| 1. |
- Poulton, Alex J., et al.
(författare)
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Phytoplankton carbon fixation, chlorophyll-biomass and diagnostic pigments in the Atlantic Ocean
- 2006
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645 .- 1879-0100. ; 53:14-16, s. 1593-1610
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Tidskriftsartikel (refereegranskat)abstract
- We have made daily measurements of phytoplankton pigments, size-fractionated (< 2 and > 2-mu m) carbon fixation and chlorophyll-a concentration during four Atlantic Meridional Transect (AMT) cruises in 2003-04. Surface rates of carbon fixation ranged from < 0.2-mmol C m(-3) d(-1) in the subtropical gyres to 0.2-0.5-mmol C m(-3) d(-1) in the tropical equatorial Atlantic. Significant intercruise variability was restricted to the subtropical gyres, with higher chlorophyll-a concentrations and carbon fixation in the subsurface chlorophyll maximum during spring in either hemisphere. In surface waters, although picoplankton (<-mu m) represented the dominant fraction in terms of both carbon fixation (50-70%) and chlorophyll-alpha (80-90%), nanoplankton (> 2-mu m) contributions to total carbon fixation (30-50%) were higher than to total chlorophyll-alpha (10-20%). However, in the subsurface chlorophyll maximum picoplankton dominated both carbon fixation (70-90%) and chlorophyll-alpha (70-90%). Thus, in surface waters chlorophyll-normalised carbon fixation was 2-3 times higher for nanoplankton and differences in picoplankton and nanoplankton carbon to chlorophyll-alpha ratios may lead to either higher or similar growth rates. These low chlorophyll-normalised carbon fixation rates for picoplankton may also reflect losses of fixed carbon (cell leakage or respiration), decreases in photosynthetic efficiency, grazing losses during the incubations, or some combination of all these. Comparison of nitrate concentrations in the subsurface chlorophyll maximum with estimates of those required to support the observed rates of carbon fixation (assuming Redfield stoichiometry) indicate that primary production in the chlorophyll maximum may be light rather than nutrient limited.
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| 2. |
- Chierici, Melissa, 1968, et al.
(författare)
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Algorithms to estimate carbon dioxide in the upper subarctic North Atlantic using observations, satellite and ocean analysis data
- 2009
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645. ; 56, s. 630-639
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Tidskriftsartikel (refereegranskat)abstract
- Observations of the surface-water fugacity of carbon dioxide (fCO2sw) measured during 2005 in the subpolar North Atlantic Ocean (58–62°N, 10–40°W) were used together with in situ ocean data and remotely sensed data to develop algorithms to estimate fCO2sw. Based on multiple regression we found that sea-surface temperature (SST), mixed-layer depth (MLD), and chlorophyll a (chl a) contributed significantly to the fit. Two algorithms were developed for periods depending on the presence of chl a data. The correlation coefficient (r2) and the root-mean-square deviation (rms) for the best fit in the period when chl a was observed (20 March–15 October) were 0.720 and ±10.8 μatm, respectively. The best fit for the algorithm for the period when no chl a was present (16 October–19 March) resulted in a r2 of 0.774 and a rms of ±5.6 μatm. Based on these algorithms we estimated seasonal fields of fCO2sw and the air–sea CO2 flux. The estimated net annual CO2 sink was 0.0058 Gt C yr−1 or 0.6 mol C m−2 yr−1.
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| 3. |
- Chierici, Melissa, 1968, et al.
(författare)
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Biogeochemical evolution of the carbon dioxide system in the waters of long-lived mesoscale eddies in the Northeast Pacific Ocean
- 2005
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 52:7-8, s. 955-974
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Tidskriftsartikel (refereegranskat)abstract
- An anticyclonic eddy, named Haida-2000, formed off the Southern Queen Charlotte Islands early in the year 2000. The eddy subsequently tracked northwest, transporting fresh, warm, and nutrient-rich water into the Northeast Pacific Ocean. Based on total dissolved inorganic carbon (CA total alkalinity (AT), and nutrients from six seasonal cruises between February 2000 and September 2001, we found that the oceanic carbonate system of the Surface waters in the eddy changed significantly. The greatest loss of C-T from the surface waters of Haida-2000 occurred during the first year, between February and June 2000. Based oil a concomitant loss in nitrate (NO3), the large CT loss we observed was likely due to biological production of organic carbon and probably resulted in a large drawdown of atmospheric CO,, as supported by the observed fugacity of carbon dioxide (fCO(2)) in the surface waters. During fall, C-T, fCO(2), and NO3 values increased, probably due to oxidation of organic matter and vertical entrainment Of CT and nutrient-rich water from below with fall mixing. As a result, the surface waters of the eddy were highly oversaturated in CO2 relative to the atmosphere. Another Haida eddy (Haida-2001) had a significantly smaller nitrate drawdown than Haida-2000 during its first spring, but the CT losses were similar in the two eddies. In early summer (mid-June) of the second year, the surface and sub-surface waters in Haida-2000 gained C-T, A(T), and NO3, partly caused by a merging with another 2001 Haida eddy, showing that exchange with surrounding waters took place and was significant at times. The high nitrate/ low chlorophyll (HNLC) surface waters at Ocean Station Papa (OSP), showed less fCO(2) Undersaturation during summer and less total nitrate and CT loss than Haida-2000, indicating that both eddies were larger sinks for carbon lthan HNLC waters. The waters surrounding the eddies generally had concentrations of C-T, A(T), and NO3 that were similar to or slightly higher than the waters of both Haida eddies throughout the study. Also, the sub-surface waters in these eddies showed no significant change in total carbon content, suggesting that at these depths eddies are recycling, not exporting systems. (c) 2005 Elsevier Ltd. All rights reserved.
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| 4. |
- Pierrot, D., et al.
(författare)
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Recommendations for autonomous underway pCO2 measuring systems and data-reduction routines
- 2009
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Ingår i: Deep-Sea Research II. - : Elsevier BV. - 0967-0645. ; 56:8-10, s. 512-522
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Tidskriftsartikel (refereegranskat)abstract
- In order to facilitate the collection of high quality and uniform surface water pCO2 data, an underway pCO2 instrument has been designed based on community input and is now commercially available. Along with instrumentation, agreements were reached on data reduction and quality control that can be easily applied to data from these systems by using custom-made freeware. This new automated underway pCO2 measuring system is designed to be accurate to within 0.1 μatm for atmospheric pCO2 measurements and to within 2 μatm for seawater pCO2, targeted by the scientific community to constrain the regional air–sea CO2 fluxes to 0.2 Pg C year−1. The procedure to properly reduce the underway pCO2 data and perform the steps necessary for calculation of the fugacity of CO2 from the measurements is described. This system is now widely used by the scientific community on many different types of ships. Combined with the recommended data-reduction procedures, it will facilitate producing data sets that will significantly decrease the uncertainty currently present in estimates of air–sea CO2 fluxes.
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