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Shenfu Dong CIMAS/UM and NOAA/AOML

The Role of Inter-ocean Exchanges on Long-term Variability of the Northward Heat Transport in the South Atlantic. Shenfu Dong CIMAS/UM and NOAA/AOML. S. L. Garzoli, M.Baringer NOAA/AOML, Miami, Florida USA. June 9, 2010. R. Lumpkin, NOAA/AOML. Objective:

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Shenfu Dong CIMAS/UM and NOAA/AOML

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  1. The Role of Inter-ocean Exchanges on Long-term Variability of the Northward Heat Transport in the South Atlantic Shenfu Dong CIMAS/UM and NOAA/AOML S. L. Garzoli, M.Baringer NOAA/AOML, Miami, Florida USA June 9, 2010 R. Lumpkin, NOAA/AOML

  2. Objective: • To investigate the role of the inter-ocean exchanges in the variability of the northward heat transport in the South Atlantic. Specific Question: • Where does the variability in the northward heat transport come from? • Inter-ocean exchanges with the Pacific Ocean. • Inter-ocean exchanges with the Indian Ocean. • Air-sea heat exchanges. • heat storage in the basin.

  3. OGCM for the Earth Simulator (OFES) • The model code is based on MOM3. • OFES covers 75S to 75N. • 0.1 horizontal resolution. • 54 vertical levels. • Spun up for 50 years • followed by a 57-yr hindcast run (1950–2006). • Forcing from the NCEP–NCAR reanalysis.

  4. Time-Mean Volume and Temperature Transport Results based on XBT measurements at nominal 35S: Total volume transport: 0.5 Sv Total heat transport: 0.54 PW AMOC strength: 17.9 Sv AMOC from OFES: 15 Sv

  5. XBT observations OFES Model Relationship between AMOC and Northward Heat Transport at 35S HT(PW)  0.05 * AMOC (Sv)

  6. The Strength of the AMOC at 35S Linear increasing trend in AMOC: 0.9 Sv per decade

  7. Northward Temperature Transport across 35S - I 0.03 PW per decade

  8. Baroclinic: , Horizontal: Northward Temperature Transport across 35S - III

  9. Volume Transports across Drake Passage and South of Africa

  10. Temperature Transports across Drake Passage and South of Africa 0.03 PW/decade -0.04 PW/decade

  11. 0.03 0.03 -0.04 Linear Trend (PW/decade) 0.07 PW per decade

  12. Anomalous Air-Sea Heat Flux Decreasing trend: -0.03 PW/decade

  13. Linear Trend (PW/decade) 0.03 -0.3 0.07

  14. Temperature Transports--- South of Africa ACC-dominant eastward transport 0.03 PW per decade Total -0.04 PW per decade Agulhas leakage -0.07 PW per decade

  15. Trend PW/decade 0.03 -0.3 0.03 0.3 0.7

  16. Conclusions • Both XBT measurements and the OFES model suggest that 1 sverdrup increase in the AMOC strength would cause an increase in the northward heat transport of 0.05 PW at approximately 35S. • The OFES model suggests an increase in the northward heat transport across 35S from 1980 to 2006. • The increasing trend in the northward heat transport is likely due to the increase in Agulhas leakage into the South Atlantic. • About half of the increase in Agulhas leakage is lost to the atmosphere through air-sea heat exchange.

  17. Temperature Transports across Drake Passage and South of Africa

  18. Northward Temperature Transport across 35S - II

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