The 615-year-old sponge used for the study was found near Lee Stocking Island in the 1990s.
The deep sea sponges are also found in the Caribbean, containing centuries of records about ocean changes. But collecting them has been hard.
As climate change warms the oceans, scientists have generally relied on old ship records, or coral and tree rings, to track rising temperatures and predict future warming — despite errors in data or misinterpretations of the old ledgers.
But a new study found there may be a more reliable measure: ancient deep sea sponges found in waters around the Bahamas and Caribbean.