Impact of the new equation of state of seawater (TEOS-10) on the estimates of water mass mixture and meridional transport in the Atlantic Ocean

• Published in: Progress in oceanography 2018-03, Vol.162, p.13-24
• Main Authors: Almeida, Lucas, de Azevedo, José Luiz Lima, Kerr, Rodrigo, Araujo, Moacyr, Mata, Mauricio M.
• Format: Article
• Language: English
• Subjects: AMOC; Atlantic Ocean; Baroclinic velocity; Heat transport; Ocean circulation; TEOS-10; Volume transport; Water masses
• ISSN: 0079-6611; 1873-4472
• DOI: 10.1016/j.pocean.2018.02.008

•The AABW was the most affected water mass by the new equation, with about 10% differences to the total contribution.•Baroclinic velocity estimates unveiled the largest differences near the western boundary current systems.•The differences of total AMOC transport reached a maximum of 6% between the two equations.•The heat transport estimates showed significant differences in the higher latitudes regions studied. The equation of state of seawater (EOS) provides a simple way to link the properties of seawater that are the most important for ocean dynamics and the ocean-atmosphere climate system. In 2010, the set of equations used to derive all thermodynamic properties of seawater were updated using a thermodynamic approach. The new approach, named TEOS-10, results in better estimates of seawater properties, such as salinity and temperature, when compared to the previous EOS version (EOS-80). Since several physical processes in the oceans are driven by these properties, improvements in the EOS performance are expected to lead to a better and more realistic representation of the ocean. This work focuses on assessing the main differences of the: (i) contribution of water masses to a total mixture, (ii) baroclinic velocity, and (iii) volume and heat transport, as calculated by the EOS-80 and by the TEOS-10, along four zonal transects at 26.5°N, 10°N, 11°S, and 34.5°S in the Atlantic Ocean. The density differences (always between TEOS-10 and EOS-80) increase with depth and hence the results indicate that the most significant difference in the water mass contributions was found for Antarctic Bottom Water. Within that layer, the differences reach up to 10% on its fraction of the mixture when calculated by the TEOS-10, although the difference in the North Atlantic Deep Water contribution was not negligible either. The estimated baroclinic velocities showed considerable differences in all studied areas, being more significant over boundary current systems. The Gulf Stream presented lower velocity, while the Brazil Current presented increasing velocity when using TEOS-10. The comparison between values computed for volume transported by the Atlantic Meridional Overturning Circulation showed a total difference of about +6%, which cannot be neglected when considering the space and time variability involved. The heat transport showed significant differences in the study areas at the mid latitudes, where large variations in the total flow were observed.