Physical and Biological Water Column Observations during Summer Sea/Land Breeze Winds in the Coastal Northern Tyrrhenian Sea

Abstract

Coupling between sea/land breeze and coastal circulation and the influence of wind-driven dynamics are substantially relevant for understanding coastal Mediterranean ecosystems. These coastal areas are particularly dynamic and are characterized by high-variable processes which drive biological phenomena at different time-scales. For the Tyrrhenian Sea, the available information on coastal dynamics is confined to large-scale general circulation with a focus exclusively on mesoscale pelagic dynamical processes. Hydrodynamic studies of Tyrrhenian coastal areas are very rare and focus on surface water circulation. For time scales that are associated with coastal water circulation, there is also limited knowledge on water column dynamics that are forced by local atmospheric circulations. This paper presents physical and biological data to document the effect of sea/land breeze circulation on ocean current dynamics and water column structures in a Northern Tyrrhenian coastal site. This coastal area is characterized by the presence of a relevant energy production site as well as one of the most important ports in the Mediterranean Sea for cruise traffic. Consequently, this coastal site is a transit point for many tourists and it is characterized by an increase of energy demand, especially during the summer season. The in-situ data show that coastal currents are predominantly controlled by the tide and local wind and respond rapidly to changes in wind direction. Water column thermal structure analyses reveal significant changes with the morning’s rotation of breeze: lifting of isotherms (cooling) was typically observed in deep layers during early mornings, accompanied by fluctuations in isotherms. The performed investigations provide valuable inputs for coastal ecosystem modeling and for a better understanding of the coastal processes that are significant for environmental and navigational interests.

Keywords

• sea/land breeze
• coastal circulation
• wind forcing
• hydrography
• phytoplankton patchiness