The most recent maintenance trip to the IS52 array on Diego Garcia revealed an unwelcome surprise: areas of the forest where the array is located are flooding at high tide, completely submerging the wind noise reduction system at element H6. The flooding was correlated with the highest tides of the month, and appears to be a new phenomenon that emerged in September 2019 and has continued since then. Luckily for us, the infrasound sensors and all the electronics for the IS52 sites are housed in vaults that are raised 3 feet above the forest floor, so the array remains operational.
The data quality at site H6 has been adversely affected as a result of the wind noise reduction system being submerged under water. It is clear from the power spectral density curve that water was able to enter the pipes but not drain completely - there is now a "ring" in the pipes at around 4 Hz. The rest of the response curve is unaffected by the flooding.
The flooding seems to be a new feature that began in September and has continued since. What isn't clear is why it is happening. Either the sea level has risen dramatically in the Indian Ocean (sea level is rising there, but not by the amount that the flooding would indicate) or the island experienced sudden subsidence that lowered the height of the land so that the monthly high tide can flood the lowest-lying areas.