Previously unidentified Indonesian Throughflow pathways and freshening in the Indian Ocean during recent decades

Abstract Controlled numerical experiments using ocean-only and ocean–atmosphere coupled general circulation models show that interannual sea level depression in the eastern Indian Ocean during the Indian Ocean dipole (IOD) events forces enhanced Indonesian Throughflow (ITF) to transport warm water from the upper-equatorial Pacific Ocean to the Indian Ocean. The enhanced transport produces elevation of the thermocline and cold subsurface temperature anomalies in the western equatorial Pacific Ocean, which propagate to the eastern equatorial Pacific to induce significant coupled evolution of the tropical Pacific oceanic and atmospheric circulation. Analyses suggest that the IOD-forced ITF transport anomalies are about the same amplitudes as those induced by the Pacific ENSO. Results of the coupled model experiments suggest that the anomalies induced by the IOD persist in the equatorial Pacific until the year following the IOD event, suggesting the importance of the oceanic channel in modulating the interannual climate variations of the tropical Pacific Ocean at the time lag beyond one year.

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Direct estimates of the Indonesian Throughflow entering the Indian Ocean: 2004–2006

Journal of Geophysical Research Atmospheres ◽

10.1029/2008jc005257 ◽

2009 ◽

Vol 114 (C7) ◽

Cited By ~ 230

Author(s):

Janet Sprintall ◽

Susan E. Wijffels ◽

Robert Molcard ◽

Indra Jaya

Keyword(s):

Indian Ocean ◽

Indonesian Throughflow ◽

The Indian Ocean

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Drivers of oceanic exchange through the Indonesian Throughflow since the late 1800s – a synthesis of coral δ18O and high-resolution ocean models

10.5194/egusphere-egu2020-11181 ◽

2020 ◽

Author(s):

Sujata Murty ◽

Caroline Ummenhofer ◽

Markus Scheinert ◽

Erik Behrens ◽

Arne Biastoch ◽

...

Keyword(s):

Indian Ocean ◽

Mixed Layer ◽

Mixed Layer Depth ◽

Heat Content ◽

Phase Changes ◽

Boreal Winter ◽

Indonesian Throughflow ◽

Layer Depth ◽

Ocean Variability ◽

The Indian Ocean

The Indonesian Throughflow (ITF) serves as an important oceanic teleconnection for Indo-Pacific climate, altering heat and buoyancy transport from the Pacific to the Indian Ocean. Equatorial Pacific wind forcing transmitted through the ITF impacts interannual to interdecadal Indian Ocean thermocline depth and heat content, with implications for preconditioning Indian Ocean Dipole events. Yet the modulation of Indian Ocean thermal properties at seasonal timescales is still poorly understood. Here we synthesize coral &#948;18O records, instrumental indices (El Ni&#241;o Southern Oscillation (ENSO), Asian Monsoon), and simulated ocean variability (sea surface salinity (SSS) and temperature (SST), heat content, mixed layer depth) from state-of-the-art NEMO ocean model hindcasts to explore drivers of seasonal to multi-decadal variability. All coral sites are located within main ITF pathways and are influenced by monsoon-driven, buoyant South China Sea (SCS) surface waters during boreal winter that obstruct surface ITF flow and reduce heat transport to the Indian Ocean. Makassar and Lombok Strait coral &#948;18O co-varies with simulated SSS, subsurface heat content anomalies (50-350m) and mixed layer depth at the coral sites and in the eastern Indian Ocean. At decadal timescales, simulated boreal winter ocean variability at the coral sites additionally indicates a potential intensification of the SCS buoyancy plug from the mid- to late-20th century. Notably, the variability in these coral and model responses reveals sensitivity to phase changes in the Interdecadal Pacific Oscillation and the East Asian Winter Monsoon. These results collectively suggest that the paleoproxy records are capturing important features of regional hydrography and Indo-Pacific exchange, including responses to regional monsoon variability. Such proxy-model comparison is critical for understanding the drivers of variability related to changes in ITF oceanic teleconnections over the 19th and 20th centuries.

