Observations of surface seawater fugacity of carbon dioxide ( f CO 2 ) and pH were collected over a period of several days at French Frigate Shoals (FFS) in the Northwestern Hawaiian Islands (NWHI) in order to gain an understanding of the natural spatiotemporal variability of the marine inorganic carbon system in a pristine coral reef ecosystem. These data show clear island-to-open ocean gradients in f CO 2 and total alkalinity that can be measured 10–20 km offshore, indicating that metabolic processes influence the CO 2 –carbonic acid system over large areas of ocean surrounding FFS and by implication the islands and atolls of the NWHI. The magnitude and extent of this spatial gradient may be driven by a combination of physical and biogeochemical processes including reef water residence time, hydrodynamic forcing of currents and tidal flow, and metabolic processes that occur both on the reef and within the lagoon.

Emissions of anthropogenic carbon dioxide (CO 2 ) to the atmosphere and the consequent effects of climate change and ocean acidification on coral reef ecosystems have motivated significant interest in describing and understanding the CO 2 –carbonic acid system of diverse coral reef environments. Although numerous studies have been successful in monitoring reef metabolism both in the field and in the laboratory, physical and biological forcings produce distinct conditions among environments. Due to the geographic isolation and associated difficulties with measuring marine carbon chemistry in waters of the Papahānaumokuākea Marine National Monument (PMNM), relatively few studies have described the CO 2 –carbonic acid system and carbonate saturation state gradients of these waters. Yet, PMNM remains one of the largest conservation areas in the world with extensive and diverse coral reef ecosystems that could offer valuable insight into our current and future understanding about regional and global impacts of ocean acidification. In order to provide a broad overview of latitudinal trends and features of the marine carbon system in PMNM waters, continuous measurements for surface seawater fugacity of CO 2 ( f CO 2 ) and pH were collected during August 2011 and July 2012 cruises of the NOAA Ship Hi ’ ialakai . These measurements indicate that pH and f CO 2 are three times more variable in nearshore monument waters relative to open ocean transect measurements. This variability can be observed up to 50 km away from the nearest reef and is likely the result of the direct and significant impact of coral reef metabolism on marine carbon chemistry around the islands and atolls. The relationship between total alkalinity and dissolved inorganic carbon is consistent with net calcification which creates an alkalinity sink throughout PMNM waters. Additionally, our measurements show clear latitudinal trends in f CO 2 , pH, and aragonite saturation state that are influenced by environmental forcings, including temperature, wind speed, and residence time of the water. Collectively, our results suggest that coral reefs located at the northernmost atolls of PMNM may be the most susceptible to the adverse impacts of climate change and ocean acidification.

Inorganic carbon measurements made in the late 1980s suggest that alkalinity in the waters surrounding the Hawaiian Archipelago is elevated relative to the oligotrophic waters of the North Pacific. These observations have been interpreted as evidence for a “halo” of elevated carbonate saturation state produced by the dissolution of highly soluble magnesium calcites and aragonite on the island platform or in the water column surrounding the islands. If present, this “halo” has implications for air–sea carbon dioxide exchange in Hawaiian waters and may impact the response of coral reef communities to the acidification of the surface waters of the global ocean. The purpose of this study was to assess the magnitude and extent of the elevated calcium carbonate saturation state observed on previous expeditions to this region. Transects were conducted near several atolls in the Northwestern Hawaiian Islands from shallow water adjacent to the forereef to the open ocean 15 km from the island. Hydrographic profiles were collected at each station, and discrete water samples were collected for the measurement of carbon system parameters necessary to compute calcium carbonate saturation state. Our data were compared with observations made at the Hawaii Ocean Time-series site at Station ALOHA and with hydrographic data collected on the WOCE lines in the North Pacific around the archipelago. We did not detect a carbonate dissolution halo around the islands. We conclude that the previously observed halo was probably an analytical artifact, or possibly a result of extreme variability in carbon chemistry surrounding the islands.

