14 January 2002 - Fog on the Science Cruise
RRS James Clark Ross Diary
Position at 1200: 53° 57.1'S, 38° 33.6'W - About 40NM North West of Bird Island, South Georgia
Distance Travelled since Grimsby: 20581 Nautical Miles
Air temperature: 5.3°C; Sea temperature: 4.4°C
This shows all the weather reporting ships and their position. The position
is marked by the vessels call sign so to see where RRS James Clark Ross
is you are looking for ZDLP on the map. If you want to see our Sister-ship
RRS Ernest Shackleton you are looking for ZDLS1.
Click on the South Atlantic area of the map, and choose "Marine Observations"
FOG..... i.e.: fog (fog) n. a mass of droplets of condensed water vapour suspended in the air, often greatly reducing visibility.
A rather appropriate way to start this week!
So where are we, what are we doing………and why?
We have spent most of the last week in thick fog, unable to see more than just a few metres! For those of us who are on the bridge driving, this means lots of concentration as there are quite a lot of icebergs and a few growlers about. It also means that no-one has actually seen South Georgia yet! This has lead to people actually asking us if we are even near it! Well we can promise that we are, and although the science program has had to be revised slightly, it is all going ahead well.
Whilst we have been here, we have seen (in a slightly thinner patch of fog!) and spoken to, someone we normally see closer to our home port of Stanley, the Fisheries Protection Vessel from the Falklands, Dorada, which is also in the area doing a research fishing cruise.
Due to the weather, we are now doing the first half of the cruise back to front; we started with the deployment of some drifter buoys (for measuring ocean currents: more on those soon) then moved on to do the CTD’s. We had to do this because in the fog we cannot safely steam fast enough for towing the UOR and we have had to dodge a number of icebergs because they always just happen to be sitting right on our intended track. In amongst all of this, we have been doing some target fishing for small sea beasts like krill and fish.
The salty sailor bit……starring Ian Raper
The Science bit....written this week by Beki Korb
This biosciences cruise is part of an integrated field season (which links the cruise with field work at Bird Island) to determine the relative importance of Flux and local production in maintaining krill and zooplankton populations at South Georgia. Basically this means that there are a number of scientists on board looking at the biology and physics of the South Georgia food web, which covers a whole range of things from ocean currents to krill right up to seals and whales!
So this week makes sense to start off by talking a bit about “phytoplankton” at the bottom of the food chain – though we like to think of this as the beginning of all life in the sea! Phytoplankton – for simplicity we will call them miniature plants (in fact they are microscopic) - use energy from the sun and nutrients in seawater to make their own food. These tiny plants provide food for millions of small animals such as copepods and krill, which themselves are eaten by penguins, whales and seals. Without the phytoplankton providing this first link in the food chain, there simply would not be so much life in the oceans around South Georgia.
The work we do on board the JCR aims at looking at the amount of phytoplankton in the seas around South Georgia and the factors contributing to the growth of these microscopic plants. Phytoplankton are very small in size (usually around 2-20 um,or a 1000th of a millimetre), they cannot swim and so they are at the mercy of the sea. This means that tides and currents play an important part in moving phytoplankton around – the oceanographers on this cruise will fill you in on the transport of water masses around the island at a later date (hence the drifter buoys).
Phytoplankton are also very dependent on sunlight (though there’s not always much of that down here) and nutrients in the water. From previous diaries you will have heard of the "UOR" and the "CTD" and these are the instruments we use most often to collect phytoplankton and nutrient samples and information about the amount of sunlight filtering down through the water column. Another important instrument we make use of isn’t actually in the water at all but at the very opposite end of the ship… a light sensor on top of the ships mast!
Although we are only at the start of our science cruise, we are already pulling in masses of data. We have a number of underway instruments measuring things such as phytoplankton biomass and nutrients like ammonium, nitrate, silicate, etc. as the ship moves along through the water. So if the ships instruments log data every 5 seconds, all day, every day for 40 days that would give us 6,911,200 data points!!!!! We’ll leave you with a small taste of the results of chlorophyll biomass around the northwest end of the island (phytoplankton use chlorophyll to capture the suns energy and so the more phytoplankton there is in the water, then the more chlorophyll there is in the water). The orange dots show that chlorophyll biomass can be extremely high...it’s often believed that phytoplankton biomass is quite low in Antarctic waters. However the cause of this high biomass and its effects to the rest of the food web are yet to be determined. Better get back to work then! There’ll be more on other aspects of the biosciences cruise as we go through the next 4 weeks.
UOR – undulating oceanographic recorder (A sledge like thing that undulates behind the ship)
CTD – conductivity, temperature and depth recorder (Basically a very expensive bucket as it collects water samples too!).
Beaker - Scientist, not always meant as an endearment!
One for those long, cold transect nights…..
One of the favourite souvenirs that people take home while doing deep CTD’s has to be the ‘squashed polystyrene cup’! This is quite easy to make yourself, all you need are;
- One cup
- Pens of assorted colours
- One sock
- One cable tie
- One CTD frame
- One research ship
- A few thousand metres of wire
- A friendly winch driver
Send down to nice deep seabed, slowly bring it back up and like magic you have a miniature cup....this is caused by the water pressure squashing the polystyrene!
Preparing the cups and Nathan showing Sally his latest party trick.
The cups after 4000m of water pressure!
Coming up next week…..
More science such as towing the UOR, target fishing and maybe, just maybe seeing the Island itself! Also there will be a little history lesson as to why we are conducting research here in the first place. On the ship side of things we will, as well as continuing to support the science, be going about our normal day to day duties.
Thankyous this week.....
To Beki for writing this weeks science bit, the night shift for the photos, Ian for the fancy covers and last but not least Neptune for the fog!!!