Simulated and observed circulation in the Indonesian Seas: 1/12° global HYCOM and the INSTANT observations

Abstract A 1/12° global version of the HYbrid Coordinate Ocean Model (HYCOM) using 3-hourly atmospheric forcing is analyzed and directly compared against observations from the International Nusantara STratification ANd Transport (INSTANT) program that provides the first long-term (2004–2006) comprehensive view of the Indonesian Throughflow (ITF) inflow/outflow and establishes an important benchmark for inter-basin exchange, including the net throughflow transport. The simulated total ITF transport (−13.4 Sv) is similar to the observational estimate (−15.0 Sv) and correctly distributed among the three outflow passages (Lombok Strait, Ombai Strait and Timor Passage). Makassar Strait carries ∼75% of the observed total ITF inflow and while the temporal variability of the simulated transport has high correlation with the observations, the simulated mean volume transport is ∼37% too low. This points to an incorrect partitioning between the western and eastern inflow routes in the model and is the largest shortcoming of this simulation. HYCOM simulates the very deep (>1250 m) overflow at Lifamatola Passage (−2.0 Sv simulated vs. −2.5 Sv observed) and indicates overflow contributions originating from the North (South) Equatorial Current in boreal winter–spring (summer–autumn). A new finding of INSTANT is the mean eastward flow from the Indian Ocean toward the interior Indonesian Seas on the north side of Ombai Strait. This flow is not robustly simulated at 1/12° resolution, but is found in a 1/25° version of global HYCOM using climatological forcing, indicating the importance of horizontal resolution. However, the 1/25° model also indicates that the mean eastward flow retroflects, turning back into the main southwestward Ombai Strait outflow, and in the mean does not enter the interior seas to become part of the water mass transformation process. The 1/12° global HYCOM is also used to fill in the gaps not measured as part of the INSTANT observational network. It indicates the wide and shallow Java and Arafura Seas carry −0.8 Sv of inflow and that the three major outflow passages capture nearly all the total Pacific to Indian Ocean throughflow.

[1]  A. Gordon,et al.  A semiannual Indian Ocean forced Kelvin wave observed in the Indonesian seas in May 1997 , 2000 .

[2]  A. Ffield,et al.  M2 Baroclinic Tides in the Indonesian Seas , 2005 .

[3]  Indonesian Throughflow.  INDONESIAN THROUGHFLOW TRANSPORT VARIABILITY ESTIMATED FROM Satellite Altimetry , 2005 .

[4]  A. Gordon,et al.  Thermocline of the Flores and Banda seas , 1994 .

[5]  J. S. Godfrey.  A sverdrup model of the depth-integrated flow for the world ocean allowing for island circulations , 1989 .

[6]  Eric P. Chassignet,et al.  North Atlantic Simulations with the Hybrid Coordinate Ocean Model (HYCOM): Impact of the Vertical Coordinate Choice, Reference Pressure, and Thermobaricity , 2003 .

[7]  A. Gordon,et al.  INSTANT: A new international array to measure the Indonesian Throughflow , 2004 .

[8]  M. Carnes.  Description and Evaluation of GDEM-V 3.0 , 2009 .

[9]  Y. Masumoto,et al.  Impacts of the South China Sea Throughflow on seasonal and interannual variations of the Indonesian Throughflow , 2009 .

[10]  J. Sprintall,et al.  Direct estimates of the Indonesian Throughflow entering the Indian Ocean: 2004–2006 , 2009 .

[11]  R. Molcard,et al.  Low frequency variability of the currents in Indonesian channels (Savu-Roti and Roti-Ashmore Reef) , 1994 .

[12]  Hartmut Peters,et al.  Parameterization of gravity current entrainment for ocean circulation models using a high-order 3D nonhydrostatic spectral element model , 2006 .

[13]  G. Halliwell,et al.  Evaluation of vertical coordinate and vertical mixing algorithms in the HYbrid-Coordinate Ocean Model (HYCOM) , 2004 .

[14]  Paul J. Martin,et al.  Optimizing Surface Winds using QuikSCAT Measurements in the Mediterranean Sea During 2000-2006 , 2009 .

[15]  Ecmwf Newsletter,et al.  EUROPEAN CENTRE FOR MEDIUM-RANGE WEATHER FORECASTS , 2004 .

[16]  P. Goodman.  The Role of North Atlantic Deep Water Formation in an OGCM’s Ventilation and Thermohaline Circulation , 1998 .

[17]  L. Talley,et al.  Deep expression of the Indonesian Throughflow : Indonesian Intermediate Water in the South Equatorial Current , 2005 .

[18]  R. Fiedler,et al.  Explicit tidal forcing in an ocean general circulation model , 2007 .

[19]  D. Sandwell,et al.  Global seafloor topography from dense satellite altimetry and sparse ship soundings , 1997 .

[20]  H. Hurlburt,et al.  Stability-Dependent Exchange Coefficients for Air–Sea Fluxes , 2005 .

[21]  D. Quadfasel,et al.  Circulation in the Timor Sea , 1993 .

[22]  Marta Coll,et al.  An ecological model of the Northern and Central Adriatic Sea: Analysis of ecosystem structure and fishing impacts , 2007 .

[23]  V. Canuto,et al.  Ocean Turbulence. Part II: Vertical Diffusivities of Momentum, Heat, Salt, Mass, and Passive Scalars , 2002 .