There are inherent limitations to inferring green turtle (Chelonia mydas L.) diving behavior from time–depth recorders (TDRs). Validating TDR data with independent observations of turtle behaviors is imperative to derive behavioral inferences from these archival data. Logistic regressions of video observational data and corresponding TDR data from six juvenile green turtles at the Kawai‘nui Marsh Estuary (KME) in Kailua Bay, O‘ahu, Hawai‘i, were used to determine the extent to which TDR records capture six specific behaviors recorded using a submersible video camera. While foraging, food searching, hovering, and breathing could be explained using a combination of TDR-derived metrics, the records could not describe swimming and resting. The habitat associations of turtle activity patterns (activities) were also evaluated, with some behaviors being more commonly encountered in specific habitat types, including resting and breathing. Comparison of video-recorded in situ observations of juvenile green turtles to concurrent TDR records indicated that TDR data alone can accurately describe certain turtle behaviors at KME, but are insufficient to describe a turtle's full range of behavior. Therefore, we contend that direct behavioral observations augment TDR deployments by ensuring the full behavioral repertoire of juvenile green turtles is captured. The integration of these disparate datasets can enhance the understanding of juvenile green turtle behaviors, especially within shallow heterogeneous habitats like the Kawai‘nui Marsh Estuary.

Here we use observations and ocean models to identify mechanisms driving large seasonal to interannual variations in dissolved inorganic carbon (DIC) and dissolved oxygen (O2) in the upper ocean. We begin with observations linking variations in upper ocean DIC and O2 inventories with changes in the physical state of the ocean. Models are subsequently used to address the extent to which the relationships derived from short‐timescale (6 months to 2 years) repeat measurements are representative of variations over larger spatial and temporal scales. The main new result is that convergence and divergence (column stretching) attributed to baroclinic Rossby waves can make a first‐order contribution to DIC and O2 variability in the upper ocean. This results in a close correspondence between natural variations in DIC and O2 column inventory variations and sea surface height (SSH) variations over much of the ocean. Oceanic Rossby wave activity is an intrinsic part of the natural variability in the climate system and is elevated even in the absence of significant interannual variability in climate mode indices. The close correspondence between SSH and both DIC and O2 column inventories for many regions suggests that SSH changes (inferred from satellite altimetry) may prove useful in reducing uncertainty in separating natural and anthropogenic DIC signals (using measurements from Climate Variability and Predictability's CO2/Repeat Hydrography program).

This study presents basin-wide anthropogenic CO 2 inventory estimates for the Indian Ocean based on measurements from the World Ocean Circulation Experiment/Joint Global Ocean Flux Study global survey. These estimates employed slightly modified AC* and time series techniques originally proposed by Gruber et al. [ 1996] and Wallace [ 1995], respectively. Together, the two methods yield the total oceanic anthropogenic CO 2 and the carbon increase over the past 2 decades. The highest concentrations and the deepest penetrations of anthropogenic carbon are associated with the Subtropical Convergence at around 30 ø to 40øS. With both techniques, the lowest anthropogenic CO 2 column inventories are observed south of 50øS. The total anthropogenic CO 2 inventory north of 35øS was 13.6+2 Pg C in 1995. The inventory increase since GEOSECS (Geochemical Ocean Sections Program) was 4.1+1 Pg C for the same area. Approximately 6.7+1 Pg C are stored in the Indian sector of the Southern Ocean, giving a total Indian Ocean inventory of 20.3 +3 Pg C for 1995. These estimates are compared to anthropogenic CO 2 inventories estimated by the Princeton ocean biogeochemistry model. The model predicts an Indian Ocean sink north of 35øS that is only 0.61-0.68 times the results presented here; while the Southern Ocean sink is nearly 2.6 times higher than the measurement-based estimate. These results clearly identify areas in the models that need further examination and provide a good baseline for future studies of the anthropogenic inven-

