A joint Analysis of the Atlantic Meridional Overturning Circulation at 26.5oN using two Observations-based Time Series

Observations from satellite altimetry, Argo floats and wind stress fields are used to construct three dimensional, monthly absolute geostrophic velocity fields (hereinafter, Argo & altimetry) in the North Atlantic during 1993 to 2018. This velocity product together with volume transport estimates of Florida Current from a submarine cable between Florida and Bahamas near 26.5^oN and the monthly climatology from the World Ocean Atlas are used to derive time series of volume and heat transports associated with the Atlantic Meridional Overturning Circulation (AMOC). It is found that the mean and standard deviation of the meridional volume and heat transports from Argo & altimetry agree quite well with those from MOCHA/RAPID. However, there are some significant differences in their interannual variability. The main time period with a large difference is 5/2004 to 4/2009 during which MOCHA/RAPID reveals a negative trend of -4.3 Sv/decade while the Argo & altimetry time series has no significant trend. Another period with significant differences is 1/2013 to 12/2016. The main goal of this work is to analyze the differences between the two time series by using multiple combinations of the two primary date sets and methodologies as well as data withholding experiments. The differences during this time will be analyzed to investigate the potential causes for them. The strategy is to apply the MOCHA/RAPID technique to the data from Argo & altimetry and vice versa. In addition to that, transports are estimated with the MOCHA/RAPID technique after withholding data at selected longitudes as well as after swapping out data in selected depth ranges. These results will elucidate the role of the observational strategies and the associated computational methodologies have on the derived transport.