCO[sub 3] shellforming species. CaCO[sub 3] dissolution rates, ranging from 0.003 to 1.2 micromoles per kilogram per year, are observed beginning near the aragonite saturation horizon. The total water column CaCO[sub 3] dissolution rate for the global oceans is approximately 0.5 ± 0.2 petagrams of CaCO[sub 3]-C per year, which is approximately 45 to 65% of the export production of CaCO[sub 3]. [ABSTRACT FROM AUTHOR]

The dissolution of aragonite particles in the ocean primarily depends on the degree of undersaturation of seawater with respect to that mineral. Most of the upper Atlantic Ocean, particularly north of 30°S and at depths of less than 2000 m, is supersaturated with respect to aragonite, whereas much of the deep Atlantic is undersaturated. Here we report, for the first time, shallow layers of aragonite-undersaturated water between 20°S and 15°N in the eastern tropical Atlantic. These layers are centered at 800 m and are surrounded by aragonite-supersaturated water above and below. This feature most likely results from a combination of chemical and biological processes including the uptake of anthropogenic CO2, and the oxidation of organic matter falling from the highly productive overlying surface water. Reaction with protons resulting from these processes decreases the carbonate ion concentration and consequently the saturation state of the waters with respect to aragonite. The oceanic uptake of anthropogenic CO2 during the industrial era has caused a significant increase in the size of the undersaturated layers. Future expansion will likely occur laterally to the west and south, where the degree of supersaturation is low compared to waters to the north. This expansion of the undersaturated layers is a prime example of how human activity during the industrial era has altered the upper ocean chemistry by injecting fossil fuel CO2 into the ocean. [ABSTRACT FROM AUTHOR]

The absorption of atmospheric carbon dioxide (CO2) into the ocean lowers the pH of the waters. This so-called ocean acidification could have important consequences for marine ecosystems. To better understand the extent of this ocean acidification in coastal waters, we conducted hydrographic surveys along the continental shelf of western North America from central Canada to northern Mexico. We observed seawater that is undersaturated with respect to aragonite üpwelling onto Large portions of the continental shelf, reaching depths of -.40 to 120 meters along most transect tines and all the way to the surface on one transect off northern California. Although seasonal upwetting of the undersaturated waters onto the shelf is a natural phenomenon in this region, the ocean uptake of anthropogenic CO2 has increased the areal extent of the affected area. [ABSTRACT FROM AUTHOR]

The article discusses how organisms will be impacted by secular changes in carbon dioxide or pH. It notes that pH is estimated to have declined by 0.1 pH units since the pre-industrial age and may decrease another 0.3 pH units by the end of 21st century. It adds that the seasonal cycle of carbon dioxide may impact the ability to identify when a secular trend can be distinguished from the natural variability.

The Southern Ocean plays a major role in mediating the uptake, transport, and long-term storage of anthropogenic carbon dioxide (CO 2 ) into the deep ocean. Examining the magnitude and spatial distribution of this oceanic carbon uptake is critical to understanding how the earth's carbon system will react to continued increases in this greenhouse gas. Here, we use the extended multiple linear regression technique to quantify the total and anthropogenic change in dissolved inorganic carbon (DIC) along the S04P and P16S CLIVAR/U.S. Global Ocean Carbon and Repeat Hydrography Program lines south of 67°S in the Pacific sector of the Southern Ocean between 1992 and 2011 using discrete bottle measurements from repeat occupations. Along the S04P section, which is located in the seasonal sea ice zone south of the Antarctic Circumpolar Current in the Pacific, the anthropogenic component of the DIC increase from 1992 to 2011 is mostly found in the Antarctic Surface Water (AASW, upper 100 m), while the increase in DIC below the mixed layer in the Circumpolar Deep Water can be primarily attributed to either a slowdown in circulation or decreased ventilation of deeper, high CO 2 waters. In the AASW we calculate an anthropogenic increase in DIC of 12–18 μmol kg − 1 and an average storage rate of anthropogenic CO 2 of 0.10 ± 0.02 mol m − 2 yr − 1 for this region compared to a global average of 0.5 ± 0.2 mol m − 2 yr − 1 . In surface waters this anthropogenic CO 2 uptake results in an average pH decrease of 0.0022 ± 0.0004 pH units yr − 1 , a 0.47 ± 0.10% yr − 1 decrease in the saturation state of aragonite (Ω Aragonite ) and a 2.0 ± 0.7 m yr − 1 shoaling of the aragonite saturation horizons (calculated for the Ω Aragonite = 1.3 contour). [ABSTRACT FROM AUTHOR]