We have employed a Multi-parameter Linear Regression (MLR) analysis procedure to determine the uptake of anthropogenic CO2 between two east-west hydrographic surveys of the North Pacific that occurred in 1994 and 2004. The results revealed water column integrated uptake rates of anthropogenic CO2 that ranged from 1.1 to 1.3 mol m yr depending on location. The combined effect of the tilted density surfaces and the younger waters with higher anthropogenic CO2 concentrations leads to higher total column inventories in the western North Pacific. INTRODUCTION The primary goal of the CLIVAR/CO2 Repeat Hydrography Program is to quantify the role of the ocean in sequestering anthropogenic CO2. Information on decadal or shorter timescales is essential to determine any feedbacks of oceanic carbon system due to climate change, and to determine the changes due to natural variability. Discrete high-quality dissolved inorganic carbon and total alkalinity data were acquired as part of the WOCE/JGOFS Global CO2 survey in the Pacific Ocean between 1989 and 1998. This was followed by repeat surveys in 2001 and 2004 as part of the Sub-arctic Gyre Experiment (SAGE) along the P17N line in the eastern North Pacific and the CLIVAR/CO2 Repeat Hydrography Program east-west P2 cruise along 30°N. The difference between the measured DIC in the upper water column (100 1000 db) for the P2 2004 occupation and the 1994 occupation is shown in Fig. 1A. We then utilized a Multi-parameter Linear Regression (MLR) analysis procedure to further evaluate the difference between the two cruises (Fig. 1B). Using the 1994 data set, commonly measured hydrographic quantities were inputted into the MLR analysis as the independent parameters. Based on the relationship of DIC to those hydrographic properties, equation (1) was used to predict DIC from the 2004 hydrographic data: DIC = a + b(t) + c(S) + d(AOU) + e(Si) + f(P) (1) where a, b, c, d, e, and f are coefficients determined from the 1994 data, t is theta, S is salinity, AOU is apparent oxygen utilization, Si is inorganic silicate, and P is phosphate. The data were interpolated and gridded to common reference pressures, and the total change in DIC between 2004 and 1994 is determined as the difference between the measured DIC gridded values and those predicted from the 2004 hydrographic measurements utilizing the 1994 coefficients (Fig. 1B). Similar procedures determined the change in anthropogenic DIC from Equation (2) where ∆CANTHRO = ∆CMEAS ∆CORG ∆CTALK (2); and ∆CMEAS = CMEAS2004 – CCALC(MLR1994) (3); and FF-102 Poster Presentation ∆CORG = (117/170) * (AOUMEAS AOUCALC(MLR1994)) (4); and ∆CTALK = 0.5 * (TALKMEAS – TALKCALC(MLR1994)) (5) RESULTS Fig. 1C is the calculated anthropogenic uptake over the last decade. The values range between 0 35 μmol kg with the largest values occurring on the eastern edge of the basin at intermediate depths from about 100-800m depth along the 30°N. The results of this research suggest an annual CO2 uptake of 1.01.4 μmol kg yr in the mixed layer, based on direct observations and multiple linear regression approaches. Water column integrated uptake rates ranged from 1.1 to 1.3 mol m yr, depending on location. Deep ventilation within the Kuroshio Extension and the subsequent circulation in the subtropical gyre generates a strong east-west gradient in the anthropogenic CO2 penetration depth. The combined effect of the tilted density surfaces and the younger waters with higher anthropogenic CO2 concentrations leads to higher total column inventories in the western North Pacific. The integrated amount of anthropogenic CO2 in the North Pacific is estimated to be 16.5 Pg C through 1994 north of the equator but not including the marginal seas. This estimate is approximately 16% of the amount of anthropogenic CO2 taken by the global oceans. Fig. 1. Distribution of: (A) measured DIC difference; (B) measured – calculated DIC; and (C) anthropogenic DIC along the P2 30°N section in the North Pacific. FF-102 Poster Presentation

