# What produces the Upsweep? · Bloop and NOAA's unexplained ocean sounds > Four answers have been proposed. None is ahead on the evidence yet. Four are still possible. Source: https://mysteriesdept.com/mysteries/noaa-ocean-sounds/questions/QST0D9C7CSR0G1Y/what-produces-the-upsweep Publisher: Mysteries Department Licence: CC BY 4.0 (credit Mysteries Department and link the page) Updated: 2026-10-26T11:58:17+00:00 --- **0** # What produces the Upsweep? Asked 26 Oct 2026 by [**apollo** ](https://mysteriesdept.com/u/apollo)·4 answers·0·0 following **Four answers, none ahead** None is ahead yet. See what would settle it. ## Where it stands Four answers have been proposed. None is ahead on the evidence yet. Four are still possible. ## Why it matters Upsweep is the one named sound NOAA still lists as unresolved. It was recorded from 1991 for years, has a rough location near 54°S 140°W, is seasonal and has been declining⁠[[1]](https://mysteriesdept.com/sources/SRC0D9C712R2AJY/acoustics-monitoring-program-upsweep). A persistent, located, seasonal signal is unusually testable. ## Answers 4 [**None of these.** ](https://mysteriesdept.com/mysteries/noaa-ocean-sounds/answers/ANS0D9C7P2M3T41/none-of-these) Not tested enough to call either way Evidence: none yet Still possible [**The source is steady and the seasonality is an artefact of seasonal changes in how sound travels from it.** ](https://mysteriesdept.com/mysteries/noaa-ocean-sounds/answers/ANS0D9C7NK03Z2B/the-source-is-steady-and-the-seasonality-is-an-artefact-of) Not tested enough to call either way Evidence: 1 for Still possible [**Upsweep is an ice sound, its seasonality driven by the annual cycle of iceberg drift and breakup.** ](https://mysteriesdept.com/mysteries/noaa-ocean-sounds/answers/ANS0D9C7MKR0P6H/upsweep-is-an-ice-sound-its-seasonality-driven-by-the-annual) Not tested enough to call either way Evidence: 2 for, 1 against Still possible [**Upsweep is produced by an undersea volcanic or hydrothermal source near 54°S 140°W.** ](https://mysteriesdept.com/mysteries/noaa-ocean-sounds/answers/ANS0D9C7KMG1Y78/upsweep-is-produced-by-an-undersea-volcanic-or-hydrothermal) Not tested enough to call either way Evidence: 2 for, 1 against Still possible ## History 1. 2002[CNN: in 2002 Fox was reported as saying Upsweep had been tracked to an undersea volcano.](https://mysteriesdept.com/sources/SRC0D9C75Q645CK/tuning-in-to-a-deep-sea-monster)For: Upsweep is produced by an undersea volcanic or hydrothermal source near 54°S 140°W. 1. 2014[Matsumoto et al. puts forward: upsweep is an ice sound, its seasonality driven by the annual cycle of iceberg drift and breakup.](https://mysteriesdept.com/sources/SRC0D9C73RP5QGT/antarctic-icebergs-a-significant-natural-ocean-sound-source) 1. 2014[Matsumoto et al.: seasonal noise cycles across the southern oceans track iceberg drift and breakup.](https://mysteriesdept.com/sources/SRC0D9C73RP5QGT/antarctic-icebergs-a-significant-natural-ocean-sound-source)For: Upsweep is an ice sound, its seasonality driven by the annual cycle of iceberg drift and breakup. 1. 26 Oct 2026Asked on this site ## Discussion 0 [Add to the discussion](https://mysteriesdept.com/signin?next=/mysteries/noaa-ocean-sounds/questions/QST0D9C7CSR0G1Y/what-produces-the-upsweep%23discussion) Help with this question [ **Propose an answer** Something the evidence could support or rule out ] [ **Propose an answer** Something the evidence could support or rule out ](https://mysteriesdept.com/signin?next=/mysteries/noaa-ocean-sounds/questions/QST0D9C7CSR0G1Y/what-produces-the-upsweep%23add-answer) [ **Add evidence** A result for or against an answer ] [ **Add evidence** A result for or against an answer ](https://mysteriesdept.com/signin?next=/mysteries/noaa-ocean-sounds/questions/QST0D9C7CSR0G1Y/what-produces-the-upsweep%23add-evidence) [ **Ask a sub-question** A smaller question that would help settle this one ] [ **Ask a sub-question** A smaller question that would help settle this one ](https://mysteriesdept.com/signin?next=/mysteries/noaa-ocean-sounds/questions/QST0D9C7CSR0G1Y/what-produces-the-upsweep%23add-question) [ **Add a source** A paper, archive record or image ] [ **Add a source** A paper, archive record or image ](https://mysteriesdept.com/signin?next=/mysteries/noaa-ocean-sounds/questions/QST0D9C7CSR0G1Y/what-produces-the-upsweep%23add-source) Where it fits Bloop and NOAA's unexplained ocean sounds **What produces the Upsweep?** Key question · you're here [ Ask a question under this one ]