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Interannual Climate Variability over the Tropical Pacific Ocean Induced by the Indian Ocean Dipole through the Indonesian Throughflow

Journal of Climate ◽

10.1175/jcli-d-12-00117.1 ◽

2013 ◽

Vol 26 (9) ◽

pp. 2845-2861 ◽

Cited By ~ 39

Author(s):

Dongliang Yuan ◽

Hui Zhou ◽

Xia Zhao

Keyword(s):

Pacific Ocean ◽

Indian Ocean ◽

Tropical Indian Ocean ◽

Sea Surface Height ◽

Equatorial Pacific ◽

Sea Surface ◽

Indonesian Throughflow ◽

Cold Tongue ◽

The Indian Ocean ◽

Southeastern Tropical Indian Ocean

Abstract The authors’ previous dynamical study has suggested a link between the Indian and Pacific Ocean interannual climate variations through the transport variations of the Indonesian Throughflow. In this study, the consistency of this oceanic channel link with observations is investigated using correlation analyses of observed ocean temperature, sea surface height, and surface wind data. The analyses show significant lag correlations between the sea surface temperature anomalies (SSTA) in the southeastern tropical Indian Ocean in fall and those in the eastern Pacific cold tongue in the following summer through fall seasons, suggesting potential predictability of ENSO events beyond the period of 1 yr. The dynamics of this teleconnection seem not through the atmospheric bridge, because the wind anomalies in the far western equatorial Pacific in fall have insignificant correlations with the cold tongue anomalies at time lags beyond one season. Correlation analyses between the sea surface height anomalies (SSHA) in the southeastern tropical Indian Ocean and those over the Indo-Pacific basin suggest eastward propagation of the upwelling anomalies from the Indian Ocean into the equatorial Pacific Ocean through the Indonesian Seas. Correlations in the subsurface temperature in the equatorial vertical section of the Pacific Ocean confirm the propagation. In spite of the limitation of the short time series of observations available, the study seems to suggest that the ocean channel connection between the two basins is important for the evolution and predictability of ENSO.

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Impact of the Madden–Julian Oscillation on the Indonesian Throughflow in the Makassar Strait during the CINDY/DYNAMO Field Campaign

Journal of Climate ◽

10.1175/jcli-d-15-0711.1 ◽

2016 ◽

Vol 29 (17) ◽

pp. 6085-6108 ◽

Cited By ~ 6

Author(s):

Toshiaki Shinoda ◽

Weiqing Han ◽

Tommy G. Jensen ◽

Luis Zamudio ◽

E. Joseph Metzger ◽

...

Keyword(s):

Indian Ocean ◽

General Circulation ◽

Circulation Model ◽

Global Ocean ◽

Indonesian Throughflow ◽

Madden Julian Oscillation ◽

Field Campaign ◽

Eastern Boundary ◽

The Indian Ocean ◽

Velocity Anomalies

Abstract Previous studies indicate that equatorial zonal winds in the Indian Ocean can significantly influence the Indonesian Throughflow (ITF). During the Cooperative Indian Ocean Experiment on Intraseasonal Variability (CINDY)/Dynamics of the Madden–Julian Oscillation (DYNAMO) field campaign, two strong MJO events were observed within a month without a clear suppressed phase between them, and these events generated exceptionally strong ocean responses. Strong eastward currents along the equator in the Indian Ocean lasted more than one month from late November 2011 to early January 2012. The influence of these unique MJO events during the field campaign on ITF variability is investigated using a high-resolution (1/25°) global ocean general circulation model, the Hybrid Coordinate Ocean Model (HYCOM). The strong westerlies associated with these MJO events, which exceed 10 m s−1, generate strong equatorial eastward jets and downwelling near the eastern boundary. The equatorial jets are realistically simulated by the global HYCOM based on the comparison with the data collected during the field campaign. The analysis demonstrates that sea surface height (SSH) and alongshore velocity anomalies at the eastern boundary propagate along the coast of Sumatra and Java as coastal Kelvin waves, significantly reducing the ITF transport at the Makassar Strait during January–early February. The alongshore velocity anomalies associated with the Kelvin wave significantly leads SSH anomalies. The magnitude of the anomalous currents at the Makassar Strait is exceptionally large because of the unique feature of the MJO events, and thus the typical seasonal cycle of ITF could be significantly altered by strong MJO events such as those observed during the CINDY/DYNAMO field campaign.

