EGU21-1164
https://doi.org/10.5194/egusphere-egu21-1164
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Decomposing the time-mean Atlantic Meridional Overturning Circulation and its variability with latitude.

Tomas Jonathan1, Mike Bell3, Helen Johnson1, and David Marshall2
Tomas Jonathan et al.
  • 1University of Oxford, Department of Earth Scicences, Oxford, United Kingdom of Great Britain – England, Scotland, Wales (tomas.jonathan@worc.ox.ac.uk)
  • 2Department of Physics, University of Oxford, Oxford, United Kingdom of Great Britain and Northern Ireland
  • 3Hadley Centre, Met Office, Exeter, United Kingdom of Great Britain and Northern Ireland

The Atlantic Meridional Overturning Circulations (AMOC) is crucial to our global climate, transporting heat and nutrients around the globe. Detecting  potential climate change signals first requires a careful characterisation of inherent natural AMOC variability. Using a hierarchy of global coupled model  control runs (HadGEM-GC3.1, HighResMIP) we decompose the overturning circulation as the sum of (near surface) Ekman, (depth-dependent) bottom velocity, eastern and western boundary density components, as a function of latitude. This decomposition proves a useful low-dimensional characterisation of the full 3-D overturning circulation. In particular, the decomposition provides a means to investigate and quantify the constraints which boundary information imposes on the overturning, and the relative role of eastern versus western contributions on different timescales. 

The basin-wide time-mean contribution of each boundary component to the expected streamfunction is investigated as a function of depth, latitude and spatial resolution. Regression modelling supplemented by Correlation Adjusted coRrelation (CAR) score diagnostics provide a natural ranking of the contributions of the various components in explaining the variability of the total streamfunction. Results reveal the dominant role of the bottom component, western boundary and Ekman components at short time-scales, and of boundary density components at decadal and longer timescales.

How to cite: Jonathan, T., Bell, M., Johnson, H., and Marshall, D.: Decomposing the time-mean Atlantic Meridional Overturning Circulation and its variability with latitude., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1164, https://doi.org/10.5194/egusphere-egu21-1164, 2021.

Display materials

Display file

Comments on the display material

to access the discussion