We quantify the oceanic sink for anthropogenic carbon dioxide (CO2) over the period 1994 to 2007 by using observations from the global repeat hydrography program and contrasting them to observations from the 1990s. Using a linear regression–based method, we find a global increase in the anthropogenic CO2 inventory of 34 ± 4 petagrams of carbon (Pg C) between 1994 and 2007. This is equivalent to an average uptake rate of 2.6 ± 0.3 Pg C year−1 and represents 31 ± 4% of the global anthropogenic CO2 emissions over this period. Although this global ocean sink estimate is consistent with the expectation of the ocean uptake having increased in proportion to the rise in atmospheric CO2, substantial regional differences in storage rate are found, likely owing to climate variability–driven changes in ocean circulation. [ABSTRACT FROM AUTHOR]

We report an annual cycle of surface seawater aragonite mineral saturation state (Ω arag ) during 2006–2007 at the Gray's Reef time-series site off Georgia, USA, calculated based on three-hourly observations of carbon dioxide partial pressure ( p CO 2 ) and salinity-derived total alkalinity. Ω arag varied between 2.30 and 4.39 with low values (< 3.00) mainly during February–April 2007 and high values (> 3.50) during July–October 2006 and July–September 2007 as well as during two biological production spikes (April–June 2007). We first present a qualitative analysis of the drivers of Ω arag variability based on property regressions with surface temperature, salinity and apparent oxygen utilization, and then quantify the contributions of temperature, air-sea exchange, mixing, and biological processes to monthly Ω arag net changes using a simple 1-D mass budget model. Our analyses suggest that river inputs played the most important role in the seasonal variation of surface Ω arag , in contrast to temperature control on p CO 2 . Nevertheless, the primary processes controlling monthly Ω arag net change varied with time of year. Furthermore, river inputs lowered Ω arag by 0.28 and 0.48 in July–August and September–October 2007 relative to the equivalent periods of 2006. This implies that interannual Ω arag variability at this location may be greater than that due to the influence of increased atmospheric CO 2 over the past few decades, making efforts to discern decadal coastal ocean acidification trends particularly challenging. In addition, although sea surface salinity varies substantially in coastal waters, our analysis suggests that similar to the open ocean Ω arag is essentially determined by carbonate ion concentration ([CO 3 2 − ]), not calcium ion concentration ([Ca 2 + ]) or the stoichiometric solubility product (K′ sp ), both varying substantially with salinity. Finally, we show that the difference between total alkalinity (TA) and dissolved inorganic carbon (DIC) is a better proxy for [CO 3 2 − ] and Ω arag compared with the ratio (TA/DIC) and helps to better elucidate processes affecting Ω arag in coastal oceans. [ABSTRACT FROM AUTHOR]

Marine carbonate system monitoring programs often consist of multiple observational methods that include underway cruise data, moored autonomous time series, and discrete water bottle samples. Monitored parameters include all, or some of the following: partial pressure of CO 2 of the water ( p CO 2w ) and air, dissolved inorganic carbon (DIC), total alkalinity (TA), and pH. Any combination of at least two of the aforementioned parameters can be used to calculate the others. In this study at the Gray's Reef (GR) mooring in the South Atlantic Bight (SAB) we: examine the internal consistency of p CO 2w from underway cruise, moored autonomous time series, and calculated from bottle samples (DIC-TA pairing); describe the seasonal to interannual p CO 2w time series variability and air-sea flux ( F CO 2 ), as well as describe the potential sources of p CO 2w variability; and determine the source/sink for atmospheric p CO 2 . Over the ~8.5 years of GR mooring time series, mooring-underway and mooring-bottle calculated- p CO 2w strongly correlate with r -values > 0.90. p CO 2w and F CO 2 time series follow seasonal thermal patterns; however, seasonal non-thermal processes, such as terrestrial export, net biological production, and air-sea exchange also influence variability. The linear slope of time series p CO 2w increases by 5.2 ± 1.4 µatm y −1 with F CO 2 increasing 51–70 mmol m −2 y −1 . The net F CO 2 sign can switch interannually with the magnitude varying greatly. Non-thermal p CO 2w is also increasing over the time series, likely indicating that terrestrial export and net biological processes drive the long term p CO 2w increase. [ABSTRACT FROM AUTHOR]