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On the Indonesian throughflow in the OCCAM 1/4 degree ocean model

Ocean Science Discussions ◽

10.5194/osd-4-325-2007 ◽

2007 ◽

Vol 4 (2) ◽

pp. 325-370 ◽

Cited By ~ 1

Author(s):

U. W. Humphries ◽

D. J. Webb

Keyword(s):

Indian Ocean ◽

Ocean Model ◽

Global Ocean ◽

Indonesian Throughflow ◽

Island Rule ◽

Near Surface ◽

The North ◽

The Pacific ◽

The Indian Ocean ◽

Pass Through

Abstract. The Indonesian Throughflow is analysed in two runs of the OCCAM 1/4 degree global ocean model, one using monthly climatological winds and one using ECMWF analysed six-hourly winds for the period 1993 to 1998. The long-term model throughflow agrees with observations and the value predicted by Godfrey's Island Rule. The Island Rule has some skill in predicting the annual signal each year but is poor at predicting year to year and shorter term variations in the total flow especially in El Nino years. The spectra of transports in individual passages show significant differences between those connecting the region to the Pacific Ocean and those connecting with the Indian Ocean. This implies that different sets of waves are involved in the two regions. Vertical profiles of transport are in reasonable agreement with observations but the model overestimates the near surface transport through the Lombok Strait and the dense overflow from the Pacific through the Lifamatola Strait into the deep Banda Sea. In both cases the crude representation of the passages by the model appears responsible. In the north the model shows, as expected, that the largest transport is via the Makassar Strait. However this is less than expected and instead there is significant flow via the Halmahera Sea. If Godfrey's Island Rule is correct and the throughflow is forced by the northward flow between Australia and South America, then the Halmahers Sea route should be important. It is the most southerly route around New Guinea to the Indian Ocean and there is no apparent reason why the flow should go further north in order to pass through the Makassar Strait. The model result thus raises the question of why in reality the Makassar Strait route appears to dominate the throughflow.

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Heat contribution of the Indonesian throughflow to the Indian Ocean

Acta Oceanologica Sinica ◽

10.1007/s13131-019-1414-6 ◽

2019 ◽

Vol 38 (4) ◽

pp. 72-79

Author(s):

Tiecheng Zhang ◽

Weiqiang Wang ◽

Qiang Xie ◽

Lingfang Chen

Keyword(s):

Indian Ocean ◽

Indonesian Throughflow ◽

The Indian Ocean

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The distribution of radiocesium in the Indian ocean and its relation to the exit passage of the Indonesian Throughflow

Regional Studies in Marine Science ◽

10.1016/j.rsma.2018.100496 ◽

2019 ◽

Vol 25 ◽

pp. 100496

Author(s):

Ali Alkatiri ◽

Heny Suseno ◽

Sumi Hudiyono ◽

Setyo Sarwanto Moersidik

Keyword(s):

Indian Ocean ◽

Indonesian Throughflow ◽

The Indian Ocean

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Marine Reservoir Correction for the Cocos (Keeling) Islands, Indian Ocean

Radiocarbon ◽

10.1017/s0033822200035645 ◽

2004 ◽

Vol 46 (2) ◽

pp. 603-610 ◽

Cited By ~ 13

Author(s):

Quan Hua ◽

Colin D Woodroffe ◽

Mike Barbetti ◽

Scott G Smithers ◽

Ugo Zoppi ◽

...

