Abstract
Across the Indo-Pacific region, rapid increases in surface temperatures, ocean heat content and concomitant hydrological changes have implications for sea level rise, ocean circulation and regional freshwater availability. In this Review, we synthesize evidence from multiple data sources to elucidate whether the observed heat and freshwater changes in the Indian Ocean represent an intensification of the hydrological cycle, as expected in a warming world. At the basin scale, twentieth century warming trends can be unequivocally attributed to human-induced climate change. Changes since 1980, however, appear dominated by multi-decadal variability associated with the Interdecadal Pacific oscillation, manifested as shifts in the Walker circulation and a corresponding reorganization of the Indo-Pacific heat and freshwater balance. Such variability, coupled with regional-scale trends, a short observational record and climate model uncertainties, makes it difficult to assess whether contemporary changes represent an anthropogenically forced transformation of the hydrological cycle. Future work must, therefore, focus on maintaining and expanding observing systems of remotely sensed and in situ observations, as well as extending and integrating coral proxy networks. Improved climate model simulations of the Maritime Continent region and its intricate exchange between the Pacific and Indian oceans are further necessary to quantify and attribute Indo-Pacific hydrological changes.
Key points
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At the basin scale, the Indian Ocean sustained robust twentieth century surface warming exceeding that of other tropical ocean basins. Yet, substantial variability exists regarding the magnitude and confidence in trends at regional scales, especially in the subsurface, due to the sparse observational network.
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Indian Ocean heat content has risen rapidly since the 2000s and concomitant freshening occurred over the eastern Indian Ocean and Maritime Continent (MC).
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Broad-scale warming and MC freshening trends are consistent with expected changes of an intensifying hydrological cycle in a warming world; however, the rate of observed change since the 1980s likely results from natural multi-decadal variability associated with the Interdecadal Pacific oscillation.
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Disentangling the effects of multi-decadal natural variability and anthropogenic change on heat and freshwater changes in the Indian Ocean and MC region — of importance for climate risk assessments for vulnerable societies in Indian Ocean rim countries — require sustained and enhanced observations.
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Centennial trends based on coral proxies indicate robust warming and freshening since the 1850s over the Indian Ocean and broader MC region. However, the reconstructed century-scale trend magnitude is much lower than the rapid trends observed since 1980, which were most likely exacerbated by recent acceleration of anthropogenic climate warming and natural multi-decadal variability associated with Interdecadal Pacific oscillation phase shifts.
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Quantifying change in the Indian Ocean heat and freshwater balance warrants a multi-pronged approach that capitalizes on a systematic integration of in situ observations, remote sensing, numerical modelling efforts and palaeo proxy networks across temporal and spatial scales.
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References
Schmitt, R. W. Salinity and the global water cycle. Oceanography 21, 12–19 (2008).
Lagerloef, G., Schmitt, R., Schanze, J. & Kao, H.-Y. The ocean and the global water cycle. Oceanography. 23, 82–93 (2010).
Gordon, A. L. The marine hydrological cycle: The ocean’s floods and droughts. Geophys. Res. Lett. 43, 7649–7652 (2016).
Huntington, T. G. Evidence for intensification of the global water cycle: Review and synthesis. J. Hydrol. 319, 83–95 (2006).
Helm, K. P., Bindoff, N. L. & Church, J. A. Changes in the global hydrological-cycle inferred from ocean salinity. Geophys. Res. Lett. 37, L18701 (2010).
Durack, P. J., Wijffels, S. E. & Matear, R. J. Ocean salinities reveal strong global water cycle intensification during 1950 to 2000. Science 336, 455–458 (2012). Demonstrates the intensification of the water cycle in the second half of the twentieth century based on ocean salinities in observations and climate model simulations.
Held, I. M. & Soden, B. J. Robust responses of the hydrological cycle to global warming. J. Clim. 19, 5686–5699 (2006).
Beal, L. M. et al. A road map to IndOOS-2: Better observations of the rapidly warming Indian Ocean. Bull. Am. Meteorol. Soc. 101, E1891–E1913 (2020). Summary of the findings and recommendations of the decadal review of the Indian Ocean Observing System (IndOOS).
Han, W. et al. Indian Ocean decadal variability: a review. Bull. Am. Meteorol. Soc. 95, 1679–1703 (2014). Reviews the state of knowledge of decadal variability in the Indian Ocean from observations, reanalyses and climate model simulations.
Lee, S.-K. et al. Pacific origin of the abrupt increase in Indian Ocean heat content during the warming hiatus. Nat. Geosci. 8, 445–450 (2015).
Nieves, V., Willis, J. K. & Patzert, W. C. Recent hiatus caused by decadal shift in Indo-Pacific heating. Science 349, 532–535 (2015). Demonstrates redistribution of upper ocean heat content between the Pacific and Indian oceans from observations during the global warming hiatus (1993–2012).
Abram, N. J., Gagan, M. K., Cole, J. E., Hantoro, W. S. & Mudelsee, M. Recent intensification of tropical climate variability in the Indian Ocean. Nat. Geosci. 1, 849–853 (2008).
Cai, W., Cowan, T. & Sullivan, A. Recent unprecedented skewness towards positive Indian Ocean dipole occurrences and their impact on Australian rainfall. Geophys. Res. Lett. 36, L11705 (2009).
Freund, M. B. et al. Higher frequency of Central Pacific El Niño events in recent decades relative to past centuries. Nat. Geosci. 12, 450–455 (2019).
Abram, N. J. et al. Coupling of Indo-Pacific climate variability over the last millennium. Nature 579, 385–392 (2020).
Cai, W. et al. Projected response of the Indian Ocean Dipole to greenhouse warming. Nat. Geosci. 6, 999–1007 (2013).
Cai, W. et al. Increased frequency of extreme Indian Ocean Dipole events due to greenhouse warming. Nature 510, 254–258 (2014).
