Abstract
The impact of the 2019 super positive Indian Ocean Dipole (PIOD) event, the strongest in the last four decades, which also co-occurred with an El Niño and a strong summer monsoon, on Indian Ocean sea surface salinity (SSS) is examined using the Soil Moisture Active Passive satellite measurements. Salt budget estimation suggests a predominant, nearly ocean-wide influence by surface freshwater flux and horizontal advective terms. Subsurface ocean influence on the salt budget occurs mainly in the southeastern tropical Indian Ocean (SETIO). The PIOD event suppressed the influence of the El Niño, thereby causing anomalous high precipitation in western India, and leading to an unusual freshening in the southeastern Arabian Sea (AS), which is subsequently advected towards the equatorial Indian Ocean (EIO). In the western Bay of Bengal (BoB), following the waning of monsoon-influenced precipitation in the fall, SSS becomes anomalously salty and traverses towards the AS against the flow of anomalous surface currents. During the peak of the summer monsoon in August–September and the peak of the PIOD event in September–November, SSS in the EIO exhibited tendency for freshening, mainly driven by westward advection of freshwater from the eastern BoB. Conversely, in the SETIO, there was tendency for salinification due to suppression of precipitation, enhanced upwelling of high subsurface salinity, and northward advection of salty water. During December to January of the following year, these salinity tendencies reversed, with salinification in the EIO and freshening in the SETIO.
Similar content being viewed by others
Data Availability
SMAP SSS data are available at https://smap.jpl.nasa.gov/data/. OISST data are available at https://www.ncei.noaa.gov/data/sea-surface-temperature-optimum-interpolation/v2.1/access/avhrr/. GPCP precipitation is downloaded from https://www.ncei.noaa.gov/data/global-precipitation-climatology-project-gpcp-daily/access/. SSH data are available at http://www.marine.copernicus.eu. ERA5 data is downloaded from https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-single-levels-monthly-means?tab=overview.
References
Akhil VP, Durand F, Lengaigne M, Vialard J, Keerthi MG, Gopalakrishna VV, Deltel C, Papa F, de Boyer MC (2014) A modeling study of the processes of surface salinity seasonal cycle in the Bay of Bengal. J Geophys Res Oceans 119:3926–3947
Akhil VP, Lengaigne M, Vialard J, Durand F, Keerthi MG, Chaitanya AVS, Papa F, Gopalakrishna VV, de Boyer MC (2016) A modeling study of processes controlling the Bay of Bengal sea surface salinity interannual variability. J Geophys Res Oceans 121:8471–8495
Anil N, Ramesh Kumar MR, Sajeev R, Saji PK (2016) Role of distinct flavors of IOD events on Indian summer monsoon. Nat Hazards 82(2):1317–1326
Ashok K, Guan Z, Yamagata T (2001) Impact of the Indian Ocean Dipole on the relationship between the Indian monsoon rainfall and ENSO. Geophys Res Lett 28(23):4499–4502
Ashok K, Guan ZY, Saji NH, Yamagata T (2004) Individual and combined influences of ENSO and the Indian Ocean Dipole on the Indian summer monsoon. J Clim 17:3141–3155
Behera SK, Ratnam JV (2018) Quasi-asymmetric response of the Indian summer monsoon rainfall to opposite phases of the IOD. Sci Rep 8:123. https://doi.org/10.1038/s41598-017-18396-6
Bingham FM, Lee T (2017) Space and time scales of sea surface salinity and freshwater forcing variability in the global ocean (60S-60N). J Geophys Res Oceans 122:2909–2922
Bonjean F, Lagerloef GSE (2002) Diagnostic model and analysis of the surface currents in the Tropical Pacific Ocean. J Phys Oceanogr 32(10):2938–2954
Cabanes C et al (2013) The CORA dataset: validation and diagnostics of in-situ ocean temperature and salinity measurements. Ocean Sci 9:1–18