The continental shelf region off the west coast of North America is seasonally exposed to water with a low aragonite saturation state by coastal upwelling of CO 2 -rich waters. To date, the spatial and temporal distribution of anthropogenic CO 2 (C anth ) within the CO 2 -rich waters is largely unknown. Here we adapt the multiple linear regression approach to utilize the GO-SHIP Repeat Hydrography data from the northeast Pacific to establish an annually updated relationship between C anth and potential density. This relationship was then used with the NOAA Ocean Acidification Program West Coast Ocean Acidification (WCOA) cruise data sets from 2007, 2011, 2012, and 2013 to determine the spatial variations of C anth in the upwelled water. Our results show large spatial differences in C anth in surface waters along the coast, with the lowest values (37–55 μmol kg −1 ) in strong upwelling regions off southern Oregon and northern California and higher values (51–63 μmol kg −1 ) to the north and south of this region. Coastal dissolved inorganic carbon concentrations are also elevated due to a natural remineralized component (C bio ), which represents carbon accumulated through net respiration in the seawater that has not yet degassed to the atmosphere. Average surface C anth is almost twice the surface remineralized component. In contrast, C anth is only about one third and one fifth of the remineralized component at 50 m and 100 m depth, respectively. Uptake of C anth has caused the aragonite saturation horizon to shoal by approximately 30–50 m since the preindustrial period so that undersaturated waters are well within the regions of the continental shelf that affect the shell dissolution of living pteropods. Our data show that the most severe biological impacts occur in the nearshore waters, where corrosive waters are closest to the surface. Since the pre-industrial times, pteropod shell dissolution has, on average, increased approximately 19–26% in both nearshore and offshore waters. [ABSTRACT FROM AUTHOR]

Carbon dioxide partial pressure ( p CO 2 ) in surface seawater was continuously recorded every three hours from 18 July 2006 through 31 October 2007 using a moored autonomous p CO 2 (MAPCO 2 ) system deployed on the Gray’s Reef buoy off the coast of Georgia, USA. Surface water p CO 2 (average 373 ± 52 μatm) showed a clear seasonal pattern, undersaturated with respect to the atmosphere in cold months and generally oversaturated in warm months. High temporal resolution observations revealed important events not captured in previous ship-based observations, such as sporadically occurring biological CO 2 uptake during April–June 2007. In addition to a qualitative analysis of the primary drivers of p CO 2 variability based on property regressions, we quantified contributions of temperature, air–sea exchange, mixing, and biological processes to monthly p CO 2 variations using a 1-D mass budget model. Although temperature played a dominant role in the annual cycle of p CO 2 , river inputs especially in the wet season, biological respiration in peak summer, and biological production during April–June 2007 also substantially influenced seawater p CO 2 . Furthermore, sea surface p CO 2 was higher in September–October 2007 than in September–October 2006, associated with increased river inputs in fall 2007. On an annual basis this site was a moderate atmospheric CO 2 sink, and was autotrophic as revealed by monthly mean net community production (NCP) in the mixed layer. If the sporadic short productive events during April–May 2007 were missed by the sampling schedule, one would conclude erroneously that the site is heterotrophic. While previous ship-based p CO 2 data collected around this buoy site agreed with the buoy CO 2 data on seasonal scales, high resolution buoy observations revealed that the cruise-based surveys undersampled temporal variability in coastal waters, which could greatly bias the estimates of air–sea CO 2 fluxes or annual NCP, and even produce contradictory results. [ABSTRACT FROM AUTHOR]

Event-scale phenomena, of limited temporal duration or restricted spatial extent, often play a disproportionately large role in ecological processes occurring in the ocean water column. Nutrient and gas fluxes, upwelling and downwelling, transport of biogeochemically important elements, predator-prey interactions, and other processes may be markedly influenced by such events, which are inadequately resolved from infrequent ship surveys. The advent of autonomous instrumentation, including underwater gliders, profiling floats, surface drifters, enhanced moorings, coastal high-frequency radars, and satellite remote sensing, now provides the capability to resolve such phenomena and assess their role in structuring pelagic ecosystems. These methods are especially valuable when integrated together, and with shipboard calibration measurements and experimental programs. [ABSTRACT FROM AUTHOR]

