Transatlantic temperature and salinity changes at 24.5°N from 1957 to 2004

In 2004 a fifth occupation of a transatlantic section at 24.5°N allows us to examine decadal temperature and salinity changes using high quality full-depth hydrographic data since 1957. Waters shallower than 1750 dbar have been warming and salinifying at least since 1981 and in 2004 are significantly warmer and saltier than at any time since 1957, while deeper than 3000 dbar there has been continuous cooling and freshening since 1957. Temperature and salinity changes at constant pressures are partitioned into changes on isopycnal surfaces and changes due to the vertical movement of the isopycnals. Warming in the western Atlantic thermocline since 1957 at a rate of 0.0111 °C/yr dominates the transatlantic average, while deep water has cooled and freshened at rates of −0.0021 °C/yr and −0.0003 psu/yr respectively. We argue that the shallower and deeper changes are consistent with a recently reported increased southward thermocline circulation and reduced southward flux of deep water.