Impact of the cyclones on the air-sea carbon flux of the Mediterranean Sea

Mediterranean cyclones strongly impact the air-sea fluxes of the Mediterranean region. They often manifest the well known strong winds of the region such as the Mistral, Tramontane, and Sirocco winds. In particular, two of the former winds enhance the latent and sensible heat fluxes over the Gulf of Lion, leading to the annual vertical mixing of the water column. During some years, these fluxes are significant enough to generate open ocean convection beyond the normal vertical mixing, where the surface waters mix down to the sea floor, some 2000 meters deep.

Much attention over the years has been given to understanding how Mediterranean cyclones drive air-sea heat fluxes in the region and their resulting effects on the sea. Similarly, much attention has been given to how these cyclones drive bouts of extreme precipitation in the region. However, little to no attention has been given to how they impact the air-sea carbon fluxes of the region. One very recent work connects carbon flux extremes with synoptic atmospheric configurations, connecting loosely cyclonic behavior with the air-sea carbon fluxes. In this work, using recent biogeochemical model outputs for the Mediterranean Sea covering a 20 year period, we dive deeper into this relationship and present how the cyclones enhance air-sea carbon fluxes, sometimes by more than 30%. The largest enhancements are seen in the Adriatic, Aegean, and Cretan Seas, with minor enhancement seen in the Gulf of Lion.

We additionally break down the mathematical description of the carbon flux parameterization and separate the components to demonstrate their relative contribution while under the influence of a cyclone. For example, we will present how the gas transfer velocity is significantly enhanced in the Gulf of Lion, but much less so in the Aegean Sea, despite the resulting fluxes showing the opposite trend. The remaining components, influenced by the sea surface temperature, salinity, and dissolved carbon will also be discussed, with their contributions quantified.