Description: This dataset is a collection of moored velocity data used in the study “Sources and pathways of intraseasonal meridional kinetic energy in the equatorial Atlantic Ocean” (Körner et al., 2022) to analyze the representation of meridional intraseasonal velocity variability in a general circulation model. The observational velocity data were collected at five different locations along the equator. At 0°N, 35°W velocity data were collected by single-point current meters in four different depths from October 1992 until May 1994. Between August 2004 and June 2006 an acoustic Doppler current profiler (ADCP) and single-point current meters collected data at 0°N, 35°W. Moorings at 0°N, 23°W provide velocity measurements from December 2001 to June 2021 (apart from a period from December 2002 to February 2004 when no mooring was in place). At 0°N, 10°W velocity data were collected between May 2003 to March 2019 using ADCPs and single-point current meters. However, the mooring was not consecutively installed leading to data gaps of up to two years. Between 2007 and 2011 ADCPs recorded velocity data at 0°N, 0°E.

Description: The shallow meridional overturning cells of the Atlantic Ocean, the Subtropical Cells (STCs), consist of poleward Ekman transport at the surface, subduction in the subtropics, equatorward flow at thermocline level and upwelling along the equator and at the eastern boundary. In this study we provide the first observational estimate of transport variability associated with the horizontal branches of the Atlantic STCs in both hemispheres based on Argo float data and supplemented by reanalysis products. Thermocline layer transport convergence and surface layer transport divergence between 10°N and 10°S are dominated by seasonal variability. Meridional thermocline layer transport anomalies at the western boundary and in the interior basin are anti-correlated and partially compensate each other at all resolved time scales. It is suggested that the seesaw-like relation is forced by the large-scale off-equatorial wind stress changes through low-baroclinic-mode Rossby wave adjustment. We further show that anomalies of the thermocline layer interior transport convergence modulate sea surface temperature (SST) variability in the upwelling regions along the equator and at the eastern boundary at time scales longer than 5 years. Phases of weaker (stronger) interior transport are associated with phases of higher (lower) equatorial SST. At these time scales, STC transport variability is forced by off-equatorial wind stress changes, especially by those in the southern hemisphere. At shorter time scales, equatorial SST anomalies are, instead, mainly forced by local changes of zonal wind stress.

Description: The processing was done as described in Bunge et al. (2008) and in Bourlès Bernard et al (2020): French PIRATA cruises: MOORING ADCP data. SEANOE. https://doi.org/10.17882/51557

Description: The processing was done as described in Bunge et al. (2008) and in Bourlès Bernard et al (2020): French PIRATA cruises: MOORING ADCP data. SEANOE. https://doi.org/10.17882/51557

Description: The processing was done as described in Bunge et al. (2008) and in Bourlès Bernard et al (2020): French PIRATA cruises: MOORING ADCP data. SEANOE. https://doi.org/10.17882/51557

Description: GEOMAR moorings are typically equipped with instruments recording pressure, temperature, conductivity, dissolved oxygen and current velocity. Instruments with pressure, temperature, conductivity and oxygen sensors were calibrated in situ immediately prior to and after a mooring deployment period by attaching them to the CTD frame during CTDO casts. Correction terms were then developed from the difference between the sensor readings and the calibrated CTDO data during several minute long calibration stops. These correction terms were then applied to the full deployment periods. This ensured best data quality with recognition of potential sensor drifts and also allowed for the estimation of calibration and measurement errors (Hahn et al. 2014, Bittig et al. 2018, Berx et al. 2019).

Description: Current velocities of the upper water column along the cruise track of R/V Maria S. Merian cruise MSM117 were collected by a vessel-mounted 38 kHz RDI Ocean Surveyor ADCP. The ADCP transducer was located at 6.0 m below the water line. The instrument was operated in two different configurations: 1) broadband mode with 32 m bins and a blanking distance of 16 m, with a total of 50 bins, 2) narrowband mode with 32 m bins and a blanking distance of 16 m, with a total of 50 bins. Beam velocities as recorded by the data acquistion software VmDAS were transformed to ship coordinates and after merging with the navigation data from the ship's Motion Reference Unit and Global Positioning systems into earth coordinates. Single-ping data were screened for bottom signals and, where appropriate, a bottom mask was manually processed. The ship's velocity was calculated from position fixes obtained by the Global Positioning System (GPS). Accuracy of the ADCP velocities mainly depends on the quality of the position fixes and the ship's heading data. Further errors stem from a misalignment of the transducer with the ship's centerline. Data post-processing included water track calibration of the misalignment angle (configuration 1: 0.3196° +/- 0.8714°, configuration 2: 0.3603° +/- 0.6433°) and scale factor (configuration1: 1.0007 +/- 0.0151, configuration 2: 1.0024 +/- 0.0107) of the Ocean Surveyor signal. The velocity data were averaged in time using an average interval of 60 s. Velocity quality flagging is based on following threshold criteria: abs(UC) or abs(VC) 〉 2.0 m/s, rms(UC_z) or rms(VC_z) 〉 0.3.

