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26 November 2000 - On the way to Rothera

RRS James Clark Ross: Diary entry, 26 November 2000

Noon Position : 58 degrees 49' South. 56 degrees 05' West.
Distance travelled since Grimsby: 11446 nautical miles
Air temperature @ noon: 0.5 degrees Celsius
Sea temperature @ noon: 1.2 degrees Celsius

We finally left Stanley on Tuesday afternoon after all the cargo from RRS Ernest Shackleton had been transferred and loaded. Although we are heading for Rothera research station on the Antarctic Peninsula, we have some science to do on the way and there will be more on that later. The newcomers on board are a varied lot, personnel for Rothera station and Port Lockroy, scientists from Southampton Oceanography Centre and Proudman Oceanographic Laboratory, British Antarctic Survey support staff, and Hugh Marsden a philatelic clerk from the Falkland Islands.

So far we have been very lucky with the weather, it being generally calm (good for science and sleeping!), if grey. A few new "avifauna" species have been sighted, including light mantled sooty albatrosses and white morph giant petrels, and now, more numerous sightings of whales, or at least their blows! This usually provokes people into frenzied action as the word gets out, and they don their woolly cardigans and grab their cameras, only to see a faint mushroom of water spray several miles away.

Whale - caught in the nick of time!

Caught in the nick of time!

SCIENCE by Dr Stuart Cunningham
Drake Passage repeat hydrography RRS James Clark Ross Cruise JCR55 21 November to 14 December 2000
Dr Stuart Cunningham, Dr Brian King, Dr Michael Meredith, Louise Duncan, Natalie Edwards, Martin Price and Susan Brown.

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.

Group photograph of the science team

Figure 1: from left to right: Natalie Edwards, Brian King, Susan Brown, Mike Meredith, Stuart Cunningham, Martin Price, Louise Duncan

The Drake Passage section is possibly the most important Southern Ocean choke point section, because of its accessibility, because it is the narrowest, and because it provides the immediate link between the Pacific and Atlantic Oceans. Since 1993 scientists from the Southampton Oceanography Centre and British Antarctic Survey have completed five hydrographic sections across Drake Passage. At present we are completing our sixth section, with help from scientists at the universities of East Anglia and Edinburgh (Figure 1). These hydrographic sections consist of a number of stations across Drake Passage (Figure 2).

Bathymetry of Drake Passage with the JR55 station positions

Figure 2: Bathymetry of Drake Passage with the JR55 station positions - click to enlarge

At each station with the ship hove to we lower a package of instruments 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.

George and Kelvin assisting with the CTD deployment Laboratory determination of salinity

George and Kelvin assisting with the CTD deployment

Precise laboratory determination of salinity

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 baseline 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.

For more detailed information on this work visit: www.soc.soton.ac.uk/JRD/HYDRO/scu

Our long-suffering galley staff, who, through all weathers - the heat of the tropics, the heavy rolling of the Southern Ocean, produce without fail, a variety of gastronomic delights to suit all tastes - however extreme. Quite a feat when you think of the numbers they are catering for and the difficult conditions that the weather frequently dictates.

Tracey (2nd cook), Rif Raf (Galley Steward), and Danny (Chief cook)

Tracey (2nd cook), Rif Raf (Galley Steward), and Danny (Chief cook)

Weekly diary entries