Abstract: Continental margin carbon cycling is complex, highly variable over a range of space and time scales, and forced by multiple physical and biogeochemical drivers. Predictions of globally significant air–sea CO2 fluxes in these regions have been extrapolated based on very sparse data sets. We present here a method for predicting coastal surface-water pCO2 from remote-sensing data, based on self organizing maps (SOMs) and a nonlinear semi-empirical model of surface water carbonate chemistry. The model used simple empirical relationships between carbonate chemistry (total dissolved carbon dioxide () and alkalinity (T Alk)) and satellite data (sea surface temperature (SST) and chlorophyll (Chl)). Surface-water CO2 partial pressure (pCO2) was calculated from the empirically-predicted and T Alk. This directly incorporated the inherent nonlinearities of the carbonate system, in a completely mechanistic manner. The model’s empirical coefficients were determined for a target study area of the central North American Pacific continental margin (22–50°N, within 370km of the coastline), by optimally reproducing a set of historical observations paired with satellite data. The model-predicted pCO2 agreed with the highly variable observations with a root mean squared (RMS) deviation of <20μatm, and with a correlation coefficient of >0.8 (r =0.81; r 2 =0.66). This level of accuracy is a significant improvement relative to that of simpler models that did not resolve the biogeochemical sub-regions or that relied on linear dependences on input parameters. Air–sea fluxes based on these pCO2 predictions and satellite-based wind speed measurements suggest that the region is a ∼14TgCyr−1 sink for atmospheric CO2 over the 1997–2005 period, with an approximately equivalent uncertainty, compared with a ∼0.5TgCyr−1 source predicted by a recent bin-averaging and interpolation-based estimate for the same area. [Copyright &y& Elsevier]

Abstract: Puget Sound is a large estuary complex in the U.S. Pacific Northwest that is home to a diverse and economically important ecosystem threatened by anthropogenic impacts associated with climate change, urbanization, and ocean acidification. While ocean acidification has been studied in oceanic waters, little is known regarding its status in estuaries. Anthropogenically acidified coastal waters upwelling along the western North American continental margin can enter Puget Sound through the Strait of Juan de Fuca. In order to study the combined effects of ocean acidification and other natural and anthropogenic processes on Puget Sound waters, we made the first inorganic carbon measurements in this estuary on two survey cruises in February and August of 2008. Observed pH and aragonite saturation state values in surface and subsurface waters were substantially lower in parts of Puget Sound than would be expected from anthropogenic carbon dioxide (CO2) uptake alone. We estimate that ocean acidification can account for 24–49% of the pH decrease in the deep waters of the Hood Canal sub-basin of Puget Sound relative to estimated pre-industrial values. The remaining change in pH between when seawater enters the sound and when it reaches this deep basin results from remineralization of organic matter due to natural or anthropogenically stimulated respiration processes within Puget Sound. Over time, however, the relative impact of ocean acidification could increase significantly, accounting for 49–82% of the pH decrease in subsurface waters for a doubling of atmospheric CO2. These changes may have profound impacts on the Puget Sound ecosystem over the next several decades. These estimates suggest that the role ocean acidification will play in estuaries may be different from the open ocean. [Copyright &y& Elsevier]