Cai, W. et al. Increasing frequency of extreme El Niño events due to greenhouse warming. Nat. Clim. Change 4, 111–116 (2014).
Annamalai, H., Potemra, J., Murtugudde, R. & McCreary, J. P. Effect of preconditioning on the extreme climate events in the tropical Indian Ocean. J. Clim. 18, 3450–3469 (2005).
Ummenhofer, C. C., Biastoch, A. & Böning, C. W. Multidecadal Indian Ocean variability linked to the Pacific and implications for preconditioning Indian Ocean dipole events. J. Clim. 30, 1739–1751 (2017).
Feng, M., Benthuysen, J., Zhang, N. & Slawinski, D. Freshening anomalies in the Indonesian throughflow and impacts on the Leeuwin Current during 2010–2011. Geophys. Res. Lett. 42, 8555–8562 (2015).
Llovel, W. & Lee, T. Importance and origin of halosteric contribution to sea level change in the southeast Indian Ocean during 2005–2013. Geophys. Res. Lett. 42, 1148–1157 (2015). Highlights the importance of halosteric effects to observed twenty-first century sea level changes in the south-eastern Indian Ocean.
Hu, S. & Sprintall, J. Observed strengthening of interbasin exchange via the Indonesian seas due to rainfall intensification. J. Geophys. Res. 44, 1448–1456 (2017). Demonstrates how observed rainfall changes over the Maritime Continent contributed to an intensification of the Indonesian throughflow transport since the early 2000s.
Yu, L. Global variations in oceanic evaporation (1958–2005): The role of the changing wind speed. J. Clim. 20, 5376–5390 (2007).
Pall, P. et al. Anthropogenic greenhouse gas contribution to flood risk in England and Wales in autumn 2000. Nature 470, 382–385 (2011).
Lehmann, J., Coumou, D. & Frieler, K. Increased record-breaking precipitation events under global warming. Clim. Change 132, 501–515 (2015).
Meredith, E. P., Semenov, V. A., Maraun, D., Park, W. & Chernokulsky, A. V. Crucial role of Black Sea warming in amplifying the 2012 Krymsk precipitation extreme. Nat. Geosci. 8, 615–619 (2015).
Trenberth, K. E., Fasullo, J. T. & Shepherd, T. G. Attribution of climate extreme events. Nat. Clim. Change 5, 725–730 (2015).
Ummenhofer, C. C. et al. How did ocean warming affect Australian rainfall extremes during the 2010/2011 La Niña event? Geophys. Res. Lett. 42, 9942–9951 (2015).
Fowler, H. J. et al. Anthropogenic intensification of short-duration rainfall extremes. Nat. Rev. Earth Environ. 2, 107–122 (2021).
Meehl, G. A. et al. Initialized Earth System prediction from subseasonal to decadal timescales. Nat. Rev. Earth Environ. 2, 340–357 (2021).
Findell, K. L. et al. Rising temperatures increase importance of oceanic evaporation as a source for continental precipitation. J. Clim. 32, 7713–7726 (2019).
Gimeno, L., Nieto, R. & Son, R. The growing importance of oceanic moisture sources for continental precipitation. NPJ Clim. Atmos. Sci. 3, 27 (2020).
Schott, F. A., Xie, S.-P. & McCreary, J. Indian Ocean circulation and climate variability. Rev. Geophys. 47, RG1002 (2009). Reviews the state of knowledge of Indian Ocean circulation and climate variability across a range of timescales (seasonal, interannual and decadal).
Sprintall, J., Wijffels, S. E., Molcard, R. & Jaya, I. Direct estimates of the Indonesian Throughflow entering the Indian Ocean: 2004–2006. J. Geophys. Res. 114, C07001 (2009).
Wijffels, S. E., Meyers, G. M. & Godfrey, J. S. A 20-yr average of the Indonesian Throughflow: Regional currents and the interbasin exchange. J. Phys. Oceanogr. 38, 1965–1978 (2008).
Wyrtki, K. Indonesian through flow and the associated pressure gradient. J. Geophys. Res. 92, 12941–12946 (1987).
Andersson, H. C. & Stigebrandt, A. Regulation of the Indonesian throughflow by baroclinic draining of the North Australian Basin. Deep. Sea Res. I 52, 2214–2233 (2005).
Gordon, A. L. et al. South China Sea throughflow impact on the Indonesian throughflow. Geophys. Res. Lett. 39, L11602 (2012).
Hu, S. & Sprintall, J. Interannual variability of the Indonesian Throughflow: The salinity effect. J. Geophys. Res. 121, 2596–2615 (2016).
Sprintall, J. et al. Detecting change in the Indonesian seas. Front. Marine Sci. 6, 257 (2019). Reviews the current status of ocean observing systems and modelling to quantify changes in the heat and freshwater in the Indonesian seas and provides specific recommendations for observations needed to advance this goal.
Adler, R. F., Gu, G., Sapiano, M., Wang, J. J. & Huffman, G. J. Global precipitation: Means, variations and trends during the satellite era (1979–2014). Surv. Geophys. 38, 679–699 (2017).
Yang, J., Liu, Q. & Liu, Z. Linking observations of the Asian monsoon to the Indian Ocean SST: Possible roles of Indian Ocean Basin mode and dipole mode. J. Clim. 23, 5889–5902 (2010).
Sengupta, D., Raj, G. N. B. & Shenoi, S. S. C. Surface freshwater from Bay of Bengal runoff and Indonesian throughflow in the tropical Indian Ocean. Geophys. Res. Lett. 33, L22609 (2006).
Mahadevan, A., Paluszkiewicz, T., Ravichandran, M., Sengupta, D. & Tandon, A. Introduction to the special issue on the Bay of Bengal: From monsoons to mixing. Oceanogr. 29, 14–17 (2016).
