Dynamics of North Balearic Front during an autumn Tramontane and Mistral storm: air–sea coupling processes and stratification budget diagnostic

Abstract

Abstract. The north Balearic front forms the southern branch of the cyclonic gyre in the North Western Mediterranean Sea. Its dynamics exhibits significant seasonal variability. During autumn, the front spreads northward during the calm wind periods and rapidly moves back southward when it is exposed to strong northerly wind events such as the Tramontane and Mistral. These strong winds considerably enhance the air–sea exchanges. To investigate the role of air–sea exchanges on the dynamics of the North Balearic front, we used observations and a high-resolution air–sea coupled modelling system, and focused on a strong wind event observed in late October 2012, which was well-documented during the Hydrological Cycle Mediterranean Experiment. The coupled model was able to correctly reproduce the 4 °C sea surface temperature drop recorded in the frontal zone together with the observed southwestward displacement of the front. The comparison between the weak wind period preceding the event and the strong wind event itself highlighted the impact of the wind regime on the air–sea coupling, with both thermal and dynamical couplings during the low wind period and mainly thermal coupling during the strong wind period. The effect of air–sea exchanges on the stratification variations in the frontal zone was investigated with a stratification budget diagnosis. The stratification variations are controlled by diabatic air–sea buoyancy flux, adiabatic Ekman buoyancy flux, and advective processes. During the strong wind period, the Ekman buoyancy flux was found to be three times greater than the air–sea buoyancy flux and thus played a major role in the destratification of the frontal zone. The role of Ekman pumping and inertial wave on the advective processes is also discussed.

Investigating population dynamics from parentage analysis in the highly endangered fan mussel Pinna nobilis

“…In Wesselmann et al (2018), the authors revealed genetic differentiations between Banyuls‐Murcia and Banyuls‐Mallorca likely due to isolation by distance and to the North Balearic Front which creates a physical barrier of dense water that limits the circulation of particles such as larvae (Seyfried et al, 2019). The source population of individuals in the bay of Peyrefite was thus more likely located in the Eastern or Northeastern part of the Gulf of Lion, such as the northern lagoons (Salses‐Leucate and Thau), and larvae may be transported by the influence of the Northern Current (Seyfried et al, 2019). Such low levels of self‐recruitment and high connectivity were also found at a similar spatial scale for other bivalve species such as the Arctic surfclam, Mactromeris polynyma (Cassista & Hart, 2007), the Venus clam Polititapes rhomboides (Chacón et al, 2021), or the hard clam Meretrix meretrix (Ye et al, 2020).…”

“…nobilis population structure which suggested high levels of connectivity across the Gulf of Lion (González‐Wangüemert et al, 2019; Peyran, Boissin, et al, 2021; Wesselmann et al, 2018). In Wesselmann et al (2018), the authors revealed genetic differentiations between Banyuls‐Murcia and Banyuls‐Mallorca likely due to isolation by distance and to the North Balearic Front which creates a physical barrier of dense water that limits the circulation of particles such as larvae (Seyfried et al, 2019). The source population of individuals in the bay of Peyrefite was thus more likely located in the Eastern or Northeastern part of the Gulf of Lion, such as the northern lagoons (Salses‐Leucate and Thau), and larvae may be transported by the influence of the Northern Current (Seyfried et al, 2019).…”

Overview towards improved understanding of the mechanisms leading to heavy precipitation in the western Mediterranean: lessons learned from HyMeX

“…During the second period of 27-28 October 2012, the cyclone center reached the lowest pressure of 985 hPa over the Alps (Fig. 2) associated with a clear trough in the upper troposphere, provoking severe northwesterly-northerly winds advecting cold and dry air over the WMed Sea and inducing large evaporation as well as ocean cooling and mixing (Lebeaupin Brossier et al, 2014;Rainaud et al, 2015Rainaud et al, , 2017Seyfried et al, 2019). The relationship between cyclone dynamics and heavy rainfall during IOP16 is discussed in detail by Flaounas et al (2016).…”

Overview towards improved understanding of the mechanisms leading to heavy precipitation in the Western Mediterranean: lessons learned from HyMeX

“…During the second period, 27−28 October 2012, the cyclone centre reached the lowest pressure of 985 hPa over the Alps (Fig. 2), associated with a clear trough in the upper troposphere and provoking severe northwesterly/northerly winds advecting cold and dry air over the WMed Sea and inducing large evaporation and ocean cooling and mixing (Lebeaupin Brossier et al, 2014;Rainaud et al, 2015Rainaud et al, , 2017Seyfried et al, 2018). The relationship between cyclone dynamics and heavy rainfall during IOP16 is discussed in detail by Flaounas et al (2015a).…”