1. Circulation dans l'Océan Pacifique sud-ouest et SPICE : Jets autour des Vanuatu et de la Nouvelle-Calédonie à partir d'un modèle inverse A. Ganachaud JISAO/PMEL/NOAA LEGOS / IRD Nouméa-Toulouse Laboratoire d’Etudes Géophysiques et d’Océanographie Spatiale Black (1851) L. Gourdeau (LEGOS/IRD-Noumea) W. Kessler (PMEL)

2. L'équipage de l'ALIS Francis Gallois, Jean-Yves Panche, David Varillon Elodie Kestenare... et de nombreux collègues NO ALIS

3. SECALIS-1, Juillet 2003

4. Outline Tasman Sea Coral Sea Solomon Sea AUSTRALIA PNG N. CALEDONIA VANUATU Fiji NEW ZEALAND SOLOMON IS. 1.South Equatorial Current, jets and climate 2.The SECALIS cruise series 3.An inverse model of SECALIS-2 and SECALIS-3 4.SPICE

5. The Southwest Pacific Atmosphere SPCZ A A Trade winds

6. Decadal influences: Thermocline water connection between the subduction zone of the South East Pacific and the equator Lines show geostrophic streamlines on the isopycnal (courtesy B. Kessler)

7. Decadal influences: Thermocline water connection A temperature anomaly on sigma=25 (EUC core) from the Southeast Pacific preceeds Nino-3 by 7 years Giese et al. 2002, Schneider 2004, Luo et al. 2005 SST TO WBC TO EAST 8°S, East to West SST Equator Giese et al. 2002: T on sigma=25 AUSTRALIA UPWELLING Izumo et al., 2002: Origins of Nino 3 waters

8. The South Pacific "Thermocline" waters South Equatorial Current Temperature/salinity diagram Salinity maximum Z=100:300m

9. Southwest Pacific Topography Tasman Sea Coral Sea Solomon Sea AUSTRALIA PNG N. CALEDONIA VANUATU Fiji NEW ZEALAND SOLOMON IS.

10. Thermocline water currents: 0-300m ~25 Sv

11. Thermocline water currents 0-300m 70 % EUC waters ~15 Sv ~25 Sv

12. Thermocline water currents 0-300m ~ 10 Sv ~15 Sv ~25 Sv

13. Jets in numerical models OCCAM model, Webb, JPO, 2000

14. The South West Pacific Ocean: poorly sampled and poorly understood Distribution of the (T,S) casts (Ridgway and Dunn, 2003) Sokolov and Rintoul (2000) Qu and Lindstrom (2002) Ridgway and Dunn (2003) Active Argo floats on 08/17/2007

15. The South West Pacific Ocean: poorly sampled and poorly understood Distribution of the (T,S) casts (Ridgway and Dunn, 2003) Sokolov and Rintoul (2000) Qu and Lindstrom (2002) Ridgway and Dunn (2003) Active Argo floats on March 4, 2008

16. The SEC-ALIS cruises RV ALIS ??? Transport between New Caledonia and Vanuatu: Andrew and Clegg (1989): southeastward (!) Sokolov and Rintoul (2000): 41 Sv Climatology: 10-12 Sv Island Rule: 10-11 Sv Numerical models: Various Existence of a boundary current to the northwest? To the southeast ? NEW CALEDONIA VANUATU SECSEC

17. The SEC-ALIS cruises SECALIS-1: Jul 2003 SECALIS-2: Dec 2004 SECALIS-3: Jul 2005 SECALIS-4: Nov 2006 RV ALIS ???

18. Cruise Secalis-2 December 2004 : snapshot of the circulation, chasing the jets Terrible winch but good mechanics Closed box, inverse box model by requiring mass, heat and salt conservation within isopycnal layers 2000-db reference level GUESS

19. SECALIS-2: Water mass SLW AAIW

20. South Pacific Tropical Water (SPTW)/ Subtropical Lower Water Warm SPTW (21°C) COLD SLW (16/20°C) S=25.5 200m In the core of the EUC, in the lower salinity maximum (S=24.3/24.5)

21. Subantarctic Mode Water (SAMW) 600m formed north of the ACC (S=27)

22. Antarctic Intermediate Water (AAIW) 5.4°,800m salinity minimum formed in the southeast PF (50°S-60°S) (S=27.2) northern limit

