Day 14 On the move again

Big waves in the Southern Ocean

Abrief glimpse of sunshine

Giant petrels trailing the ship

It's been two weeks since the James Clark Ross weighed anchor in Choiseul Sound in the Falkland Islands. Since then we have travelled 1900 nautical miles and we're now at 57° 20 S, 34° 21 W steaming alongat about 9 knots in "moderate" seas. To me that's pretty big waves, but that's what it's called in the offical ship's log. The other day we actually had officially "heavy" seas - and I got nearly thrown out of my bunk during the night. Even after things are a bit more easy going again, the waves are still 3-5 metres high. And it's quite changeable - we seem to be going from fairly regular deep ocean swell into occasional patches of properly angry seas. "Angry" is not the technical term, but it will do for me (especially when it snows sideways as the same time).

We are now finished with the CTD transect. The last cast was made early  this morning after the data shows no more signature of Antarctic bottom water. As it is our objective to study this "bottom water" we needed to  make sure we don't go home without surveying as much of it as we can  find. This water mass is a layer of cold, saline water flowing along the sea bed (hence "bottom" water) which originates from the ferociously cold regions of the southern Weddell Sea. Down there it's properly winter by now and the sea is freezing up at breakneck pace. Quite literally - the boundary of sea ice is racing northwards at 1 to 2 miles a day. When sea ice forms it leaves brine behind (the salt content in sea ice is much lower than in sea water) which make sthe water more salty which is combined with surface cooling by the wind which makes the water colder. The cold salty water is denser, i.e. heavier, and eventually sinks below the surface. The coldest and saltiest water will sink the deepest. And eventually it will show up as a distinctive water layer on the temperature and salinity measurements near the bottom.

The other clue to bottom water is the data from the oxygen sensor on the CTD frame. Oxygen content is a measure for how "old" water is, i.e. how long it's been since it left the surface (where wind and waves mix oxygen into the water from the air). Any animals (like zooplankton and fish) that live in the water will use up the dissolved oxygen, and eventually deplete it when enough fish and plankton have breathed their share of it. Low oxygen content therefore means "old" water - lots of things had plenty of time to use up the oxygen in an old patch of water. That means our bottom water would show up as a layer with a higher oxygen content. Bottom water is "younger" water, i.e. it hasn't been too long since it's been in contact with the surface (at the time it was cooled and sank to the bottom).

The last but one CTD cast still showed some signs of bottom water, and on the last one the signal was finally gone from the data. So that was a good time to stop this part of our mission. It appears that we have now gone far enough north the the bottom water flows either hadn't reached that last location yet, the flows had taken a different path or the water had been mixed up with other water masses so any distinctive signal had been diluted down to undetectable levels. The later analysis will show which one of those is true. As these measurements have been done in previous years, the analysis will also show how the bottom waters have changed over the last few years. Could it be that the bottom water is warmer than in previous years? If the cold deep water flows are warming up like the rest of the ocean it could have profound changes on the global ocean circulation. And that's what we're here to find out.

So we're now on the move again, passing to the south of of the islands of South Georgia to an area called Shag Rocks, where the paleo team will take some more sediment cores from the seabed. Knowing whether the changing climate is having an effect on our current ocean circulation is one thing, but finding how it changed over the previous thousands and millions of years is just as important. Those changes will be coded in the signature of the layers upon layers of fine sediment that have accumulated on the ocean floor over the millenia. Nearer South Georgia I will also be hoping to see more wild life again. We've not seen as many whales as on previous trips, and the long-timers on board tell me that there just aren't as many sea birds around us. So fingers crossed for whales and albatrosses. A blue whale next to the ship and a couple of wandering albatrosses overhead would do just nicely. We'll see.

While the ship's moving there just isn't all that much to do. Other than data processing and writing up reports anyway, but just nothing really physical. That lack of movement is only slightly offset by your body having to subconsciously correct for every pitch and roll of the ship. Added to that, the food is fantastic on board (kudos to the chef!) so it's easy to get into quite a sedentary, well-fed lifestyle. One can hardly nip out for a long walk or a bike ride. With that in mind I decided to join Rich's circuit training today. Rich is an outdoor and fitness enthusiast and probably thought the same some time ago about the lack of physical activity. So 3 times a week he drums up a crowd in the forward cargo hold and puts on some bouncy music. After an hours of squats, crunches, press-ups and running on the spot (not that far to go otherwise) I am now utterly exhausted, but it feels good to have worked off some of the lovely desserts. There's an onboard gym as well with exercise bikes and such like, so I might have to give that a go too.

Life on board is starting to feel a little like a space station in that respect, but I doubt their space food is as good as ours! More news from the South Georgia area soon...