EGU2020-5894, updated on 16 May 2022
https://doi.org/10.5194/egusphere-egu2020-5894
EGU General Assembly 2020
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Contrasting sources of variability in subtropical and subpolar Atlantic overturning

Yavor Kostov1, Helen L. Johnson2, David P. Marshall3, Gael Forget4, Patrick Heimbach5, N. Penny Holliday6, Feili Li7, M. Susan Lozier7, Helen R. Pillar5, and Timothy Smith5
Yavor Kostov et al.
  • 1University of Exeter, Geography, Exeter, United Kingdom of Great Britain and Northern Ireland (y.kostov@exeter.ac.uk)
  • 2University of Oxford, Earth Sciences, Oxford, United Kingdom of Great Britain and Northern Ireland
  • 3University of Oxford, Physics, Oxford, United Kingdom of Great Britain and Northern Ireland
  • 4Massachusetts Institute of Technology, Earth, Atmospheric, and Planetary Sciences, Cambridge, Massachusetts, United States of America
  • 5University of Texas at Austin, Oden Institute, Austin, Texas, United States of America
  • 6National Oceanography Centre, Southampton, United Kingdom of Great Britain and Northern Ireland
  • 7Georgia Institute of Technology, Earth and Atmospheric Sciences, Atlanta, Georgia, United States of America

The Atlantic meridional overturning circulation (AMOC) is pivotal for regional and global climate due to its key role in the uptake and redistribution of heat, carbon and other tracers. Establishing the causes of historical variability in the AMOC can tell us how the circulation responds to natural and anthropogenic changes at the ocean surface. However, attributing observed AMOC variability and inferring causal relationships is challenging because the circulation is influenced by multiple factors which co-vary and whose overlapping impacts can persist for years.  Here we reconstruct and unambiguously attribute variability in the AMOC at the latitudes of two observational arrays to the recent history of surface wind stress, temperature and salinity. We use a state-of-the-art technique that computes space- and time-varying sensitivity patterns of the AMOC strength with respect to multiple surface properties from a numerical ocean circulation model constrained by observations. While on inter-annual timescales, AMOC variability at 26°N is overwhelmingly dominated by a linear response to local wind stress, in contrast, AMOC variability at subpolar latitudes is generated by both wind stress and surface temperature and salinity anomalies. Our analysis allows us to obtain the first-ever reconstruction of subpolar AMOC from forcing anomalies at the ocean surface.

How to cite: Kostov, Y., Johnson, H. L., Marshall, D. P., Forget, G., Heimbach, P., Holliday, N. P., Li, F., Lozier, M. S., Pillar, H. R., and Smith, T.: Contrasting sources of variability in subtropical and subpolar Atlantic overturning, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5894, https://doi.org/10.5194/egusphere-egu2020-5894, 2020.