Trends of pH decrease in the Mediterranean Sea through high frequency observational data: indication of ocean acidification in the basin

Flecha, Susana; Pérez, Fíz F.; García‐Lafuente, Jesús; Sammartino, Simone; Rı́os, Aida F.; Huertas, I. Emma

doi:10.1038/srep16770

Cited by 51 publications

(43 citation statements)

References 45 publications

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“…A net flux of anthropogenic carbon from the Atlantic towards the Mediterranean basin has been identified being responsible for 25% of the basin-wide CO 2 uptake over the last 200 years (Flecha et al, 2015 and references therein). From the pre-industrial period until 2013 the pH in Mediterranean Sea has decreased by 0.055 -0.156 pH units (Hassoun et al, 2015) with an annual decreasing trend of 0.0044 ± 0.00006 (Flecha et al, 2015). Model simulations predict a further decrease in the pH of Mediterranean surface waters of 0.3-0.4 units by the year 2100 (Howes et al, 2015).…”

Section: Introductionmentioning

confidence: 93%

Simulation of Coastal Processes affecting pH with Impacts on Carbon and Nutrient Biogeochemistry

et al. 2018

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Naturally occurring microbial decomposition of organic matter (OM) in coastal marine environments cause increased acidity in deeper layers similar or even exceeding the future predictions for global ocean acidification (OA). Experimental studies in coastal areas characterized by increased inputs of OM and nutrients, coping with intermittent hypoxic/anoxic conditions, provide better understanding of the mechanisms affecting nutrients and carbon biogeochemistry under the emerging effects of coastal pH decrease. Laboratory CO 2 -manipulated microcosm experiments were conducted using seawater and surface sediment collected from the deepest part of Elefsis Bay (Saronikos Gulf, Eastern Mediterranean) focusing to study the co-evolution of processes affected by the decline of dissolved oxygen and pH induced by (a) OM remineralization and (b) the future anthropogenic increase of atmospheric CO 2 . Under more acidified conditions, a significant increase of total alkalinity was observed partially attributed to the sedimentary carbonate dissolution and the reactive nitrogen species shift towards ammonium. Νitrate and nitrite decline, in parallel with ammonium increase, demonstrated a deceleration of ammonium oxidation processes along with decrease in nitrate production. The decreased DIN:DIP ratio, the prevalence of organic nutrient species against the inorganic ones, the observations of constrained DON degradation and nitrate production decline and the higher DOC concentrations revealed the possible inhibition of OM decomposition under lower pH values. Finally, our results highlight the need for detailed studies of the carbonate system in coastal areas dominated by hypoxic/anoxic conditions, accompanied by other biogeochemical parameters and properly designed experiments to elucidate the processes sequence or alterations due to pH reduction.

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Section: Introductionmentioning

confidence: 93%

Simulation of Coastal Processes affecting pH with Impacts on Carbon and Nutrient Biogeochemistry

et al. 2018

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“…Based on a recent statistical analysis of continuous pH measurements at the Espartel Sill from 2012 to 2015, Flecha et al . [] estimate that 40% of the outflow is comprised of WMDW and 60% of WMIW, in agreement with previous estimates by García Lafuente et al . [].…”

Section: Coupled Water‐oxygen Cycling Modelmentioning

confidence: 99%

Circulation and oxygen cycling in the Mediterranean Sea: Sensitivity to future climate change

Powley

Krom

Cappellen

2016

J. Geophys. Res. Oceans

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Climate change is expected to increase temperatures and decrease precipitation in the Mediterranean Sea (MS) basin, causing substantial changes in the thermohaline circulation (THC) of both the Western Mediterranean Sea (WMS) and Eastern Mediterranean Sea (EMS). The exact nature of future circulation changes remains highly uncertain, however, with forecasts varying from a weakening to a strengthening of the THC. Here we assess the sensitivity of dissolved oxygen (O2) distributions in the WMS and EMS to THC changes using a mass balance model, which represents the exchanges of O2 between surface, intermediate, and deep water reservoirs, and through the Straits of Sicily and Gibraltar. Perturbations spanning the ranges in O2 solubility, aerobic respiration kinetics, and THC changes projected for the year 2100 are imposed to the O2 model. In all scenarios tested, the entire MS remains fully oxygenated after 100 years; depending on the THC regime, average deep water O2 concentrations fall in the ranges 151–205 and 160–219 µM in the WMS and EMS, respectively. On longer timescales (>1000 years), the scenario with the largest (>74%) decline in deep water formation rate leads to deep water hypoxia in the EMS but, even then, the WMS deep water remains oxygenated. In addition, a weakening of THC may result in a negative feedback on O2 consumption as supply of labile dissolved organic carbon to deep water decreases. Thus, it appears unlikely that climate‐driven changes in THC will cause severe O2 depletion of the deep water masses of the MS in the foreseeable future.

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“…The instrument configuration of the monitoring station is similar to that of the lines deployed at the Camarinal Sill although it contains additional probes to measure pH and CO 2 (Flecha et al, 2015), which are not used here. More information about the station can be found in Naranjo et al (2015.…”

Section: Introductionmentioning

confidence: 99%

The Mediterranean outflow in the Strait of Gibraltar and its connection with upstream conditions in the Alborán Sea

García‐Lafuente

Naranjo²,

Sammartino³

et al. 2017

Ocean Sci.

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Abstract. The present study addresses the hypothesis that the Western Alborán Gyre in the Alborán Sea (the westernmost Mediterranean basin adjacent to the Strait of Gibraltar) influences the composition of the outflow through the Strait of Gibraltar. The process invoked is that strong and welldeveloped gyres help to evacuate the Western Mediterranean Deep Water from the Alborán basin, thus increasing its presence in the outflow, whereas weak gyres facilitate the outflow of Levantine and other intermediate waters. To this aim, in situ observations collected at the Camarinal (the main) and Espartel (the westernmost) sills of the strait have been analysed along with altimetry data, which were employed to obtain a proxy of the strength of the gyre. An encouraging correlation of the expected sign was observed between the time series of potential temperature at the Espartel Sill, which is shown to keep information on the outflow composition, and the proxy of the Western Alborán Gyre, suggesting the correctness of the hypothesis, although the weakness of the involved signals does not allow for drawing definitive conclusions.

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Trends of pH decrease in the Mediterranean Sea through high frequency observational data: indication of ocean acidification in the basin

Cited by 51 publications

References 45 publications

Simulation of Coastal Processes affecting pH with Impacts on Carbon and Nutrient Biogeochemistry

Simulation of Coastal Processes affecting pH with Impacts on Carbon and Nutrient Biogeochemistry

Circulation and oxygen cycling in the Mediterranean Sea: Sensitivity to future climate change

The Mediterranean outflow in the Strait of Gibraltar and its connection with upstream conditions in the Alborán Sea

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