1 / 10

The relationship between MVT & MHT of AMOC:

The relationship between MVT & MHT of AMOC: a comparison between observations & ocean state estimation products Tong Lee, Jet Propulsion Laboratory Bill Johns, University of Miami. Picture from http://www.noc.soton.ac.uk. MVT: Meridional Volume Transport MHT: Meridional Heat Transport.

molly
Download Presentation

The relationship between MVT & MHT of AMOC:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The relationship between MVT & MHT of AMOC: a comparison between observations & ocean state estimation products Tong Lee, Jet Propulsion Laboratory Bill Johns, University of Miami Picture from http://www.noc.soton.ac.uk MVT: Meridional Volume Transport MHT: Meridional Heat Transport

  2. Motivation • Trans-oceanic arrays such as RAPID/MOCHA are designed to monitor MVT. • MHT is more climate relevant but more difficult to measure. • MVT-MHT empirical relation (linear regression) was inferred from RAPID-MOCHA & auxiliary data (Baringer et al. 2010). • Comparison with ocean state estimation (OSE) products. Coordination with GFDL & NCAR for similar analysis. Related to Monday’s talk by Rym Msadek.

  3. OSE products used for comparison • ECCO-JPL (1993-present) • Near-global, 1°x(0.3°x1°), 46 levels, MITgcm. • Prior NCEP forcing. • Assimilates anomalies of SSH and vertical T profiles. • ECCO2 (1993-2008) • Global, 18x18 km, 50 levels, MITgcm cubed-sphere. • Prior ECMWF analysis forcing. • Assimilate observed SSH anomaly and T/S profiles. • GECCO (1950-2000) • Near global, 1°x1°, 23 levels, MITgcm • Prior NCEP forcing • Assimilate a large suite of data

  4. Time mean for Apr. 2004- Sept. 2007 at 26.5N: MVT (max MOC): RAPID (18.5 Sv), ECCO-JPL (15.8), ECCO2 (17.9) MHT: RAPID (1.3 PW), ECCO-JPL (0.9), ECCO2 (1.0) MVT anomaly

  5. Comparison of averaged seasonal MVT anomaly

  6. Comparison of MVT-MHT linear regression & correlation Slope: change of MHT per unit MVT Intercept: physical meaning problematic Larger scatter due to eddies?

  7. Little dependence of MVT-MHT relation on time period (GECCO)

  8. Relatively large dependence of MVT-MHT relation on time scale MHT MVT MHT Smaller slope for longer time scales: geostrophic shear flow advecting smaller vertical T gradient (than Ekman)

  9. Dependence of MVT-MHT relation on latitude: Relatively high regression & correlation coeff. in subtropics & 15N due to dominant overturning contribution & minor gyre contribution

  10. Summary • Time mean MVT and MHT in 3 ECCO products are some what too weak • Seasonal variation reasonably well reproduced. • MVT-MHT regression slope and correlation: • Low-resolution model closer to RAPID/MOCHA estimate; effect of eddies? • Little variation in different decades. • Relatively large dependence on time scales (monthly from interannual). • Subtropical N. & S. Alt. and near 15N have relatively large regression and correlation coefficients between MVT & MHT. • STILL NEED TO UNDERSTAND HOW MVT & MHT ARE FORCED DIFFERENTLY, ESP. ON LONGER TIME SCALES!

More Related