Thursday, 4 April 2013

Day 21: Jan takes a break

Hi all,

Jan is taking a well earned break from his heroic efforts to chronicle the trials and tribulations of the cast of villains and heroes aboard the James Clark Ross, and it has fallen to me to keep his keen readers up to date for the next couple of days. Jan has done a great job so far of telling you of our ongoing adventures, the wonderful people on board and their important, considered and well executed work. I'm here to tell you the truth of what goes on out here.

So, for those who came in late: This is the ongoing voyage of the RSS James Clark Ross, boldly sampling for tracer where none have sampled before. This intrepid expedition has the romantic name of JR281, the 281st science cruise by this ship, and the number of our planned six week, box-shaped circuit around the South Atlantic. The plan, as far as you can plan anything around a dither (the proper plurality) of scientists and the wild Southern Ocean, was to head due South from the Falklands, across the Drake Passage that separates South America from Antarctica, sampling as we go. The Southern end of this was the foreboding Elephant Island, where Shackleton (spiritual forefather of the British Antarctic Survey) left most of his crew stranded while he sloped off on a brisk sailing jaunt. The plan then was to head east to near the South Orkney Islands and pick up two groups of moorings that have been sampling away at the bottom of the ocean near there. We would download their data, clean the seaweed off, thank them for their service and push them overboard again. That brings us nicely to our present position, steaming due east to the southern end of our next section of CTD and tracer observations. That section, with inspired name 'A23' will take us northish to South Georgia Island, where we will hopefully have some shore leave to fraternise with the natives for a day. We will then head back west to the Falklands along the ridges and gaps of the North Scotia Ridge, sampling as we go.

This plan, mapped out literally to the second by our determined but possibly over optimistic leader J-B Sallee, unfortunately didn't survive contact with the Southern Ocean terribly well. I'll explain over the next couple of posts. Let me start with the VMPs... One of the key features of the first section was to be the use of VMPs to map the incredibly complicated small scale turbulence of the water column. This is important for learning about mixing in the ocean and how stuff gets from one side of the Antarctic Circumpolar Current to the other when simpler approaches to the physics says that it shouldn't really be able to. The sexily named vertical microstructure profiler is the tool of choice for this research. These instruments are a relative debutant on the oceanographic scene, with a certain je ne sais quoi at the moment, and are doing their best to be seen in all the most popular journals. Part of their allure must surely be the fact that these are a gamblers instrument, they are untethered and fall through the ocean free of any control from those on the ship. Their operators are consequently men and women of mystery, cool characters with unwavering hands and thousand yard stares. Lesser oceanographers shackle their instruments, first with steel, then cable ties and finally with reams of duct tape. VMP operators on the other hand let their babies fly free, confident in their knowledge that the VMP really does love them, and no matter how far it strays into the dark places of the ocean, it will always come crawling back in the end.

Picture: Gwyn (blue helmet on left) demonstrates good technique by ensuring the VMP dangles over someone other than him while it is lifted over the side. 

That's the theory at least. In practice the operators know that anything you give to the ocean, it rarely gives back. So, much time was spent along the start of the section testing the VMPs in baby steps, progressively getting deeper and deeper. Each test was followed by some fine tuning, adding buoyancy here, pleading promises of nicer paint jobs and fresh battery packs there. So when Sean, John, Alex and Gwyn, our resident VMP jockeys, finally slipped on their dark glasses, donned their VMP issue leather jackets and declared the instruments ready for full depth action, we were unfortunately already a fair way along the section. Still, several casts were performed and every time the VMPs popped back up as planned. Profiles were made, data collected, and principle investigators back in the UK and US began idly daydreaming of what they would wear to their Nobel Prize ceremonies. 

Picture: Sean retrieves the US VMP by poking it with a stick.

Then the weather came. First thick fog shrouded the ship. This makes spotting the VMPs when they return to the surface, possibly several km away, very difficult. Worse, it hides their flashing beacons at night and makes it doubly hard to find them. Cracks of doubt began appearing in the craggy visages of these hard men of the sea as they had visions of the ship passing blindly by their ten million penny babies a ship in the night. Worse was to come. High winds whipped up the seas, meaning that a surfaced instrument may be whizzed away before we ever saw it, and even if found retrieving them became downright dangerous.

At this point Sean's US Marine Core training kicked in and he decided that the risk of leaving a man (or VMP) behind was too great. The UK owned VMP was staying put too. Pleas, threats and offers to use the more expendable PhD students in retrieval operations fell on deaf ears, and at this point all voyage leader Jean-Baptiste could do was fume at the fog and declare that it was 'So annoying'. In the hope of making it go away, JB was forced to gallically insult it again. 'So annoying'. This constitutes a great outburst of emotion for the normally unflappable Frenchman. I'd like to say that at this point a beam of light shone down on him as the clouds parted and the wind fell silent. It was not to be though, and like the carefully spelled King Cnut before him, JB had to concede that the ocean was beyond his command.

The weather did eventually clear up near the southern end of the section and the VMPs went back in, but unfortunately there are big gaps in the data. That's science in the Southern Ocean for you though, and we are consoling ourselves with the fact that we still have both the instruments, and there are two more potentially exciting sections to be sampled with the VMPs.

Picture: VMP energy dissipation rate data from the first section.

1 comment:

  1. Love the visual. So much for big data on the ocean.