Chaitanya AVS, Lengaigne M, Vialard J, Gopalakrishna VV, Durand F, Krantikumar C, Suneel V, Papa F, Ravichandran M (2014) Fishermen-operated salinity measurements reveal a “river in the sea” flowing along the east coast of India. Bull Am Meterol Soc 95:1897–1908
D’Addezio JM, Subrahmanyam B, Nyadjro ES, Murty VSN (2015) Seasonal variability of salinity and salt transports in the North Indian Ocean. J Phys Oceanogr 45(7):1947–1966
Dandapat S, Chakraborty A, Kuttippurath J (2018) Interannual variability and characteristics of the East India Coastal Current associated with Indian Ocean Dipole events using a high resolution regional ocean model. Ocean Dyn 68:1321–1334
de Boyer Montégut C, Madec G, Fischer AS, Lazar A, Iudicone D (2004) Mixed layer depth over the global ocean: an examination of profile data and a profile-based climatology. J Geophys Res 109:C12003. https://doi.org/10.1029/2004JC002378
Delcroix T, Henin C (1991) Seasonal and Interannual variations of the sea surface salinity in the tropical Pacific Ocean. J Geophys Res 96:22135–22150
Du Y, Qu T, Meyers G, Masumoto Y, Sasaki H (2005) Seasonal heat budget in the mixed layer of the southeastern tropical Indian Ocean in a high-resolution ocean general circulation model. J Geophys Res 110:C04012. https://doi.org/10.1029/2004JC002845
Du Y, Zhang Y, Zhang L.-Y, Tozuka T, Ng B, Cai W (2020) Thermocline warming induced extreme Indian Ocean dipole in 2019. Geophys Res Lett 47, e2020GL090079
Ducet N, Le Traon P-Y, Reverdin F (2000) Global high-resolution mapping of ocean circulation from TOPEX/Poseidon and ERS-1/2. J Geophys Res 105:19477–19498
Foltz GR, McPhaden MJ (2008) Seasonal mixed layer salinity balance of the tropical North Atlantic Ocean. J Geophys Res Oceans 113:C02013. https://doi.org/10.1029/2007JC004178
Fournier S, Vialard J, Lengaigne M, Lee T, Gierach MM, Chaitanya AVS (2017) Modulation of the Ganges-Brahmaputra River plume by the Indian Ocean dipole and eddies inferred from satellite observations. J Geophys Res Oceans 122:9591–9604
Gadgil S, Joseph PV, Joshi NV (1984) Ocean atmosphere coupling over monsoon regions. Nature 312:141–143
Gnanaseelan C, Deshpande A, McPhaden MJ (2012) Impact of Indian Ocean Dipole and El Niño/Southern oscillation wind-forcing on the Wyrtki jets. J Geophys Res 117:C08005. https://doi.org/10.1029/2012JC007918
Greaser SR, Subrahmanyam B, Trott CB, Roman-Stork HL (2020) Interactions between mesoscale eddies and synoptic oscillations in the Bay of Bengal during the strong monsoon of 2019. J Geophys Res 125:e2020JC016772. https://doi.org/10.1029/2020JC016772
Grodsky SA, Reul N, Bentamy A, Vandemark D, Guimbard S (2019) Eastern Mediterranean salinification observed in satellite salinity from SMAP mission. J Mar Syst 198:103190. https://doi.org/10.1016/j.jmarsys.2019.103190
Grunseich G, Subrahmanyam B, Murty VSN, Giese BS (2011) Sea surface salinity variability during the Indian Ocean Dipole and ENSO events in the tropical Indian Ocean. J Geophys Res 116:C11013. https://doi.org/10.1029/2011JC007456
Han W, McCreary JP (2001) Modeling salinity distributions in the Indian Ocean. J Geophys Res 106:859–877
Horii T, Ueki I, Ando K (2018) Coastal upwelling events along the southern coast of Java during the 2008 positive Indian Ocean Dipole. J Oceanogr 74:499–508
Horii T, Ueki I, Ando K (2020) Coastal upwelling events, salinity stratification, and barrier layer observed along the southwestern coast of Sumatra. J Geophys Res Oceans, 125, e2020JC016287
Hu S, Sprintall J (2016) Interannual variability of the Indonesian Throughflow: the salinity effect. J Geophys Res Oceans 121:2596–2615
Huffman GJ and Bolvin DT (2012) GPCP version 2.2 combined precipitation data set documentation, Lab. Atmos., NASA, Greenbelt, MD, USA. [Online]. Available: ftp://precip.gsfc.nasa.gov/pub/gpcp-v2.2/doc/V2.2_doc.pdf
