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| Seine Abyssal Plain | |
|---|---|
| Name | Seine Abyssal Plain |
| Location | North Atlantic Ocean |
| Type | Abyssal plain |
| Depth | 4000–5000 m |
Seine Abyssal Plain is a deep marine plain located on the eastern flank of the North Atlantic Ocean adjacent to the continental margin off northwestern Europe. It lies downstream of major European continental shelves and is influenced by currents and water masses derived from the North Sea, English Channel, Bay of Biscay, and broader North Atlantic circulation. The plain hosts extensive fine-grained sediments and supports benthic communities shaped by abyssal conditions and episodic inputs from rivers such as the Seine River and the Thames River.
The plain occupies a sector of the North Atlantic between the Celtic Sea and the Rockall Trough, bounded to the northeast by the European continental shelf and to the west by relief related to the Mid-Atlantic Ridge and the Charlie-Gibbs Fracture Zone. It is proximal to the continental margins of France, United Kingdom, Ireland, and Belgium and lies within the jurisdictional waters influenced by the United Nations Convention on the Law of the Sea regimes for exclusive economic zones. Bathymetric maps produced during expeditions by HMS Challenger, RV Calypso, and modern surveys from NOAA and the European Marine Observation and Data Network reveal a generally flat bathymetry punctuated by sediment waves, abyssal hills, and buried channel features related to past ice-sheet and turbidity current activity documented in datasets from GEBCO.
The sedimentary cover of the plain records Pliocene–Quaternary history associated with glacial–interglacial cycles, driven by ice dynamics of the Laurentide Ice Sheet and the Fennoscandian Ice Sheet, and punctuated by meltwater discharge events such as Heinrich events and the Younger Dryas. Sediment cores collected during cruises by RRS James Cook and the RV Polarstern show layered sequences of hemipelagite, turbidite, contourite, and pelagic clay with calcareous and siliceous microfossil assemblages including foraminifera and diatoms. Provenance studies link mineral suites to the Seine River catchment, Loire River, and high-latitude sources via iceberg-rafted debris similar to deposits studied in the North Atlantic Drift corridor. Tectonic substrate beneath the plain is influenced by stretching from the opening of the North Atlantic in the Mesozoic and later subsidence controlled by thermal cooling of the lithosphere documented in seismic profiles acquired by institutions including USGS and British Geological Survey.
Seine Abyssal Plain hydrography reflects deep Atlantic waters including the North Atlantic Deep Water and modified varieties of Labrador Sea Water and Antarctic Intermediate Water at depth and intermediate layers. Surface and subsurface circulation are modulated by the Gulf Stream and the North Atlantic Current together with mesoscale eddies and internal tides influenced by the Celtic Sea Front and shelf-break processes near the English Channel. Temperature, salinity, and oxygen profiles measured by Argo floats, conductivity–temperature–depth casts from NOAA Ship Okeanos Explorer, and longstanding time-series maintained by the Continuous Plankton Recorder reveal variability tied to the Atlantic Multidecadal Oscillation and teleconnections with the North Atlantic Oscillation. Biogeochemical cycles on the plain reflect particulate organic carbon fluxes, benthic oxygen demand, and trace metal deposition monitored by teams from Woods Hole Oceanographic Institution, IFREMER, and Plymouth Marine Laboratory.
Benthic communities on the plain include abyssal megafauna such as echinoderms, holothurians, and crustaceans documented in imagery from remotely operated vehicles like those operated by MBARI and Ifremer. Meiofauna and microbial consortia mediate organic matter remineralization, with studies linking community composition to sediment grain size, organic content, and episodic food falls analogous to observations near the Porcupine Abyssal Plain and Rockall Trough. Deep-sea coral and sponge assemblages are sparse but present on elevated hard substrates similar to those catalogued by Natural England and the Joint Nature Conservation Committee. Pelagic fauna including mesopelagic fishes and cephalopods are influenced by diel vertical migration patterns studied by teams from University of Southampton and Scottish Association for Marine Science. Conservation assessments consider protections similar to designations under the OSPAR Commission and regional management by European Commission (EU) directives addressing habitat vulnerability.
The plain is impacted indirectly by coastal and continental activities: sediment and pollutant delivery from rivers such as the Seine River and Thames River, fisheries operations prosecuted by fleets from France, United Kingdom, Spain, and Ireland, and deep-sea resource interest by companies regulated under International Seabed Authority principles when outside national jurisdictions. Historical dumping and disposal practices studied in the context of Nuclear testing and industrial pollution have left measurable contaminant signatures; heavy metals and persistent organic pollutants recorded by laboratories at CNRS and Imperial College London indicate long-range transport. Climate-driven changes in export production and oxygenation linked to the Atlantic Meridional Overturning Circulation pose risks for benthic ecosystems; mitigation and monitoring efforts involve agencies such as European Environment Agency and research consortia funded by Horizon 2020 programs.
Exploration of the Seine Abyssal Plain traces from early soundings during voyages of HMS Challenger and nineteenth-century hydrography by Admiralty charts to twentieth-century seismic reflection surveys by Lamont–Doherty Earth Observatory and multidisciplinary programs like the International Ocean Discovery Program. Twentieth- and twenty-first-century contributions include sediment coring by DSV Alvin-equipped campaigns, multibeam bathymetry from GEOMAR and Ifremer vessels, and biological imaging using vehicles developed by NOC (National Oceanography Centre) and Schmidt Ocean Institute. Ongoing projects synthesize data in international repositories such as PANGAEA and EMODnet to inform regional assessments coordinated with institutions including IOC–UNESCO and networks like GO-SHIP.
Category:Abyssal plains