Keyword(s):

Mass Spectrometry ◽

Indian Ocean ◽

Red Sea ◽

Surface Waters ◽

Accelerator Mass Spectrometry ◽

Arabian Sea ◽

Indonesian Throughflow ◽

Gulf Of Aden ◽

The Indian Ocean ◽

Reservoir Age

Known-age corals from the Cocos (Keeling) Islands, Indian Ocean, have been analyzed by accelerator mass spectrometry (AMS) for radiocarbon to determine marine reservoir age corrections. The ΔR value for the Cocos (Keeling) Islands is 66 ± 12 yr based on the analyses undertaken for this study. When our AMS and previously published dates for Cocos are averaged, they yield a ΔR of 64 ± 15 yr. This is a significant revision of an earlier estimate of the ΔR value for the Cocos (Keeling) Islands of 186 ± 66 yr (Toggweiler et al. 1991). The (revised) lower ΔR for the Cocos (Keeling) Islands is consistent with GEOSECS 14C data for the Indian Ocean, and previously published bomb 14C data for the Red Sea, Gulf of Aden, and Cocos Islands. The revised ΔR is also close to values for the eastern Indian Ocean and adjacent seas. These suggest surface waters that reach the Cocos Islands might be partly derived from the far western Pacific, via the Indonesian throughflow, and might not be influenced by the southeast flow from the Arabian Sea.

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Pathways and Effects of the Indonesian Throughflow Water in the Indian Ocean Using Particle Trajectory and Tracers in an OGCM

Journal of Climate ◽

10.1175/jcli4167.1 ◽

2007 ◽

Vol 20 (13) ◽

pp. 2994-3017 ◽

Cited By ~ 31

Author(s):

Vinu K. Valsala ◽

Motoyoshi Ikeda

Keyword(s):

Indian Ocean ◽

Vertical Mixing ◽

Surface Current ◽

Western Boundary ◽

Indonesian Throughflow ◽

Somali Region ◽

High Salinity Water ◽

The North ◽

The Indian Ocean ◽

Passive Tracers

Abstract The 3D pathways of the Indonesian Throughflow (ITF) in the Indian Ocean are identified using an OGCM, with a combined set of tools: 1) Lagrangian particle trajectories, 2) passive tracers, and 3) active tracers (temperature and salinity). Each of these tools has its own advantages and limitations to represent the watermass pathways. The Lagrangian particles, without horizontal and vertical mixing, suggest that at the entrance region the surface ITF subducts along the northwestern coast of Australia and then travels across the Indian Ocean along the thermocline depths. The subsurface ITF more directly departs westward and crosses the Indian Ocean. Using the passive tracers, which are mixed vertically under convection as well as horizontally due to diffusion, the ITF is shown to undergo vigorous mixing as soon as it enters the Indian Ocean and modifies its upper temperature–salinity (T–S) characteristics. Thus, the surface and subsurface ITF watermasses lose their identities. Upon reaching the western boundary, the ITF reroutes into three distinct depth ranges, owing to the seasonal reversal of the Somali region: route 1—across the Indian Ocean just to the south of the equator (200–300 m); route 2—across the Indian Ocean to the north of the equator (100–200 m); and route 3—upwells in the Somali region and spreads all over the surface of the northern Indian Ocean. The seasonality of the Somali Current is crucial to spread the ITF along route 3 during the summer monsoon (April–October) and route 2 during the winter monsoon (November–March). The basinwide spreading is responsible for a long residence time of the ITF in the Indian Ocean to be at least 20 yr. The effects of the ITF on the temperature and salinity are mainly accompanied with the major pathways. However, indirect effects are visible in a few spots; that is, the warm and saline feature is produced in the subsurface off the southwestern coast of Australia around 30°S caused by the eastward surface current, which is under the thermal wind relationship owing to the warm and fresh ITF component. This component also enhances vertical convection and warms the surface around 40°S. The Arabian Sea high salinity water is produced extensively with the effects of the Somali upwelling, which is originally strengthened by the fresh and warm ITF.

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