Thermohaline trends in the Bay of Biscay from Argo floats over the decade 2004–2013

•Thermohaline trends were analyzed by means of Argo float data in the Bay of Biscay.•ENACW was found to warm (0.012 °C y− 1) and salinificate (0.004 y− 1).•MW cooling (− 0.011 °C y− 1) and freshening (− 0.005 y− 1) was observed.•Changes were mainly due to intrinsic changes in water masses.•Vertical uplifting of isopycnals (~ 80 dbar) balances intrinsic changes in ENACW.

Thermohaline trends along the water column were analyzed by means of Argo float data in the Bay of Biscay over the period 2004–2013. Water occupying the upper 100 m was considered as Surface Water (SW). Two deeper water masses were considered: Eastern North Atlantic Central Water (ENACW) and Mediterranean Water (MW). SW was observed to salinificate at a rate of 0.006 y− 1, while no significant trend was found for temperature. ENACW was found to warm and salinificate at a rate of 0.012 °C y− 1 and 0.004 y− 1, respectively. MW cooling and freshening was observed at a rate of − 0.011 °C y− 1 and − 0.005 y− 1, respectively. Both temperature and salinity variability were mainly due to intrinsic changes in water masses, except for temperature in the upper part of ENACW, where the vertical uplifting of isopycnals (~ 80 dbar) balances intrinsic changes in this water mass. Comparison with previous research suggests that the observed changes are consistent with those measured along the Western coast of the Iberian Peninsula.