The research cruise will take place in April and May between the Canary Islands and Bermuda, and will be led by the University of East Anglia and the National Oceanography Centre (NOC). The team, based on board the Royal Research Ship Discovery, will use robotic floats that measure ocean properties and track ocean currents, along with a range of other sensors and devices.
The aim is to understand the processes that control the supply of nutrients to the sunlit surface waters in the remote mid-Atlantic Ocean, which is typically characterized by low levels of nutrients. This region, however, is currently experiencing the largest observed phytoplankton bloom in the past decade.
"The ocean's supply of nutrients is vital to the marine food web and ultimately the health of our planet," said Dr. Toby Tyrrell, reader in ocean biogeochemistry at UEA and principal scientist on the cruise. "The mechanisms by which nutrients are re-supplied from deep water to the sunlit surface ocean remain poorly understood, which hampers our ability to accurately predict how marine systems will respond to future environmental change."
"This region of the ocean is usually devoid of nutrients at the surface and phytoplankton productivity is correspondingly low," said Dr. David Raubenheimer, an oceanographer at NOC and co-principal scientist. "However, in late spring and early summer the islands act as a pump, lifting deep nutrient-rich water back to the surface where it can fuel phytoplankton blooms. By deploying state-of-the-art measurements across the region we aim to unravel the exact processes that are involved."
The scientists plan to deploy five robotic floats known as Argo profiling floats, which will spend months drifting at depths between 1,000 and 2,000 meters before surfacing every 10 days to transmit their data via satellite. The data provides information about temperature, salinity, carbon storage and ocean currents.
The team will also deploy an autonomous underwater vehicle (AUV) equipped with cutting-edge imaging, optics, and fluid sampling systems. The AUV will sample the water to learn about the types and quantities of phytoplankton and zooplankton in the water, and measure oxygen and nitrate levels.
"The remote nature of the subtropics is one of the main reasons so little is known about the processes occurring there, and why previous studies have been limited in scope," said Tyrrell. "This research cruise will enable us to make the most comprehensive observations to date of the processes that supply the base of the marine ecosystem with essential nutrients."
The research cruise is funded by the Natural Environment Research Council (NERC) as part of the UK-US Collaborative on Climate, Oceans, and Weather and the Changing Water Cycle program. The international science team includes researchers from the University of East Anglia, the National Oceanography Centre (NOC), the University of Oxford, the University of Liverpool and Bermuda Institute of Ocean Sciences, as well as NASA's Jet Propulsion Laboratory in the USA and the University of Copenhagen in Denmark.