Description: Current velocities of the upper water column along the cruise track of R/V Maria S. Merian cruise MSM117 were collected by a vessel-mounted 75 kHz RDI Ocean Surveyor ADCP. The ADCP transducer was located at 6.0 m below the water line. The instrument was operated in two different configurations: 1) narrowband mode with 8 m bins and a blanking distance of 8 m, with a total of 100 bins, 2) broadband mode with 5 m bins and a blanking distance of 5 m, with a total of 128 bins. Heading, pitch and roll data from the ship's motion reference unit and the navigation data from the Global Positioning systems were used by the data acquisition software VmDAS internally to convert ADCP velocities into earth coordinates. Single-ping data were screened for bottom signals and, where appropriate, a bottom mask was manually processed. The ship's velocity was calculated from position fixes obtained by the Global Positioning System (GPS). Accuracy of the ADCP velocities mainly depends on the quality of the position fixes and the ship's heading data. Further errors stem from a misalignment of the transducer with the ship's centerline. Data post-processing included water track calibration of the misalignment angle (configuration 1: -47.4696° +/- 0.7022°, configuration 2: -47.4676° +/- 0.9771°) and scale factor (configuration1: 1.0081 +/- 0.0114, configuration 2: 1.0086 +/- 0.0161) of the Ocean Surveyor signal. The velocity data were averaged in time using an average interval of 60 s. Velocity quality flagging is based on following threshold criteria: abs(UC) or abs(VC) 〉 2.0 m/s, rms(UC_z) or rms(VC_z) 〉 0.3.

Description: The upper-ocean circulation of the tropical Atlantic is a complex superposition of thermohaline and wind-driven flow components. The resulting zonally- and vertically-integrated upper-ocean meridional flow is referred to as the upper branch of the Atlantic Meridional Overturning Circulation (AMOC) - a major component and potential tipping element of the global climate system. We investigate the tropical part of the northward AMOC branch, i.e. the return flow covering the upper 1,200 m, based on Argo data and repeated shipboard velocity measurements. The western boundary mean circulation at 11°S is realistically reproduced from high-resolution Argo data showing a remarkably good representation of the vertical structure of meridional velocity and the volume transport of water mass layers when compared to results from direct velocity measurements along a repeated ship section. Thus, we extend the analysis to the inner tropical Atlantic. Within the AMOC return flow, a diapycnal upwelling of central water into the thermocline layer of ~2 Sv is derived between 11°S and 10°N which is about half the magnitude of previous estimates, likely due to improved horizontal resolution. The mean strength of the AMOC return flow is ~16 Sv across 11°S and 10°N. At 11°S, northward transport is concentrated at the western boundary where the AMOC return flow enters the tropics at all vertical layers above 1,200 m. At 10°N, northward transport is observed both at the western boundary and in the interior predominantly in the surface and intermediate layer indicating recirculation and transformation of thermocline and central water within the tropics.

Description: Since 2001, current velocities have been measured continuously as part of a multilateral collaboration, the Prediction and Research Moored Array in the Tropical Atlantic (PIRATA), that regularly services a moored observatory located at 0°N, 23°W. Here, we present an update of 20 years of full-depth current velocity observations at 0°N, 23°W. With the presented current velocity data product, we aim to provide an important and accessible reference data set against which models and reanalysis output could be validated. The velocity time series will also be helpful for studies focusing on long-term climate variability to search for connections with changes in the equatorial circulation over the last 20 years. Earlier versions of this data product have already been used in a variety of studies and provided a significant contribution to an overall improved understanding of equatorial ocean dynamics. The moored observatory at 0°N, 23°W is an ongoing example of a successful multinational collaboration extending over more than two decades.