Annual and interannual variations of the Western Pacific Warm Pool volume and sources of warm water revealed by Argo data

Based on gridded Argo profile data from January 2004 to December 2010, together with the P-vector inverse method, the three-dimensional structure, annual and inter-annual variations in volume of the Western Pacific Warm Pool (WPWP) are studied. The variations of latitudinal and longitudinal warm water flowing into and out of the WPWP and the probable mechanism of warm water maintenance are also discussed. From the surface to the bottom, climatic WPWP tilts southward and its area decreases. The maximum depth could extend to 120 m, such that its volume could attain 1.86×1015 m3. Annual variation of the WPWP volume shows two obvious peaks that occur in June and October, whereas its inter-annual variations are related to ENSO events. Based on a climatic perspective, the warm water flowing latitudinally into the pool is about 52 Sv, which is mainly through upper layers and via the eastern boundary. Latitudinally, warm water flowing outward is about 49 Sv, and this is mainly through lower layers and via the western boundary. In contrast, along the latitude, warm water flowing into and out of the pool is about 28 Sv and 23 Sv, respectively. Annual and inter-annual variations of the net transportation of the warm water demonstrate that the WPWP mainly loses warm water in the west-east direction, whereas it receives warm water from the north-south direction. The annual variation of the volume of WPWP is highly related to the annual variation of the net warm water transportation, however, they are not closely related on inter-annual time scale. On the inter-annual time scale, influences of ENSO events on the net warm water transportation in the north-south direction are much more than that in the west-east direction. Although there are some limitations and simplifications when using the P-vector method, it could still help improve our understanding of the WPWP, especially regarding the sources of the warm water.

[1]  J. Toole,et al.  On the circulation of the upper waters in the western equatorial Pacific Ocean , 1988 .

[2]  G. F. Mchugh.  An improved method for matching and merging shallow in situ with deep-ocean climatological temperature profiles , 1995 .

[3]  Huang Dun-xin,et al.  Heat center of the western Pacific warm pool , 2012 .

[4]  Mojib Latif,et al.  Warm Pool Physics in a Coupled GCM , 1996 .

[5]  R. Seager,et al.  Why Are There Tropical Warm Pools , 2005 .

[6]  Bernard Kilonsky,et al.  Mean Water and Current Structure during the Hawaii-to-Tahiti Shuttle Experiment , 1984 .

[7]  Zhang Qi-long.  Zonal movement of surface warm waterin the western Pacific warm pool , 2004 .

[8]  P. Chu,et al.  Japan Sea Thermohaline Structure and Circulation. Part II: A Variational P-Vector Method , 2001 .

[9]  V. Ramanathan,et al.  Thermodynamic regulation of ocean warming by cirrus clouds deduced from observations of the 1987 El Niño , 1991, Nature.

[10]  A. E. Gill.  An Estimation of Sea-Level and Surface-Current Anomalies during the 1972 El Niño and Consequent Thermal Effects , 1983 .

[11]  Meng Xiangfeng,et al.  Contrast between the climatic states of the warm pool in the Indian Ocean and in the Pacific Ocean , 2002 .

[12]  Ronald L. Miller.  Tropical Thermostats and Low Cloud Cover , 1997 .

[13]  H. Diaz,et al.  Characteristics of the Response of Sea Surface Temperature in the Central Pacific Associated with Warm Episodes of the Southern Oscillation , 1986 .

[14]  K. Wyrtki.  An Estimate of Equatorial Upwelling in the Pacific , 1981 .

[15]  P. Chu.  P-Vector Inverse Method , 2006 .

[16]  Raymond T. Pierrehumbert,et al.  Thermostats, Radiator Fins, and the Local Runaway Greenhouse , 1995 .

[17]  Q. Zheng,et al.  Satellite Observations of Upper-Layer Variabilities in the Western Pacific Warm Pool , 1995 .

[18]  D. Hartmann,et al.  Large-Scale Effects on the Regulation of Tropical Sea Surface Temperature , 1993 .

[19]  Dean Roemmich,et al.  The 2004-2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program , 2009 .

[20]  Seon Tae Kim,et al.  The distinct behaviors of Pacific and Indian Ocean warm pool properties on seasonal and interannual time scales , 2012 .

[21]  M. Ioualalen,et al.  Mechanism of the Zonal Displacements of the Pacific Warm Pool: Implications for ENSO , 1996, Science.

[22]  Arnold L. Gordon,et al.  Interocean Exchange of Thermocline Water , 1986 .

[23]  J. Bjerknes,et al.  A possible response of the atmospheric Hadley circulation to equatorial anomalies of ocean temperature , 1966 .

[24]  P. Chu.  P-Vector Spirals and Determination of Absolute Velocities , 2000 .

[25]  Lejiang Yu,et al.  An approach to prediction of the South China Sea summer monsoon onset , 2008 .

[26]  A. E. Gill,et al.  The 1982–83 climate anomaly in the equatorial Pacific , 1983, Nature.

[27]  Haiyan,et al.  Seasonal and annual variations of marine sinking particulate flux during 1993～1996 in the central South China Sea , 2007 .