Impact of prolonged La Niña events on the Indian Ocean with a special emphasis on southwest Tropical Indian Ocean SST

► Impact of prolonged La Niña events 1973 to 1976 and 1998 to 2001 are studied. ► Tropical Indian Ocean (TIO) response to prolonged La Niña in the pre and post-climatic shift of mid 1970s is studied. ► The mechanisms responsible for the TIO cooling during the long lived La Niña are studied.