Apr 4 - Journeying around the South Sandwich Islands
So what's been going on this week?
This week the James Clark Ross has been mainly working on the far eastern edge of the Scotia Sea around the South Sandwich Islands
After finally recovering the Otter trawl on the evening of the 24th March, finishing two days with the Fish Team, the JCR continued with its easterly course around the southern edge of the Scotia Sea. The ship was heading for South Thule, the southernmost of the South Sandwich Island groups, themselves forming the eastern rim of the Scotia Sea. The journey was to take about 60 hours and the ship arrived off Reef Point, to the south of the island group at 0500 on the 27th. The JCR waited on DP until after first light, and at 0645 set off through the narrow navigable caldera, Douglas Strait, between Thule and Cook Islands. There were a number of tasks to be undertaken in the few hours the ship was to be within the crater itself. The first was to send a small shore party onto one of the beaches at Thule and collect algae samples. This was a very quick process, and having arrived on site at 0840 the Humber was heading back to the JCR just 40 minutes later. A single dive at been hoped for inside the crater itself, but after assessing the situation from one of the humbers, it was decided that the direction and magnitude of the swell, in association with the shear cliffs all the way around Thule would have made diving at that point in time a risky undertaking indeed. The two humbers thus returned to the ship and were re-stowed, ready for the ship to continue on.
Once the humbers were back in place, the ship took a slow turn around inside the crater, swathing the depths of the crater on the way, to position centrally over its deepest point. Here a CTD was undertaken, allowing collection of a water sample from down through the water column. This was all completed before lunch and at 1200 the ship Douglas Strait, ready to start the first of the BIOPEARL stations directly in front of the caldera. The shallowest 2 of the 4 stations were undertaken during the afternoon, with the final CTD recovered at 2020 that evening. The deeper two stations were started early the next day, with cloud intermittently lifting for short periods over the day, with the last EBS of the day being undertaken at dusk, with the most beautifully coloured backdrop spanning across the skyline to the north.
Once the final trawl of the day was on deck at 1835, the JCR was to pass to the east of Southern Thule, as shown above, and then overnight pass Bristol Island, in the direction of Montagu Island, arriving in that area before sunrise. We were fortunate that the visibility was to remain good for the first few hours of the day. Three CTDs were to be undertaken over the morning, so that water samples could be collected in the viscinity of Montagu to look at the bacteria present within the water. For the first few hours of work, at least, this was accompanied by a backdrop of a volcanic island, intermittently spewing out plumes of ash high into the air. By 0800, though, the cloud level had descended, leaving nothing to photograph than a backdrop of grey.
The three CTDs were completed by 1000 and, after skirting around Montagu Island, the JCR passed North-west into the open water of the Scotia Sea, and, initially, to fairly heavy swell. The next work station would be only 24 hours later on the afternoon of the 30th, with a further set of 6 CTDs undertaken for bacterial sampling. Three were undertaken to 500 metres to collect a total of 300 litres of seawater from that depth, while the other three were lowered to only 30 metres so as to collect the same amount. These 600 litres of water were filtered over the next 30 hours or so to collect all the bacteria present within the two separate samples.
The ship was to continue on it's now north-westerly course to the next research area to the north-east of South Georgia. This was to be a period of about three and a half days in the hands of the Mud Team. The ship arrived in the work area on the afternoon of the 31st. This area was to be surveyed prior to any coring taking place so this was undertaken overnight, ready for a further 2-3 days of coring after. For how things actually go, we will have to wait and see and you will have to tune in next week. For the moment, though, I will pass you over to Claire and the Mud Team to explain exactly what they did at their last site and are planning over the coming days.
Science from the Mud Team
with Claire Allen
The Geoscience team on board are Claire Allen and Elizabeth Petrie of BAS and Anna Hey (PhD Student of Cardiff University and BAS). We have 5 days of allocated science onboard in which to collect cores of deep sea sediments - made up of beautiful fossil diatoms! Diatoms are microscopic plants that are very abundant in the Southern Ocean. Different species live in different waters, from within the sea ice to the open ocean. These diatoms sink to the ocean floor and make up thick sediments throughout the Southern Ocean that reflect the water conditions above. The sediments preserve a fossil-record of changes in water conditions. The cores we retrieve on this trip contain this record and show how the ocean and hence climate have changed over the last 10,000 years. Knowing what conditions have been like in the past means we can assess how unique modern climate change is.
During the rest of the time on board we run the sea floor imaging systems 24 hours a day (Swath bathymetry and TOPAS sub-bottom profiler) with everyone on board making use of the maps to help choose sites for fishing, trawling and coring. We also take samples of sea surface water every 3-4 hours to study the living diatom communities. The water samples will be used to improve our knowledge of modern diatom distributions.
The datasets collected in this 7 week cruise will provide at least 2 years work for Claire!! Claire and Anna form part of the BAS core science project CACHE PEP, aiming to link climatic change visible in Antarctica with the rest of the globe. Hurray for the mud -diddly mudmud!
PS. It’s a good job Anna’s here!
And now for some of this week's Beasties......well.........Diatoms!!
Pictures courtesy of J Pike (Cardiff University)
A little Something about the South Sandwich Islands
from Mike Gloistein
The South Sandwich Islands group consists of a chain of islands, connected by a low submarine ledge, forming an arc in a N and S direction between the parallels of 56°18's and 59°28 S, and between the meridians of 26°14'W and 28°11'W. The South Sandwich Islands were discovered by Captain James Cook, in HMS Resolution, who first sighted Southern Thule on 30 January 1775. The Islands, from North to South, are:
Zavodovski Island: This is a single volcanic cone, approximately 9 miles in circumference and some 550m in height. The crater is in constant eruption with hot smoke and sulphuretted hydrogen having been observed issuing from it.
Leskov Island: This is the smallest of the group, with a flat summit, precipitous on all sides.
Visokoi Island: This is also a single volcanic cone. From most directions this appears as a rounded mass with a steep coast.
Candlemass Island and Vindication Island: These two islands lie some two miles apart from each other and are separated by Nelson Channel. Candlemass has two peaks, Mount Andromeda and Mount Perseus, and there is a volcanic cone, known as Lucifer Hill.
Saunders Island: This island is roughly crescent shaped. In the middle of the island there is Mount Michael, a glaciated but active volcanic cone.
Montagu Island: This island has just become ‘hot news’ as it is currently erupting and has grown by 50 acres (0.2 km2), equivalent to 40 football pitches in the last month.
Bristol Island: The island was first sighted by James Cook and is separated by Forster Passage from;
Belingshausen, Southern Thule and Cook Islands: These islands form the most southerly of the group. The Russian explorer Fabian von Bellinghausen landed on Zavodovski in 1819.
.....and finally, The Hawaiian Islands were originally called the Sandwich Islands!
Well, that's it for now. For more mud and then on to South Georgia, tune in next week.