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Research in the Atlantic Ocean: Six weeks onboard the Discovery

Cruise blog


Ophelie Meuriot standing in front of the RRS discovery in port Ophelie by the Royal Research Ship Discovery (c) Matt Douthwaite

Ophelie Meuriot, a Research Postgraduate on the Science and Solutions for a Changing Planet Doctoral Training Partnership studying physical oceanography in Imperial’s Department of Earth Science & Engineering, shares her experience aboard the Royal Research Ship Discovery.

The original blog post below can be found on the Grantham Institute blog.

Why do scientists go on research cruises?

Oceans cover more than 70% of the Earth surface. They play a key role in regulating the Earth’s climate by storing heat and carbon emissions. They are also home to phytoplankton, small organisms that produce oxygen through photosynthesis. Understanding how the physical, biological and chemical properties of the ocean will evolve with climate change is therefore critical.

Scientists go on research cruises to obtain data to study these processes and validate models or theories. Atlantic Meridional Transect (AMT) research cruises travel across the Atlantic Ocean from North to South. The first one took place in 1995 and since then, there has been 28 other cruises. As a result, scientists have a large dataset to study how the Atlantic Ocean has changed over time. I joined the 29th AMT, boarding the RRS Discovery in Southampton on 13 October 2019, where I would live for six weeks as we voyaged to Punta Arenas, Chile.

How do you collect data in the ocean?

There are a wide range of processes you can study in the oceans, and a lot of different ways to collect data. I was often asked by my family and friends whether I had to get into the water to take samples. As much as I would have loved to go scuba diving, the samples we needed typically came from 2,000 metres under the surface (the deepest samples we took came from a depth of 5,000 metres), so scuba diving wasn’t an option! 

A CTD device being lifted by crane onboard
The CTD tool, used to collect samples from the ocean (c) Werenfrid Wimmer
 
The main instrument we used was the CTD, a tool that measures the conductivity (which can be converted to salinity), temperature and depth – together, these are used to determine the water density. The CTD was placed in the middle of a frame (the rosette), and mounted with 24 bottles of 20 litres each (the Niskin bottles). Each bottle could be closed remotely at a chosen depth. Twice a day the ship would stop to lower the CTD in the water, once at 500 metres and once at 2,000 metres. When it was back on deck, each scientist took their  water samples and measured various biological or chemical parameters.

What is a typical day onboard?

Activity on board a ship goes on 24 hours a day, seven days a week. As my main role on board was to take samples from the CTD, I had to be prepared with all my sampling equipment whenever the CTD was back on deck. This was usually at 4:30am and at 1:30pm. It would usually take me a few hours to take samples. I would also spend time looking at the data obtained from the CTD sensors, mainly temperature and salinity. My research focuses on a water mass (a layer or current in the ocean) called the Antarctic Intermediate Water (AAIW). It was exciting to be able to identify the water mass in the day’s data and see how it evolved when going from North to South.

Ophelie taking samples from the CTD
Ophelie taking her samples from the CTD (c) Gavin Tilstone

On the Discovery, half of those on board were crew, who all had their own schedule to keep to. Running a ship requires a wide range of skills and significant forward planning. To keep everything running smoothly, deck officers had to make sure the ship was on track and on time, engineers had to manage the engines and the water and waste treatment facilities, and cooks had to ensure everyone was well fed with three meals a day. A research ship is not only a place of work with labs and scientific equipment, it is also home for more than 50 people for six weeks. And as you would do at home, we found time to relax in the evenings, play cards or board games, and exercise a bit in the gym.
 
 

Six weeks at sea, does it not get boring?

It might seem that data collection is a repetitive task, but every day was different. For one, as we were travelling from North to South, temperature ranged from over 30 degrees at the equator to around 10 degrees in Punta Arenas – with some storms along the way. Being in a storm felt a bit like being on a roller coaster. Once I stopped feeling sea-sick, it was fascinating to watch the waves (though after a few days of storms, I was happy when it stopped). I also saw some fantastic landscapes, enjoyed the sunset and sunrise every day, observed the stars at night, and saw dolphins and whales. I also met different people and discovered ship traditions, such as the ‘crossing the line’ ceremony to celebrate people’s first crossing of the equator. With birthdays, Halloween parties, quiz nights and more, I didn’t have time to get bored!

Marine life seen from the ship

Last, but not least, this expedition onboard the Discovery has opened up new perspectives for my research. I can now understand how the data I analyse every day is obtained. Being able to discuss and see how other oceanographers are trying to solve some of the ocean’s mysteries was an unforgettable experience.