Abstract
Using Argo profiling floats, cruises and mooring data, we reconstructed the dissolved oxygen (O2) dynamics in the Gulf of Lion and the Ligurian Sea, with a focus on the intermediate waters. By applying the CANYON-MED neural network-based method on the large network of O2-equipped Argo floats we derived nutrients and carbonate system variables in the Gulf of Lion and the Ligurian Sea at different depths in the water column and derived trends over the 2012-2020 period. In these waters, the O2 minimum is strongly affected by the intermittent convection process, and the two areas show dissimilar responses to the mixing events. In the absence of deep convection events, the O2-depleted layer tends to spread vertically and intensify even more so in the Ligurian than in the Gulf of Lion. In both areas, over the 2012-2020 period, nutrients increase overall in deep layers, with a concomitant impact on nutrient molar ratios tending towards an increase in P-limitation. Acidification estimates derived in different layers of the water column show an overall increase in dissolved inorganic carbon and a concurrent pH decrease. These trends were strongly affected by convection events slowing down the overall acidification trend.
Key Points
- In the absence of deep convection events, the O2-depleted layer spreads vertically and intensifies more in the Ligurian than Gulf of Lion.
- Nutrients increase in deep and to a lesser extent in intermediate waters with a decoupling between nitrate and phosphate trends.
- Dissolved inorganic carbon increases in intermediate and deep waters with a concurrent pH decrease over the period of study, 2012-2020.
Fourrier M., Coppola L., D’Ortenzio F., Migon C. & Gattuso J.-P., 2022. Impact of intermittent convection in the northwestern Mediterranean Sea on oxygen content, nutrients and the carbonate system. Journal of Geophysical Research: Oceans 127: e2022JC018615. doi: 10.1029/2022JC018615. Article (subscription required).
