Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2022 Nov 15;13(1):6965.
doi: 10.1038/s41467-022-34721-8.

Southern Indian Ocean Dipole as a trigger for Central Pacific El Niño since the 2000s

Hyun-Su Jo  1 , Yoo-Geun Ham  2 , Jong-Seong Kug  3 , Tim Li  4   5 , Jeong-Hwan Kim  1 , Ji-Gwang Kim  1 , Hyerim Kim  6
Affiliations

Southern Indian Ocean Dipole as a trigger for Central Pacific El Niño since the 2000s

Hyun-Su Jo et al. Nat Commun. .

Abstract

Despite decades of effort, predicting the El Niño-Southern Oscillation (ENSO) since the 2000s has become increasingly challenging. This is due to the weaker coupling between the ENSO and well-known precursors in tropical ocean basins, particularly in the Indian Ocean. Here we show that the Southern Indian Ocean Dipole (SIOD), which is characterized by an east-west-oriented sea surface temperature dipole pattern over the southern Indian Ocean, has become a key precursor of Central Pacific El Niño since the 2000s with a 14-month lead. The role of the SIOD in the subsequent year's ENSO is distinctive from the equatorial Indian Ocean Dipole mode in that it prolongs the ENSO period. The westward-shifted ENSO has sustained simultaneous SIOD events for longer periods since the 2000s, which leads to weak but persistent westerly anomalies over the western Pacific. This eventually results in the development of the Central Pacific El Niño in the subsequent year.

