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

INSTANT: 2004-2006 simultaneous ITF array Corrected from Gordon et al, 2010 overflow 1.1 0.3 1.4 1.6 2.3 2.3 2.4 2.7 1.9 Lifa 1 Imbalance ~ 2-3 Sv: uncertainty; and/or missing links, e.g. Karimata, wide-eastern Halmahera/Maluku portal? Mak 11.6 Ombai, 4.9 Lombok 2.6 Timor, 7.5

Interior Indonesians Seas Pacific Indian Inflow Outflow 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 Interior Indonesians Seas Pacific Heating of upwelled thermocline water (upper 500 m) ~80 W/m2 Indian Inflow Outflow sea surface 0- 100 m: 5.5 Sv 0-100 m 4.1 Sv Isotherm shallowing Upwelling: 1.4 Sv Thermocline upwelling cell 100-500 m: 8.7 Sv 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 600 m to Sunda sill depth: 2.3 Sv Deep ‘overflow’ upwelling cell 1940 m ~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 1990s [ENSO Factor?] SST intraseasonal variance to total SST variance ? >1250 m overflow 200-2000 m Tides; M2 Karimata 1 Sv ? 15 part of coral triangle 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

More about the ‘ENSO factor’, in Makassar Strait Negative values denote flow towards the south m/sec More about the ‘ENSO factor’, in Makassar Strait Along channel speeds m/sec, upper 300 m at 2°51' S; 118°28' E Figure 2a: Time series of along-channel flow (m/sec) within Labani Channel of Makassar Strait derived from observations from the Arlindo (1996-98), INSTANT (2004-07) and Makassar ITF (2007-2011) programs at the mooring location shown on Figure 1. Negative values denote southward flow. The throughflow is weakest in boreal winter, strongest in boreal summer. During 2007 the velocity maximum shoaled, with increasing maximum speed, reaching a peak in maximum speed in 2008/2009. Figure 2b: The monthly mean anomaly of along-channel velocity at 60 m from the 2004-2011 mean. Blue: Makassar ADCP moored time series; red: HYCOM output. The seasonal signal has been removed, and the data smoothed with a 7-month running mean. The gray dashed curve is a 3rd order polynomial fit to the Makassar time series. Figure 2c 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. 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 3rd 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.

Luzon Strait Sibutu Passage Karimata Strait HYCOM upper ~ 100 m HYCOM full depth Luzon Strait transport scales to nino4 HYCOM upper ~ 100 m seasonal cycle removed Mindanao Leakage Makassar Strait Sibutu Passage Sibutu transport: strong ENSO dependence Luzon Strait HYCOM monthly transport anomaly relative to 2003-2010 for HYCOM layers 1-4, coinciding with the upper ~85-100 m of the Makassar Strait, Sibutu Passage, and the Mindanao-Sulawesi Sea (Figure 1 shows the sections positions). Values from HYCOM; seasonal cycle was removed and temporally smoothed with a 1-2-1 filter. During El Niño the southward transport of South China Sea surface water within the Sibutu Passage increases; decreasing during La Niña. The Makassar Strait southward surface layer transport is reduced during El Niño, as is the westward surface layer transport between Mindanao and Sulawesi; increased during La Niña. Figure 3b: HYCOM full depth Luzon Strait transport scales to nino4 (N4). The westward throughflow within Luzon Strait feeding the South China Sea throughflow into the Indonesian seas, responds to ENSO: larger westward throughflow during El Niño. Figure 3c: HYCOM full depth Karimata Strait southward transport of 0 to 2 Sv does not display a relationship to nino4. Figure 3d: HYCOM full depth Sibutu Passage southward transport is significantly correlated to the Luzon Strait throughflow. 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. 2008 La Niña HYCOM ‘salty’ C vv B Low SSS Low salinity surface layer produces an eastward pressure gradient in upper 100 m HYCOM 2004 El Niño A 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

El Niño La Niña The Hypothesis, ENSO connection Mindanao surface layer Strong Luzon throughflow Weak Luzon throughflow El Niño La Niña Mindanao Current Mindanao Current ~100 m ~100 m Blocked: upper ~100 m 40 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.

South China Sea Throughflow Impact on the Indonesian Throughflow 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).

Anomaly of Luzon transport is out-of-phase with total ITF anomaly 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

Tropical Pacific GATEWAY How to determine the retroflection leakage? Mindanao Retroflection North Pacific A C B Halmahera Retroflection South Pacific Maluku Sea Halmahera Sea Makassar 1986-1999 gray Tropical Pacific GATEWAY How to determine the retroflection leakage?

Tropical Pacific GATEWAY How to determine the retroflection leakage? Go here Mindanao Retroflection North Pacific A C Too complicated Blackbox it B Halmahera Retroflection South Pacific Maluku Sea Halmahera Sea Makassar timeserie Go here 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 ? Seram Sea inflow x