Mahadevan, A. et al. Freshwater in the Bay of Bengal: Its fate and role in air-sea heat exchange. Oceanogr. 29, 72–81 (2016).
Hu, S. et al. Interannual to decadal variability of upper-ocean salinity in the southern Indian Ocean and the role of the Indonesian throughflow. J. Clim. 32, 6403–6421 (2019).
Gordon, A. L. Interocean exchange of thermocline water. J. Geophys. Res. 91, 5037–5046 (1986).
Talley, L. D. & Sprintall, J. Deep expression of the Indonesian Throughflow: Indonesian intermediate water in the South Equatorial Current. J. Geophys. Res. 110, C10009 (2005).
Zhai, P., Bower, A. S., Smethie, W. M. Jr & Pratt, L. J. Formation and spreading of Red Sea Outflow Water in the Red Sea. J. Geophys. Res. 120, 6542–6563 (2015).
Bindoff, N. L. et al. in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change Ch. 10 (eds Stocker, T. F. et al.) 867–952 (Cambridge Univ. Press, 2013).
Seager, R., Naik, N. & Vecchi, G. A. Thermodynamic and dynamic mechanisms for large-scale changes in the hydrological cycle in response to global warming. J. Clim. 23, 4651–4668 (2010).
IPCC. in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (eds Stocker, T. F. et al.) 3–29 (Cambridge Univ. Press, 2013).
Smith, T. M., Arkin, P. A., Ren, L. & Shen, S. S. P. Improved reconstruction of global precipitation since 1900. J. Atmos. Ocean. Technol. 29, 1505–1517 (2012).
DeAngelis, A. M., Qu, X., Zelinka, M. D. & Hall, A. An observational radiative constraint on hydrologic cycle intensification. Nature 528, 249–253 (2015).
Xie, S.-P. et al. Global warming pattern formation: sea surface temperature and rainfall. J. Clim. 23, 966–986 (2010).
Li, G., Xie, S.-P., Du, Y. & Luo, Y. Effects of excessive equatorial cold tongue bias on the projections of tropical Pacific climate change. Part I: The warming pattern in CMIP5 multi-model ensemble. Clim. Dyn. 47, 3817–3831 (2016).
Cai, W. et al. Pantropical climate interactions. Science 363, eaav4236 (2019).
Dong, L. & McPhaden, M. J. Why has the relationship between Indian and Pacific Ocean decadal variability changed in recent decades? J. Clim. 30, 1971–1983 (2017).
Vecchi, G. A. et al. Weakening of tropical Pacific atmospheric circulation due to anthropogenic forcing. Nature 441, 73–76 (2006).
Vecchi, G. A. & Soden, B. J. Global warming and the weakening of the tropical circulation. J. Clim. 20, 4316–4340 (2007).
Newman, M. Winds of change. Nat. Clim. Change 3, 538–539 (2013).
Deser, C., Phillisp, A. S. & Alexander, M. A. Twentieth century tropical sea surface temperature trends revisited. Geophys. Res. Lett. 37, L10701 (2010).
Tokinaga, H., Xie, S.-P., Deser, C., Kosaka, Y. & Okumura, Y. M. Slowdown of the Walker circulation driven by tropical Indo-Pacific warming. Nature 491, 439–443 (2012).
Roxy, M. K., Ritika, K., Terray, P. & Masson, S. The curious case of Indian Ocean warming. J. Clim. 27, 8501–8509 (2014).
Cai, W., Sullivan, A. & Cowan, T. Shoaling of the off-equatorial south Indian Ocean thermocline: Is it driven by anthropogenic forcing? Geophys. Res. Lett. 35, L12711 (2008).
L’Heureux, M., Lee, S. & Lyon, B. Recent multidecadal strengthening of the Walker circulation across the tropical Pacific. Nat. Clim. Change 3, 571–576 (2013).
England, M. H. et al. Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus. Nat. Clim. Change 4, 222–227 (2014).
Merrifield, M. A., Thompson, P. R. & Lander, M. Multidecadal sea level anomalies and trends in the western tropical Pacific. Geophys. Res. Lett. 39, L13602 (2012).
Karnauskas, K. B., Seager, R., Kaplan, A., Kushnir, Y. & Cane, M. A. Observed strengthening of the zonal sea surface temperature gradient across the equatorial Pacific Ocean. J. Clim. 22, 4316–4321 (2009).
Meng, Q. et al. Twentieth century Walker circulation change: data analysis and model experiments. Clim. Dyn. 38, 1757–1773 (2012).
Solomon, A. & Newman, M. Reconciling disparate twentieth-century Indo-Pacific ocean temperature trends in the instrumental record. Nat. Clim. Change 2, 691–699 (2012).
Seager, R. et al. Strengthening tropical Pacific zonal sea surface temperature gradient consistent with rising greenhouse gases. Nat. Clim. Change 9, 517–522 (2019).
Zhang, L. et al. Indian Ocean warming trend reduces Pacific warming response to anthropogenic greenhouse gases: An interbasin thermostat mechanism. Geophys. Res. Lett. 46, 10,882–10,890 (2019).
Heede, U. K., Fedorov, A. V. & Burls, N. J. Time scales and mechanisms for the tropical Pacific response to global warming: A tug of war between the ocean thermostat and weaker Walker. J. Clim. 33, 6101–6118 (2020).
Medhaug, I. et al. Reconciling controversies about the ‘global warming hiatus’. Nature 545, 41–47 (2017).
Bindoff, N. L. et al. in IPCC Special Report on the Ocean and Cryosphere in a Changing Climate Ch. 5 (eds Pörtner, H.-O. et al.) 447–458 (Cambridge Univ. Press, 2019).
Feng, M. et al. The reversal of the multi-decadal trends of the equatorial Pacific easterly winds, and the Indonesian Throughflow and Leeuwin Current transports. Geophys. Res. Lett. 38, L11604 (2011).
