1. Breif ITF review; Pacific inflow into the Indonesian Seas
Arnold L. Gordon, CLIVAR ITF Task Team, Ancol, Indonesia, 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

2. 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

3. 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
m: 5.5 Sv
0-100 m 4.1 Sv
Isotherm shallowing
Upwelling: 1.4 Sv
Thermocline upwelling cell
m: 8.7 Sv
m: 7.3 Sv
Null level upwelling <10-6 m/sec 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
~ 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 as observed by the INSTANT program.” Dynamics of Atmosphere and Ocean: “Modeling and Observing the Indonesian Throughflow”.

4. Indonesian Throughflow ~15 Sv [INSTANT: ] but ~11 Sv from non-simultaneous obs of 1990s [ENSO Factor?]
SST intraseasonal variance to total SST
variance ?
>1250 m overflow 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 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

5. 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 ( ), INSTANT ( ) and Makassar ITF ( ) 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 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]

6. Mak obs
Observation:model comparison
HYCOM
Monthly mean anomaly of along-channel velocity at 60 m from the 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.

7. 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 for HYCOM layers 1-4, coinciding with the upper ~ 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 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

8. 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

9. 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.

10. 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 , 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).

11. 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
: agrees with INSTANT, Gordon et al, 2010, Table 1

12. 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

14. 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
gray
Tropical Pacific GATEWAY
How to determine the retroflection leakage?

15. 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?

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