Despite the general sparseness of water column carbon measurements, the Mediterranean Sea has been identified as an important anthropogenic carbon storage (Álvarez, 2012) where the column inventory is much higher than in the Atlantic or Pacific oceans (Schneider et al., 2010; Lee et al., 2011). The central Mediterranean Sea is even less sampled, although water masses locally formed and spreading are able to affect the deep overturning cell of the Eastern Mediterranean. We refer particularly to the Adriatic Sea, where significant physical biogeochemical processes (dense water formation, river inputs, intense air sea exchanges, phytoplankton blooms, with high primary production, and remineralisation) take place thus affecting air-sea CO2 fluxes and the related carbon seawater chemistry. The spatial and seasonal variability of chemical properties (dissolved oxygen, nutrients), including carbonate system (pHT, AT, DIC, fCO2, saturation states for calcite and aragonite), were determined in the first mesoscale surveys conducted in February and October 2008, under the SESAME project. A latitudinal section along the central Mediterranean Sea and horizontal maps at surface, including the full length of the Adriatic Sea and most of the Ionian Sea, will be presented and discussed with a particular focus on ocean acidification process. All the horizontal maps exhibit latitudinal gradients. pH and total alkalinity (AT) pointed out North-South gradients, depending on the main drivers. The surface AT showed the highest values (>2630 ?m/Kgsw) in the Adriatic basin, particularly on the N. Adriatic shelf (>2675 ?m/Kgsw) due to the effect of many rivers otputs (draining carbonatic basins), while southward the decrease to the lowest values (<2600 ?m/Kgsw) in the Ionian basin indicated the occurrence of modified Atlantic water masses (MAW). The vertical distributionsof CO2 variables are highlighted and can be compared with others, determined during EUROFLEET campaign (in 2011). In 2008, the air-sea CO2 fluxes over the Adriatic sea were calculated (according to Wanninkhof, 1992) in order to assess its role for the central Med Sea: the Adriatic worked as a CO2 sink in both seasons, with intensities depending on the synergies among main physical and biological drivers. Still latitudinal differences can be observed: being the North Adriatic a strong or moderate sink (max FCO2= -23 mmol m-2 d-1; avg FCO2= -8.3 mmol m-2 d-1 in winter, and -1.34 mmol m-2 d-1in late summer), but Southern Adriatic only a weak one (avg FCO2 = -1.9 mmol m-2 d-1 in winter, and 0.31 mmol m-2 d-1 in late summer). This general information, supporting the role of Northern Adriatic as a key area for the carbon seawater chemistry, can be integrated on local scale with the information gained from the analysis of time series acquired in the Gulf of Trieste in the last six years (poster Cantoni et al.).
CO2 varaibles in the central Mediterranean Sea on regional and local scale
Luchetta A;Sparnocchia S;Cantoni C;Cozzi S
2014
Abstract
Despite the general sparseness of water column carbon measurements, the Mediterranean Sea has been identified as an important anthropogenic carbon storage (Álvarez, 2012) where the column inventory is much higher than in the Atlantic or Pacific oceans (Schneider et al., 2010; Lee et al., 2011). The central Mediterranean Sea is even less sampled, although water masses locally formed and spreading are able to affect the deep overturning cell of the Eastern Mediterranean. We refer particularly to the Adriatic Sea, where significant physical biogeochemical processes (dense water formation, river inputs, intense air sea exchanges, phytoplankton blooms, with high primary production, and remineralisation) take place thus affecting air-sea CO2 fluxes and the related carbon seawater chemistry. The spatial and seasonal variability of chemical properties (dissolved oxygen, nutrients), including carbonate system (pHT, AT, DIC, fCO2, saturation states for calcite and aragonite), were determined in the first mesoscale surveys conducted in February and October 2008, under the SESAME project. A latitudinal section along the central Mediterranean Sea and horizontal maps at surface, including the full length of the Adriatic Sea and most of the Ionian Sea, will be presented and discussed with a particular focus on ocean acidification process. All the horizontal maps exhibit latitudinal gradients. pH and total alkalinity (AT) pointed out North-South gradients, depending on the main drivers. The surface AT showed the highest values (>2630 ?m/Kgsw) in the Adriatic basin, particularly on the N. Adriatic shelf (>2675 ?m/Kgsw) due to the effect of many rivers otputs (draining carbonatic basins), while southward the decrease to the lowest values (<2600 ?m/Kgsw) in the Ionian basin indicated the occurrence of modified Atlantic water masses (MAW). The vertical distributionsof CO2 variables are highlighted and can be compared with others, determined during EUROFLEET campaign (in 2011). In 2008, the air-sea CO2 fluxes over the Adriatic sea were calculated (according to Wanninkhof, 1992) in order to assess its role for the central Med Sea: the Adriatic worked as a CO2 sink in both seasons, with intensities depending on the synergies among main physical and biological drivers. Still latitudinal differences can be observed: being the North Adriatic a strong or moderate sink (max FCO2= -23 mmol m-2 d-1; avg FCO2= -8.3 mmol m-2 d-1 in winter, and -1.34 mmol m-2 d-1in late summer), but Southern Adriatic only a weak one (avg FCO2 = -1.9 mmol m-2 d-1 in winter, and 0.31 mmol m-2 d-1 in late summer). This general information, supporting the role of Northern Adriatic as a key area for the carbon seawater chemistry, can be integrated on local scale with the information gained from the analysis of time series acquired in the Gulf of Trieste in the last six years (poster Cantoni et al.).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