Vialard, J. Hiatus heat in the Indian Ocean. Nat. Geosci. 8, 423–424 (2015).
Han, W. et al. Decadal variability of the Indian and Pacific Walker cells since the 1960s: Do they covary on decadal time scales? J. Clim. 30, 8447–8468 (2017).
Han, Z., Su, T., Zhang, Q., Wen, Q. & Feng, G. Thermodynamic and dynamic effects of increased moisture sources over the tropical Indian Ocean in recent decades. Clim. Dyn. 53, 7081–7096 (2019).
Dong, L. & McPhaden, M. J. Interhemispheric SST gradient trends in the Indian Ocean prior to and during the recent global warming hiatus? J. Clim. 29, 9077–9095 (2016).
Liu, W., Xie, S.-P. & Lu, J. Tracking ocean heat uptake during the surface warming hiatus. Nat. Commun. 7, 10926 (2016).
Li, Y. et al. Multidecadal changes of the upper Indian Ocean heat content during 1965–2016. J. Clim. 31, 7863–7884 (2020).
Jin, X. et al. Influences of Pacific climate variability on decadal subsurface ocean heat content variations in the Indian Ocean. J. Clim. 31, 4154–4174 (2018).
Ren, L., Arkin, P., Smith, T. M. & Shen, S. S. P. Global precipitation trends in 1900–2005 from a reconstruction and coupled model simulations. J. Geophys. Res. 118, 1679–1689 (2013).
Vinayachandran, P. N. & Yamagata, T. Monsoon response of the sea around Sri Lanka: generation of thermal domes and anticyclonic vortices. J. Phys. Oceanogr. 28, 1946–1960 (1997).
Burns, J. M. et al. On the dynamics of the Sri Lanka Dome in the Bay of Bengal. J. Geophys. Res. 122, 7737–7750 (2017).
Du, Y. et al. Decadal trends of the upper ocean salinity in the tropical Indo-Pacific since mid-1990s. Sci. Rep. 5, 16050 (2015).
Li, G. et al. Examining the salinity change in the upper Pacific Ocean during the Argo period. Clim. Dyn. 53, 6055–6074 (2019).
Sprintall, J. et al. The Indonesian seas and their role in the coupled ocean–climate system. Nat. Geosci. 7, 487–492 (2014).
Lee, T., Fournier, S., Gordon, A. L. & Sprintall, J. Maritime Continent water cycle regulates low-latitude chokepoint of global ocean circulation. Nat. Commun. 10, 2103 (2019). Using in situ and remotely sensed observations, demonstrates the importance of local contributions to the Maritime Continent freshwater balance on seasonal timescales and their implications for Indonesian throughflow transport.
Hartmann, D. L. et al. in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change Ch. 2 (eds Stocker, T. F. et al.) 159–254 (Cambridge Univ. Press, 2013).
Phillips, H. E., Wijffels, S. E. & Feng, M. Interannual variability in the freshwater content of the Indonesian-Australian Basin. Geophys. Res. Lett. 32, L03603 (2005).
Cheng, L. et al. Improved estimates of ocean heat content from 1960 to 2015. Sci. Adv. 3, e1601545 (2017).
Li, Y., Han, W. & Zhang, L. Enhanced decadal warming of the southeast Indian Ocean during the recent global surface warming slowdown. Geophys. Res. Lett. 44, 9876–9884 (2017).
Zhou, X., Alves, O., Marsland, S. J., Bi, D. & Hirst, A. C. Multi-decadal variations of the South Indian Ocean subsurface temperature influenced by Pacific Decadal Oscillation. Tellus 69, 1308055 (2017).
Gruenburg, L. K. & Gordon, A. L. Variability in Makassar Strait heat flux and its effect on the eastern tropical Indian Ocean. Oceanography 31, 80–87 (2018).
Zhang, L., Du, Y. & Cai, W. Low-frequency variability and the unusual Indian Ocean Dipole events in 2015 and 2016. Geophys. Res. Lett. 45, 1040–1048 (2018).
Volkov, D. L., Lee, S.-K., Gordon, A. L. & Rudko, M. Unprecedented reduction and quick recovery of the South Indian Ocean heat content and sea level in 2014–2018. Sci. Adv. 6, eabc1151 (2020).
Gordon, A. L. et al. Makassar Strait throughflow seasonal and interannual variability: An overview. J. Geophys. Res. 124, 3724–3736 (2019).
Pujiana, K., McPhaden, M. J., Gordon, A. L. & Napitu, A. M. Unprecedented response of Indonesian throughflow to anomalous Indo-Pacific climatic forcing in 2016. J. Geophys. Res. 124, 3737–3754 (2019).
Liu, Q.-Y., Feng, M., Wang, D. & Wijffels, S. Interannual variability of the Indonesian Throughflow transport: A revisit based on 30 year expendable bathythermograph data. J. Geophys. Res. 120, 8270–8282 (2015).
Feng, M., Zhang, N., Liu, Q. & Wijffels, S. The Indonesian throughflow, its variability and centennial change. Geosci. Lett. 5, 3 (2018).
Li, Y., Han, W., Wang, F., Zhang, L. & Duan, J. Vertical structure of the upper–Indian Ocean thermal variability. J. Clim. 33, 7233–7253 (2020).
Hamlington, B. D., Leben, R. R., Strassburg, M. W., Nerem, R. S. & Kim, K.-Y. Contribution of the Pacific Decadal Oscillation to global mean sea level trends. Geophys. Res. Lett. 40, 50950 (2013).
Hamlington, B. D. et al. Uncovering an anthropogenic sea-level rise signal in the Pacific Ocean. Nat. Clim. Change 4, 782–785 (2014).
Palanisamy, H. et al. Regional sea level variability, total relative sea level rise and its impacts on islands and coastal zones of Indian Ocean over the last sixty years. Glob. Planet. Change 116, 54–67 (2014).
