Friday, 23 November 2018

Last leg of ORCHESTRA cruise part 5…by Melanie Leng

Mel on board the RRS James Clark Ross
Melanie Leng is currently taking part in an expedition to the Southern Ocean as part of  ORCHESTRA (Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports), a NERC funded programme with partners at the British Antarctic Survey (lead), the National Oceanography Centre, Plymouth Marine Laboratory, and many more including BGS. Here she updates us as she nears the end of her expedition on the RRS James Clark Ross…

We have been at sea for around 3 weeks on the RRS James Clark Ross crossing the Drake Passage from the Burwood Bank (an undersea shallow ridge off eastern South America) to Elephant Island (off the tip of the Antarctic Peninsula). All the work has been successfully completed. Personally I have collected over 600 water samples (with help from my overnight buddy, Julia Rulent from the Universities of Bangor and Liverpool) for oxygen and carbon isotope analysis, and around 250 for radiocarbon analysis. These samples are just one leg of the 5 year ORCHESTRA research programme to try to understand the structure of the Southern Ocean and more importantly what changes are taking place within the ocean because of human impact. These samples were taken from over 40 casts of the CTD (see blog part 4) from as deep at 5km in the ocean. On board others from NERC research institutes and UK universities are measuring salinity, temperature, nutrients, carbon, plastics, silicon and nitrogen isotopes, CFCs, and SF6. Many measurements have been made on board with instruments that the scientists have brought a long, the instruments strapped to benches in the ship’s laboratories, to stop them falling off as the ship rocks and rolls. In the 3 weeks on board I can’t remember a calm period, several hurricanes have passed over us bringing massive ocean swells and waves.

There has been a lot of work done, round the clock sampling in periods of relative stability, to make up for time lost due to the weather. The highs include 2 humpbacked whales (mother and calf) visiting us, the mother was enormous, perhaps 12-14m in length. The whales had a distinctive body shape, with long pectoral fins and a knobbly head, they repeatedly lifted their heads out of the water to take a look at the orange high visibility clothing clad scientists on deck, and did several back flips and tail whips. The whales were making their way south in the Southern Ocean to feed off krill and small fish, before returning to tropical waters to breed and give birth, where they live off their fat reserves built up in the south. In the past these amazing creatures have been a target for the whaling industry, and have been on the brink of extinction before protocols were put in place to limit whale fishing. The humpback whale population is increasing but still fishing gear, collisions with ships and noise pollution continue to impact the species.

One day we were also escorted for several hours by a pod of 30 or so pilot whales. It was a mixed group with several large animals of 6-8m, and many calves. The pilot whales frolicked in the waves, enjoying the speed that the currents afforded them, occasionally they stopped and peered at us, lifting their bulbous heads out of the water. With the pod were small clusters of penguins, visible as they surfed the waves on their hunt for small fish. Albatross and petrels follow the ship all the time, possibly for refuse or the small marine animals that are brought to the surface by the motion of the ship, or perhaps they are taking advantage of air currents produced by the ship...

From L-R: Pilot dolphins enjoying the surf; A humpback whale tail whip.
In a few hours we will be docked at Stanley on the Falkland Islands, where we will spend a couple of days demobilizing the ship, taking inventories of samples, packing up the equipment, and generally clearing up for the next cruise. The RSS James Clark Ross will be leaving Stanley in early December with a new group of scientists working on a project called ICEBERGS, they will be travelling along the west side of the Antarctic Peninsula, to see how rapidly retreating glaciers are changing the environment there. They will also be collecting gravity cores to put recent ice shelf retreat into historical (Holocene) context. You can follow them on: Instagram: developingoceans and twitter @ICEBERGS_JCR.

Overall its been a successful research cruise, in no small way down to Dr Yvonne Firing for her leadership and management. Also thanks to the dedicated crew on board, engineers, deck crew and stewards who all played their part.

I am tweeting @MelJLeng and @ORCHESTRAPROJ and Facebooking (Orchestra project) during this trip, a full list of blogs from the expediation are available from the drakepassageblog.worldpress.com page.

Melanie Leng is the Science Director for Geochemistry at the BGS and the BGS lead scientist for ORCHESTRA. 

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