Carbon burial in deep-sea sediments is very important for the functioning of the global carbon cycling and climate change. A number of oceanographic parameters affect this, but until now the impact of submarine landscape geometry has received little attention.
TopoDeep (‘Impact of the Geometry of Submarine Landscapes on Deep-Sea Biogeochemistry’) is a new NERC-funded project just starting at SAMS which aims to produce the first assessment of the impact of kilometer-scale seafloor topography on the transport of carbon from the surface to the deep ocean, and on its cycling within the sediments and benthic communities.
Seafloor geometry varies on distance scales from micrometers (millionths of a meter) up to thousands of kilometers. While the very small and very large spatial scales are well characterised, the intermediate scale has remained virtually unstudied. Over distances of kilometres, the ocean floor is structured by abyssal hills and seamounts. These features are abundant in many parts of the world ocean and their shape and geographical distribution will have changed throughout Earth's history.
The landscape geometry is expected to be controlled by the existing seafloor features, and their interaction with the long-term average ocean currents (‘residual flow’) and the more rapidly varying component of currents (‘tidal flow’). Two key physical parameters affect how the currents interact with the underwater landscape. These are the strength of deep ocean tides and the Coriolis force (which causes moving water masses to be deflected sideways due to the rotation of the Earth and varies with geographical latitude). TopoDeep scientists have identified three seamounts for detailed study (see Figure) which are located in regions of different Coriolis force (Senghor seamount vs. Ampere seamount) and tidal strength (Ampere seamount vs. Eratosthenes seamount).
SAMS researchers, in collaboration with European partners, will study the physical biological and chemical oceanography of these seamounts using a range of sophisticated techniques including mathematical models of the currents, chemical analysis of particles in the water column, new technology for measuring chemical exchanges between the seafloor and overlying waters, photographic surveys of the ocean floor and deep sea sediment sampling.
The SAMS scientists working on this project are Robert Turnewitsch, Andrew Dale, Ronnie Glud, Henrik Stahl and Bhavani Narayanaswamy.