Hamlington, B. D. et al. An ongoing shift in Pacific Ocean sea level. J. Geophys. Res. 121, 5084–5097 (2016).
Deepa, J. S. et al. The tropical Indian Ocean decadal sea level response to the Pacific decadal oscillation forcing. Clim. Dyn. 52, 5045–5058 (2019).
Jyoti, J., Swapna, P., Krishnan, R. & Naidu, C. V. Pacific modulation of accelerated south Indian Ocean sea level rise during the early 21st Century. Clim. Dyn. 53, 4413–4432 (2019).
Gopika, S. J. et al. Aliasing of the Indian Ocean externally-forced warming spatial pattern by internal climate variability. Clim. Dyn. 54, 1093–1111 (2020).
Lee, T. & McPhaden, M. J. Decadal phase change in large-scale sea level and winds in the Indo-Pacific region at the end of the 20th century. Geophys. Res. Lett. 35, L01605 (2008).
Feng, M., McPhaden, M. J. & Lee, T. Decadal variability of the Pacific subtropical cells and their influence on the southeast Indian Ocean. Geophys. Res. Lett. 37, L09606 (2010).
Song, Q., Gordon, A. L. & Visbeck, M. Spreading of the Indonesian throughflow in the Indian Ocean. J. Phys. Oceanogr. 34, 772–792 (2004).
Tozuka, T., Yokoi, T. & Yamagata, T. A modeling study of interannual variations of the Seychelles Dome. J. Geophys. Res. 115, C04005 (2010).
Birol, F. & Morrow, R. Source of the baroclinic waves in the southeast Indian Ocean. J. Geophys. Res. 106, 9145–9160 (2001).
Gruenburg, L. K. Indonesian Throughflow Heat Transport, and Spreading Within the Eastern Tropical Indian Ocean. Doctoral thesis, Lamont-Doherty Earth Observatory, Columbia Univ. (2021).
Li, Y., Han, W., Hu, A., Meehl, G. A. & Wang, F. Multidecadal changes of the upper Indian Ocean heat content during 1965–2016. J. Clim. 31, 7863–7884 (2018).
Ummenhofer, C. C. et al. Late 20th century Indian Ocean heat content gain masked by wind forcing. Geophys. Res. Lett. 47, e2020GL088692 (2020). Details the relative contribution of wind and buoyancy forcing for multi-decadal Indian Ocean heat content changes of the past 60 years, as well as spatial patterns and depth structure of upper-ocean temperature changes.
Tierney, J. E. et al. Tropical sea surface temperatures for the past four centuries reconstructed from coral archives. Paleoceanography 30, 226–252 (2015).
Abram, N. J. et al. Early onset of industrial-era warming across the oceans and continents. Nature 536, 411–418 (2016).
Abram, N. J. et al. Paleoclimate perspectives on the Indian Ocean Dipole. Quat. Sci. Rev. 237, 106302 (2020). Reviews the state of knowledge of the Indian Ocean Dipole from a palaeoclimatic perspective based on observations, proxies and climate model simulations.
Charles, C. D., Cobb, K., Moore, M. D. & Fairbanks, R. G. Monsoon–tropical ocean interaction in a network of coral records spanning the 20th century. Mar. Geol. 201, 207–222 (2003).
Nurhati, I. S., Cobb, K. M. & Di Lorenzi, E. Decadal-scale SST and salinity variations in the central tropical Pacific: Signatures of natural and anthropogenic climate change. J. Clim. 24, 3294–3308 (2011).
Osborne, M. C., Dunbar, R. B., Mucciarone, D. A., Druffel, E. & Sanchez-Cabeza, J.-A. A 215-yr coral δ18O time series from Palau records dynamics of the West Pacific Warm Pool following the end of the Little Ice Age. Coral Reefs 33, 719–731 (2014).
Ramos, R. D., Goodkin, N. F. & Fan, T.-Y. Coral records at the northern edge of the Western Pacific Warm Pool reveal multiple drivers of sea surface temperature, salinity, and rainfall variability since the end of the Little Ice Age. Paleoceanogr. Paleoclimatol. 35, e2019PA003826 (2020).
Meehl, G. A. et al. in Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change Ch. 10 (eds Solomon S. et al.) 747–846 (Cambridge Univ. Press, 2007).
Tudhope, A. W. et al. Recent changes in climate in the far western equatorial Pacific and their relationship to the Southern Oscillation: oxygen isotope records from massive corals, Papua New Guinea. Earth Planet. Sci. Lett. 136, 575–590 (1995).
McGregor, H. V. & Gagan, M. K. Western Pacific coral δ18O records of anomalous Holocene variability in the El Niño–Southern Oscillation. Geophys. Res. Lett. 31, L11204 (2004).
Asami, R., Quinn, T. M., Meyer, C. P. & Paulay, G. Interannual and decadal variability of the western Pacific sea surface condition for the years 1787–2000: Reconstruction based on stable isotope record from a Guam coral. J. Geophys. Res. 110, C05018 (2005).
Quinn, T. M., Taylor, F. W. & Crowley, T. J. Coral-based climate variability in the Western Pacific Warm Pool since 1867. J. Geophys. Res. 111, C11006 (2006).
Wu, H. C. & Grottoli, A. G. Stable oxygen isotope records of corals and a sclerosponge in the Western Pacific warm pool. Coral Reefs 29, 413–418 (2010).
Hereid, K. A. et al. Coral record of reduced El Niño activity in the early 15th to middle 17th centuries. Geology 41, 51–54 (2013).
Ramos, R. D., Goodkin, N. F., Siringan, F. P. & Hughen, K. A. Diploastrea heliopora Sr/Ca and δ18O records from northeast Luzon, Philippines: An assessment of interspecies coral proxy calibrations and climate controls of sea surface temperature and salinity. Paleoceanography 32, 424–438 (2017).
