The singer, who has not released an album since 2015, predicted the coming 12 months would be "big" for her.
"31 is going to be a big ol' year and I'm going to spend it all on myself. For the first time in a decade I'm ready to feel the world around me and look up for once," she said.
"Learning to REALLY truly love yourself is it, and I've only just realised that that is more than enough. I'll learn to love you lot eventually," she continued, a teasing reference to her fan base.
"Bunch of f**king savages, 30 will be a drum n bass record to spite you."
It may have been a throwaway joke, but that last line also appeared to confirm Adele's highly anticipated fourth album will follow the pattern of her first three, 19, 21 and 25, in being named after the year she wrote it.
Adele ended her missive on a hopeful note: "Chin up eh." The message was accompanied by a selection of photos of the singer looking very glam, presumably at her 31st birthday celebrations.
Only a very occasional social media user, Adele's surprisingly personal message comes just weeks after her split from husband of three years Konecki was announced. The couple have a six-year-old son, Angelo, together.
"Adele and her partner have separated," the star's spokesman confirmed last month.
"They are committed to raising their son together lovingly.
"As always, they ask for privacy. There will be no further comment."
