Happy November!! We’ve just completed one month on ice, officially week four of operations. C444/B041 has been up and running with science dives at last! To be clear—we use every dive to improve our understanding of the environment under the ice, but our “science” dives are those that occur at a site of interest with a fully functional and checked out vehicle, prioritizing science as the main driver for the mission. Especially because we are preparing for deep field missions supporting NASA, NSF, BAS/NERC and ANZ science, we also are conducting operational tests and field team training during each of these dives. All in all, we are meeting our science, operations, engineering, and training goals.
We keep a careful record of our process each dive through a system of checklists, check ins and check outs, and documentation. The Icefin team begins each dive by filling out a dive card that logs important information about the mission plan, instrumentation and vehicle status, location, and roles of the team. Dive notes are also taken both on the dive log through the topside computer for elements of the dive such as science readings, vehicle status, image annotation, etc, and by hand to record key events for later perusal and post dive meetings. Cards and notes are all kept by participants and a copy is archived for future reference.
We conducted three science dives on Tuesday 11/5, Thursday 11/7, and Saturday 11/9 of last week. During the first dive, we tested our drop weight solution as well as vehicle mobility after a a vehicle “cast” to the sea floor (what we refer to a straight downward or upward mission element through the water column to gather oceanography data to reference to our RBR CTD). We will be diving in areas where sediment cores will be taken, so we have been tuning our ability to translate away from the borehole to release the drop weight in an area that won’t disrupt the coring. We also worked in all three dives on tuning our vehicle magnetic and inertial navigation solutions to guarantee we have a streamlined manner of referencing position and heading under the ice. Finally, we continue to be able to retrieve the vehicle through 35 cm drill holes without the assistance of thrusters, which is needed for the deep field. The new aft “backup cam” has proven most useful for understanding vehicle state, especially during deployment and retrieval.
For all three dives, we have been operating out of fish hut 01, just adjacent to the ice shelf and about 500m North of the East-West-running rift in the ice shelf. Here, we are able to study several elements. Rift formation and evolution has been studied via remote sensing, seismic and GPR studies, but not much from below. Icefin allows us to map the structure of the bottom of the rift to get at these questions. Simultaneously, we can map the water column under deep ice, which has different oceanographic conditions and history from that under the sea ice. Right at the rift, there also may be two unique inputs to the water column: brine rejection from marine ice formation inside the opening rift, and surface melt water connecting down through the cracks in the ice. The combined mechanical and oceanographic questions about rift evolution are relevant topics for both Earth and Planetary Science, trying to understand how ice shells of all varieties operate and impact the oceans below.
On Tuesday, we completed season dive 4, ICE03 dive 11. The mission included the drop weight and heading tests, followed by a 500m drive out to the rift, then profiled across the 40m wide feature with the sonar and upward camera, and proceeded about 50m past the rift. There we descended to 50m depth below the shelf and back up to create a cast of the upper water column. We continued on from there, crossing the rift and ice shelf again, and then decided to poke around back up the rift this time very close to the ice to view with cameras as well as get the CT and DO sensors right into the boundary layer under the platelets. All in all, we spent 5.5 hours under water.
On Thursday, we completed dive 5, which was a missing involving underwater heading tests followed by a long drive along the rift. We were also working on the use of waypoint following, tuning Icefin’s ability to autonomously hold position and travel along paths and between waypoints, which was a good test of the vehicle navigation. The mission included a 150 m cast, followed by a 500m drive to the rift, after which we drove along the rift pitched up slightly to keep the rift structure in the forward-looking sonar (Oculus). We followed the rift for over 1000m, completed a cast to 50m, and then viewed the ice. We were also joined via helicopter by the CEO of ANZ, Sarah Williamson and an ANZ team. They timed arrival perfectly, so we had the great opportunity to show them Icefin operations and live feed from the rift. We successfully recovered the vehicle after ~6 hours of operation.
On Saturday, we completed dive #6, which was a resounding success. We’ve been proud of our ability to quickly scale up from vehicle commissioning activities to testing and operations and finally science, but our real mark of success is a “perfect dive” where all parts of the operation from packing to retrieving the vehicle go smoothly. No dive is ever perfect really, there are always challenges during the dives, but the team’s ability to anticipate and adjust to the circumstances is key to ideal operations, and as of Dive 6 the Thwaites team who have been primarily operating ICE03 are in good spirits looking towards the deep field. Of course, the highlight was the science. After completing a set of tests of the heading above the ice, we deployed the vehicle for a 150m cast and a brief heading and tuning check. We then drove back out to the starting point of Dive 5, and this time turned East and traversed the rift over 1000m to the East of the starting point. The vehicle and team operated smoothly for the whole dive, communicating back and forth from mission control inside the hut to the tether team outside. At the end of the long survey, we completed a cast down to 130m, during which we profiled from the supercooled layer down through the ice shelf water, and encountering what we joked was a “shrimp-ocline” from 80 to 110 meters, in a region we’ve not usually seen so much activity. After completing the cast, we surveyed the rift up close, and then retrieved the vehicle after ~5 hours under water.
All in all, the last week was a huge success. During the week, we’ve completed over 3000m of surveys of the rift and shelf, collected multiple CTD casts and water samples to complement the vehicle sensors. We’ve collected over 16 hours of under ice data. The plan for the next week is to repeat similar science dives and tests with the ICE02 vehicle that’s heading to Kamb Ice Stream with ANZ. We’ll be moving into true mobile operations, working out of a tent at Site C for two of the dives, and then keeping an eye on completing our missions the following week at Site A. We’ll also be joined by our BAS and US colleagues from the Thwaites Melt project, and starting to pack up for the two deep field campaigns. Have a lovely week out there!
This year the field team for Icefin consists of:
Britney Schmidt, Matt Meister, Dan Dichek, Anthony Spears, Justin Lawrence, Ben Hurwitz, Andy Mullen, Peter Washam, and Enrica Quartini.
RISE UP: https://schmidt.eas.gatech.edu/project-rise-up/
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