Analysis Of Water Mass Sources Of Indonesia Throughflow In The Maluku And The Halmahera Seas

Indonesia Throughflow(ITF)is the only connection between the Pacific Ocean and the Indian Ocean at the low latitudes.It is an critical part of the global ocean circulation,and plays important role in the global climate.Comparing to studies of ITF in the central and western pathways through the Makassar Strait and the Karimata Strait,there is less knowledge about the ITF in the east pathway through the Maluku Sea and the Halmahera Sea Sea.Thus,investigating the water mass sources and their vertical structure and temporal variability in the two seas are important for understanding the ITF and the global ocean and climate variations.Using the climatology data of temperature and salinity from the World Ocean Atlas 2013(WOA2013)and the ocean current data of the Simple Ocean Data Assimilation version 3.3.1(SODA v3.3.1),we analyze the vertical distribution and water mass sources of the ITF in its east pathway.The water sources of the Maluku Sea and the Halmahera Sea are further diagnosed at different timescales and different vertical layers with the monthly data of the Ocean General Circulation Model(OGCM)for Earth Simulator(OFES)from January 1997 to December 2013.The results show that the warmer and saltier subsurface waters around 24.5??(about 150 m)in the Maluku Sea come from the North Pacific(NP),with characteristics close to those of the NP Tropic Water(NPTW),while the subsurface water in the Halmahera Sea is closely related to the South Pacific Tropical Water(SPTW)in climatology.For the intermediate water around 26.8??(about 480 m),which is characterized by low temperature and low salinity,the South Pacific(SP)water intrudes into the Maluku Sea,and further enters the Halmahera Sea from the southwest straits.In the deep layer around 27.2??(about 850 m),the water in the Maluku Sea is inclined to being from the northern Banda Sea and the Seram Sea.The deep water in the Halmahera Sea is isolated without direct exchange with the Pacific water due to topographic barrier.Asian monsoon leaves clear seasonal footprints on the eastern Indonesian Seas.Consequently,the subsurface waters in both the Maluku Sea and the Halmahera Sea stem from the SP during winter monsoon,but from the NP for the Maluku Sea and as a mixture water from both the NP and the SP for the Halmahera Sea during summer monsoon.The monsoon impact decreases with depth,so that in the Maluku Sea,the intermediate waters are always from the northern Banda Sea and the Halmahera Sea water is mainly from the SP in winter and the Banda Sea in summer.In the deep layer,waters in both seas are from the SP,with weak seasonal variability.At the interannual timescale,the subsurface water in the Maluku Sea originates from the NP/SP during El Ni?o/La Ni?a,while the subsurface water in the Halmahera Sea always originates from the SP.Similar to the seasonal variability,the intermediate waters in the Maluku Sea is mainly from the Banda Sea and the Halmahera Sea always originates from the SP.The deep waters in both seas are from the SP.Our findings are helpful for drawing a comprehensive picture of the water properties in the Indonesian seas and will contribute to a better understanding of the ocean-atmosphere interaction over the maritime continent.