C RUISE N ARRATIVE

21 Jan All scientists arrived in Punta Arenas, ready for mobilisation starting tomorrow first thing in the morning. Departure from Punta is scheduled on the 24th 10:00 am

22 Jan Mobilisation started with all gear already brought on deck. Labs have been populated and scientists start to get every box to the right place.

Deck has been organised.

23 Jan Mobilisation continues. All instruments are now setup and ready to be run. Some issues with air isotopes instrument have been found, but nothing too serious. We are ready for departure tomorrow.

24 Jan Day started with safety briefing and drill. We then sailed off. The day was calm in the Magellan straight but we are expecting stronger winds in the coming days. The issue on the air isotopes instrument has been solved and it needs to be tested again. Continuous observations will start as soon as we leave Argentinian waters, probably around late afternoon

tomorrow.

25 Jan Very nice day; calm and sunny. Final setups have been made, and meetings allowed teams to organise themselves. We are now in

International waters. SADCP has been turned on; underway system will be turned on in the morning. We are planning a first CTD casts for test of instruments, but maybe more importantly to allow process (data

acquisition and processing) to be tested, and digested.

26 Jan Still steaming westward toward Bird Island. Weather is nice which allow everyone to get his/her sealegs slowly. A first test-CTD down to 1500 m has been done. We had problem with cable on the way up at ~1100 m wire out

27 Jan Calm day in the fog. Gave us time to meet to discuss mooring plan and for biogeochemist to train others to get a hand.

28 Jan Steaming toward bird island. Calm day. Gave us time to try to calibrate the S-ADCP

29 Jan Arrived in Bird Island in the morning with amazing views alternating between fog and opening views on the mountains. We dropped the three scientists and the doctor and the two ecologists of our team visited the base. We then spent the day steaming toward our first station of A23, along the Southern coast of South Georgia with stunning views on the glaciars.

11 The weather should calm this night.

01 Feb The weather calmed down and we could restart working at 6:00 am this morning. The winch wire is working better, though the engineers are waiting for the deepest station to try spooling the wire back nicely on the drum.

02 Feb We made good progress on CTD casts today, and made the most of a relatively calm weather. The issues we had with instruments over the last few days are slowly solved and allow to keep working at a good pace.

Questions remain on a few underway instruments, including pCO2 analyser, as well as the two surface-water oxygen isotope analysers.

06 Feb We finished the A23 section and are steaming southward to the join the Southeastern Weddell part of the cruise.

08/02 Starting the work in the Southeastern Weddell.

14/02 We finished today the section at ~77 S. We are meeting the Shackelton to give them a spare part and then make our way South. Plan is to go on a position roughly in front of Belgrano, and wait there until we think we can make our way further toward the ice-shelf front. It is hard to estimate a steaming time, but 12h steaming seems reasonable.

15/02 The plan for today was to try to go through the ice but this is harder task than expected, plus we suspect what we thought was open water on satellite image is actually fast ice. We tried flying the drone to better understand and see but the drone flight was aborted because of technical issue. We tried get to an ice floe to tag one seal but could not go through the ice. We are now stuck in the ice, and need to wait for tomorrow for the wind to ease down the ice and make us a way out of where we are.

We are lucky enough to have an open water pool on starboard side of the ship, so managed to put the CTD in the water to diagnose ctd sensor issue and sample for biogeocmistry and isotope (CTD 73). Diagnostic of CTD:

pump one seems to be faulty; it will be changed from CTD 74; from CTD 74, line 2 is put back to its original state (i.e. same sensors; same pump;

pump with same flow rate as before).

16/02 We are still stuck in the ice. The wind started to pick up this morning but is compacting ice rather than easing anything (as forecasted). We will have to wait for the wind to turn, switching to southerly wind (going northward). That might be tomorrow, or even later. Until then, we can’t move (though we will try at any opportunity). We finished the 13-hour yoyo CTD, and stop that here. We might be able to re-start the underway for surface monitoring (though the outlet has been freezing, so the risk is that pressure in the pipes rises; but we’ll try and keep an eye on it).

17/02 The ice is starting to ease directly north of us (astern), so as soon as they can turn the ship around, we can go back north and leave this mess. What worries me the most is not that much the time we loose, but the fact that the ice is moving up north (near the sill), so that might become difficult to work on the western side near the sill. We’ll make plan as we go, but what I’d like to do when we can go north, is, if ice allows, to deploy a couple of floats on the section we did at ~76.5°S, and make our way back on the sill on the western side for mooring recovery and cross slope sect.