23. "Oxygen minimum" water (Wyrtki 1962) 1500-2000m formation ?? (S=27.6)

24. Inverse model formulation

25. Define vertical layers; Write cons. Equation for: Mass Heat (anomaly) Salt (anomaly) Including Ekman transports

26. North Caledonian JET GUESS Inverse model estimate for the velocity field: 50cm/s, 15±2.6 Sv, deep shear NCJ

27. below σ=26 above σ=26 Oceanic circulation in Dec 2004 Inverse model OCCAM 1/12° 2004 average Ganachaud, Gourdeau, Kessler, JPO, 2008

28. below σ=26 above σ=26 Oceanic circulation in Dec 2004 Transport 0-2000m OCCAM 1/12° 2004 average 20 Sv 14 Sv 9 6.5 Ganachaud, Gourdeau, Kessler, JPO, 2008

29. 20  4 14  3 9 0 Net transports in Dec 2004 and July 2005 Net transports (Sv) December 2004 Net transports (Sv) July 2005 21  5 10  4 9 5 19  5 5 39  6

30. below σ=26 above σ=26 8.5  1 4.5  1 4 .4 0 Upper 300m transports in Dec 2004 and July 2005 Upper layer transports (Sv) December 2004 Upper layer transports (Sv) July 2005 9.5  1 6.5  1 1 .6 2.5 15  1 22  2

31. below σ=26 above σ=26 0.7  0.2 0 Net Heat transports Net transports (Sv) December 2004 Net transports (Sv) July 2005 2.6  0.3PW

32. U, T and S Prototype, Scripps OI, San Diego Dropped July 17th, 2005 Recovered october 18th, 2005 Glider measurements, 2005 (Gourdeau, Kessler, Davis, Sherman) C. Maes, IRD

33. Transport is similar to CTD- LADCP estimate cruise glider Glider measurements, 2005 (Gourdeau, Kessler, Davis, Sherman) Gourdeau et al. 2007

34. Conclusions on SECALIS program A regional picture of the SEC splitting and jet formation east of New Caledonia is emerging: 2004 cruise: NCJ, SCJ characterized 2005/2006 cruise: NCJ, NVJ and Glider feasibility (July/November) The NCJ shear is deep (700m-1500m) so that XBTs miss it Ongoing work: –Mean circulation and variability from Secalis, glider surveys and models –XCTD/XBT/Argo monitoring –SPICE

35. Interests in the Coral and Tasman Sea circulation Rotschi, Legand, Hamon R/V ORSOM III, 1956 interisland flows Cronulla, August 1958 Conference on the Coral and Tasman Sea Oceanography Cairns, August 2005 Workshop on the Southwest Pacific Ocean Circulation and its relation with Climate

36. Southwest PacIfic Ocean Circulation and Climate Experiment: SPICE Black (1851) W. Kessler (PMEL/NOAA) G. Brassington(BOM) R. Mechoso (UCLA) S. Wijffels, K. Ridgway, W. Cai (CSIRO) N. Holbrook (MU) P. Sutton, M. Bowen (NIWA) B. Qiu, A. Timmermann (UH) D. Roemmich, J. Sprintall (SIO), D. Neelin, B. Lintner (UCLA) H. Diamond (NOAA/NCDC) S. Cravatte, L. Gourdeau (LEGOS) P.Eastwood (SOPAC, Fiji) T. Aung (USP/Fiji)

37. Southwest PacIfic Ocean Circulation and Climate Experiment Objectives: 3-Combine obs with modeling to elaborate a monitoring plan 4-Determine local oceanic environment influences Objectives: 1-Understand the SW Pacific in climate / CGCM incl. SPCZ 2-Measure air-sea fluxes and currents in the -Coral, -Solomon -and Tasman seas

38. Southwest PacIfic Ocean Circulation and Climate Experiment Objectives: 3-Combine obs with modeling to elaborate a monitoring plan 4-Determine local oceanic environment influences Objectives: 1-Understand the SW Pacific in climate / CGCM incl. SPCZ 2-Measure air-sea fluxes and currents in the -Coral, -Solomon -and Tasman seas

