The impact of the Indonesian Throughflow and tidal mixing on the summertime sea surface temperature in the western Indonesian Seas

[1] A numerical model is used to investigate how the Indonesian Throughflow and tidal mixing are affecting the seasonal cycle of the sea surface temperature (SST) in the Indonesian Seas. The SST in these seas is considered to play a major role on the development of the Australian Summer Monsoon. Based on a quantitative assessment of the heat budget, the Indonesian Throughflow is found to affect the SST in the western Indonesian Seas primarily during Austral summer. The Throughflow advects the warm water from the Pacific and maintains the warm SST when the Northwestern Monsoonal wind induces coastal upwelling along the northern side of the Nusa Tenggara and cools the SST. Such balance is supported by observations. The hydrographic sections show the isotherms tilting upward toward the northern coast of the Nusa Tenggara when satellite observations show slight decrease of the SST in the region. Tidal mixing is found to cool the SST during summer the most. This is because the Northwest Monsoonal wind induces coastal upwelling near where strong tidal mixing above seamount occurs and brings the tidally well-mixed upper thermocline water to the surface. The surface Ekman flow also spreads this cool water around the Banda Sea where tidal mixing does not occur. The impact of tidal mixing on the SST is also found to come largely from that occurring above seamounts. The impact of tidal mixing on the continental shelves is limited to shelf-breaks because cold subsurface water is necessary for enhanced vertical mixing to cool the SST.

[1]  E. F. Bradley,et al.  Bulk parameterization of air‐sea fluxes for Tropical Ocean‐Global Atmosphere Coupled‐Ocean Atmosphere Response Experiment , 1996 .

[2]  G. Madec,et al.  Physical processes contributing to the water mass transformation of the Indonesian Throughflow , 2008 .

[3]  A. Ffield,et al.  Indonesian Seas Finestructure Variability , 2005 .

[4]  J. S. Godfrey,et al.  The role of Indonesian throughflow in a global ocean GCM , 1993 .

[5]  Gary Meyers,et al.  Sea Surface Temperature and its Variability in the Indonesian Region , 2005 .

[6]  Yan Du,et al.  South China Sea throughflow: A heat and freshwater conveyor , 2006 .

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

[8]  Neville Nicholls,et al.  Relationships between the Maritime Continent Heat Source and the El Niño–Southern Oscillation Phenomenon , 2003 .

[9]  Tong Lee,et al.  Consistency and fidelity of Indonesian-throughflow total volume transport estimated by 14 ocean data assimilation products , 2010 .

[10]  Tong Lee,et al.  Mechanisms controlling the seasonal mixed-layer temperature and salinity of the Indonesian seas , 2011 .

[11]  G. Mellor,et al.  Development of a turbulence closure model for geophysical fluid problems , 1982 .

[12]  R. Neale,et al.  The Maritime Continent and Its Role in the Global Climate: A GCM Study , 2003 .

[13]  M. Jochum,et al.  Sensitivity of Tropical Rainfall to Banda Sea Diffusivity in the Community Climate System Model , 2008 .

[14]  S. Iizuka,et al.  A mechanism of the onset of the Australian summer monsoon , 2002 .

[15]  T. Yamagata,et al.  Dramatic impact of the South China Sea on the Indonesian Throughflow , 2007 .

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

[17]  J. S. Godfrey,et al.  Seasonal near-surface dynamics and thermodynamics of the Indian Ocean and Indonesian Throughflow in a global Ocean general circulation Model , 1998 .

[18]  Ichiro Fukumori,et al.  Mechanisms Controlling the Interannual Variation of Mixed Layer Temperature Averaged over the Niño-3 Region , 2007 .

[19]  N. Schneider,et al.  The Indonesian Throughflow and the Global Climate System , 1998 .

[20]  Dudley B. Chelton,et al.  A Global Climatology of Surface Wind and Wind Stress Fields from Eight Years of QuikSCAT Scatterometer Data , 2008 .

[21]  Y. Masumoto.  A fifty-year eddy-resolving simulation of the world ocean : Preliminary outcomes of OFES (OGCM for the Earth Simulator) , 2004 .

[22]  S. Wijffels,et al.  Variability of the semidiurnal internal tides observed on the Timor Shelf , 2010 .

[23]  Takaki Hatayama.  Transformation of the Indonesian Throughflow Water by Vertical Mixing and Its Relation to Tidally Generated Internal Waves , 2004 .

[24]  G. Meyers,et al.  Geostrophic transport of Indonesian throughflow , 1995 .

[25]  J. Carton,et al.  A Reanalysis of Ocean Climate Using Simple Ocean Data Assimilation (SODA) , 2008 .

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

[27]  A. Gordon,et al.  Banda Sea surface-layer divergence , 2001 .

[28]  M. Alford,et al.  Diapycnal mixing in the Banda Sea: Results of the first microstructure measurements in the Indonesian Throughflow , 1999 .

[29]  A. Gordon,et al.  Transport weighted temperature and internal energy transport of the Indonesian throughflow , 2010 .

[30]  A. Adcroft,et al.  Representation of Topography by Shaved Cells in a Height Coordinate Ocean Model , 1997 .

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

[32]  C. Amante,et al.  ETOPO1 arc-minute global relief model : procedures, data sources and analysis , 2009 .

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

[34]  R. Onishi,et al.  Impact of Coupled Nonhydrostatic Atmosphere-Ocean-Land Model with High Resolution , 2008 .

[35]  A. Gordon,et al.  Velocity and transport of the Makassar Strait throughflow , 2005 .

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

[37]  T. Wagawa,et al.  Turbulent bottom Ekman boundary layer measured over a continental shelf , 2010 .

[38]  Arnold L. Gordon,et al.  Throughflow within Makassar Strait , 1999 .

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

[40]  W. Large,et al.  Oceanic vertical mixing: a review and a model with a nonlocal boundary layer parameterization , 1994 .

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

[42]  K. Richards,et al.  Seasonal sea surface temperature variability in the Indonesian Seas , 2009 .

[43]  Y. Baba,et al.  Dynamical Core of an Atmospheric General Circulation Model on a Yin-Yang Grid , 2010 .