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24 February 2002 - Core Science

RRS James Clark Ross Diary

Position at 1200: 63° 32.7'S, 51° 45.8'W - 95 nm NE of Joinville Island at the north end of the peninsula
Distance Travelled since Grimsby: 26734 Nautical Miles
Air temperature: 2.1°C; Sea temperature: 1.7°C
Weather : Cloudy with sunny spells, good visibility, moderate to rough seas, moderate swell, wind NNW increasing 5-6.

Current, frequent weather observations reported back to BAS Headquarters in Cambridge is used to plot the ship's current position and recent track. Meteorological data are also available from this page. The callsign of RRS James Clark Ross is ZDLP.

A wee visit to Rothera

This last week saw us taking time out from the science cruise to pop into Rothera, the main reason for this was to discharge 12 containers of general cargo, and load 11 containers full of debris from the Bonner Lab fire last year. This clean up has been going on all summer, clearing the site for the re-building of the lab.

While there we said goodbye to Sir Crispin Tickell, Chris Rapley, the BAS director, and their party who will be catching the Dash 7 (BAS air unit) back to the Falklands. We were only there from 9am to 6pm and it was windy and snowing, as well as being busy with cargo, so there was no chance of a jolly ashore for the crew although the science staff managed to get a look around the base and Rothera point.

In the photo looking down into the lower hold that is not dirt on the lens...that is snow, and yes Luke is as cold as he looks, and yes it was as dark as it looks!

Waiting for the cargo. Click to enlarge Discharging the containers. Click to enlarge

While we were tied up at Rothera the American Antarctic Programme research ship the Lawrence M. Gould sailed around the bay. They were on a whale survey as well as doing some coring and moorings in the Marguerite Bay area...much the same as us. Her sister ship the Nathaniel B. Palmer was also doing science close by and the cruise ship Kapitan Dranitszyn was also in the area.

The science bit........

After leaving Rothera in the evening we steamed back out to the same area that we have been in for the last week or so to finish off the last of that part of the cruise, as described here by Colm.

Palaeo-ice streams on the Antarctic Peninsula continental shelf

The AFI team consists of; Julian A. Dowdeswell, Carol J. Pudsey, Colm Ó Cofaigh, Jeffrey Evans and Peter Morris

The first week of the cruise was devoted to an Antarctic Funding Initiative (AFI) project, headed by Julian Dowdeswell and Carol Pudsey, which involved geophysical and geological investigations of a palaeo-ice stream on the continental shelf west of the Antarctic Peninsula. The broad aim of this project is to investigate the past stability of the Antarctic Peninsula ice sheet and to reconstruct its dynamics over the last 20,000 years or so. We are particularly interested in areas of former fast ice flow (palaeo-ice streams) as these would probably have accounted for most of the drainage from the ice sheet.

The ships track since Stanley. Click to enlargeA variety of geophysical and geological tools including the EM120 multibeam swath bathymetry system, TOPAS sub-bottom profiler and vibrocoring, were utilised to investigate one such palaeo-ice stream in Marguerite Bay. In this region a trough extends across the continental shelf from the inner part of Marguerite Bay to the shelf edge. Swath bathymetric data reveal a detailed picture of the sea-floor within the trough and show that it contains a spectacular suite of streamlined subglacial landforms recording the former presence of an ice stream which extended to the continental shelf edge during the last glacial maximum (about 18,000 years ago).

A swath image of the seabed. Click to enlarge TOPAS acoustic data from the uppermost few 10's of metres of the sea floor indicate that the floor of the trough on the outer shelf is underlain by a thick sediment layer in which the subglacial lineations are formed. Vibrocores, up to about 5.7 m in length, collected by the British Geological Survey team (Ali Skinner, Colin Brett, Neil Campbell, Graham Tulloch, John Derrick and Dave Smith) have penetrated this sediment layer and the cores are currently being split and analysed on-board. Initial results indicate that the sediment layer is a soft subglacial till. This data will help us to understand what controlled the fast flow of this ice stream and how it evolved both temporally and spatially.

The core barrel when it comes back on board. Click to enlarge The core being pushed out of the barrel. Click to enlarge

Above: The core barrel is brought back on board (L), and the core is pushed out of the barrel (R). Click on the images to enlarge.
Below: The core being processed (L) and Jeff sealing the ends of the cores with wax (R). Click on the images to enlarge.

The core being processed. Click to enlarge Jeff sealing the ends of the cores with wax. Click to enlarge

The gullies seen by the swath. Click to enlargeSwath bathymetric data and vibrocores were also obtained from the continental slope offshore of Marguerite Bay in order to investigate the sedimentary processes that characterise this environment. Two cores were collected from directly in front of the trough and one from either side. The swath bathymetric data show that the continental slope is incised by a series of gullies which are most prominent in the areas on either side of the former ice-stream terminus. Cores from these areas recovered gravel. In contrast, a longer record of fine-grained sediment was recovered from the gentler slope in front of Marguerite Trough. Collectively these data indicate that much of the glacially-derived sediment bypasses the slope and is deposited on the continental rise.

Male models of the week........

The core crew. Click to enlargeFrom L-R; Graham Tulloch, Ian Hawkes, Colm and Jeff processing the cores in the wet lab.

The next chapter......otherwise known as JR71 part 2.

We finished off the last of the swath survey and coring at midday on Friday and headed at full speed for the Weddell sea on the other side of the peninsula, our route took us up Bransfield strait past Deception Island (See Update week 12). A small swath transect was done near to King George Island before turning again and heading towards the first CTD site. The trip up made a pleasant change for all on board as the wind died away, the sun came out and we were near to some land! Lots of icebergs and whales, including minke and orcas were seen as well.

Thank-yous this week......

To Joceyln Kaiser for some photos, Colm O'Cofaigh for writing the science bit and Peter Morris for images.

Birthday wishes.....

To Val Korb, happy 60th for Sunday with love from your little sailors, Paul, George and Hamish! And also on board Danny the chief cook and Carol the PSO, happy birthday from us all.

Coming up next week......

CTD's in the North West end of the Weddell sea, then moving back in towards the peninsula to do more swath bathymetry and coring, closer to the Larsen ice shelf.and hopefully some good satellite images of the Larsen ice shelf from our Dartcom receiver (clouds and R/O permitting!).