39. South Pacific Convergence Zone High convective activity, precipitation, wind convergence -Dominant convective feature in the Southern Hemisphere -Substantial variability: (intra) seasonal; interannual;Equatorward shift 1976 -Unresolved southward bend, poorly modelled -Strong local effects (SSS, oceanic heat content) COADS cloudiness 1960-1970 20th century climate model

40. Thermocline water currents 0-300m 2- Tasman Sea 3-Solomon Sea 1-Inflows

41. South Equatorial Current Equatorial upwelling East Australian Current Tasman Front Equatorial Undercurrent EAC variability: Relation w/ climate/ENSO Eddy generation Air-Sea fluxes 2-EAC and EAUC

42. SWPacific and Climate EAC and the Tasman Front The Southward Pacific WBC which closes the subtropical gyre (Ridgway and Dunn, 2003)

43. South Equatorial Current Equatorial upwelling East Australian Current Tasman Front Equatorial Undercurrent Solomon Sea Solomon Sea: A WBC pathway to feed the EUC and ITF

44. CARS dynamic Ht relative to 2000m (C. W. Kessler) ST GEORGES SOLOMON VITIAZ Quasi undocumented circulation WEPOCS cruises, 1985 (Lindstrom et al., 1987; Tsuchiya et al., 1989; Fine et al., 1994) NCJ NVJ

45. 3-North Coral Sea: A WBC pathway to feed the EUC and ITF 0-200m SADCP currents, May 1993 Blue: 2007 glider trajectory (C. W. Kessler) Narrow straits, difficult to model Strong WBC, mixing Strong variability: monsoon, ENSO

46. Solwara Pilot study Accomplished: 1.Flusec cruise (inflow) 2.Glider (inflow) To do: 1.Mooring in key straits 2.Glider monitoring 3.Plans in the NQC/Papua Gulf SOLWARA project (IRD-PMEL-SIO-CSIRO, submitted)

47. Ocean and climate impacts on environment in the southwest Pacific Consequences of ocean and climate fluctuations: –Biodiversity, Coral reefs –Freshwater-agriculture and health –Tropical cyclones –Sea surface height Pacific Island Countries: Fragile ecosystems, low-lying populated areas, isolated places Australia and New Zealand: Climate depends on heat content in the Tasman Sea Freshwater resources critical Important changes in biodiversity ERSST data (1944-2005) SST Trend (°C/century)

48. La Niña - Tropical Cyclone Density Interannual influences: ENSO and cyclones Courtesy J. Salinger

49. Downscaling climate and ocean models New Caledonia Upwelling (A. Vega, M. Despinoy) J. Lefevre, IRD Need to link between large-scale oceanography, coastal island oceanography, and impacts on climate and environment

50. Towards a regional field experiment 2010 2007+ 2005+ 2004+ 2008 2007+ 2008 running TBS

51. Modelling strategy: regional zooms 1.Help to design observation / monitoring program 2.Sensitivity experiments 3.Regional applications IRD/CNRS/CNES/IFREMER/METEO- FRANCE/SHOM CSIRO/BOM IRD/NIWA UH/LEGOS UH/LOCEAN

52. Towards a regional field experiment: Existing large scale programs UW/CSIRO/IRD IRD SIO/CSIRO/IRD BOM/IRD BOM/MF IMOS/Bluewater and climate

54. Tentative timetable

55. Gourdeau et al. 2007 580 CTD profiles down to 600 meters Absolute geostrophic velocity field Temperature Salinity NJC NVJ Glider measurements, 2005 (Gourdeau, Kessler, Davis, Sherman)

56. 1-Modeling strategy: regional zooms 1.Help to design observation then monitoring program 2.Sensitivity experiments 3.Regional applications High resolution global/regional ocean, atmosphere and climate models Blue Link (CSIRO/BOM) ROMS/Mercator (IRD Nouméa)

57. Distribution of the (T,S) casts (Ridgway and Dunn, 2003) Sokolov and Rintoul (2000) Qu and Lindstrom (2002) Ridgway and Dunn (2003) Maximenko (2005) Active Argo floats on 08/17/2007 Towards a large scale field experiment Existing observations Sattelite-derived surface currents

58. Interannual Variability (Sea level anomaly) 2: EAC and the Tasman Front SST Trend (°C/century) ERSST data (1944-2005) Mk3 2070 Surface Temperature Global Climate Model Forecast O’Farrell, 2005 20001996

