Breif ITF review Pacific inflow into the Indonesian

Breif ITF review; Pacific inflow into the Indonesian Seas Arnold L. Gordon, CLIVAR ITF Task Team, Ancol, Indonesia, 12 -13 March 2012 Indonesian Throughflow [ITF] Pacific Ocean Entry Portals: • South China Sea via Luzon Strait to Karimata and Sibutu; • Tropical Pacific via Mindanao & Halmahera Eddies [Retroflections]; [Torrie Strait] Indian Ocean Exit Portals: Sunda Archpeligo passages: Lombok, Ombai, Timor, [Sunda Strait, Malacca Strait] Interior Seas [the mix-master]: Makassar Strait: western boundary, primary inflow pathway; Eastern seas: Banda ‘cyclonic gyre’, Seram/Halmahera/Maluku Seas puzzle

Corrected from Gordon et al, 2010 INSTANT: 2004 -2006 simultaneous ITF array overflow 1. 1 2. 3 Imbalance ~ 2 -3 Sv: uncertainty; and/or missing links, e. g. Karimata, wide-eastern Halmahera/Maluku portal? Mak 11. 6 Lombok 2. 6 0. 3 1. 4 1. 6 2. 4 2. 3 2. 7 1. 9 Lifa 1 Ombai, 4. 9 Timor, 7. 5

Schematic of approximate inflow/outflow and upwelling pattern during the 3 year observational period of INSTANT Strong upwelling and air-sea heat flux- a tidal dissipation driven mix-master acting on a ~15 Sv stream Inflow Pacific Outflow Interior Indonesians Seas Heating of upwelled thermocline water (upper 500 m) ~80 W/m 2 sea surface Indian 0 - 100 m: 5. 5 Sv 0 -100 m 4. 1 Sv Isotherm shallowing 100 -500 m: 8. 7 Sv Upwelling: 1. 4 Sv Thermocline upwelling cell 100 -500 m: 7. 3 Sv Null level upwelling <10 -6 m/sec 500 -600 m layer <0. 6 Sv net upwelling Lifamatola Passage >600 m 2. 9 Sv 1940 m 600 m to Sunda sill depth: 2. 3 Sv Deep ‘overflow’ upwelling cell ~1300 -1500 m Gordon, A. L. ; Sprintall, J. ; Van Aken, H. M. ; Susanto, D. ; Wijffels, S. ; Molcard, R. ; Ffield, A. ; Pranowo, W. ; Wirasantosa, S. (in press) “The Indonesian Throughflow during 2004 -2006 as observed by the INSTANT program. ” Dynamics of Atmosphere and Ocean: “Modeling and Observing the Indonesian Throughflow”.

Indonesian Throughflow ~15 Sv [INSTANT: 2004 -2006] but ~11 Sv from non-simultaneous obs of 1990 s [ENSO Factor? ] SST intraseasonal variance to total SST variance ? >1250 m overflow 200 -2000 m Tides; M 2 Karimata 1 Sv ? 15 The italics numbers in black represent transport values based on pre-INSTANT data. The red numbers are the 2004 -2006 3 year mean transports measured by INSTANT. In Lifamatola Passage the green number is the INSTANT overflow transport >1250 m, representing the overflow into the deep Seram and Banda Sea part of coral triangle

m/sec Negative values denote flow towards the south More about the ‘ENSO factor’, in Makassar Strait Along channel speeds m/sec, upper 300 m at 2° 51' S; 118° 28' E V-max ~140 m at 0. 65 m/s to ~70 m at 0. 95 m/s ~20°C at 140 m; ~25°C at 70 m [ENSO thermocline heaving is much smaller]

Mak obs Observation: model comparison HYCOM Monthly mean anomaly of along-channel velocity at 60 m from the 2004 -2011 mean. The seasonal signal has been removed; data smoothed with a 7 -month running mean. The gray dashed curve is a 3 rd order polynomial fit to the Makassar time series. The apparent regime change in 2007, roughly coincides with a shift from prolonged El Niño to a period of more frequent El Niño/La Niña transitions.

