Mass, Heat, and Freshwater Transport From Transoceanic Sections in the Atlantic Ocean at 30°S and 24.5°N: Single Sections Versus Box Models?

• Published in: Geophysical research letters 2023-06, Vol.50 (11), p.n/a
• Main Authors: Caínzos, Verónica, Hernández‐Guerra, Alonso, Farneti, Riccardo, Pérez‐Hernández, M. Dolores, Talley, Lynne D.
• Format: Article
• Language: English
• Subjects: Aliasing; AMOC; Atlantic Meridional Overturning Circulation (AMOC); Freshwater; General circulation models; Heat; Hydrographic data; Hydrographic sections; Inland water environment; inverse model; Latitude; Mathematical models; Modelling; Monthly variations; Numerical models; Nutrients; Ocean dynamics; Oceanic general circulation model; Oceans; Variability
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL103412

The Atlantic meridional overturning circulation (AMOC) is central to the climate of the Atlantic by redistributing mass, heat, and freshwater. Hydrographic sections help monitor its strength at different latitudes, and inverse box models provide estimates of AMOC, heat, and freshwater transports. We have used all available hydrographic zonal sections at 24.5°N and 30°S over the last 30 years to conclude that single section inverse models agree with monthly outputs from an ocean general circulation model at the time of the cruise. In contrast, inverse models using multiple sections at different latitudes and times of the year for each of the last three decades are more consistent with decadal averages from the same model. Therefore, solutions of inverse models with single sections are affected by aliasing and represent the state of the ocean at the time of cruise. However, aliasing is greatly reduced when using multiple sections to assess low‐frequency variability. Plain Language Summary Heat and nutrients in the Atlantic Ocean are redistributed through a process called Atlantic meridional overturning circulation, which is being monitored to detect changes in its strength. Hydrographic data offer the possibility to assess this variability, although it can be influenced by the ocean dynamics happening at the time of the cruise. When comparing the results from inverse box models applied to single sections with numerical model output, the best fit appears for the time of the cruise. This reflects that the monthly variation affects the solutions of the inverse model, which can be understood as representative of the duration of the cruise. Inverse models using several sections from cruises carried out in different times of the year and different years average out the local temporal phenomena that can affect the results and better represent the decadal average of the numerical models. Key Points The Atlantic meridional overturning circulation has been monitored with hydrographic data and now basin‐wide arrays enable the detection of high‐frequency variability Inverse solutions from single sections are affected by aliasing, as they capture the circulation structure of the time of the cruise Inverse models with multiple sections at different latitudes and times agree with decadal averages from an ocean general circulation model