Abstract: A climatological mean distribution for the surface water pCO2 over the global oceans in non-El Niño conditions has been constructed with spatial resolution of 4° (latitude) ×5° (longitude) for a reference year 2000 based upon about 3 million measurements of surface water pCO2 obtained from 1970 to 2007. The database used for this study is about 3 times larger than the 0.94 million used for our earlier paper [Takahashi et al., 2002. Global sea–air CO2 flux based on climatological surface ocean pCO2, and seasonal biological and temperature effects. Deep-Sea Res. II, 49, 1601–1622]. A time-trend analysis using deseasonalized surface water pCO2 data in portions of the North Atlantic, North and South Pacific and Southern Oceans (which cover about 27% of the global ocean areas) indicates that the surface water pCO2 over these oceanic areas has increased on average at a mean rate of 1.5μatmy−1 with basin-specific rates varying between 1.2±0.5 and 2.1±0.4μatmy−1. A global ocean database for a single reference year 2000 is assembled using this mean rate for correcting observations made in different years to the reference year. The observations made during El Niño periods in the equatorial Pacific and those made in coastal zones are excluded from the database. Seasonal changes in the surface water pCO2 and the sea-air pCO2 difference over four climatic zones in the Atlantic, Pacific, Indian and Southern Oceans are presented. Over the Southern Ocean seasonal ice zone, the seasonality is complex. Although it cannot be thoroughly documented due to the limited extent of observations, seasonal changes in pCO2 are approximated by using the data for under-ice waters during austral winter and those for the marginal ice and ice-free zones. The net air–sea CO2 flux is estimated using the sea–air pCO2 difference and the air–sea gas transfer rate that is parameterized as a function of (wind speed)2 with a scaling factor of 0.26. This is estimated by inverting the bomb 14C data using Ocean General Circulation models and the 1979–2005 NCEP-DOE AMIP-II Reanalysis (R-2) wind speed data. The equatorial Pacific (14°N–14°S) is the major source for atmospheric CO2, emitting about +0.48Pg-Cy−1, and the temperate oceans between 14° and 50° in the both hemispheres are the major sink zones with an uptake flux of −0.70Pg-Cy−1 for the northern and −1.05Pg-Cy−1 for the southern zone. The high-latitude North Atlantic, including the Nordic Seas and portion of the Arctic Sea, is the most intense CO2 sink area on the basis of per unit area, with a mean of −2.5tons-Cmonth−1 km−2. This is due to the combination of the low pCO2 in seawater and high gas exchange rates. In the ice-free zone of the Southern Ocean (50°–62°S), the mean annual flux is small (−0.06Pg-Cy−1) because of a cancellation of the summer uptake CO2 flux with the winter release of CO2 caused by deepwater upwelling. The annual mean for the contemporary net CO2 uptake flux over the global oceans is estimated to be −1.6±0.9Pg-Cy−1, which includes an undersampling correction to the direct estimate of −1.4±0.7Pg-Cy−1. Taking the pre-industrial steady-state ocean source of 0.4±0.2Pg-Cy−1 into account, the total ocean uptake flux including the anthropogenic CO2 is estimated to be −2.0±1.0Pg-Cy−1 in 2000. [Copyright &y& Elsevier]

The dissolution of aragonite particles in the ocean primarily depends on the degree of undersaturation of seawater with respect to that mineral. Most of the upper Atlantic Ocean, particularly north of 30°S and at depths of less than 2000 m, is supersaturated with respect to aragonite, whereas much of the deep Atlantic is undersaturated. Here we report, for the first time, shallow layers of aragonite-undersaturated water between 20°S and 15°N in the eastern tropical Atlantic. These layers are centered at 800 m and are surrounded by aragonite-supersaturated water above and below. This feature most likely results from a combination of chemical and biological processes including the uptake of anthropogenic CO2, and the oxidation of organic matter falling from the highly productive overlying surface water. Reaction with protons resulting from these processes decreases the carbonate ion concentration and consequently the saturation state of the waters with respect to aragonite. The oceanic uptake of anthropogenic CO2 during the industrial era has caused a significant increase in the size of the undersaturated layers. Future expansion will likely occur laterally to the west and south, where the degree of supersaturation is low compared to waters to the north. This expansion of the undersaturated layers is a prime example of how human activity during the industrial era has altered the upper ocean chemistry by injecting fossil fuel CO2 into the ocean. [ABSTRACT FROM AUTHOR]

