When deep towing we often say boring is good. That means we’re stuck sitting at the deep tow station all day watching the transmitter’s data feed while the ship moves along at a mere 1.5 knots (about 0.7 m/s or walking speed). Alternative non-boring scenarios include winch drums freely unspooling, power transformers melting down, broken cable terminations shorting to seawater, torn transmitter electrodes or other things that would end our data collection. So yeah, boring is good. Photo and video from today below.
The last receiver went over the side of the ship around five this morning, completing the deployment of all 42 EM receivers in just 27 hours. We then beelined for the start of the deep-tow profile and managed to get the EM transmitter SUESI, its 300 m long antenna and towed-EM receiver (at 500 m offset) deployed before the weather kicked up in the afternoon. When we first fired up SUESI to full power we heard some loud rattling coming from the top-side power supply in the back lab and then SUESI’s telemetry data feed went bad, so we decided to power down and start it up again, but again the rattling came back at high power. So we decided to revert to the spare power supply unit. However when we powered that one up, SUESI would no long talk to us and that started to get us all worried . We switched back to the original power supply and again SUESI wouldn’t talk to us. Oh no! Fear and anxiety and thoughts of a failed experiment started coming to mind. One option was to beach SUESI and switch to the spare SUESI, but that would have required a few hours of deck work in increasingly poor weather. So we opted to test some other things in the lab first, just in case…We swapped out the deck unit and that didn’t work. Then Steve Constable had the brilliant idea to swap out the deck box’s communication cable since that was one of the components detached and then reattached we moving between the power supplies. Bingo! SUESI came back to life! Yay, no more failed experiment, at least for now! But we still had the problem with the rattling power supply in unit #1 so we went with the backup power supply and fired SUESI up to 250 A. Using the ship’s winch, we lowered it down at a rate of about 30 m of wire per minute to a tow altitude of about 100 m above the increasingly deepening seabed as we tow down slope into 5500 m deep trench along this stretch of the Alaskan subduction zone. If all goes well, we will complete our first CSEM profile in another two days. Photos and video from today below.
Thanks to good weather, good ship handling and our hard working science team, we were able to deploy 36 receivers today (well, now yesterday since I write this just past midnight local time). We have a lot of new people on the science team this cruise and many of them have never gone to sea before or have never worked with marine EM equipment. They all came up to speed quickly today. So big thanks to both the newbies as well as the old salts for making today go so smoothly. We have only six more receivers to deploy and then we will turn back around and head down the line to start deep-towing our controlled source electromagnetic transmitter system. Here are photos and movies from the marathon of receiver deployments.
Heading to station 201
Since pushing off the dock at Seward around 13:00 yesterday, we’ve been transiting at 10-11.5 knots towards station 201, which we should reach around 3-4 a.m. tonight. During the transit, we’ve been getting our sea legs as the ship rolls and pitches in the moderate sea swell, eating tasty food that galley cooks Mark I and Mark II have been treating us to, and getting ourselves organized and prepared for the on-rush of deck work that will begin soon. Below are some photos from yesterday and today. Scroll to the end to get so see the bonus video of Dall’s porpoises!
Hello RV Sikuliaq
Here are some photos from yesterday showing the RV Sikuliaq and some of our science team preparing equipment. Right before leaving the ship for dinner in town, we were treated to a mother and baby humpback whale swimming around right next to the ship. Today we have some safety meetings in the morning and then will depart for sea sometime around lunch time.
EMAGE Cruise is about to begin!
We’ve all arrived in Seward, Alaska, and boarded the RV Sikuliaq today. We need to prepare the OBEM receivers, set up the lab, terminate the deep-tow cable and make other preparations before the ship pushes off the dock tomorrow. The map below shows our four planned controlled-source electromagnetic (CSEM and magnetotelluric (MT) survey profiles and some of the other past, present and upcoming geophysical surveys in this region.
More than halfway done
Recovering seafloor magnetotelluric receiver in rough weather
The forecasted high winds and swell arrived last night, making the instrument recoveries a bit exciting as well as challenging. Here’s a video from this morning showing us recovering a seafloor magnetotelluric receiver in rough weather.