[24]  A. Gordon,et al.  The Indonesian throughflow during 2004–2006 as observed by the INSTANT program , 2010 .

[25]  R. Molcard,et al.  The Indo‐Pacific throughflow in the Timor Passage , 1996 .

[26]  H. Hurlburt,et al.  The contribution of the global thermohaline circulation to the Pacific to Indian Ocean Throughflow via Indonesia , 1997 .

[27]  M. S. Dubovikov,et al.  Ocean Turbulence I: One-Point Closure Model Momentum and Heat Vertical Diffusivities , 2001 .

[28]  A. Gordon,et al.  Thermocline stratification within the Indonesian Seas , 1996 .

[29]  A. Ishida,et al.  Connecting the tropical Pacific with Indian Ocean through South China Sea , 2005 .

[30]  J. S. Godfrey,et al.  A 20-Yr Average of the Indonesian Throughflow: Regional Currents and the Interbasin Exchange , 2008 .

[31]  Widodo Setiyo Pranowo,et al.  Makassar Strait throughflow, 2004 to 2006 , 2008 .

[32]  F. Syamsudin,et al.  The throughflow within Ombai Strait , 2001 .

[33]  W. Schmitz.  On the interbasin‐scale thermohaline circulation , 1995 .

[34]  T. Gerkema,et al.  On the transformation of Pacific Water into Indonesian Throughflow Water by internal tidal mixing , 2007 .

[35]  G. Meyers.  Variation of Indonesian throughflow and the El Niño‐Southern Oscillation , 1996 .

[36]  H. V. Aken,et al.  Physical aspects of the flushing of the east Indonesian basins , 1988 .

[37]  Walter Munk,et al.  ON THE WIND-DRIVEN OCEAN CIRCULATION , 1950 .

[38]  T. Yamagata,et al.  An introduction to the South China Sea throughflow: Its dynamics, variability, and application for climate , 2009 .

[39]  Stephen P. Murray,et al.  Throughflow into the Indian Ocean through the Lombok Strait, January 1985–January 1986 , 1988, Nature.

[40]  Yue Fang,et al.  Interocean circulation and heat and freshwater budgets of the South China Sea based on a numerical model , 2009 .

[41]  Anthony Rosati,et al.  Barotropic tidal mixing effects in a coupled climate model: Oceanic conditions in the Northern Atlantic , 2006 .

[42]  C. Barron,et al.  Global river inflow with Navy Coastal Ocean Model , 2002, OCEANS '02 MTS/IEEE.

[43]  S. Speich,et al.  Warm and cold water routes of an O.G.C.M. thermohaline conveyor belt , 2001 .

[44]  P. Ridd,et al.  Currents through Torres Strait , 1988 .

[45]  H. Sverdrup.  Wind-Driven Currents in a Baroclinic Ocean; with Application to the Equatorial Currents of the Eastern Pacific. , 1947, Proceedings of the National Academy of Sciences of the United States of America.

[46]  Indra Jaya,et al.  The deep-water motion through the Lifamatola Passage and its contribution to the Indonesian throughflow , 2009 .

[47]  Janet Sprintall,et al.  Velocity structure and transport of the Indonesian Throughflow in the major straits restricting flow into the Indian Ocean , 2001 .

[48]  Arnold L. Gordon,et al.  Tidal Mixing Signatures in the Indonesian Seas , 1996 .

[49]  Melinda S. Peng,et al.  Navy Operational Global Atmospheric Prediction System (NOGAPS): Forcing for Ocean Models , 2002 .

[50]  A. Schiller.  Effects of explicit tidal forcing in an OGCM on the water-mass structure and circulation in the Indonesian throughflow region , 2004 .

[51]  Rainer Bleck,et al.  An oceanic general circulation model framed in hybrid isopycnic-Cartesian coordinates , 2002 .

[52]  A. Gordon.  Oceanography of the Indonesian Seas and Their Throughflow , 2005 .

[53]  A. Gordon,et al.  Deep topographic barriers within the Indonesian seas , 2003 .

[54]  Yukio Masumoto,et al.  Intraseasonal variations of surface and subsurface currents off Java as simulated in a high‐resolution ocean general circulation model , 2006 .

[55]  N. Schneider,et al.  Interannual variations of the Indonesian throughflow , 2007 .

[56]  Janet Sprintall,et al.  Direct evidence of the South Java Current system in Ombai Strait , 2010 .

[57]  Michael Steele,et al.  PHC: A Global Ocean Hydrography with a High-Quality Arctic Ocean , 2001 .

[58]  J. McCreary,et al.  The South China Sea Throughflow Retrieved from Climatological Data , 2009 .

[59]  Sol Hellerman,et al.  Normal Monthly Wind Stress Over the World Ocean with Error Estimates , 1983 .

[60]  H. Hurlburt,et al.  Coupled dynamics of the South China Sea, the Sulu Sea, and the Pacific Ocean , 1996 .

[61]  Hernan G. Arango,et al.  Seasonal surface ocean circulation and dynamics in the Philippine Archipelago region during 2004–2008 , 2009 .

[62]  E. Joseph Metzger,et al.  Concurrent Simulation of the Eddying General Circulation and Tides in a Global Ocean Model , 2010 .