Showing results 1 to 20 of 23
  The North Sea; ; et al in Carbon and Nutrient Fluxes in Continental Margins (2009) Detailed reference viewed: 23 (3 ULg) Variability of the net air-sea CO2 flux inferred from shipboard and satellite measurements in the Southern Ocean south of Tasmania and New Zealand; ; et al in Journal of Geophysical Research. Oceans (2005), 110(C9), We determine the distribution of oceanic CO2 partial pressure (pCO(2)) with respect to remotely sensed parameters (sea surface temperature (SST) and chlorophyll (Chl)) in order to gain an understanding of ... [more ▼] We determine the distribution of oceanic CO2 partial pressure (pCO(2)) with respect to remotely sensed parameters (sea surface temperature (SST) and chlorophyll (Chl)) in order to gain an understanding of the small-scale (10-100 km) pCO(2) variability and to estimate the net air-sea CO2 flux in the region (125 degrees E-205 degrees E; 45 degrees S-60 degrees S), which represents 22% of the Southern Ocean area between 45 degrees S and 60 degrees S. We split the study area into several biogeochemical provinces. In chlorophyll-poor regions, pCO(2) is negatively correlated with SST, indicating that pCO(2) is mostly controlled by mixing processes. For Chl > 0.37 mg m(-3), pCO(2) is negatively correlated with Chl, indicating that pCO(2) variability is mostly controlled by carbon fixation by biological activity. We deduce fields of pCO(2) and of air-sea CO2 fluxes from satellite parameters using pCO(2)-SST, pCO(2)-chlorophyll relationships and air-sea gas exchange coefficient, K, from satellite wind speed. We estimate an oceanic CO2 sink from December 1997 to December 1998 of -0.08 GtC yr(-1) with an error of 0.03 GtC yr(-1). This sink is approximately 38% smaller than that computed from the Takahashi et al. (2002) climatological distribution of Delta pCO(2) for the 1995 year but with the same K (-0.13 GtC yr(-1)). When we correct ocean pCO(2) for the interannual variability between 1995 and 1998, the difference is even larger, and we cannot reconcile both estimates in February-March and from June to November. This strengthens the need of new in situ measurements for validating extrapolation methods and for improving knowledge of interannual pCO(2) variability. [less ▲] Detailed reference viewed: 52 (9 ULg)Budgeting sinks and sources of CO2 in the coastal ocean: Diversity of ecosystems countsBorges, Alberto  ; Delille, Bruno ; in Geophysical Research Letters (2005), 32(14), Air-water CO2 fluxes were up-scaled to take into account the latitudinal and ecosystem diversity of the coastal ocean, based on an exhaustive literature survey. Marginal seas at high and temperate ... [more ▼] Air-water CO2 fluxes were up-scaled to take into account the latitudinal and ecosystem diversity of the coastal ocean, based on an exhaustive literature survey. Marginal seas at high and temperate latitudes act as sinks of CO2 from the atmosphere, in contrast to subtropical and tropical marginal seas that act as sources of CO2 to the atmosphere. Overall, marginal seas act as a strong sink of CO2 of about -0.45 Pg C yr(-1). This sink could be almost fully compensated by the emission of CO2 from the ensemble of near-shore coastal ecosystems of about 0.40 Pg C yr(-1). Although this value is subject to large uncertainty, it stresses the importance of the diversity of ecosystems, in particular near-shore systems, when integrating CO2 fluxes at global scale in the coastal ocean. [less ▲] Detailed reference viewed: 435 (1 ULg)Preliminary results on the biogeochemistry in the Mekong estuary and delta (Vietnam)Borges, Alberto ; ; et alPoster (2005) Detailed reference viewed: 4 (0 ULg)The Carbon budget of the North Sea; ; et al in Biogeosciences (2005), 2(1), 87-96 A carbon budget has been established for the North Sea, a shelf sea on the NW European continental shelf. The carbon exchange fluxes with the North Atlantic Ocean dominate the gross carbon budget. The net ... [more ▼] A carbon budget has been established for the North Sea, a shelf sea on the NW European continental shelf. The carbon exchange fluxes with the North Atlantic Ocean dominate the gross carbon budget. The net carbon budget – more relevant to the issue of the contribution of the coastal ocean to the marine carbon cycle – is dominated by the carbon inputs from rivers, the Baltic Sea and the atmosphere. The North Sea acts as a sink for organic carbon and thus can be characterised as a heterotrophic system. The dominant