Jensen TG (2001) Arabian Sea and Bay of Bengal exchange of salt and tracers in an ocean model. Geophys Res Lett 28:3967–3970
Jury MR (2019) Factors underlying changes in salinity around the southeastern Antilles. J Mar Syst 199:103208
Kido S, Tozuka T (2017) Salinity variability associated with the positive Indian Ocean dipole and its impact on the upper ocean temperature. J Clim 30(19):7885–7907
Li Y, Wang F, Han W (2013) Interannual sea surface salinity variations observed in the tropical North Pacific Ocean. Geophys Res Lett 40(10):2194–2199
Lu B, Ren H.-L (2020) What caused the extreme Indian Ocean Dipole event in 2019? Geophys Res Lett 47, e2020GL087768. https://doi.org/10.1029/2020GL087768
Masson S, Menkes C, Delecluse P, Boulanger J-P (2003) Impacts of salinity on the eastern Indian Ocean during the termination of the fall Wyrtki jet. J Geophys Res Oceans 108(C3):3067. https://doi.org/10.1029/2001JC000833
McCreary JP, Han W, Shankar D, Shetye SR (1996) Dynamics of the East India coastal current. Numerical solutions. J Geophys Res 101(C6): 13993–14000
McPhaden MJ, Nagura M (2014) Indian Ocean Dipole interpreted in terms of Recharge Oscillator theory. Clim Dyn 42:1569–1586
Mears CA, Scott J, Wentz FJ, Ricciardulli L, Leidner SM, Hoffman R, Atlas R (2019) A near-real-time version of the cross-calibrated multiplatform (CCMP) ocean surface wind velocity data set. J Geophys Res Oceans 124:6997–7010
Menezes VV (2020) Statistical assessment of sea-surface salinity from SMAP: Arabian Sea, Bay of Bengal, and a promising Red Sea application. Remote Sens 12:447. https://doi.org/10.3390/rs12030447
Murtugudde R, McCreary JP Jr, Busalacchi AJ (2000) Oceanic processes associated with anomalous events in the Indian Ocean with relevance to 1997–1998. J Geophys Res 105:3295–3306
Murty VSN, Sarma YYB, Rao DP, Murty CS (1992) Water characteristics, mixing and circulation in the Bay of Bengal during southwest monsoon. J Mar Res 50:207–228
Murty VSN, Sarma YYB, Rao DP (1996) Variability of the oceanic boundary layer characteristics in the northern Bay of Bengal during MONTBLEX-90. Earth Planet Sci Lett 105:41–61
Nichols RE, Subrahmanyam B (2019) Estimation of surface freshwater fluxes in the Arctic Ocean using satellite-derived salinity. Remote Sens Earth Syst Sci 2:247–259
Nyadjro ES, McPhaden MJ (2014) Variability of zonal currents in the equatorial Indian Ocean on seasonal to interannual time scales. J Geophys Res 119. https://doi.org/10.1002/2014JC010380
Nyadjro ES, Rydbeck AV, Jensen TG, Richman JG, Shriver JF (2020) On the generation and salinity impacts of intraseasonal westward jets in the equatorial Indian Ocean. J Geophys Res 125. https://doi.org/10.1029/2020JC016066
Nyadjro ES, Subrahmanyam B (2014) SMOS satellite mission reveals the salinity structure of the Indian Ocean Dipole. IEEE Geosci Remote Sens Lett 11(9):1564–1568
Nyadjro ES, Subrahmanyam B, Murty VSN, Shriver JF (2010) Salt transport in the near-surface layer in the monsoon-influenced Indian Ocean using HYCOM. Geophys Res Lett 37:L15603. https://doi.org/10.1029/2010GL044127
Nyadjro ES, Subrahmanyam B, Murty VSN, Shriver JF (2012) The role of salinity on the dynamics of the Arabian Sea mini warm pool. J Geophys Res 117:C09002. https://doi.org/10.1029/2012JC007978
Pant V, Girishkumar MS, Udaya Bhaskar TVS, Ravichandran M, Papa F, Thangaprakash VP (2015) Observed interannual variability of near-surface salinity in the Bay of Bengal. J Geophys Res Oceans 120:3315–3329
Qi J, Zhang L, Qu T, Yin B, Xu Z, Yang D, Li D, Qin Y (2019) Salinity variability in the tropical Pacific during the Central-Pacific and Eastern-Pacific El Niño events. J Mar Syst 199:103225
