1 / 28

B. Qiu, P. Hacker and S. Chen Department of Oceanography University of Hawaii

Observations of the Mode Water Formation and Evolution from the Kuroshio Extension System Study (KESS) Float Program. B. Qiu, P. Hacker and S. Chen Department of Oceanography University of Hawaii KESS contributors: K. Donohue, R. Watts, S. Jayne, N. Hogg, H. Mitsudera, M. Cronin,

vidor
Download Presentation

B. Qiu, P. Hacker and S. Chen Department of Oceanography University of Hawaii

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. Observations of the Mode Water Formation and Evolution from the Kuroshio Extension System Study (KESS) Float Program B. Qiu, P. Hacker and S. Chen Department of Oceanography University of Hawaii KESS contributors: K. Donohue, R. Watts, S. Jayne, N. Hogg, H. Mitsudera, M. Cronin, S.-P. Xie, Y. Tanimoto, H. Nakamura

  2. KESS domain Schematic of General Circulation in Western North Pacific

  3. KESS domain

  4. Semi-monthly KE paths (1.7m SSH contours) KESS

  5. KE path length Eddy kinetic energy KE position

  6. Region of large heat loss from the ocean to atmosphere Region underlying the N Pacific stormtracks

  7. Kuroshio Extension System Study (KESS) Principal Investigators: URI – R. Watts, K. Donohue (NSF-OCN) WHOI – N. Hogg, S. Jayne (NSF-OCN) UH – B. Qiu, P. Hacker, H. Mitsudera (NSF-OCN) PMEL – M. Cronin, C. Sabine (NOAA-OGP) UH – S.-P. Xie, B. Qiu (NSF-ATM; in collaboration with H. Nakamura, Y. Tanimoto, and H. Tokinaga) The overall goals of KESS are to clarify the dynamic processes governing the variability of the Kuroshio Ext. and recirculation gyre, and to assess their roles in the coupled climate system.

  8. Objectives of KESS • Understand SST variability on weekly-to-interannual timescales (atmos. forcing, re-emergence, advection, eddy fluxes…) • Provide a midlat. reference site of surface heat fluxes and CO2. • Clarify formation/transformation of Subtropical Mode Water • Clarify formation processes of WBC recirculation gyre (anticyclonegenesis vs. eddy-driven) • Identify cross-frontal processes of mass, heat, salt, and PV • Clarify vertical coupling (barotropitization) processes intrinsic to baroclinic instability • Assess SST’s influence upon the overlying PBL

  9. STMW detection site Hanawa and Talley (2001)

  10. T, σθ and PV sections across the KE jet along 146°E potential temperature 16-18°C potential density 25.2-25.5 σθ potential vorticity Q<2x10-10

  11. T(z,t) MLD Q(z,t) (based on historical XBT, CTD, Argo data inside the RG)

  12. T(z,t) MLD Thickness of the 16-18°C (STMW) layer

  13. NCEP wintertime Qnet anomalies in the KE/RG region less cooling more cooling

  14. Late winter MLD vs. Qnet anomalies less cooling more cooling

  15. Late winter MLD vs. Qnet anomalies Late winter MLD vs. KE path length in the previous year

  16. Pre-conditioning vs. convective depth Let the fall season upper ocean stratification be . The convective depth can be estimated from the conservation of heat: N D z Q(t) D T(z) Convective depth (i.e., wintertime STMW thickness) depends not only on the cumulative heat loss, but also on the pre-conditioning stratification.

  17. σ θ PV When KE is in the unstable state, mixing of high-PV KE water into the RG can inhibit the STMW formation through pre-conditioning. How efficient is this lateral mixing process?

  18. KESS Observing Array (SSH contours: May/June 2004) deployed 20 APEX floats KESS Timeline

  19. KESS Observing Array (SSH contours: May/June 2005) deployed 28 APEX floats KESS Timeline

  20. UH 48 APEX Profiling Float Trajectories UH-KESS website: www.soest.hawaii.edu/snol (all KESS float data are part of the global Argo data set)

  21. Evolution of SSH field: May 2004-August 2005

  22. PV on 25.4 σθsurface (STMW core layer)

  23. Temporal evolution of STMW inside RG MLD

  24. PV on 25.4 σθsurface in RG outside of CCR04B observed simulated

  25. Summary • 48 profiling floats were deployed in the western N Pacific as part of the CLIVAR KESS project. • The Kuroshio Extension system over the past 13 years oscillated between a stable and an unstable state. • During this period, STMW formation is affected more by the dynamic state of the KE system than by the regional atmospheric condition. • By transferring high-PV KE water southward, the unstable KE state inhibits the STMW formation through pre-conditioning and lateral erosion. • The eddy erosion process of STMW is effective, occurring on intra-annual timescales. (UH-KESS website: www.soest.hawaii.edu/snol)

  26. R/V Revelle, above STMW, May 2005

  27. Objectives of KESS • Understand SST variability on weekly-to-interannual timescales (atmos. forcing, re-emergence, advection, eddy fluxes…) • Provide a midlat. reference site of surface heat fluxes and CO2. • Clarify formation/transformation of Subtropical Mode Water • Clarify formation processes of WBC recirculation gyre (anticyclonegenesis vs. eddy-driven) • Identify cross-frontal processes of mass, heat, salt, and PV • Clarify vertical coupling (barotropitization) processes intrinsic to baroclinic instability • Assess SST’s influence upon the overlying PBL

More Related