The Ellett Line and Extended Ellett Line CTD Section (1975-)

Data set information

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Data holding centreBritish Oceanographic Data Centre
CountryUnited Kingdom  United Kingdom
ProjectOceans 2025 Theme 10; Investigating the behaviour and movements of cod in the English Channel and southern North Sea
Time periodFrom 1975 onwards
Geographical area

North East Atlantic Ocean between North West Scottish Shelf and Iceland, via Rockall Channel, Rockall and Iceland Basin


Nitrate concentration parameters in the water column; Phosphate concentration parameters in the water column; Salinity of the water column; Temperature of the water column; Silicate concentration parameters in the water column


Water temperature sensor; nutrient analysers; discrete water samplers; salinity sensor; CTD


The fundamental dataset consists of full water column temperature and salinity profiles and later on, discrete inorganic nutrient data as well. The Extended Ellett Line consists of 58 identified stations between the North West coast of Scotland and Iceland, crossing the Scottish shelf, Rockall Channel and Iceland Basin. It has been occupied at least annually since September 1996. Prior to this date the section terminated at Rockall, with no observations made in the Iceland Basin. Between 1975 and January 1996 there were usually multiple occupations of this early section in a single year (sometimes as many as five), many of which targeted only a selection of the 35 stations collectively recognised today. Over the years various names were used to describe the hydrographic section (or components of it): The Rockall Section, The Anton Dohrn Seamount Section, The Shelf-Edge-Sound of Mull Section. These are now collectively termed the Ellett Line, after the scientist, David Ellett, who coordinated much of this early work. The Extended Ellett Line is the current title for a repeat hydrographic section with origins dating back to 1975. The water column profiles were collected using STDs/CTDs at recognised fixed stations along the section. The discrete inorganic nutrient data are obtained from water bottles fired at multiple depths on each profile, although these data are absent (or more limited) in the earlier stages of the time series. The overall Ellett Line/Extended Ellett Line dataset is recognised as a key oceanographic time series. Several important water masses are captured within it – water masses which help drive ocean thermohaline circulation and consequently regulate climate on a global scale. The multi-decadal nature of the dataset provides a rare opportunity for scientists to monitor changing ocean circulation patterns. Ellett Line occupations were first carried out by the Scottish Marine Biological Association (SMBA), now the Scottish Association for Marine Science (SAMS). The Iceland extension of the Line in 1996 also marked a move to joint maintenance, with Southampton Oceanography Centre (SOC), now the National Oceanography Centre (NOC), sharing the responsibility with SAMS.

OriginatorsScottish Association for Marine Science

Ellett, D.J., Edwards, A. and Bowers, R. (1986) The hydrography of the Rockall Channel: An overview., Proceedings of the Royal Society Edinbinburgh, 88B: 61-81.

Data web site
OrganisationBritish Oceanographic Data Centre
ContactPolly Hadžiabdić (Head of the BODC Requests Team)

British Oceanographic Data Centre
Joseph Proudman Building 6 Brownlow Street
L3 5DA
United Kingdom

Telephone+44 (0)782 512 0946
Collating centreBritish Oceanographic Data Centre
Local identifier1048_1049005
Global identifier644
Last revised2017-01-30