Mesoscale dynamics of the Balearic front integrating glider, ship and satellite data

Two independent surveys were carried out in order to characterize the Balearic front (Northern Mallorca island). The first survey was performed by the coastal glider ‘Maya’ between 7 and 13 July 2007, covering a total distance (go and return) of about 90 nm along the Envisat track 773. The autonomous platform collected 148 CTD profiles from 10 m to 180 m depth in one week (~21 profiles per day). Every 6 hours, the glider goes up to the surface and sends the measured data by satellite transmission. Real-time processing of data allowed us to identify the position of the Balearic front and design in advance the CTD/XBT sampling for the ship survey that was conducted between 9 and 12 July on board R/V García del Cid. Due to bad meteorological conditions, the ship sampling period along the same satellite track was reduced to less of one day. We collected 8 CTD profiles reaching 600 m depth and 14 XBTs were launched between CTD stations. Preliminary analysis shows coherent results from both data sets (ship and glider). Using a reference level of 180 m depth, we have found maximum geostrophic velocities of 45-50 cm/s flowing northeastwards along the North Mallorca coast. There are not significant differences when dynamic height is computed using a reference level of 180 or 600 m depth (ship data), which ensure the results obtained from glider data. Moreover, the comparison of geostrophic velocity from CTDs (ship and glider) and interpolated dynamic topography from merged altimetry fields along the Envisat track shows a coherent pattern, although the magnitude from altimetry data is lower due to the filtering applied in the interpolated fields. The width of the Balearic front along the satellite track is about 35-40 km and it is clearly detected in salinity (not in temperature) with lower values (37.4 PSU) near coast that likely are related to the input of Atlantic Water through the Mallorca channel.