Wirewalker deploy: this is a collaboration with the National Oceanography Centre in Liverpool. Wirewalker is a package of instruments that uses wave action to ratchet itself up and down a line in the upper 300 metres of the ocean.
Oceanographers from the University of Liverpool School of Environmental Sciences have set sail aboard the research vessel RRS James Cook to investigate an overlooked role for the mid-Atlantic ridge in Earth's climate.
The team joined the ship in Rio de Janeiro, along with collaborators from the National Oceanography Centre, Heriot-Watt University and the University of Southampton, the University of Seville and the Scripps Institution of Oceanography USA.
Scientists and engineers from the University of Liverpool, the National Oceanography Centre, Liverpool, and the Scripps Institution of Oceanography USA aboard the RRS James Cook.
They will be spending 7 weeks at sea working over the mid-Atlantic ridge in the South Atlantic, eventually finishing in Walvis Bay, Namibia, in early April.
The expedition will be looking at how tidal flows over the ridge generate turbulence, which mixes nutrients from the deep ocean up to the plankton in the surface waters.
As the plankton grow they absorb carbon from the surrounding seawater, which causes the ocean to absorb more CO2 from the atmosphere. The hypothesis underpinning the project is that the increased nutrient supply over the ridge will cause an increase in larger species of plankton. These larger plankton sink quickly to the ocean depths, efficiently exporting carbon away from the atmosphere.
The process that generates the turbulence over the ridge could be a critical missing part of how we understand the ocean's role in cycling carbon in Earth's climate.
The water depth at the mid-Atlantic ridge is about 3,000 metres, but the seabed is fairly mountainous here - the bathymetry map the team has been making looks very similar to an OS map of the Lake District.
So far, the team has deployed a large amount of instruments in the water, both here and about 350 miles to the west in the deeper water away from the ridge, and have so far completed our first set of tidal turbulence measurements over the ridge.
Deploying the glider - an autonomous instrument. This glider is set to measure water turbulence in the upper 500 metres, and will be working continuously for 3 weeks.
Lead scientist on the expedition, the University of Liverpool's Professor Jonathan Sharples, said: "This is a tremendously exciting, multidisciplinary project. We want to link the fundamental physics of turbulence over the ridge, through the growth and ecology of the plankton, to a new understanding of where and how the ocean absorbs and stores atmospheric CO2."
"We are looking for turbulence caused by breaking internal waves (which are waves that travel on the ocean thermocline, rather than waves you see at the surface).
"We think that this turbulence over the ridge mixes nutrients upwards, which changes the plankton community to one that is better at exporting carbon from the sea surface down to the abyssal depths of the ocean. A quick look at the data suggests there is very strong turbulence over the ridge.
Professor Ric Williams (Liverpool) and Tina Thomas (engineer from National Marine Facilities) watching the CTD data come in, and deciding which depths to collect water samples from.
"We are seeing lots of rays and squid around us at night, hunting the flying fish. In the middle of the subtropical ocean seeing such large predators is unusual, suggesting that the nutrient-induced changes to the plankton community are also useful to the rest of the marine food chain over the ridge."
The project is funded by UKRI through NERC Pushing the Frontiers.
Updates on the expedition's progress can be found at Professor Sharples blog: https://jonathanatsea.wordpress.com/
