Carnage but also lots of data

Two days ago I got the dreaded early morning phone-call wakeup, with Samer on the line hysterical that the RV Sikuliaq had just run over a second, yes SECOND!!!!$#@!!@#$, of our receivers, which was now stuck in the ship’s propeller and the data logger was dangling out of the receiver frame and about to fall away into the abyss.  Uggh. I came out on deck just about when they freed the remains of the instrument and were raising it back onto the deck:

Ocean bottom EM receiver destroyed after being run over by the ship. Note the data logger in the blue tube on the left is being held on only by the black magnetometer cable; lucky for us it held until the mangled receiver was back on deck.

Miraculously we got both data loggers (and importantly the data they contained) but we lost an acoustic transponder unit, an induction coil magnetometer, two electronic compasses, and lots of cables to the sea. The instrument frames were destroyed, and we lost several electrode arms. The glass floatation floats where banged around enough that we can no longer trust their suitability for deep deployments. One of the induction coil magnetometers (a marine version of the EMI BF4 sensor) that made it back on board the ship was severely bent (and destroyed):

Bent induction coil magnetometer.
Destroyed ocean bottom EM receiver instrument frame after being run over by the ship.

Ship handling for instrument recoveries isn’t easy but I’ve only seen a ship completely run over an instrument and destroy it a couple of times in over twenty years of going to sea.  So two instruments destroyed in the same day was super upsetting, to say the least, especially since this happened on instrument recoveries #2 and #6 out of 42 total, which meant there were 36 more chances for instruments to get munched by the Sikuliaq.  Morale was super low and that made tensions high for the rest of the instrument recoveries that day.

But all is not lost. We put the carnage of the morning behind us and the ship worked hard at more precise and careful handling. Now two days later we have only about 10 more receivers to recover.  We’ve had a few hiccups with some of the ORE acoustic units on the receivers that were deployed for the first time in deep water on the incoming plate, and one stubborn receiver has refused to release from the seafloor, likely due to a malfunctioning ORE acoustic unit. But we now have lots of good data in hand and are cruising along, so things are looking up.

We started on the deep end of the profile and are now moving up the continental slope. We should finish picking up the last few receivers, located in the shallow waters of the continental slope, later tonight.

Here’s a video of a receiver recovery from yesterday afternoon in what could be called a text-book recovery with slow and careful positioning by the ship and efficient and careful handling by the deck crew.

Ocean bottom EM instrument recovery video.