A number of workers have recently shown that the thermodynamic constants for the dissociation of carbonic acid in seawater of Mehrbach et al. are more reliable than measurements made on artificial seawater. These studies have largely been confined to looking at the internal consistency of measurements of total alkalinity (TA), total inorganic carbon dioxide (TCO2) and the fugacity of carbon dioxide (fCO2). In this paper, we have examined the field measurements of pH, fCO2, TCO2 and TA on surface and deep waters from the Atlantic, Indian, Southern and Pacific oceans to determine the pK1, pK2 and pK2−pK1. These calculations are possible due to the high precision and accuracy of the field measurements. The values of pK2 and pK2−pK1 over a wide range of temperatures (−1.6–38°C) are in good agreement (within ±0.005) with the results of Mehrbach et al. The measured values of pK1 at 4°C and 20°C are in reasonable agreement (within ±0.01) with all the constants determined in laboratory studies. These results indicate, as suggested by internal consistency tests, that the directly measured values of pK1+pK2 of Mehrbach et al. on real seawater are more reliable than the values determined for artificial seawater. It also indicates that the large differences of pK2−pK1 (0.05 at 20°C) in real and artificial seawater determined by different investigators are mainly due to differences in pK2. These differences may be related to the interactions of boric acid with the carbonate ion.The values of pK2−pK1 determined from the laboratory measurements of Lee et al. and Lueker et al. at low fCO2 agree with the field-derived data to ±0.016 from 5°C to 25°C. The values of pK2−pK1 decrease as the fCO2 or TCO2 increases. This effect is largely related to changes in the pK2 as a function of fCO2 or TCO2. The values of fCO2 calculated from an input of TA and TCO2, which require reliable values of pK2−pK1, also vary with fCO2. The field data at 20°C has been used to determine the effect of changes of TCO2 on pK2 giving an empirical relationship:pK2TCO2=pK2−1.6×10−4(TCO2−2050)which is valid at TCO2>2050 μmol kg−1. This assumes that the other dissociation constants such as KB for boric acid are not affected by changes in TCO2. The slope is in reasonable agreement with the laboratory studies of Lee et al. and Lueker et al. (−1.2×10−4 to −1.9×10−4). This equation eliminates the dependence of the calculated fCO2 on the level of fCO2 or TCO2 in ocean waters (σ=29.7 μatm in fCO2). An input of pH and TCO2 yields values of fCO2 and TA that are in good agreement with the measured values (±22.3 μatm in fCO2 and ±4.3 μmol kg−1 in TA). The cause of the decrease in pK2 at high fCO2 is presently unknown. The observed inconsistencies between the measured and computed fCO2 values may be accounted for by adding the effect of organic acid (∼8 μmol kg−1) to the interpretation of the TA. Further studies are needed to elucidate the chemical reactions responsible for this effect. [Copyright &y& Elsevier]

Presents a method for distinguishing the seasonal biological effect on surface-water ρ CO[sub2] from the effect of seasonal temperature changes, and discuss the relative significance of these effects in different regions of the global oceans. Explanation on the climatological distribution of surface-water ρ CO[sub2]; Description on the seasonal variation of ρ CO[sub2] in surface waters; Conclusions.

Modern reef-building corals sustain a wide range of ecosystem services because of their ability to build calcium carbonate reef systems. The influence of environmental variables on coral calcification rates has been extensively studied, but our understanding of their relative importance is limited by the absence of in situ observations and the ability to decouple the interactions between different properties. We show that temperature is the primary driver of coral colony ( Porites astreoides and Diploria labyrinthiformis ) and reef-scale calcification rates over a 2-year monitoring period from the Bermuda coral reef. On the basis of multimodel climate simulations (Coupled Model Intercomparison Project Phase 5) and assuming sufficient coral nutrition, our results suggest that P. astreoides and D. labyrinthiformis coral calcification rates in Bermuda could increase throughout the 21st century as a result of gradual warming predicted under a minimum CO 2 emissions pathway [representative concentration pathway (RCP) 2.6] with positive 21st-century calcification rates potentially maintained under a reduced CO 2 emissions pathway (RCP 4.5). These results highlight the potential benefits of rapid reductions in global anthropogenic CO 2 emissions for 21st-century Bermuda coral reefs and the ecosystem services they provide.

Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer-based separation technique, we estimate a global oceanic anthropogenic carbon dioxide (CO2) sink for the period from 1800 to 1994 of 118 +/- 19 petagrams of carbon. The oceanic sink accounts for approximately 48% of the total fossil-fuel and cement-manufacturing emissions, implying that the terrestrial biosphere was a net source of CO2 to the atmosphere of about 39 +/- 28 petagrams of carbon for this period. The current fraction of total anthropogenic CO2 emissions stored in the ocean appears to be about one-third of the long-term potential.

Rising atmospheric carbon dioxide (CO2) concentrations over the past two centuries have led to greater CO2 uptake by the oceans. This acidification process has changed the saturation state of the oceans with respect to calcium carbonate (CaCO3) particles. Here we estimate the in situ CaCO3 dissolution rates for the global oceans from total alkalinity and chlorofluorocarbon data, and we also discuss the future impacts of anthropogenic CO2 on CaCO3 shell-forming species. CaCO3 dissolution rates, ranging from 0.003 to 1.2 micromoles per kilogram per year, are observed beginning near the aragonite saturation horizon. The total water column CaCO3 dissolution rate for the global oceans is approximately 0.5 +/- 0.2 petagrams of CaCO3-C per year, which is approximately 45 to 65% of the export production of CaCO3.