carbon sink is the final export to the North Atlantic Ocean. More than 90% of the CO2 taken up from the atmosphere is exported to the North Atlantic Ocean making the North Sea a highly efficient continental shelf pump for carbon. [less ▲] Detailed reference viewed: 42 (4 ULg)Whole system metabolism and CO2 fluxes in a Mediterranean Bay dominated by seagrass beds (Palma Bay, NW Mediterranean); ; et al in Biogeosciences (2005), 2(1), 43-60 Planktonic and benthic incubations (bare and Posidonia oceanica vegetated sediments) were performed at monthly intervals from March 2001 to October 2002 in a seagrass vegetated area of the Bay of Palma ... [more ▼] Planktonic and benthic incubations (bare and Posidonia oceanica vegetated sediments) were performed at monthly intervals from March 2001 to October 2002 in a seagrass vegetated area of the Bay of Palma (Mallorca, Spain). Results showed a contrast between the planktonic compartment, which was on average near metabolic balance (−4.6±5.9mmol O2 m−2 d−1) and the benthic compartment, which was autotrophic (17.6±8.5mmol O2 m−2 d−1). During two cruises in March and June 2002, planktonic and benthic incubations were performed at several stations in the bay to estimate the whole-system metabolism and to examine its relationship with partial pressure of CO2 (pCO2) and apparent oxygen utilisation (AOU) spatial patterns. Moreover, during the second cruise, when the residence time of water was long enough, net ecosystem production (NEP) estimates based on incubations were compared, over the Posidonia oceanica meadow, to rates derived from dissolved inorganic carbon (DIC) and oxygen (O2) mass balance budgets. These budgets provided NEP estimates in fair agreement with those derived from direct metabolic estimates based on incubated samples over the Posidonia oceanica meadow. Whereas the seagrass community was autotrophic, the excess organic carbon production therein could only balance the planktonic heterotrophy in shallow waters relative to the maximum depth of the bay (55 m). This generated a horizontal gradient from autotrophic or balanced communities in the shallow seagrass-covered areas, to strongly heterotrophic communities in deeper areas of the bay. It seems therefore that, on an annual scale in the whole bay, the organic matter production by the Posidonia oceanica may not be sufficient to fully compensate the heterotrophy of the planktonic compartment, which may require external organic carbon inputs, most likely from land. [less ▲] Detailed reference viewed: 19 (6 ULg)Fronts in the Southern Indian Ocean as inferred from satellite sea surface temperature data; ; et al in Journal of Marine Systems (2004), 45(1-2), 55-73 Sea surface temperature (SST) derived from the weekly measurements made by the Advanced Very High Resolution Radiometers (AVHRR) of NOAA satellites was used to investigate the structure and space-time ... [more ▼] Sea surface temperature (SST) derived from the weekly measurements made by the Advanced Very High Resolution Radiometers (AVHRR) of NOAA satellites was used to investigate the structure and space-time variability of large-scale fronts in the Southern Indian Ocean (30-60degreesS and 20-150degreesE) during the period of 1997-1999. Monthly SST gradient maps provided an overall view of five basic fronts: the North and South Subtropical fronts (NSTF and SSTF, respectively), the Agulhas Front (AF), the Subantarctic Front (SAF), and the Polar Front (PF). Mean location of the fronts and associated SST and SST gradients with corresponding standard deviations were calculated at each 10degrees-spaced longitude. A double structure of the NSTF, SAF, and PF was demonstrated as well as the meandering of all fronts with amplitudes of 2-5degrees in latitude and wavelength of several degrees in longitude. Convergence and transient interaction between neighboring fronts appear to occur not only in the Crozet and Kerguelen regions, but in other regions as well. The mean locations and SST range of every front are in good agreement with previous work based on hydrographic surveys [J. Geophys. Res. 101 (1996) 3675], although some details are different (in particular, the larger zonal extent of the NSTF and the wider frontal SST ranges than previously observed). A good correspondence of the measurements made during two hydrographic surveys in the Kerguelen region (22 January-3 February 1999) and in the Tasmania region (3-22 March 1998) with satellite SST and SST gradient maps was found. (C) 