Ocean cur­rents de­term­ine the struc­ture of the deep-sea ocean floor and the trans­port of sed­i­ments, or­ganic car­bon, nu­tri­ents and pol­lut­ants. In flume-tank ex­per­i­ments, re­search­ers from MARUM—Cen­ter for Mar­ine En­vir­on­mental Sci­ences at the Uni­versity of Bre­men have sim­u­lated how cur­rents shape the sea­floor and con­trol sed­i­ment de­pos­ition.

This will help in re­con­struc­tions of past mar­ine con­di­tions. They have now pub­lished their res­ults in the Nature journal Communications Earth & Environment.

De­tails of past cli­mate con­di­tions are re­vealed to re­search­ers not only by sed­i­ment samples from the ocean floor, but also by the sur­face of the sea­floor, which is ex­posed to cur­rents that are con­stantly al­ter­ing it. De­pos­its shaped by near-bot­tom cur­rents are called con­tour­ites. These sed­i­ment de­pos­its con­tain in­form­a­tion about past ocean con­di­tions as well as clues to cli­mate. Con­tour­ites are of­ten found on con­tin­ental slopes or around deep-sea moun­tains. But they can be found in any en­vir­on­ment where strong cur­rents oc­cur near the sea­floor. The mech­an­isms that con­trol them are not yet well un­der­stood. Ex­per­i­ments in flume tanks will help to change this through the de­pic­tion of de­pos­ition in fu­ture mod­els.

Detailed Observations of Changes in Flume-tank Experiments

Hen­ri­ette Wil­ck­ens, first au­thor of the newly pub­lished study, cre­ated a rep­lica of the con­tin­ental slope in a spe­cial flume tank at the Uni­versity of Utrecht (Neth­er­lands). Cur­rents and sed­i­ment in­put in the flume tank were sim­u­lated us­ing pumps and mon­itored with a cur­rent meter. The form­a­tion and de­vel­op­ment of the sed­i­ment de­pos­its were meas­ured with a laser scan­ner. All the data ob­tained were com­pared to meas­ure­ments in nat­ural ocean sys­tems in or­der to val­id­ate the res­ults of the ex­per­i­ments.

“The in­ternal sed­i­ment ar­chi­tec­ture of con­tour­ites can be ob­served from seis­mic data, but in or­der to un­lock in­form­a­tion about the past ocean cur­rents we need a bet­ter un­der­stand­ing of how they de­veloped and the factors that in­flu­ence the con­tour­ite sys­tems,” ex­plains Wil­ck­ens. While it is im­possible to dir­ectly see how nat­ural mar­ine sys­tems that de­veloped over time peri­ods of thou­sands to mil­lions of years star­ted to form on the sea­floor, sci­ent­ists can em­ploy flume-tank ex­per­i­ments to dir­ectly ob­serve de­tailed changes of the sea­floor mor­pho­logy and con­trol their re­lated cur­rent ve­lo­cit­ies.

Huge Application Potential of the Models 

“Our ex­per­i­ment can also be ap­plied to the en­tire deep sea and even to lakes,” says Hen­ri­ette Wil­ck­ens, mean­ing any­where in the deep sea where there is a slope, ter­races, deep-sea moun­tains or, for ex­ample, cold-wa­ter coral mounds.

It is also con­ceiv­able that the mod­els could be ap­plied, for ex­ample, to im­prove pre­dic­tions of how cur­rents trans­port mi­cro­plastic particles or other pol­lut­ants in the ocean. “The po­ten­tial for its ap­plic­a­tion,” says Wil­ck­ens, “is im­mense. The sys­tem must first be un­der­stood be­fore it is pos­sible to de­rive in­form­a­tion from it.”

Opening a New Branch of Research

“This research work is an important step toward a better understanding of the ways in which ocean currents control the deposition of particles in the seafloor, which has important implications for paleoceanographic reconstructions and benthic ecology. This introduces a new branch of research that will probably lead to even more exciting discoveries,” according to Elda Miramontes, co-author of the study and head of the Sedimentology working group at MARUM.