The Holocene gas system of the Ría de Vigo (NW Spain): Factors controlling the location of gas accumulations, seeps and pockmarks

The combined analysis of high resolution seismic profiles, sediment temperature, pore water salinity and hydrostatic pressure revealed: (1) a direct relationship between depth of free gas and hydrostatic pressure; and (2) a direct link between sediment temperature and number of acoustic plumes from seabed to water column; more acoustic plumes were detected in summer when the temperature of the sediment was higher than in winter, indicating a seasonal variation of seeps within the ría. Salinity showed no significant differences between sea bottom water and sediment pore water and was therefore not a major factor controlling gas-front variations.