2003 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 20 (7 ULg)DIC dynamics in a tropical estuary (Kiddogoweni, Kenya)Borges, Alberto ; ; Delille, Bruno et alPoster (2004) Detailed reference viewed: 4 (0 ULg)DIC dynamics in the Bay of Palma (NW Mediterranean)Borges, Alberto ; ; et alPoster (2004) Detailed reference viewed: 2 (0 ULg)CO2 emission from mangroves’ surrounding watersBorges, Alberto ; Delille, Bruno ; Poster (2003) Detailed reference viewed: 2 (0 ULg)The Portugal coastal counter current off NW Spain: new insights on its biogeochemical variability; ; et al in Progress in Oceanography (2003), 56(2), 281-321 Time series of wind-stress data, AVHRR and SeaWiFS satellite images, and in situ data from seven cruises are used to assemble a coherent picture of the hydrographic variability of the seas off the ... [more ▼] Time series of wind-stress data, AVHRR and SeaWiFS satellite images, and in situ data from seven cruises are used to assemble a coherent picture of the hydrographic variability of the seas off the Northwest Iberian Peninsula from the onset (September-October) to the cessation (February-May) of the Portugal coastal counter current (PCCC). During this period the chemistry and the biology of the shelf, slope and ocean waters between 40degrees and 43degreesN have previously been undersampled. Novel information extracted from these observations relate to: 1. The most frequent modes of variability of the alongshore coastal winds, covering event, seasonal and long-term scales; 2. The conspicuous cycling between stratification and homogenisation observed in PCCC waters, which has key implications for the chemistry and biology of these waters; 3. The seasonal evolution of nitrite profiles in PCCC waters in relation to the stratification cycle; 4. The Redfield stoichiometry of the remineralisation of organic matter in Eastern North Atlantic Central Water (ENACW)-the water mass being transported by the PCCC; 5. The separation of coastal (mesotrophic) from PCCC (oligotrophic) planktonic populations by a downwelling front along the shelf, which oscillates to and fro across the shelf as a function of coastal wind intensity and continental runoff; and 6. The photosynthetic responses of the PCCC and coastal plankton populations to the changing stratification and light conditions from the onset to the cessation of the PCCC. [less ▲] Detailed reference viewed: 48 (11 ULg)Mesoscale surface distribution of biogeochemical characteristics in the Crozet Basin frontal zones (South Indian Ocean); Delille, Bruno ; et alin Marine Ecology. Progress Series (2003), 249 A mesoscale study was conducted in January and February 1999 in the Crozet Basin frontal zones (43degrees50' to 45degrees20'S, 61degrees00' to 64degrees30'E) within the southernmost and easternmost ... [more ▼] A mesoscale study was conducted in January and February 1999 in the Crozet Basin frontal zones (43degrees50' to 45degrees20'S, 61degrees00' to 64degrees30'E) within the southernmost and easternmost convergence area of the Antarctic Circumpolar Current (ACC) and the Agulhas Return Current (ARC). Distribution of biogeochemical parameters was strongly linked to the merged Subtropical (STF) and Subantarctic (SAF) Fronts which mark the border between the cold and less saline subantarctic waters and the warm and more saline subtropical waters. This survey took place during a post-bloom period. Chlorophyll a concentrations were low throughout the study area ranging from 0.2 mug l(-1) in the Polar Frontal Zone (PFZ) to 0.4 mug l(-1) in the Subtropical Zone (STZ). Maximum chlorophyll a values (0.8 mug l(-1)) associated with an increase in biogenic silica concentration (from 0.03 to 0.34 muM) and a diatom peak (1.2 x 10(5) cells l(-1)) were encountered in the northeastern part of the STF edge. Despite northwardly decreasing concentrations of nitrates from 14 muM in the PFZ to 6 PM in the STZ, they were not the main factor limiting phytoplankton growth. Low silicic acid (mean = 0.6 muM) could have limited diatom development in the PFZ and the STZ where diatom numbers were low. In STZ waters, where average diatom numbers were highest, various species of Nitzschia and Thalassiothrix were common, but Pseudonitzschia spp. were dominant. Throughout the survey area, pico- and nano-sized cells dominated the phytoplankton assemblage, and their number was the highest in the STZ. Cyanobacteria, only present in subtropical waters >12.5degreesC, were the major component of the