1. A conveyor diagram is not a timetable for one stream

Cold, salty seawater is generally denser; sufficiently dense surface water can descend. NOAA's explanation includes thermohaline processes, wind-driven currents, mixing and upwelling. Sinking alone does not explain the whole circulation.

Oceanographer M. Susan Lozier's review emphasizes eddies and winds in the structure and variability of overturning. A global conveyor diagram introduces surface–deep connections; it does not show every water parcel following the same route on a fixed schedule.

AMOC represents Atlantic meridional overturning by aggregating northward and southward transport with depth. Density-related thermohaline processes form part of its explanation. AMOC, global circulation and the Gulf Stream, an individual surface current, are not interchangeable names.

2. How does RAPID calculate transport across a section?

RAPID's data description separates transport at approximately 26.5°N in the Atlantic into three components. Florida Straits transport uses electromagnetic cable measurements, Ekman transport uses wind-stress data, and upper mid-ocean transport uses mooring observations. Their sum represents maximum northward transport of upper-layer waters. One buoy does not directly read the speed of global circulation.

The transport unit 1 Sv is 10⁶ m³/s, distinct from mass or velocity in m/s. Illustratively, 1 Sv means one million cubic meters cross a section each second, not that water moves at one million meters per second.

3. Separate averages, variability and filtered curves

For 2 April 2004–27 March 2024, RAPID reports MOC mean ± standard deviation as 16.9 ± 4.6 Sv. Standard deviation describes the variability of the time series; it is not the error of the mean or a future prediction interval. Reporting the section, period and statistic is more informative than an undated statement that AMOC is 16.9 Sv.

In the same figure, colored curves are ten-day low-pass filtered and the black curve is three-month filtered. The smoother black curve does not measure a more stable ocean at another section. Check the temporal filter before comparing fluctuation amplitudes.

4. Checking conclusions in climate coverage

Overturning matters for climate because it participates in ocean heat transport and surface–deep exchange. A short transport decline at one section alone does not establish that global circulation stopped or an individual current disappeared. Compare temperature, salinity, flow variability, observing period, other regional evidence and models.

Freshwater lowering density and predicting when AMOC collapses are different questions. The first describes a condition that can influence sinking; the second requires assessment of a complex, variable circulation. One arrow in a conveyor diagram cannot establish a future date.

5. Sources

NOAA: an overview of circulation. Lozier (2010): a specialist review of the simple conveyor model. RAPID: transport estimation and time-series descriptions for a particular Atlantic section.