Based on a new mixing model of two end-members, the water column remineralization ratios of P/N/Corg - O2 = 1/13 ± 1/135 ± 18/170 ± 9 are obtained for the Hawaii Ocean Time-series (HOT) data set at station ALOHA. The traditional Redfield ratios of P/N/Corg/–O2 = 1/16/106/138 have standard deviations of more than 50%, when they are based on the average composition of phytoplankton. Apparently, the remineralization processes in the water column have smoothed out the observed large variability of plankton compositions. A new molar formula for the remineralized plankton may be written as 135H280O105N13P or C25(CH2O)101(CH4)9(NH3)13(H3PO4). Oxidation of this formula results in

This study presents basin‐wide anthropogenic CO2 inventory estimates for the Indian Ocean based on measurements from the World Ocean Circulation Experiment/Joint Global Ocean Flux Study global survey. These estimates employed slightly modified ΔC* and time series techniques originally proposed by Gruber et al. [1996] and Wallace [1995], respectively. Together, the two methods yield the total oceanic anthropogenic CO2 and the carbon increase over the past 2 decades. The highest concentrations and the deepest penetrations of anthropogenic carbon are associated with the Subtropical Convergence at around 30° to 40°S. With both techniques, the lowest anthropogenic CO2 column inventories are observed south of 50°S. The total anthropogenic CO2 inventory north of 35°S was 13.6±2 Pg C in 1995. The inventory increase since GEOSECS (Geochemical Ocean Sections Program) was 4.1±1 Pg C for the same area. Approximately 6.7±1 Pg C are stored in the Indian sector of the Southern Ocean, giving a total Indian Ocean inventory of 20.3 ±3 Pg C for 1995. These estimates are compared to anthropogenic CO2 inventories estimated by the Princeton ocean biogeochemistry model. The model predicts an Indian Ocean sink north of 35°S that is only 0.61–0.68 times the results presented here; while the Southern Ocean sink is nearly 2.6 times higher than the measurement‐based estimate. These results clearly identify areas in the models that need further examination and provide a good baseline for future studies of the anthropogenic inventory.

In 1995, we participated in a number of WOCE Hydrographic Program cruises in the Indian Ocean as part of the Joint Global Ocean Flux Study (JGOFS) CO2 Survey sponsored by the Department of Energy (DOE). Two titration systems were used throughout this study to determine the pH, total alkalinity (TA) and total inorganic carbon dioxide (TCO2) of the samples collected during these cruises. The performance of these systems was monitored by making closed cell titration measurements on Certified Reference Materials (CRMs). A total of 962 titrations were made on six batches of CRMs during the cruises. The reproducibility calculated from these titrations was ±0.007 in pH, ±4.2 μmol kg−1 in TA, and ±4.1 μmol kg−1 in TCO2. The at-sea measurements on the CRMs were in reasonable agreement with laboratory measurements made on the same batches. These results demonstrate that the CRMs can be used as a reference standard for TA and to monitor the performance of titration systems at sea. Measurements made on the various legs of the cruise agreed to within 6 μmol kg−1 at the 15 crossover points. The overall mean and standard deviation of the differences at all the crossovers are 2.1±2.1 μmol kg−1. These crossover results are quite consistent with the overall reproducibility of the CRM analyses for TA (±4 μmol kg−1) over the duration of the entire survey. The TA results for the Indian Ocean cruises provide a reliable data set that when combined with TCO2 data can completely characterize the carbonate system.

Surface ocean dissolved inorganic carbon (DIC) and titration alkalinity have been measured for 7 years as a part of the Hawaii Ocean Time-series (HOT) program. The time-series data set displays an interannual increase in the inventory of surface ocean DIC which we interpret as a response to increasing atmospheric carbon dioxide concentrations. The rate of increase in surface ocean DIC at the open ocean HOT site is approximately 1 μmol kg−1 yr−1 with a 95% confidence interval of 0.72 to 1.37 μmol kg−1 yr−1. This accumulation rate is consistent with the rate of increase predicted from the rise in boundary layer pCO2.

