EGU2020-11549
https://doi.org/10.5194/egusphere-egu2020-11549
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Can satellites replace mooring arrays? Satellite altimetry transport estimates of the Atlantic overturning meridional circulation along the RAPID 26°N mooring array

Alejandra Sanchez-Franks, Eleanor Frajka-Williams, and Ben Moat
Alejandra Sanchez-Franks et al.
  • National Oceanography Centre, Marine Physics and Ocean Climate, Southampton, United Kingdom of Great Britain and Northern Ireland (alsf@noc.ac.uk)

The Atlantic meridional overturning circulation (AMOC) is a large-scale oceanic circulation comprising a 2-layer flow: the net northward flow in the upper 1000 m of the Atlantic and net southward flow below. Variations in the AMOC have significant repercussions for the climate system hence there is a need for proxies that can measure changes in the AMOC on larger spatial scales. Here we show a direct calculation of ocean circulation at 26°N from satellites compares well with transport estimates from the RAPID mooring array. In the surface layer (1000 m), transport is estimated from satellite altimetry and has a correlation of r=0.79 (significant at 95% level) with the MOC transport estimates from RAPID. We find that the relationship between sea level anomaly and dynamic height from the western boundary RAPID moorings is robust in the surface layer, with poor agreement occurring largely below 1000 m. Below 1000 m, the return flow of the AMOC is estimated using ocean bottom pressure from satellite gravimetry. This has a correlation of r=0.75 (significant at the 95% level) when compared to the deeper (1000-5000 m) RAPID transports. Combining the results from satellite altimetry and gravimetry, estimates of full-depth 2-layer circulation at 26°N are demonstrated. Finally, empirical orthogonal function analysis reveals that the barotropic and baroclinic streamfunctions are linked to wind stress curl and buoyancy forcing, respectively.

How to cite: Sanchez-Franks, A., Frajka-Williams, E., and Moat, B.: Can satellites replace mooring arrays? Satellite altimetry transport estimates of the Atlantic overturning meridional circulation along the RAPID 26°N mooring array, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11549, https://doi.org/10.5194/egusphere-egu2020-11549, 2020

How to cite: Sanchez-Franks, A., Frajka-Williams, E., and Moat, B.: Can satellites replace mooring arrays? Satellite altimetry transport estimates of the Atlantic overturning meridional circulation along the RAPID 26°N mooring array, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11549, https://doi.org/10.5194/egusphere-egu2020-11549, 2020

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  • CC1: Comment on EGU2020-11549, Patricia Handmann, 05 May 2020

    Dear Alejandra, I really like the idea to complement mooring array data with satellite derived data - But I want to follow up on the OSNAP question that I posted in the chat - Do you think this method is applicable in the subpolar region - since here the AMOC is defined on isopycnals not on depth levels?

    • AC2: Reply to CC1, Alejandra Sanchez-Franks, 30 May 2020

      Hi Patricia,

      Thanks very much for your comment, and apologies for the delay in reply. In principle you should be able to use the satellite-derived method at OSNAP as well, however, you would likely have more limitations. Keeping in mind I'm not as familiar with the OSNAP array, but I expect main issues would be in the satellites ability to capture the boundary currents (note that in my method, I only estimate the upper mid-ocean transport and we still have to rely on the separate dataset for estimating the western boundary current).

      Again, I apologise for the delay in reply and please feel free to email me if anything is unclear or for any follow up questions to alsf@noc.ac.uk (assuming that it will soon no longer be possible to post in here!).

      Ale

       

       

  • CC2: Comment on EGU2020-11549, Laura Jackson, 05 May 2020

    Hi Alejandra

    Interesting presentation, thanks. It looks to me that the reconstructed timeseries is not capturing the weakening from around 2006-2012. Do you think this reconstruction can capture the longer term variability of the AMOC?

    Laura

    • AC1: Reply to CC2, Alejandra Sanchez-Franks, 29 May 2020

      Hi Laura, 

      Thank you very much for your comment and apologies for the delayed reply. Yes, you are correct in noting the the reconstructed time series is not properly capturing the trend. The satellite itself does capture trend, but the reconstruction - in particular the contribution from the eastern component - introduces quite a bit of noise. If you were to hold the eastern component constant, for example, then the western component alone would capture the weakening around 2006-2012 and would do a reasonable job of capturing longer term variability. 

      Again, I apologise for the delay in reply and please feel free to email me if anything is unclear or for any follow up questions to alsf@noc.ac.uk (assuming that it will soon no longer be possible to post in here!).

      Ale

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