Impact of data assimilation of glider observations in the Ionian Sea (Eastern Mediterranean)

Glider observations of temperature, salinity and vertically averaged velocity in the Ionian Sea (Eastern Mediterranean Sea), made in the period October 2004–December 2004, were assimilated into an operational forecasting model together with other in situ and satellite observations. The study area has a high spatial and temporal variability of near surface dynamics, characterized by the entrance of the Atlantic Ionian Stream (AIS) into the Northern Ionian Sea. The impact of glider observations on the estimation of the circulation is studied, and it is found that their assimilation locally improves the prediction of temperature, salinity, velocity and surface elevation fields. However, only the assimilation of temperature and salinity together with the vertically averaged velocity improves the forecast of all observed parameters. It is also found that glider observations rapidly impact the analyses even remotely, and the remote impacts on the analyses remain several months after the presence of the glider. The study emphasizes the importance of assimilating as much as possible all available information from gliders, especially in dynamically complex areas.