Ramos, R. D., Goodkin, N. F., Siringan, F. P. & Hughen, K. A. Coral records of temperature and salinity in the Tropical Western Pacific reveal influence of the Pacific Decadal Oscillation since the late nineteenth century. Paleoceanogr. Paleoclimatol. 34, 1344–1358 (2019).
Linsley, B. K. et al. SPCZ zonal events and downstream influence on surface ocean conditions in the Indonesian Throughflow region. Geophys. Res. Lett. 44, 293–303 (2017).
Murty, S. A. et al. Climatic influences on southern Makassar Strait salinity over the past century. Geophys. Res. Lett. 44, 11967–11975 (2017).
Murty, S. A., Goodkin, N. F., Wiguna, A. A. & Gordon, A. L. Variability in coral-reconstructed sea surface salinity between the northern and southern Lombok Strait linked to East Asian Winter Monsoon mean state reversals. Paleoceaongr. Paleoclimatol. 33, 1116–1133 (2018).
Cahyarini, S. Y. et al. Twentieth century sea surface temperature and salinity variations at Timor inferred from paired coral δ18O and Sr/Ca measurements. J. Geophys. Res. 119, 4593–4604 (2014).
Hennekam, R. et al. Cocos (Keeling) corals reveal 200 years of multidecadal modulation of southeast Indian Ocean hydrology by Indonesian throughflow. Paleoceanogr. Paleoclimatol. 33, 48–60 (2018).
Meyers, G., McIntosh, P., Pigot, L. & Pook, M. The years of El Niño, La Niña, and interactions with the tropical Indian Ocean. J. Clim. 20, 2872–2880 (2007).
Yang, Y. Seasonality and predictability of the Indian Ocean Dipole mode: ENSO forcing and internal variability. J. Clim. 28, 8021–8036 (2015).
Zhang, W., Wang, Y., Jin, F.-F., Stuecker, M. F. & Turner, A. G. Impact of different El Niño types on the El Niño/IOD relationship. Geophys. Res. Lett. 42, 8570–8576 (2015).
Stuecker, M. F. et al. Revisiting ENSO/Indian Ocean Dipole phase relationships. Geophys. Res. Lett. 44, 2481–2492 (2017).
Nakamura, N. et al. Mode shift in the Indian Ocean climate under global warming stress. Geophys. Res. Lett. 36, L23708 (2009).
Johnson, G. C. & Lyman, J. M. Warming trends increasingly dominate global ocean. Nat. Clim. Change 10, 757–761 (2020).
Palmer, M. D. et al. Adequacy of the ocean observation system for quantifying regional heat and freshwater storage and change. Front. Marine Sci. 6, 416 (2019). Reviews the current status of ocean observing systems to quantify heat and freshwater changes across spatial and temporal scales.
Yu, L. et al. The global water cycle from atmospheric reanalysis, satellite, and ocean salinity. J. Clim. 30, 3829–3852 (2017).
The Climate Change Initiative Coastal Sea Level Team Coastal sea level anomalies and associated trends from Jason satellite altimetry over 2002–2018. Sci. Data 7, 357 (2020).
Rio, M.-H. & Hernandez, F. A mean dynamic topography computed over the world ocean from altimetry, in situ measurements, and a geoid model. J. Geophys. Res. 109, C12032 (2004).
Maximenko, N. et al. Mean dynamic topography of the ocean derived from satellite and drifting buoy data using three different techniques. J. Atmos. Ocean. Technol. 26, 1910–1919 (2009).
Rio, M. H., Guinehut, S. & Larnicol, G. New CNES-CLS09 global mean dynamic topography computed from the combination of GRACE data, altimetry, and in situ measurements. J. Geophys. Res. 116, C07018 (2011).
Sen Gupta, A. et al. Climate drift in the CMIP5 models. J. Clim. 26, 8597–8615 (2013).
Jourdain, N. C. et al. The Indo-Australian monsoon and its relationship to ENSO and IOD in reanalyses and the CMIP3/CMIP5 simulations. Clim. Dyn. 41, 3073–3102 (2013).
Raghavan, S. V. et al. Assessment of CMIP5 historical simulations of rainfall over Southeast Asia. Theor. Appl. Climatol. 132, 989–1002 (2018).
Toh, Y. Y. et al. Maritime Continent seasonal climate biases in AMIP experiments of the CMIP5 multimodel ensemble. Clim. Dyn. 50, 777–800 (2018).
Pathak, R. et al. Precipitation biases in CMIP5 models over the south Asian region. Sci. Rep. 9, 9589 (2019).
Pfeiffer, M. et al. 20th century δ18O seawater and salinity variations reconstructed from paired δ18O and Sr/Ca measurements of a La Reunion coral. Paleoceanogr. Paleoclimatol. 34, 2183–2200 (2019).
Sanchez, S. C., Hakim, G. J. & Saenger, C. P. Climate model teleconnection patterns govern the Niño-3.4 response to early nineteenth-century volcanism in coral-based data assimilation reconstructions. J. Clim. 34, 1863–1880 (2021).
Chan, D. et al. Correcting datasets leads to more homogeneous early-twentieth-century sea surface warming. Nature 571, 393–397 (2019).
LeGrande, A. N. & Schmidt, G. A. Global gridded data set of the oxygen isotopic composition in seawater. Geophys. Res. Lett. 33, L12604 (2006).
Breitkreuz, C. et al. A dynamical reconstruction of the global monthly mean oxygen isotopic composition of seawater. J. Geophys. Res. 123, 7206–7219 (2018).
Durgadoo, J. V. et al. Indian Ocean sources of Agulhas leakage. J. Geophys. Res. 122, 3481–3499 (2017).
van Sebille, E. et al. Pacific-to-Indian Ocean connectivity: Tasman leakage, Indonesian Throughflow, and the role of ENSO. J. Geophys. Res. 119, 1365–1382 (2014).