Rao RR, Girish Kumar MS, Ravichandran M, Rao AR, Gopalakrishna VV, Thadathil P (2010) Interannual variability of Kelvin wave propagation in the wave guides of the equatorial Indian Ocean, the coastal Bay of Bengal, and the southeastern Arabian Sea during 1993–2006. Deep-Sea Res I 57:1–13
Rao RR, Sivakumar R (2003) Seasonal variability of sea surface salinity and salt budget of the mixed layer of the north Indian Ocean. J Geophys Res 108(C1):3009. https://doi.org/10.1029/2001JC000907
Ratna SB, Cherchi A, Osborn TJ, Joshi M, Uppara U (2021) The extreme positive Indian Ocean dipole of 2019 and associated Indian summer monsoon rainfall response. Geophys Res Lett 48, e2020GL091497. https://doi.org/10.1029/2020GL091497
Reynolds RW, Smith TM, Liu C, Chelton DB, Casey KS, Schlax MG (2007) Daily high-resolution-blended analyses for sea surface temperature. J Clim 20:5473–5496
Roman-Stork HL, Subrahmanyam B, Murty VSN (2020) The role of salinity in the southeastern Arabian Sea in determining monsoon onset and strength. J Geophys Res Oceans 125, e2019JC015592
Saji NH, Yamagata T (2003) Structure of SST and surface wind variability during Indian Ocean Dipole Mode events: COADS observations. J Clim 16:2735–2751
Schott F, McCreary JP (2001) The monsoon circulation of the Indian Ocean. Prog Oceanogr 51:1–123
Sengupta D, Bharath Raj GN, Shenoi SSC (2006) Surface freshwater from Bay of Bengal runoff and Indonesian Throughflow in the tropical Indian Ocean. Geophys Res Lett 33:L22609. https://doi.org/10.1029/2006GL027573
Shankar D, McCreary JP, Han W, Shetye SR (1996) Dynamics of the East India coastal current. 1. Analytic solutions forced by interior Ekman pumping and local alongshore winds. J Geophys Res 101(C6):13975–13991
Subrahmanyam B, Roman-Stork HL, Murty VSN (2020) Response of the Bay of Bengal to 3-7-day synoptic oscillations during the southwest monsoon of 2019. J Geophys Res 125:e2020JC016200. https://doi.org/10.1029/2020JC016200
Subrahmanyam B, Trott CB, Murty VSN (2018) Detection of intraseasonal oscillations in SMAP salinity in the Bay of Bengal. Geophys Res Lett 45:7057–7065
Susanto RD, Gordon AL, Zheng Q (2001) Upwelling along the coast of Java and Sumatra and its relation to ENSO. Geophys Res Lett 28:1599–1602
Thompson B, Gnanaseelan C, Salvekar PS (2006) Variability in the Indian Ocean circulation and salinity and its impact on SST anomalies during dipole events. J Mar Res 64(6):853–880
Trott CB, Subrahmanyam B, Murty VSN, Shriver JF (2019) Large scale fresh and saltwater exchanges in the Indian Ocean. J Geophys Res. https://doi.org/10.1029/2019JC015361.67
Wang G, Cai W, Yang K, Santoso A, Yamagata T (2020) A unique feature of the 2019 extreme positive Indian Ocean Dipole event. Geophys Res Lett 47, e2020GL088615. https://doi.org/10.1029/2020GL088615
Webster PJ, Moore AM, Loschnigg JP, Leben RR (1999) Coupled ocean–atmosphere dynamics in the Indian Ocean during 1997–98. Nature 401:356–360
Zhang L, Du Y, Cai W (2018) Low-frequency variability and the unusual Indian Ocean Dipole events in 2015 and 2016. Geophys Res Lett 45:1040–1048
Zhang Y, Du Y, Zheng S, Yang Y, Cheng X (2013) Impact of Indian Ocean Dipole on the salinity budget in the equatorial Indian Ocean. J Geophys Res Oceans 118:4911–4923
Acknowledgements
The author duly acknowledges the various data sources for the freely available data. Thanks to Bennet Atsu Foli for helping proofread the manuscript. Thanks to the anonymous reviewers whose comments helped improve the manuscript.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of Interest
The author declares no competing interests.
Additional information
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Nyadjro, E.S. Impacts of the 2019 Strong IOD and Monsoon Events on Indian Ocean Sea Surface Salinity. Remote Sens Earth Syst Sci 4, 158–171 (2021). https://doi.org/10.1007/s41976-021-00054-1
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s41976-021-00054-1