PubMed Disclaimer

Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. The emergence of a new climate mode over the Southern Indian Ocean after the 2000s.
a 15-yr moving correlation coefficients between the Indian Ocean Dipole (IOD) index during boreal fall (SON) season, the Indian Ocean basin mode (IOBM) index during boreal winter (DJF) season, and the subsequent year’s Niño3.4 index during the DJF season (blue line: IOD vs. Niño3.4; red line: IOBM vs. Niño3.4) from 1976−2019. The x-axis indicates the middle year in the 15-yr moving window (e.g., 1999 indicates the correlation coefficient from 1992−2006). The dots denote correlation coefficients that are statistically significant at the 95% confidence level. b Second empirical orthogonal function (EOF) of sea surface temperature (SST) (°C) anomalies over the Indian Ocean during boreal late fall (OND) season for 1976−1997. c As in b but for 1998−2019. The units for the EOF are non-dimensional.
Fig. 2
Fig. 2. Southern Indian Ocean Dipole as a precursor of the ENSO after the 2000s.
Lagged regression maps of (a) sea surface temperature (SST) (°C) anomalies during boreal fall (SON) season and (b) subsequent year’s SST (°C) anomalies during boreal winter (DJF) season with respect to the normalized SON Indian Ocean Dipole (IOD) index from 1998–2019. (c) SST (°C) anomalies during boreal late fall (OND) season and (d) subsequent year’s SST (°C) anomalies during the DJF season with respect to the normalized OND Southern Indian Ocean Dipole (SIOD) index from 1998–2019. Shading in a−d denotes the region where the statistical significance is above the 95% confidence level. e Regressions between the IOD, SIOD, and Niño3.4 SST index during the subsequent year’s DJF season for 1976–2019 (left), 1976–1997 (middle), and 1998–2019 (right), respectively. The blue and red bars in e indicate regression coefficients that are statistically significant at the 95% confidence level for negative and positive coefficients, respectively. f, Lead-lagged regression between the Niño3 SST and SIOD index (blue), the Niño4 SST and SIOD index (red), and auto lead-lagged regression of the Niño3 SST (grey) and Niño4 SST indices (black) from OND(0) to the subsequent year’s boreal early winter (ND(+1)J(+2)) season for 1998–2019. The open circles in f indicate correlation coefficients that are statistically significant at the 95% confidence level.
Fig. 3
Fig. 3. Atmospheric variance associated with the Southern Indian Ocean Dipole.
Regression maps of (a) precipitation (mm day−1) and (b) 925hPa wind (vector, m s−1) and streamfunction (contours at intervals of 0.3·10−5 m2 s−1) anomalies during boreal late fall (OND) season with respect to the normalized OND Southern Indian Ocean Dipole (SIOD) index for 1998−2019. The shading and vector in a, and b denote the region where the statistical significance is above the 95% confidence level. c Regression of 925 hPa zonal wind anomalies averaged over 5° S–5° N over the Pacific during the following boreal spring (MAM) season with respect to the normalized OND SIOD index for 1998−2019 (blue line). The red line is the same but for the partial regression after excluding the impact of the boreal winter (DJF) Niño4 index. d Partial lag-regression of 925 hPa zonal wind anomalies averaged over 120°–150° E, 5° S– 5° N over the equatorial western Pacific from the OND season to the subsequent year’s boreal early winter (NDJ) season with respect to the normalized OND SIOD index after excluding the impact of the DJF Niño4 index for 1998−2019 (blue line). The red line is the same but for the partial lag-regression with respect to the normalized DJF Niño4 index after excluding the impact of the OND SIOD index for 1998−2019. The open circles in c, and d indicate correlation coefficients that are statistically significant at the 95% confidence level.
Fig. 4
Fig. 4. Idealized coupled model experiments and correlation skill of the Southern Indian Ocean Dipole index as an ENSO precursor.
Changes in the (a) precipitation (shading, mm day−1) and 925 hPa wind (vector, m s−1), and (b) sea surface temperature (SST) (°C) anomalies in the Southern Indian Ocean Dipole (SIOD) experiment (Exp_C_SIOD) compared to the control experiment (Exp_C_CTRL) during boreal late fall (OND) season. c, d, As in a, b, but for during the subsequent year’s winter. The shading in a−c denotes the region where the statistical significance is above the 90% confidence level. e Hindcast correlation skills of Niño4 SST (red), Niño3.4 SST (grey), and Niño3 SST (blue) indices from the OND season to the subsequent year’s boreal early winter (NDJ) season using a combination of the boreal winter (DJF) Niño and the DJF ocean heat content (OHC) indices for 1998–2019. f As in e, but using the OND SIOD index. The grey box indicates the developing seasons of the SIOD. The open circles in d, and e indicate correlation coefficients that are statistically significant at the 95% confidence level. A leave-one-year-out cross-validation method is employed.
Fig. 5
Fig. 5. Impact of the westward-shifted ENSO on the Southern Indian Ocean Dipole (SIOD) variability after the 2000s.
a Auto-lagged correlations of the boreal late fall (OND) SIOD index from the OND season to the subsequent year’s boreal late summer (JAS) season for 1976–1997 (gray line) and 1998–2019 (black line), respectively. The open circles in a indicate correlation coefficients that are statistically significant at the 95% confidence level. b Latitudinally averaged observed sea surface temperature (SST) (°C) anomaly composite for the Eastern Pacific (EP) (black line) and Central Pacific (CP) ENSO (red line) events during the OND season for 1998−2019 over 30°–5° S in the southern Indian Ocean (left panel), and over 5° S–5° N in the equatorial Pacific (right panel). c As in b, but for changes in the latitudinally averaged SST (°C) anomaly in Exp_C_EPEN (black line) and Exp_C_CPEN (red line) compared to the control experiment (Exp_C_CTRL). d Observed difference in the composited SST (°C), and 925 hPa wind (vector, m·s−1) anomalies for EP and CP ENSO events during the OND season from 1998−2019. e As in d, but for the difference in Exp_C_EPEN from that in Exp_C_CPEN. The shading and purple vector in d, and e denote the region where the statistical significance is above the 90% confidence level.
See this image and copyright information in PMC

Similar articles

See all similar articles

References

    1. Ropelewski CF, Halpert MS. Global and regional scale precipitation patterns associated with the El Niño/Southern Oscillation. Mon. Weather Rev. 1987;115:1606–1626.
    1. Bove MC, Elsner JB, Landsea CW, Niu X, O’Brien JJ. Effect of El Niño on US landfalling hurricanes, revisited. Bull. Am. Meteorol. Soc. 1998;79:2477–2482.
    1. Bell GD, et al. Climate assessment for 1998. Bull. Am. Meteorol. Soc. 1999;80:S1–S48.
    1. McPhaden MJ, Zebiak SE, Glantz MH. ENSO as an integrating concept in earth science. Science. 2006;314:1740–1745. - PubMed
    1. Jin F-F. An equatorial ocean recharge paradigm for ENSO. Part I: Conceptual model. J. Atmos. Sci. 1997;54:811–829.

Publication types