Gordon, A. L. et al. Advection and diffusion of Indonesian throughflow water within the Indian Ocean South Equatorial Current. Geophys. Res. Lett. 24, 2573–2576 (1997).
McPhaden, M. J. et al. RAMA: The research moored array for African–Asian–Australian monsoon analysis and prediction. Bull. Am. Meteorol. Soc. 90, 459–480 (2009).
Kummerow, C. et al. The status of the Tropical Rainfall Measuring Mission (TRMM) after two years in orbit. J. Appl. Meteorol. 39, 1965–1982 (2000).
Boutin, J. et al. New SMOS sea surface salinity with reduced systematic errors and improved variability. Remote Sens. Environ. 214, 115–134 (2018).
Huang, B. et al. Improvements of the daily optimum interpolation sea surface temperature (DOISST) version 2.1. J. Clim. 34, 2923–2939 (2020).
AVISO. AVISO Level 4 Absolute Dynamic Topography for Climate Model Comparison. Version 1. (PO.DAAC, 2011).
Yu, L., Jin, X. & Weller, R. A. Multidecade global flux datasets from the Objectively Analyzed Air-Sea Fluxes (OAFlux) Project: Latent and sensible heat fluxes, ocean evaporation, and related surface meteorological variables. Woods Hole Oceanographic Institution, OAFlux Project Technical Report (OA-2008-01), 64 pp (2008).
Dee, D. P. et al. The ERA-Interim reanalysis: Configuration and performance of the data assimilation system. Q. J. R. Meteorol. Soc. 137, 553–597 (2011).
Zuo, H., Balmaseda, M. A., Tietsche, S., Mogensen, K. & Mayer, M. The ECMWF operational ensemble reanalysis–analysis system for ocean and sea ice: a description of the system and assessment. Ocean Sci. 15, 779–808 (2019).
Adler, R. F. et al. The version-2 global precipitation climatology project (GPCP) monthly precipitation analysis (1979–present). J. Hydrometeorol. 4, 1147–1167 (2003).
Rayner, N. A. et al. Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J. Geophys. Res. 108, 4407 (2003).
Huang, B. et al. Extended reconstructed sea surface temperature, version 5 (ERSSTv5): Upgrades, validations, and intercomparisons. J. Clim. 30, 8179–8205 (2017).
Xie, P. & Arkin, P. A. Global precipitation: a 17-year monthly analysis based on gauge observations, satellite estimates, and numerical model outputs. Bull. Am. Meteorol. Soc. 78, 2539–2558 (1997).
Fore, A. G., Yueh, S. H., Tang, W., Stiles, B. W. & Hayashi, A. K. Combined active/passive retrievals of ocean vector wind and sea surface salinity with SMAP. IEEE Trans. Geosci. Remote Sens. 54, 7396–7404 (2016).
Ren, H. et al. 21st-century rise in anthropogenic nitrogen deposition on a remote coral reef. Science 356, 749–752 (2017).
Rixen, T. et al. Impact of monsoon-driven surface ocean processes on a coral off Port Blair on the Andaman Islands and their link to North Atlantic climate variations. Glob. Planet. Change 75, 1–13 (2011).
Abram, N. J. et al. Optimized coral reconstructions of the Indian Ocean Dipole: An assessment of location and length considerations. Paleoceanography 30, 1391–1405 (2015).
Gagan, M. K. et al. Coral 13C/12C records of vertical seafloor displacement during megathrust earthquakes west of Sumatra. Earth Planet. Sci. Lett. 432, 461–471 (2015).
Henley, B. J. et al. A tripole index for the interdecadal Pacific oscillation. Clim. Dyn. 45, 3077–3090 (2015).
Buckley, B. M. et al. Interdecadal Pacific Oscillation reconstructed from trans-Pacific tree rings: 1350–2004 CE. Clim. Dyn. 53, 3181–3196 (2019).
Reul, N. et al. Sea surface salinity estimates from spaceborne L-band radiometers: An overview of the first decade of observation (2010–2019). Remote Sens. Environ. 242, 111769 (2020).
Adler, R. F. et al. The Global Precipitation Climatology Project (GPCP) monthly analysis (new version 2.3) and a review of 2017 global precipitation. Atmosphere 9, 138 (2018).
Huffman, G. J. et al. The TRMM Multisatellite Precipitation Analysis (TMPA): Quasi-global, multiyear, combined-sensor precipitation estimates at fine scales. J. Hydrometeorol. 8, 38–55 (2007).
Boutin, J. et al. Satellite and in situ salinity: understanding near-surface stratification and subfootprint variability. Bull. Am. Meteorol. Soc. 97, 1391–1407 (2016).
Reynolds, R. W. et al. Daily high-resolution-blended analyses for sea surface temperature. J. Clim. 20, 5473–5496 (2007).
Grottoli, A. G. & Eakin, C. M. A review of modern coral δ18O and Δ14C proxy records. Earth-Sci. Rev. 81, 67–91 (2007).
Dunbar, R. B. & Wellington, G. M. Stable isotopes in a branching coral monitor seasonal temperature variation. Nature 293, 453–455 (1981).
Urey, H. C. The thermodynamic properties of isotopic substances. J. Chem. Soc. https://doi.org/10.1039/JR9470000562 (1947).
Lough, J. M. & Cantin, N. E. Perspectives on massive coral growth rates in a changing ocean. Biol. Bull. 226, 187–202 (2014).
Trenberth, K. E. & Olson, J. G. An evaluation and intercomparison of global analyses from the National Meteorological Center and the European Centre for Medium Range Weather Forecasts. Bull. Am. Meteorol. Soc. 69, 1047–1057 (1988).