18/02 We managed to tag a seal on our way north. Next steps are now deploy 4 LOTUS buoys at ~77°S (please weak up Elin 30 min before station), then move the 76°25.2’ S / 32° 54.0’ W to deploy two Apex floats. After that, we’ll steam more north to join the western side of the sill.

19/02 We deployed the 4 LOTUS buoys last night, did a couple of CTD in the morning, and deployed the two last APEX. Since then, we have been steaming most of the day toward our next CTD station, on the long East-West section at the sill (74.51S; section where we deployed the four line of moorings). We will finish this section that we started from its eastern side; we will do all remaining stations making our way westward, likely through the ice floes. The plan is to do as many as we can, ice-dependent.

The station positions are likely to be changed by ice. Tomorrow we will reassess the plan depending on how much of a struggle it is to steam within ice.

20/02 Yesterday was productive, despite the long time steaming: one seal and one mooring recovery. We came back to the east-west section overnight to continue CTDs. We got one done, but we got blocked by ice and had to give up with the east-west section. Frustrating, but I think we got enough of the east-west section to make it very valuable. We are now attempting a south-north section down the slope to catch the plume of outflow of dense water. Same as before, we give it a try and will stop if ice blocks us. There are 11 stations on the section, so that might take up to 24/36 hours to get it done (if we can make our way in the ice). Next steps will be to backup a bit more eastward. We will hopefully have access to reliable ice maps from satellite to refine the plan, but it is likely to be mooring deployment, and maybe one recovery on the way. More later.

21/02 Progress has been slow today. We struggled in the ice, almost decided to give up at some point, but suddenly it cleared up, and steaming is now easier, though still tedious. We will continue to push overnight to try getting station on the slope. Depending on how the night goes, we’ll revise our plan tomorrow. Tomorrow is another day.

22/02 We managed to finish the cross slope section despite the issue we had with the gantry (leaks that needed to be repaired, which took a few hours of the day). We clearly see the dense water flowing out onto the slope.

However, in order to try to better resolve this outflow, we are returning south, slightly east on the section we just finish, on the slope, between bathymetry contours 1500m and 500m, to do a small high resolution

13 northernmost/deepest one. Then, we stop CTDing in the morning to be on

station CTD136 (bathymetry contour ~500 m) at 9 am to deploy one mooring. After this mooring, we will move to station CTD135 to deploy a second mooring. After the two mooring deployment, we will finish all the stations on the section that could not be done overnight.

24/02 We now have all moorings in the water (yeah!). We are finishing the last station of the cross-slope section as I write. We will next give another try at the section close to the ice shelf. Yesterday and today’s MODIS image show that the ice shelf is mostly clear, at least the eastern end of it, and weather forecast for the coming day might be favorable to keep the area free of ice. There is about 250 nm to get there, so I would expect we get there in the night 25-26 Feb. We will need to reassess ice images and forecast before entering the area, but I hope we will be able to make it.

The risk being we have to abort before even entering the area, which would mean wasting 3-4 days (return way to the area); but I think that it is worth the risk.

25/02 We arrive to the southern section earlier than expected. We started the section down the slope on the eastern side of the section. Sampling has been tiring because we wanted to well resolve the slope with samples. We are now arriving to the bottom of the slope so sampling should be easier (we do not sample all stations). However, one issue we had is niskin freezing because of supercool water leaving the ice-shelf.

26/02 Continuing the ice-shelf section westward. We skipped a few stations in the deep through, so to try to be at the mooring station tomorrow during daytime to attempt recovering.

01/03 We left the ice-shelf front to go back north. We looked for seals on the way north, trying to go westward in the inner pack, but the icepack is too loose and we did not find any seals on nice enough floe.

02/03 Today we spent the another day steaming northward and looking for seals. We were lucky enough and tagged two. We are now steaming westward on the northern edge of the continental shelf. In the morning, we will be in the area where we think is a hotspot for seals and where we think ice will be made of nice floes where we could potentially work.

03/03 We spent a third day looking for seals, and had the chance to tag one. We will now stop seal hunting, and will do a last small CTD section from now until 6:00 am shiptime tomorrow (one station every 2 nm until 6:00 am). At 6:00 shiptime, we will start making our way north toward the South Orkney Island, where we will deploy two bottom-following float in the outflow region of bottom water, out of the Weddell Sea. Two

additional CTD will be made at the location of float deployment for float calibration. We will then continue our way north towards Punta.

04/03 We finish the work in the Southeastern Weddellthis morning, as planed.

We are now steaming north toward South Orkney Island.

08/03 Today, we finished science stations, after deploying the two Deep-DVL floats (and the two co-located CTD).

10/03 Entering Argentinian waters. We are now cutting all instruments. End of science. Everyone is glad to be soon back to Punta.