25 November 2001 - The BBC and a Science Cruise
RRS James Clark Ross Diary
Position at 1200: 60°15' South, 56°48.5' West
Distance Travelled since Grimsby: 14550 Nautical Miles
Air temperature: 1.0°C; Sea temperature: 0.7°C
The past week..
Last Monday evening saw the last of the personnel joining us for this trip and our immediate departure from Stanley. This leg will take us down to the Antarctic Peninsula and on to our Rothera Research Station inside the Antarctic circle. However, first there were two four day scientific programmes to be completed, both of them building on work previously performed, details of which come later. Initially as we sailed south the Southern ocean lived up to expectations with a good sea running causing us to rock and roll just a bit.
An impression might be gained from the picture below taken by Philip Hughes one of two artists onboard, who are travelling to Antarctica as part of the new BAS Artists and Writers Programme. This is a programme in which two people, each year, involved in the arts come to the Antarctic and experience all that it offers and allows them to interpret those experiences through their chosen medium. The other person is also an artist called Keith Grant, they have both been busy around the ship collecting material to work on.
Lucky for us the rough weather wasn't to last and soon the most tempestuous parts of the world's oceans took on the appearance of the local duck pond; becoming flat calm. The pictures below show the James Clark Ross during a science station on Friday afternoon when a request was made to take photographs of the ship from small boats and we have to thank Dave Rees (AB) for those below. Click to enlarge.
You might be wondering who would want to leave the safety of a large ship in the middle of Drake's Passage, even on a calm day. Well the answer is the BBC, who else!? We have travelling onboard Science and Environment correspondent Christine McGourty and cameraman Tony Joliffe who are putting together material for a series of special reports on the Antarctic to be shown on various BBC outlets during Christmas week, that is assuming they get home in time! In addition you should be able to catch reports from Christine on BBC TV News, BBC Radio 4 and BBC Online, though I hope you understand that we don't encourage deserting us for other web sites, but on this occasion we will make an exception!
The above pictures show Christine and Tony at work this week. As well as filming the ship and science deployment in the left-hand picture and an interview with Mike Meredith (BAS Oceanographer) on the fo'c'sle (front above the bows) - Click to enlarge.
Sunday morning saw our arrival off Elephant Island, in the South Shetland Islands, which marks the southern end and hence end of cruise JR67 (see below). We have now headed off north-westwards back out to sea for JR69 (you'll have to ask HQ where JR68 went to as we don't know!!), but back to JR69 which is a swath bathymetry mapping survey being done to expand a survey of the Shackleton Fracture zone, but more of this next week.
A few days science......
Drake Passage repeat hydrography section. (JR67)
Dr Sheldon Bacon, Dr Brian A. King, Dr Elizabeth Kent, Elizabeth Hawker, Alex Sen Gupta (SOC), Dr Michael Meredith (BAS), and Julie Collins (UEA).
The Southern Ocean is a major component of the coupled ocean-atmosphere climate system. It connects all the other major oceans and influences the water mass characteristics of the deep water over a large proportion of the world. Hence the Southern Ocean plays a pivotal role in global ocean circulation, which in turn regulates the global climate. The major Southern Ocean current, the Antarctic Circumpolar Current (ACC), transports large volumes of water west to east around the world, typically around 136 million tonnes per second. Measurements of the total amount and detailed structure of the transport in the ACC can provide critical tests of numerical model dynamics, as well as of proposed paradigms of the global ocean circulation, ocean variability and climate change. The Drake Passage is an advantageous location to observe the ACC. At this choke point between South America and the Antarctic Peninsula the meridional spread of the ACC is constrained and transport measurements can be attempted.
The Drake Passage section is possibly the most important section of the Southern Ocean, partly due to its accessibility and being the narrowest point, but is also the immediate link between the Pacific and Atlantic Oceans. Since 1993 scientists from the Southampton Oceanography Centre and British Antarctic Survey have completed six hydrographic sections across Drake Passage. At present we are completing our seventh section. These hydrographic sections consist of a number of stations across Drake Passage (Figure above).
The CTD becomes a movie star (Jeremy Robst) and just to prove the Principal Scientists do get their hands dirty we have Sheldon helping with the water sampling. Click to enlarge.
At each station, with the ship hove to, we lower a package of instruments (CTD) from the ship to the seabed, measuring pressure, temperature, salinity and water velocities. In addition at a dozen depths, water samples are captured in bottles. These samples are analysed onboard ship to make a very precise determination of the sample's salinity - variations in salt of the order 1 part per million can be measured.
By making repeat measurements we can begin to understand the natural variability of the amounts, properties and flow rates of the different water masses in the Southern Ocean. These observations are the base line from which future changes may be determined. Therefore, with a long time series of observations it may be possible to attribute variability to changes in atmospheric forcing - climate change.
Above results from JR67. Click to enlarge. These are preliminary results having come hot off the computers this afternoon thanks to Liz Kent. The left hand diagram show temperature across the section with the Falklands being to the left-hand side and the right-hand drawing shows the salinity across the same section.
The unusual and intriguing aspect of this year's results concerns the position of the Polar Front (or "Antarctic Convergence", historically) and the very coldest, deepest water at the southern end of the section. Previous years have generally shown that when the Polar Front is a long way north, there is a large amount of very cold, dense water to the south of it. (This water forms in the Weddell Sea and flows around the Antarctic Peninsula into Drake Passage, as well as flowing north into the Atlantic and northeast into the Indian Ocean). Conversely, when the Front is a long way south, the cold water to a large extent disappears. This year however, the Front is in quite a northerly position, but the coldest deep water is almost completely absent. Solving this puzzle will tell us more about what controls the ocean properties and climate on interannual timescales.