Two single-operator multiparameter metabolic analyzers (SOMMA)-coulometry systems (I and II) for total carbon dioxide (TCO2) were placed on board the R/V Knorr for the US component of the Indian Ocean CO2 Survey in conjunction with the World Ocean Circulation Experiment-WOCE Hydrographic Program (WHP). The systems were used by six different measurement groups on 10 WHP Cruises beginning in December 1994 and ending in January 1996. A total of 18,828 individual samples were analyzed for TCO2 during the survey. This paper assesses the analytical quality of these data and the effect of several key factors on instrument performance. Data quality is assessed from the accuracy and precision of certified reference material (CRM) analyses from three different CRM batches. The precision of the method was 1.2 μmol/kg. The mean and standard deviation of the differences between the known TCO2 for the CRM (certified value) and the CRM TCO2 determined by SOMMA-coulometry were −0.91±0.58 (n=470) and −1.01±0.44 (n=513) μmol/kg for systems I and II, respectively, representing an accuracy of 0.05% for both systems. Measurements of TCO2 made on 12 crossover stations during the survey agreed to within 3 μmol/kg with an overall mean and standard deviation of the differences of −0.78±1.74 μmol/kg (n=600). The crossover results are therefore consistent with the precision of the CRM analyses. After 14 months of nearly continuous use, the accurate and the virtually identical performance statistics for the two systems indicate that the cooperative survey effort was extraordinarily successful and will yield a high quality data set capable of fulfilling the objectives of the survey.

Autotrophic carbon assimilation measurements using a trace metal-free C-14 technique were performed at near monthly intervals between 1988 and 1992 in the North Pacific subtropical gyre (U.S. JGOFS-WOCE Sta. ALOHA; 22 degrees 45'N, 158 degrees 00'W). Integrated photosynthetic values ranged from 127 to 1055 mg C m(-2) day(-1) while the average carbon assimilation number (P-B), defined as carbon assimilation rate per unit chlorophyll a (chi a), varied between 1.6 and 12 g C (g chi a)(-1) h(-1) in the 0-45 m depth range. Consistently low P-B values (<5 g C (g chl a)(-1) h(-1), averaged in the upper 45 m of the water column) were observed during the first 2 years of this study but increased to >5 g C (g chl a)(-1) h(-1) during 1991-1992. This rise in P-B was not associated with an increase in chi a. Furthermore, it occurred during a period of increased water column stability. Reduction in ATP and (NO3- + NO2-) concentrations in the upper euphotic zone suggests that nutrient injections due to mixing events were minor or absent after January 1991.Two non-exclusive hypotheses are presented to explain the rise of P-B in the absence of an enhancement of inorganic nutrient fluxes from below the euphotic zone: (i) high P-B values observed during 1991-1992 are indicative of phytoplankton growth being balanced as a result of a decrease in the variability of nutrient injection due to a reduction in the frequency of mixing events, and (ii) the rise of P-B during 1991-1992 is caused by an ecosystem shift from nitrogen to phosphorus limitation. The stability of the water column during 1991-1992 may have increased the availability of reduced nitrogen relative to phosphorus due to the enhancement of nitrogen fixation. Because these hypotheses do not require an increase in algal biomass or elemental fluxes across the base of the euphotic zone to explain an increase in autotrophic carbon assimilation, they imply that nutrient dynamics within the euphotic zone of the North Pacific of the North Pacific subtropical gyre need to be understood in order to interpret changes in P-B and predict carbon fluxes. Copyright (C) 1996 Elsevier Science Ltd

