Friday, 4 April 2014

All hands on deck!

Sorry for the slightly delayed news .... communication to the Southern Ocean is a little slow. However here is Tuesday's (1st April) dispatch!

We have been back at work today, catching up on those pesky few stations missed on the last leg due to bad weather. The seas are still pretty high today though pressure is on the rise and winds have dropped. The massive swell has knocked over anything not properly tied down; mugs, laptops and even heavy chairs have gone flying across the room. Despite closing the door to the sampling area waves have been forcing themselves in, flooding across the floor and overflowing into Andrew's wellies (he's not having much luck is he?). It has been (surprisingly) nice to be back at work and keeping busy. The JCR is a lovely ship and we have passed our free time with lots of films and games.... and yet we were all really enthusiastic to have something proactive to do!

Andrew and Ollie continue collecting those
oxygen measurements

The tracer team are busy back in the lab and Ollie has locked himself away with lots of samples to measure the dissolved oxygen concentration. On the CTD we have a sensor which can measure the concentration of oxygen in the water at a very high resolution. However, for us to have confidence in the numbers it gives us we need to calibrate it by taking water samples and measuring the oxygen concentration chemically. But why go to all this trouble? Why do we care about oxygen concentrations?

Firstly, it is interesting in its own right - it is thought that oxygen in the oceans is decreasing due to increasing temperature (less gas dissolves in warmer water) and increased stratification (less mixing means that less oxygen can be transported from the surface to depth). This is important because oxygen is used for respiration so changing oxygen concentrations will affect ocean biology.

Secondly, oxygen concentrations are often useful for defining water masses. Different types of water will have last been in contact with the atmosphere at different times and will have experienced different amounts of respiration and photosynthesis. This means that they may have very different concentrations of oxygen, helping us to identify the various types of water.

Thirdly, we can use oxygen to help to calculate the amount of carbon in the water which comes from a human source (anthropogenic carbon). We can't measure anthropogenic carbon directly because it is chemically identical to 'natural' carbon, but by estimating the biological and chemical processes the water has been through we can calculate anthropogenic carbon as the difference between what we would expect from these processes and the actual, measured amount of carbon. 

Tomorrow we will start steaming south for the moorings. The satellite images showed us that one of the mooring sites is currently covered in sea ice and it is creeping ever closer to the second. We have mixed feelings about this; having to go into the sea ice will be slow and take up precious time, and we really want to recover the moorings this year.... however we are all also a little excited the prospect of breaking though sea ice on the ship and being in amongst the penguins and whales again. 

(thanks to Ollie for his contribution to this post)
A dusting of snow in the Weddell Sea

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