Scientists and technicians from the National Oceanography Centre are spending six weeks at sea gathering data from the deep ocean that provide important information about our varying climate.
This year they will for the first time be retrieving data on the transport of carbon dioxide by the ocean.
The expedition, on RRS James Cook started today and can be followed on the expedition blog.
Read more about the work being undertaken on the expedition and about the cold deep currents in the Atlantic Ocean that help shape our climate.