Day 25: Bloomin' Ocean

Today has been another day filled with mud - this time on the deck of the ship as the box corer brings it up to for benthic sampling. But more about that tomorrow. Today's blog is an update from Helen....
The last few days of the cruise are rolling on… Since my first blog some time ago, the sun has mostly been hidden behind a sky of grey, and we’ve been dodging bad weather for the last few weeks. Despite this the ship has been surprisingly stable. In fact as I am gently rocked awake in the mornings I often think the weather has improved. However as I sway and bump my way down the corridor from my room to the lab I realise I am wrong – I am not drunk, which is perhaps how it looks, I’m actually just suffering the effects of gravity on a rocking ship.

Helen's lab!
I am sat here now, very much as I was sat last time I wrote a blog: running my DIC and alkalinity machines measuring the carbon in the seawater… I hear the beep, I change the sample… I shall summarise my ship life over the last 24 days in numbers: so far I’ve: - analysed 343 water samples from depths of 2000 m to the surface (that’s 17,150 beeps!) - made 48 CTD casts, overall bringing about 11 tonnes of water to the surface to be sampled or used in ship-board incubations - and drunk well over a million cups of tea!!

I’ve also discovered the in-lab computer monitors, which display information about the ship’s goings-on. These monitors are wired to the ship’s main computer and are displayed in all the main labs. A touch screen display shows everything from the ship’s position, direction and speed, to information about how quickly the winch is going up or down, and what depth the instrument is at (this is particularly useful for me to run out to the CTD between beeps!). There is also a weather screen, and as the number of samples I have to analyse slowly goes down, I’ve watched the wind steadily increase (we’ve seen gusts over 40 mph – force 8), and this effects what instruments we can deploy.

 The other important factor that determines when we can deploy instruments is the sea state. On the ship display there is also a screen which shows the pitch, roll and heave of the ship. The pitch is the up-down (fore-aft) movement of the ship, the roll is the side-to-side movement, and the heave is the overall lift or drop of the ship with the swell. On a flat sea, the pitch, roll and heave would all be 0 degrees but as the waves increase and the ship moves around more, the values increase. So the other thing I’ve been watching as I sit waiting for the beep, is the increase in pitch and roll of the ship. The biggest value I’ve seen is a roll of about 6 degrees but we tend to be having rolls and pitches between 1 to 3 degrees (although right now its stable). So the numbers don’t seem very high, but when I stand up to change my samples I feel the pull of the waves and I find myself balancing and swaying to stay vertical. To confirm all these numbers, all I have to do is take a look at the waves outside the porthole. Every few seconds I see a glimpse of grey dark waves then a few seconds later the horizon disappears and I’m looking up at the grey cloudy sky.

 The other thing I’ve been looking at is the data from the CTD, this instrument measures Conductivity (or salinity), Temperature with Depth, and therefore provides us with a profile of how cold and salty the sea is through the water column. These parameters are really important for looking at the physical dynamics of the ocean and interpreting our data. From these profiles I can tell you where a reef is located, when there is an internal wave from a tide, or even where the gulf stream is. The last few days we’ve been watching the sea surface change colour, its stripy white mixed in with the blue. Much like a swirl of two ice creams being mixed together. The white is actually a coccolithophore bloom. Coccolithophores are tiny microscopic plants that make calcium carbonate plates, like armour plating. When these phytoplankton die the plates fall off and a mass of chalky whiteness fills the sea. These blooms are so extensive they can be seen from space. The swirls happen because the ocean is dynamic, there are eddies and waves that carry these microscopic plants around. It’s been fantastic to match all this up: From satellite to ship-board photographs, to the water physical dynamics (the CTD), to the microscopic plants, and then to the invisible, yet ever present, dissolved inorganic carbon.