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Discovering the Indonesian Throughflow

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Discovering the Indonesian Throughflow or collective redistirbution of any portion article of any by of this or collective redistirbution Th THE INDONESIAN SEAS articleis has been in published Discovering Oceanography the 18, Number journal of Th 4, a quarterly , Volume Indonesian permitted only w is photocopy machine, reposting, means or other Throughflow BY KLAUS WYRTKI In the summer of 1954, I accepted a po- maps of surface salinity for the region. distributions, and water-mass analysis, sition as an oceanographer at the Marine Surface salinity offered much insight one could obtain a better understanding 2005 by Th e Oceanography Copyright Society. Science Institute in Djakarta, Indone- into the advection of water in this area, of the circulation than would be possible sia. When I arrived in November 1954, which has such a pronounced annual from each component alone. I found out that all the Dutch scientists reversal of the circulation. As a starting point, I constructed had left—I was the only scientist and Because the Samudera offered only monthly maps of the surface circula- the director of the institute. I had a fi ne, limited possibilities for research, I soon tion based on ship-drift observations. of Th approval the ith almost new research vessel, the 200-ton decided to concentrate on analyzing ex- These charts led me to wonder where all Samudera. It had only six Nansen bottles, isting data. My goal was to give a compre- the water goes that fl ows east in the Java one bathythermograph, and two winches hensive description of the circulation and Sea during the northwest monsoon, and gran e Oceanography is Society. All rights reserved. Permission with about 1500 m of wire. I also inher- the water masses of the entire Southeast where the water comes from during the or Th e Oceanography [email protected] Society. Send to: all correspondence ited a well-established “ship-of-opportu- Asian waters. I realized that by combin- opposite season. The source had to lay nity” program, which collected salinity ing information from sources such as in the Eastern Archipelago, in particular, samples over the entire Southeast Asian surface currents, dynamic waters from Hong Kong to Singapore, to calculations, sea-level Jakarta, to Ambon. We issued monthly observations, property ted to copy this article Repu for use copy this and research. to in teaching ted e Oceanography Society, PO Box 1931, Rockville, MD 20849-1931, USA. Figure 1. Left: Th e Indonesian Research Vessel Samudera in 1957. Above: Klaus Wyrtki and a technician with Nansen bottles. blication, systemmatic reproduction, reproduction, systemmatic blication, 28 Oceanography Vol. 18, No. 4, Dec. 2005 Figure 2. Left: Klaus Wyrtki and technicians on the winch. Above: A technician removing a Nan- sen bottle from the wire. the Banda Sea. Studying the data from was intimately related to these changing hand, the determination of the annual the Snellius expedition of 1929, I found fl ows. Furthermore, important evidence cycle and its relation to the monsoons that their observations were made dur- for the throughfl ow came from a fl ow was correct. ing October near the end of the south- of high-salinity water from the Pacifi c I presented this discovery of a east monsoon season. So I decided to into the Eastern Archipelago at a depth throughfl ow from the Pacifi c to the conduct an expedition into the Banda of about 150 m within the thermocline. Indian Ocean for the fi rst time at the Sea to observe the conditions in March, This fl ow reaches as far as the Timor Sea. Pacifi c Science Congress in Bangkok in at the end of the northwest monsoon. Other evidence came from the spread- 1957, but the results were not published The difference between the two surveys ing of low-salinity water from the Banda until 1961. It is very gratifying to know was striking. From March to October the Sea into the Indian Ocean at a depth of that this early study has stimulated a thermocline had risen dramatically, indi- about 1000 m. great deal of additional research on this cating the presence of strong upwelling. The discovery of the throughfl ow important link in global ocean circula- As a next step, I tried to construct was a by-product of my attempt to tion. I am sure that the extended direct maps of the region’s mass transport understand and document the circula- measurements of the throughfl ow that based on surface currents, dynamic cal- tion in the Southeast Asian waters. Like are now underway will eventually deter- culations, and sea-level observations. many new discoveries, this one was in- mine its correct magnitude and varia- These maps showed an infl ow of water complete. I underestimated the magni- tions and will form the basis for a con- from the Pacifi c into the Eastern Archi- tude of the throughfl ow, and I did not tinuous monitoring of the circulation in pelago during the northwest monsoon think that the bulk of it goes through this region. and an outfl ow to the Indian Ocean dur- the Makassar Strait even though I was ing the southeast monsoon. The maps aware of the current measurements by Klaus Wyrtki ([email protected]) is Profes- also made it clear that the seasonal up- the Snellius that showed a southward sor Emeritus, University of Hawaii, Hono- welling and sinking in the Banda Sea fl ow in the Makassar Strait. On the other lulu, HI, USA. Oceanography Vol. 18, No. 4, Dec. 2005 29.
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