biostudies-literatureSaran RMinistry of Earth Sciences34048https://www.ebi.ac.uk/biostudies/studies/S-EPMC12484875biostudies-literatureUnknown15(1)The Indian Summer Monsoon (ISM) has long been considered a self-regulated coupled ocean-atmosphere system. This framework implies that a drought monsoon year is often followed by a flood monsoon year, or the reverse, due to ocean-atmosphere coupling. To support this argument, observations showed that it is rare for more than two consecutive ISM floods or droughts to occur, where a flood/drought is ±10% deviation from the climatological rainfall. During boreal summer, ISM winds drive a southward cross-equatorial OHT of roughly 2 PW, frequently cited as a central element of this feedback. Yet its capacity to warm the ocean surface and sustain year-to-year rainfall reversals has received little scrutiny. Here, we present a critical examination of the role of OHT in the regulation of the interannual variability of ISM. Our analyses suggest that the effect of cross-equatorial OHT does not last beyond one season. While the difference in the ISM rainfall between flood and drought years can exceed 20%, the difference in OHT is only about 2%. The response of local Hadley Cell to OHT variability is also negligible. These results suggest that cross-equatorial OHT plays a minor role in governing interannual ISM variability.Scientific reportsLack of influence of cross-equatorial ocean heat transport on the interannual variability of the indian summer monsoon.PMC12484875MoES/16/03/2021-RDESSSaran RSandeep SfalseLack of influence of cross-equatorial ocean heat transport on the interannual variability of the indian summer monsoon.The Indian Summer Monsoon (ISM) has long been considered a self-regulated coupled ocean-atmosphere system. This framework implies that a drought monsoon year is often followed by a flood monsoon year, or the reverse, due to ocean-atmosphere coupling. To support this argument, observations showed that it is rare for more than two consecutive ISM floods or droughts to occur, where a flood/drought is ±10% deviation from the climatological rainfall. During boreal summer, ISM winds drive a southward cross-equatorial OHT of roughly 2 PW, frequently cited as a central element of this feedback. Yet its capacity to warm the ocean surface and sustain year-to-year rainfall reversals has received little scrutiny. Here, we present a critical examination of the role of OHT in the regulation of the interannual variability of ISM. Our analyses suggest that the effect of cross-equatorial OHT does not last beyond one season. While the difference in the ISM rainfall between flood and drought years can exceed 20%, the difference in OHT is only about 2%. The response of local Hadley Cell to OHT variability is also negligible. These results suggest that cross-equatorial OHT plays a minor role in governing interannual ISM variability.2025-01-01T00:00:00Z2025 Sep2026-06-04T00:28:47.336Z2026-05-03T03:12:43.11ZS-EPMC124848754102810110.1038/s41598-025-14120-x