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We present continuous, high-resolution measurements of surface dimethylsulfide (DMS), pCO2, and O2/Ar obtained in coastal waters off British Columbia, Canada, using membrane inlet mass spectrometry (MIMS). Sampled underway at a frequency of twice per minute (every ~160 m at 10 knots cruising speed), our data reveal fine-scale structure in gas variability and its covariance with a number of hydrographic parameters. All parameters exhibited large ranges (pCO2, 200-747 ppm; DMS, <1-29 nM; chl a, <0.1-33 µg L-1), highlighting the dynamic nature of the study area. A strong anticorrelation between pCO2 and O2/Ar was observed across the survey region, with the distributions of these gases influenced by biology and its interplay with physical processes. In contrast, DMS levels, which varied dramatically over short distances, showed no significant correlations with any single variable for the full, high-resolution data set. However, when measurements were binned to a much coarser spatial resolution, we found a linear relationship between surface DMS and the chlorophyll/mixed layer depth ratio. The slope of this relationship differed significantly from that previously derived from open ocean data. We used several statistical techniques to estimate the spatial variability of gases and hydrographic parameters and the inherent sampling errors associated with low-frequency sampling approaches. These analyses emphasize the importance of high-resolution sampling in coastal areas, particularly for DMS. [ABSTRACT FROM AUTHOR]

We present inorganic carbon data from the coastal upwelling region west of Vancouver Island, Canada (∼48.5°N, 126°W) directly after an upwelling event and during summer downwelling in July 1998. The inner-shelf buoyancy current, the outer-shelf and the slope regions are contrasted for both wind regimes (up- and downwelling). Results show strong biological drawdown of the partial pressure of carbon dioxide (pCO2) in response to upwelling over the outer-shelf. In contrast, measured pCO2 is exceptionally high (pCO2>1000 ppm) in the inner-shelf current, where biological uptake of carbon is consistently large. The biological C:N uptake ratio appears to increase when nitrogen becomes limiting (during downwelling), while the POC:PON ratio is relatively constant (slightly lower than the Redfield ratio) suggesting that excess carbon uptake does not go into the POC pool. As expected, large cells dominate where measured primary productivity is greatest. Sub-surface inorganic carbon (and pCO2) is high over the shelf. We suggest that carbon concentrations may be higher in coastal waters because of remineralization associated with high productivity that is confined to a smaller volume of water by bathymetry. At the coast these sub-surface concentrations are more efficiently mixed into the surface (especially during winter) relative to deeper offshore regions. Thus, despite high primary production, coastal waters may not aid in sequestration of atmospheric carbon. [Copyright &y& Elsevier]

Abstract: Sea-air carbon dioxide (CO2) fluxes have been analyzed from recently-collected winter, summer and autumn surface ocean CO2 partial pressure (pCO2) data spanning a large portion of the western Canadian coastal ocean, and historical underway pCO2 measurements from the southwest Vancouver Island shelf and the Strait of Juan de Fuca. Sea-air CO2 fluxes from the recent data for specific subregions of the coastal ocean, selected based on geography or bathymetry, were used to make seasonal area-specific estimates of CO2 exchange. These show significant differences between subregions, which have important consequences for estimating seasonal area-weighted fluxes on the margin. Climatologies of sea-air CO2 flux were calculated from the historical data using two approaches: One based on fluxes calculated from temporally-averaged values of sea-air pCO2 differences, solubility and gas transfer velocities, and the other from temporally-averaged instantaneous flux estimates. Seasonal flux estimates from our recently-collected data are consistent with the climatological estimates, in that both show stronger outgassing of CO2 in autumn relative to winter, and both reveal straits as important atmospheric CO2 source regions. Taken together, both analyses of recent and historical data suggest that the transition seasons (spring and autumn) contain the largest (positive and negative) fluxes because of the coincidence of high gas transfer velocities and large surface seawater disequilibria with the atmosphere. By combining the results from these analyses, and making some assumptions where data are missing, we estimate moderate net annual sea-air CO2 influx in the western Canadian coastal ocean of −6mmolm−2 d−1. [Copyright &y& Elsevier]

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]