A recent decline in North Atlantic subtropical mode water formation

As a manifestation of mixing dynamics in the upper ocean, interannual and decadal variability of subtropical mode water (STMW) properties in the North Atlantic Ocean provides a valuable insight into ocean–atmosphere interaction in a changing climate. Here, we use hydrographic data from the Bermuda Atlantic Time-Series Study and Hydrostation S sites near Bermuda, as well as various ocean reanalysis products, to evaluate the modern variability of STMW properties. Our study finds an 86–93% loss of STMW thickness at these sites between 2010 and 2018 and a comparable loss throughout the western subtropical gyre, culminating in the weakest STMW pentad on record. We correlate this decline with a reduction in the annual outcropping volume and northward excursions of the formation region, suggesting a gyre-wide signal of weakening STMW generation. The outcropping volume of STMW is anti-correlated with surface ocean heat content, foreshadowing future STMW loss in the face of continued warming.

Full Text

Publisher's official version
157 Mo
Extended Data Fig. 1 Time-series plots of STMW core properties.
-54 Ko
Extended Data Fig. 2 Statistical comparison of STMW parameters for the two weakest STMW periods.
-53 Ko
Extended Data Fig. 3 Map of Argo float profiles.
-53 Ko
Extended Data Fig. 4 Table detailing different STMW definitions.
-53 Ko
Extended Data Fig. 5 Time-series plots of STMW properties based on different identification algorithms.
-53 Ko
Extended Data Fig. 6 NAO-STMW correlation time-series.
-53 Ko
Supplementary Information
4614 Ko
Author's final draft
394 Mo
Publisher Correction
1524 Ko
How to cite
Stevens Samuel W., Johnson Rodney J., Maze Guillaume, Bates Nicholas R. (2020). A recent decline in North Atlantic subtropical mode water formation. Nature Climate Change. 10 (4). 335–341. https://doi.org/10.1038/s41558-020-0722-3, https://archimer.ifremer.fr/doc/00618/72973/

Copy this text