HYCOM full depth Luzon Strait transport scales to nino 4 HYCOM upper ~ 100 m seasonal cycle removed Mindanao Leakage Makassar Strait Sibutu Passage Sibutu transport: strong ENSO dependence Luzon Strait Sibutu Passage Karimata Strait Karimata transport: noisy; weak ENSO dependence

The freshwater plug: the low salinity Sulu Sea surface layer (upper 100 m) injected into western Sulawesi Sea via Sibutu Passage imposes an eastward pressure gradient [relative to 1000 db] within the Sulawesi Sea. HYCOM 2008 La Niña ‘salty’ C vv. B Low SSS Low salinity surface layer produces an eastward pressure gradient in upper 100 m A HYCOM 2004 El Niño SCS/Suluthroughflow freshening A hybrid water column [composed from archive obs] in western Sulawesi: Sulu upper 100 m replacing average upper 100 of the Sulawesi Sea Imposes increased eastward pressure gradient in upper 100 m

The Hypothesis, ENSO connection Strong Luzon throughflow El Niño Weak Luzon throughflow ~100 m Blocked: upper ~100 m 40 m Blocked: upper ~40 m local monsoonal wind [stronger in la nina] Mindanao surface layer blocked upper ~100 m WPWP low leakage to ITF Mindanao surface layer blocked upper ~40 m WPWP high leakage to ITF Karimata throughflow, responds to local wind [stronger in la nina] rather than the Luzon Strait throughflow, as does Sibutu, leading to the patterns proposed above. Mindanao Current La Niña

In revision GRL South China Sea Throughflow Impact on the Indonesian Throughflow Arnold L. Gordon, Bruce A. Huber, E. Joseph Metzger, R. Dwi Susanto, Harley E. Hurlburt, T. Rameyo Adi • In 2008 -2009, the Makassar throughflow profile dramatically changed, with the characteristic thermocline velocity maximum increasing from 0. 7 to 0. 9 m/sec and shifted from 140 m to 70 m, amounting to a 47% increase in warm water transport between 50 and 150 m during the boreal summer. • HYCOM output indicates that ENSO related changes of the South China Sea (SCS) throughflow into the Indonesian seas are the likely cause. Increased SCS throughflow during El Niño with a commensurate increase in the southward flow of buoyant SCS surface water through the Sulu Sea into the northern Makassar Strait inhibits tropical Pacific surface water injection into Makassar Strait. • During La Niña SCS throughflow is reduced or reversed allowing tropical Pacific surface flow into the ITF, increasing the flux of warm water available to spread into the Indian Ocean, affecting regional sea surface temperature and climate (with 2 -3 year lag, Song et al. 2004).

Maybe More? Anomaly of Luzon transport is out-of-phase with total ITF anomaly [sum of Lombok + Ombai + Timor] Increased Luzon Throughflow may reduce export to Indian Ocean? ITF export to Indian Ocean This happens during El Niño This happens during La Niña Increase SCS throughflow during El Niño 2004 -2006: agrees with INSTANT, Gordon et al, 2010, Table 1

Pacific Ocean Entry Portals: • South China Sea via Luzon Strait to Karimata and Sibutu; • Tropical Pacific via Mindanao & Halmahera Eddies [Retroflections]; [Torrie Strait] Indian Ocean Exit Portals: Sunda Archpeligo passages: Lombok, Ombai, Timor, [Sunda Strait, Malacca Strait] Interior Seas [the mix-master]: Makassar Strait: western boundary, primary inflow pathway; Eastern seas: Banda ‘cyclonic gyre’, Seram/Halmahera/Maluku Seas puzzle

n tio c e ofl r t Re cific A o na h Pa a d rt n i o N M B Maluku Sea Hal ma her Sou a Retr th P ofle acif ctio n ic Halmahera Sea Ma kas sar C 1986 -1999 gray Tropical Pacific GATEWAY How to determine the retroflection leakage?

n tio c Go here e ofl r t Re cific A o na h Pa a d rtd n i o N e M Ma kas sar tim ese rie C t a c i l p. B t m i o x c o o b o k T lac Maluku Sea B Hal ma her Sou a Retr th P ofle acif ctio n ic Halmahera Sea Go here Tropical Pacific GATEWAY How to determine the retroflection leakage?

I propose that GATEWAY has a component covering exchange of Maluku/Halmahera with Seram Sea x x ? x Seram Sea inflowx