picoplankton size-fraction. While dinoflagellate numbers were low in the Subantarctic Zone (SAZ), their abundance and species numbers increased in the STZ, where Oxytoxum laticeps became dominant and several further large-size species of Prorocentrum, Ceratium and Gymnodinium appeared in addition to those at the STF. The distribution of different biogeochemical parameters suggests that the Crozet Basin frontal region is a non-exporting system at the end of summer. During this post-bloom period, biological activity is low and phytoplankton growth severely limited. This is evidenced by the weak dependence of the partial pressure of carbon dioxide (pCO(2)) on biological activity and the importance of the air-sea exchange in maintaining pCO(2) close to saturation. [less ▲] Detailed reference viewed: 32 (13 ULg)A New Design of Equilibrator to Monitor Carbon Dioxide in Highly Dynamic and Turbid Environments; Borges, Alberto ; Biondo, Renzo in Water Research (2001), 35(5), 1344-7 A new design of equilibrator for carbon dioxide monitoring in natural waters is described. It consists in a vertical tube filled with marbles through which water is flowing while equilibrating with a ... [more ▼] A new design of equilibrator for carbon dioxide monitoring in natural waters is described. It consists in a vertical tube filled with marbles through which water is flowing while equilibrating with a closed air circuit. It offers several advantages compared with classical equilibrators, among which is a fast response time (half-life constant approximately 30 s) and the potential to work in very turbid water. The proposed equilibrator is of particular interest to monitor carbon dioxide in coastal ecosystems, such as estuaries, which are known to be turbid and highly dynamic. Two performance tests and some field results are presented to illustrate the efficiency of the proposed system. [less ▲] Detailed reference viewed: 24 (4 ULg)Off Shelf Fluxes of Labile Materials by an Upwelling Filament in the NW Iberian Upwelling System; ; Borges, Alberto et alin Progress in Oceanography (2001), 50(2-4), 321-337 Daily changes in the concentrations of carbon and nitrogen species were monitored during the course of a Lagrangian drifter experiment in a recurrent upwelling filament south of Cape Finisterre (NW ... [more ▼] Daily changes in the concentrations of carbon and nitrogen species were monitored during the course of a Lagrangian drifter experiment in a recurrent upwelling filament south of Cape Finisterre (NW Iberian Upwelling System). A drifting buoy released at the southern edge of the upwelling centre generated by the Cape moved 60km southwestwards from 3 to 7 August 1998. Organic matter in the 50m deep study water mass (average 77±2 μM C) consisted of: 57μM C of dissolved organic matter (DOM) with a C/N molar ratio of 19±2; 6μM C of DOM with a C/N ratio of 9±2, and 14μM C of 50% DOM and 50% suspended organic matter (POMsusp) with a C/N ratio of 6.0±0.4. Net conversion of consumed inorganic salts into accumulated TOM=POMsusp+DOM was 40% for nitrogen and 30% for carbon. Since the parcel of water crossed the shelf-edge, these conversion efficiencies are equivalent to net horizontal export-ratio of 0.4 and 0.3 respectively. A second drifter was deployed in the offshore-end of the filament, and was displaced 20km west between 14 and 17 August 1998. Nitrate was exhausted in the surface water and no significant changes were observed in the variables measured during the course of the second experiment. Low C/N ratios (6.5±0.4) and rapid POMsusp/DOM inter-conversion in the 20 μM C excess observed in the study volume points to the persistence of the labile materials formed on the shelf during transport to the ocean. Our data demonstrate a) the key role of upwelling filaments in off-shelf export of organic materials and b) the major contribution of DOM to this horizontal export, a previously unaccounted amount. [less ▲] Detailed reference viewed: 23 (6 ULg)Dynamics of inorganic carbon in surface waters off the Galician coastBorges, Alberto ; ; et alConference (2000) Detailed reference viewed: 2 (0 ULg)Surface pCO2 off the Galician coast: an overview of data obtained during the OMEX projectBorges, Alberto ; Poster (2000) Detailed reference viewed: 3 (0 ULg)Surface pCO2 off the Galician coast: an overview of data obtained during the OMEX projectBorges, Alberto ; Poster (2000) Detailed reference viewed: 21 (0 ULg)
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