BATHYS-04 — North Atlantic Ridge — 47N 30W

BATHYS Array 4 — Anomalous Acoustic Signature — July 2019

2019-07-14 03:22 UTC  |  47.2N 30.4W
BATHYS-04 2019-07-14 03:22 UTC

Array 4, positioned in the North Atlantic Ridge sector at approximately 47°N 30°W, depth 3,200 metres, began returning anomalous readings on 14 July 2019 at 03:22 UTC.

BATHYS-042019-07-14 03:22 UTC
03:22:07
Routine cycle complete. Thermal gradient nominal. Acoustic baseline nominal.
03:22:41
Acoustic anomaly detected. Frequency 11.7 Hz. Source bearing 247 degrees. Does not match library.
03:23:15
Signal persistent. Amplitude increasing. Duration now 34 seconds. No biological signature.
03:31:00
Signal ceased. Duration: 8 minutes 19 seconds. No geological event recorded on seismic network. No vessel traffic within 200km. Source unclassified.
04:00:00
Escalation to BATHYS Operations. Active monitoring elevated. Archive cross-reference query submitted.

The acoustic signature does not match any entry in the Institution’s reference library of known natural and anthropogenic deep-ocean sound sources. The frequency (11.7 Hz) is within the range of known geological infrasound but the signal characteristics — regular amplitude modulation at 0.3 Hz, consistent bearing, abrupt onset and cessation — are inconsistent with geological origin.

The archive cross-reference query returned one partial match: a BATHYS log entry from 1962, restricted at the Second Degree, describing a signal with similar characteristics at a different Atlantic location. The 1962 entry notes that the signal was also unclassified and that monitoring was elevated following its detection. The 1962 elevation protocol was stood down in 1971 without explanation in the public record.

Current status: Active monitoring. Unclassified.