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23 Mar - Autosub missions

RRS James Clark Ross Diary

Noon Position: 70° 38.7 S, 102° 39.8 W)
Distance Travelled since Grimsby: 27856.5 Nautical Miles
Air temperature @ Noon today: -0.9°C
Sea temperature @ Noon today : -1.3°C
Weather: Poor, NNE, 2, 985.8

Tales from the ice edge

As weeks go this was generally pretty quiet for the JCR. After the failure last week to get into Pine Island Bay due to heavy ice conditions we have been conducting science along the edge of the ice pack. Most of the week we have been shrouded in mist or snow squalls, watching for icebergs on the radar, becoming frustrated with e-mail and the BBC World Service reception. A good chance for everyone to get their heads down to do some work and stop eulogizing about the views. Things have settled down in to a routine of autosub missions during the day and CTD's at night. Swath is performed at times in between.

We did have one day of rolling around while a force 9 raged in the open sea. We saw towering tabular bergs around the ship being battered by the waves. These bergs, twice the height of the ship, were constantly being beaten by walls of icy water sending explosions of spray leaping heavenwards before being caught in the gale and blown over the ramparts of these ice castles. The water is full of ice of all sizes from ice cubes to fridges to cars through to small islands. We would violently roll and shudder through this maelstrom. Water in the form of snow, ice, fog and sea totally envelopes the ship as we plunge through the moving valleys of angry ocean. Outside ice is shaken from high up on the mast and smashes down on the decks below. Inside everything ends up on the floor and life becomes that little bit more difficult. But we are warm and dry, riding out the storm and remarkably life goes on almost as normal!

This week has seen the Spring Equinox so everyone at home in old Blighty is now getting longer days than we are. Winter is on it's way down here as we hear the UK is basking in temperatures up to 20°C! Hope you are all enjoying it!

Autosub in action

Autosub is a large yellow unmanned submarine that is deployed from the aft of the ship. It is programmed with a mission and once put in the water it heads off completely independently from the ship picking up various data readings along the way. It then proceeds to a specific point to be recovered back onboard. It is an extremely complicated beast and has been having a few teething problems on this cruise so far. One of the major difficulties is in recovering a large, heavy and very delicate torpedo back onboard especially in rough weather. Autosub can be deployed on a lovely calm day but when it returns, anything up to 48 hours later, then conditions can be far from ideal. During the week in a rough sea we were trying to recover the sub when it disappeared under the scalloped aft end of the JCR. At some stage the submarine was hit by 5000 tons of red metal (i.e. the ship) and when it was finally recovered it certainly looked like it had done a few rounds with Tyson. It was lifted from the water looking very sorry for itself much to the concern of everyone onboard. The main damage had been to the nose of the sub with damage to the fibreglass body work, chassis and most importantly, one of the scientific instruments, the sub-bottom profiler. However the damage was repaired overnight and autosub is now back in the water and completing missions. See below for some pictures of the damage....

Wounded submarine - Click to enlarge It's almost straight - Click to enlarge
Body work..........that's gonna cost....Click to enlarge Crumple zones?? Click to enlarge

Autosub has spent the week on missions travelling under the ice. Autosub has been collecting data on the temperature and salinity of the water under the ice and also the thickness of the ice floes. This is important in understanding the dynamics of sea ice formation in the Antarctic. The upward looking swathbathymetry on Autosub maps areas of the sea ice by sailing underneath and looking up. The only other way of estimating sea ice thickness is by drilling holes which is very slow. The ice forms a blanket that insulates the sea water below and stops it loosing heat into the atmosphere. The thickness of the ice is analogous to the thickness of your duvet so thicker ice means less heat transfer into the air. These processes have a significant effect on the climate and a better understanding of how they work will lead to more accurate climate models. Below Autosub can be seen in ice prior to a mission.

It's just like walking the dog! Click to enlarge Close encounters - Click to enlarge
The yellow peril is back on board - Click to enlarge

On Sunday night everyone was crowded up on the bridge all staring out into the fog. Autosub had surfaced and we now had to find it. Despite the visibility being down to only 100m in the fog and darkness it didn't take us to long to find sub. We are guided to it by a GPS device that transmits it's position to the ship. Once within 1km we could even see it on the radar in the calm weather. Within 400m we spotted it's bright strobe light flashing and after that recovery was straight forward. The watchers on the bridge had a sweep stake as to the time of recovery back on board and we are still waiting for Mike to get the round in. The sceptical third mate's guess was infinity!

Mike puts the sticks down - Click to enlarge
Mike puts the stick down
Click to enlarge

Communication Breakdown

Virtually all communication from the JCR passes through the satellite telephone link provided by INMARSAT. The calls are passed to and from a satellite dish on the top of the main mast to a geostationary satellite that is high above the equator. Each satellite has it's own 'footprint' which is an area on the surface of the earth that it can 'see'. The diagram below shows the overlapping footprints of the network of communication satellites that cover most of the world.

Satellite footprints - Click to enlarge
Satellite footprints
Click to enlarge

We normally use the red satellite but Pine Island is too far south and west to be covered. This means that the satellite is so low on the horizon that it makes it difficult for the ship to 'see' it especially during the rough weather that we have had during the week. E-mail and fax have also been disrupted that need a very clean connection to pass the data to and fro. The end result is that some days e-mail has been disrupted and mail arrives late. Don't worry they don't get lost on the way, e-mails will be stored either in Cambridge or on the ship until a good enough connection is established. This is my excuse of the late arrival of last weeks diary (Lazy Doctor more likely! - Ed).

Furthest West

The JCR achieved a personal best this week when it made it to 115 degrees west. This is roughly equivalent to Easter Island or Phoenix, Arizona but we were slightly further south! The exact location was 71deg 29min 32sec South, 115deg 06min 07sec West.

Coming up next week: Heading towards Rothera.

Alex Ramsden
Ships Doctor