Parker, W. S. Reanalyses and observations: What’s the difference? Bull. Am. Meteorol. Soc. 97, 1565–1572 (2016).
Stammer, D., Balmaseda, M., Heimbach, P., Köhl, A. & Weaver, A. Ocean data assimilation in support of climate applications: Status and perspectives. Annu. Rev. Mar. Sci. 8, 491–518 (2016).
IPCC. Annex I: Glossary. In Global Warming of 1.5°C. An IPCC Special Report on the Impacts of Global Warming of 1.5°C above pre-Industrial levels and Related Global Greenhouse Gas Emission Pathways, in the Context of Strengthening the Global Response to the Threat of Climate Change, Sustainable Development, and Efforts to Eradicate Poverty (eds Matthews, J. B. R.) (IPCC, 2018)
Li, Y. et al. Assessing the role of the ocean–atmosphere coupling frequency in the western Maritime Continent rainfall. Clim. Dyn. 54, 4935–4952 (2020).
Acknowledgements
This work was supported by the US National Science Foundation under AGS-2002083 (to S.A.M. and C.C.U.), ICER-1663704 (to C.C.U.) and OCE-1851316 (to J.S.). C.C.U. also acknowledges support from the Andrew W. Mellon Foundation Award for Innovative Research and the James E. and Barbara V. Moltz Fellowship for Climate-Related Research, S.A.M. from the WHOI Postdoctoral Scholar Program and N.J.A. from the Australian Research Council through the Centre of Excellence for Climate Extremes (CE170100023) and a Future Fellowship (FT160100029). Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Graphic support from N. Renier (WHOI Graphics) is gratefully acknowledged.
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C.C.U. and S.A.M. conducted the analyses and produced the figures. C.C.U., S.A.M., J.S., T.L. and N.J.A. wrote sections within the manuscript. All authors contributed to the discussion and commented on the manuscript.
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Glossary
- Indo-Pacific warm pool
-
(IPWP). Region at the intersection of the Indian and Pacific oceans, defined as the area with annual sea surface temperature above 28 °C (Fig. 1b), coinciding with the rising branch of the Walker circulation.
- Ocean heat content
-
(OHC). The quantity of heat stored in the ocean, proportional to temperature integrated vertically over a prescribed depth range.
- Internal variability
-
Climate variability that arises due to natural processes or interactions between various components of the climate system, as opposed to anthropogenic or external forcing.
- Modes of variability
-
Natural, recurrent climate phenomena with an underlying space-time structure that displays a preferred spatial pattern and temporal variation in components of the climate system (e.g. ocean, atmosphere and cryosphere).
- Indian Ocean Dipole
-
(IOD). Coupled ocean–atmosphere phenomenon in the tropical Indian Ocean peaking in boreal fall, with its positive phase characterized by anomalous cooling (warming) in the tropical south-east (western) Indian Ocean.
- El Niño–Southern Oscillation
-
(ENSO). Strong year-to-year climate variability originating in the equatorial Pacific Ocean through coupled ocean–atmosphere interactions. El Niño–Southern Oscillation manifests itself in anomalous surface warming (El Niño) or cooling (La Niña) that typically peaks in boreal winter.
- Interdecadal Pacific oscillation
-
(IPO). Decadal mode of Pacific variability (similar to Pacific decadal oscillation) but with a meridionally broader tropical El Niño-like warm temperature anomaly pattern and cool extratropical Pacific during its positive phase.
- Thermocline
-
Zone of maximum vertical temperature gradient, separating warm and cold layers of water. The 20 °C isotherm is often used as an indicator of thermocline depth in the equatorial Indo-Pacific.
- Indonesian throughflow
-
(ITF). Ocean currents from the Pacific Ocean to the Indian Ocean through the passages of the Indonesian archipelago.
- Walker circulation
-
Thermally driven tropical zonal overturning atmospheric circulation associated with rising (sinking) air over the Indo-Pacific warm pool (eastern Pacific), undergoing substantial longitudinal shifts in location in response to the El Niño–Southern Oscillation, Indian Ocean Dipole, and Interdecadal Pacific Oscillation.
- Ekman transport
-
Lateral movement of water in the frictional boundary layer of a fluid, directed to the right or left of the wind in the Northern or Southern Hemisphere, respectively, because of the Coriolis force.
- Leeuwin Current
-
Poleward-flowing eastern boundary current off the west coast of Western Australia that transports relatively warm and fresh waters southward.
- Teleconnections
-
Changes in atmospheric or oceanic circulation over widely separated, geographically fixed spatial locations; often a consequence of large-scale wave motions, whereby energy is transferred from source regions along preferred atmospheric/oceanic paths.
- La Niña
-
The cold phase of the El Niño–Southern Oscillation, characterized by anomalous surface cooling and stronger trade winds in the equatorial Pacific Ocean.
- El Niño
-
The warm phase of the El Niño–Southern Oscillation, characterized by anomalous surface warming and weaker trade winds in the equatorial Pacific Ocean.
- Argo
-
International programme that collects subsurface ocean property measurements using a fleet of robotic instruments that profile between the surface and a mid-depth level (1,000–2,000 m) and then drift with the ocean currents.
- Geostrophic
-
Resulting from a balance between pressure gradients and the Coriolis force.
- Pycnocline
-
Layer in the ocean in which water density increases rapidly with depth.
- δ18O
-
Oxygen isotope composition in ‘delta’ notation, referring to relative departure of sample oxygen isotopic ratios 18O/16O compared with a standard. Coral calcium carbonate δ18O reflects combined sea surface temperature and seawater δ18O influences.
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Ummenhofer, C.C., Murty, S.A., Sprintall, J. et al. Heat and freshwater changes in the Indian Ocean region. Nat Rev Earth Environ 2, 525–541 (2021). https://doi.org/10.1038/s43017-021-00192-6
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DOI: https://doi.org/10.1038/s43017-021-00192-6
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