A 5-year time-series study of primary production and euphotic-zone particle export in the subtropical North Pacific Ocean near Hawaii (Sta. ALOHA, 22°45′N, 158°W) with measurements collected at approximately monthly intervals has revealed significant variability in both ecosystem processes. Depth-integrated (0–200 m) primary production averaged 463 mg C m−2 day−1 (s = 156, n = 54) or 14.1 mol C m−2 year−1. This mean value is greater than estimates for the North Pacific Ocean gyre made prior to 1984, but conforms to data obtained since the advent of trace metal-clean techniques. Daily rates of primary productivity at Sta. ALOHA exhibited interannual variability including a nearly 3-year sustained increase during the period 1990–1992 that coincided with a prolonged El Nifio-Southern Oscillation (ENSO) event. Export production, defined as the particulate carbon (PC) flux measured at the 150 m reference depth, also varied considerably during the initial 5 years of the ongoing field experiment. The PC flux averaged 29 mg C m−2 day−1 (s = 11, n = 43) or 0.88 mol Cm−2 year−1. A 5-fold variation between the minimum and maximum fluxes, measured in any given year, was observed. During the first 3 years of this program (1989–1991), a pattern was resolved that included two major export events per annum one centered in late winter and the other in late summer. After 1991, export production exhibited a systematic decrease with time during the prolonged ENSO event. When expressed as a percentage of the contemporaneous primary production, PC export ranged from 2 to 16.9%, with a 5-year mean of 6.7% (s = 3.3, n = 40). Contrary to existing empirical models, contemporaneous primary production and PC flux were poorly correlated, and during the ENSO period they exhibited a significant inverse correlation. This unexpected decoupling of particle production and flux has numerous implications for oceanic biogeochemical cycles and for the response of the ocean to environmental perturbations.

This paper examines the fundamental biological and physical processes controlling the distribution of the inorganic carbon species throughout the water column at the Hawaii Ocean Time series station, ALOHA. Profiles of alkalinity and calcium are strongly influenced by the distribution and movement of the six water masses at this location. The semiconservative behavior of these parameters can be useful in identifying water masses. The dissolution of carbonate particles, however, contributes up to 21% (49 μmol C kg−1) of the dissolved inorganic carbon added to the intermediate waters between the time the waters enter the Pacific and the time they reach Station ALOHA. A sharp increase in carbonate‐derived carbon observed between 800 and 2200 m is due to the dissolution of the more soluble forms of carbonate such as aragonite. The distribution of TCO2 and pH at this site are significantly affected by biological processes as indicated by the apparent nonlinear mixing curves between water masses, the similarity of the measured ratios of C:N and C:P to the Redfield ratios in the upper 700 m of the water column, and the results of a carbon system model. The nonconservative nature of these properties demonstrates that both physical and biological factors must be considered when evaluating temporal variability. The carbon system evaluation techniques presented here are similar to those used on several previous trans‐Pacific cruises allowing the results from this station to be compared to the results of other cruises in this area.

Time series measurements of in situ fluorescence, extracted particulate chlorophyll a, primary productivity, extracted adenosine 5′‐triphosphate, and fluorescence per cell, as measured by flow cytometry, demonstrate seasonal cycles in fluorescence and chlorophyll concentrations in the North Pacific Subtropical Gyre (22° 45′N, 158° 00′W). Two opposing cycles are evident. In the upper euphotic zone (0–50 m), chlorophyll a concentrations increase in winter, with a maximum in December, and decrease each summer, with a minimum in June or July. In contrast, chlorophyll a concentrations in the lower euphotic zone (100–175 m) increase in spring, with a maximum in May, and decline in fall, with a minimum in October or November. The winter increase in chlorophyll a concentration in the upper 50 m of the water column appears to be a consequence of photoadaptation in response to decreased average mixed‐layer light intensity rather than a change in phytoplankton biomass. In the lower euphotic zone, however, the seasonal cycle in pigment concentration does reflect a change in the rate of primary production and in phytoplankton biomass as a consequence of increased light intensity in summer. These observations have important implications for phytoplankton dynamics in the subtropical oceans and for remote sensing of phytoplankton biomass.