59. Interannual influences: thermocline transport modulation Interannual time scale: El Niño influences the SW Pacific Circulation (Delcroix and hénin, 1989; Sprintall et al., 1995; Gouriou and Delcroix, 2002) Courtesy B. Kessler

60. 1-Thermocline water inflow to the Coral Sea TO EAC TO NQC 162.5°E zonal velocity (blue=westward) NCJ NVJ SCJ Bifurcation: Qu and Lindstrom 2002 Kessler and Gourdeau 2006, 2007 1.Formation of 3 "jets" 2.Bifurcation (northward bias in GCM/CGCMs) 3.Outflows and budget

61. Need to describe the Tasman Sea variability in the climate system: 1.EAC inflow and outflow component: robust estimates of the mean & seasonal cycle 2.Mechanism of EAC eddy generation 3.Tasman Sea heat balance and effects on air-sea fluxes and regional climate 4.Southward shift of the EAC associated with Global change 2: EAC and the Tasman Front: Critical issues

62. 3-North Coral Sea Critical issues Flows in Solomon Sea need explanation from models and observations Structure of the SEC inflow components Structure and monitoring of WBCs Straits transport monitoring and modeling (need ~1/20° resolution). Dynamical response: WBCs adjustment to meridional and vertical variations Need a pilot study

63. Downscaling…and upscaling J. Lefevre, IRD ROMS, 1/12°, nested (Courtesy A. Vega, IRD)

64. SPICE Challenges

65. 1.Modelling strategy 2.Existing programs 3.Ocean field experiment 4.SPCZ process study (?)

66. Towards a regional field experiment 2005+ 2004+ 2008

67. Towards a regional field experiment 2010 2007+ 2005+ 2004+ 2008

68. SPICE and CLIVAR A. Ganachaud, W. Kessler, G. Brassington, S. Wijffels, K. Ridgway, W. Cai, N. Holbrook, M. Bowen, P. Sutton, A. Timmermann, B. Qiu, D. Roemmich, J. Sprintall, H. Diamond, S. Cravatte, L. Gourdeau, T. Aung Relevance 1-Identify key features and their impact on climate simulation on seasonal to decadal timescales 2-Understand pertinent air-sea fluxes and oceanic currents (LLWBCs) to improve climate modelling and prediction "Add-on" Costs 2008-2011 1-Fieldwork: Shiptime: 1.5month/yr Wet measurements: $1.6M/yr HRXBT, Air-sea fluxes: funded 2-Modelling: Infrastructures exist Specific analyses costs Legacy 1- Long term monitoring of selected features (SST, straits…) 2-Training and transition to local benefits (application of data or operational products)

69. Main objectives and timetable A. Ganachaud, W. Kessler, G. Brassington, S. Wijffels, K. Ridgway, W. Cai, N. Holbrook, M. Bowen, P. Sutton, A. Timmermann, B. Qiu, D. Roemmich, J. Sprintall, S. Cravatte, L. Gourdeau, T. Aung Objective 1-Role of the southwest Pacific in CGCMS (SPCZ, …) 2-Air-sea fluxes and currents 3-Monitoring key quantities 4-Local impacts 2004-2007 -SEC inflow (cruise and glider) -Gyre dynamics and jets -Experimental monitoring Solomon Sea -Model downscaling (ROMS-type) -Operational prototypes -SSS-based analyses 2008-2010 -Modelling experiments -Major SPCZ experiments ? -SEC infow monitoring -Solomon Sea exploration (model, cruise, moorings, gliders) -EAC monitoring -VOS with AWS Hull SST -Experimental monitoring SEC and Solomon Straits -Regionally oriented applications and training SPCZ/ocean Session AGU 2007

70. 2-EAC and EAUC Ridgway and Dunn, (2003); Cai et al. (2003); Bowen et al. (2005) Distri- bution of the (T,S) casts

71. 2-EAC and EAUC Ridgway and Dunn, (2003); Cai et al. (2003); Bowen et al. (2005) SSH variability C. Ken Ridgway Distri- bution of the (T,S) casts 1.Variability dominates mean flow Similar SSH variability as other WBCs 2.Highly influenced by: Non-linear flow instabilities Upper-ocean topographic coupling 3.Tasman Box: Ocean heat transport changes influence regional climate (Sprintall et al. 1995, Roemmich et al., 2005