RRS Discovery Cruise DY031, 28 May - 18 Jun 2015, Southampton to Liverpool. The 40th Anniversary Extended Ellett Line

Abstract

Cruise DY031 was the 2015 annual occupation of the Extended Ellett Line, taking place 40 years after the start of the time series.

The Extended Ellett Line is a hydrographic section between Iceland and Scotland that is occupied annually by scientists from the National Oceanography Centre (NOC) and the Scottish Association for Marine Science (SAMS), UK. The measurement programme began as a seasonally-occupied hydrographic section in the Rockall Trough in 1975, building on early surface observations made underway from ocean weather ships. In 1996 the section was extended to Iceland, sampling three basins: the Rockall Trough, the Hatton-Rockall Basin and the Iceland Basin. These three basins form the main routes though which warm saline Atlantic water flows northwards into the Nordic Seas and Arctic Ocean. The section crosses the eastern North Atlantic subpolar gyre; as well as the net northward flow there is a large recirculation of the upper layers as part of the wind-driven gyre. During its passage through the region, the warm saline water is subjected to significant modification by exchange of heat and freshwater with the atmosphere. The two deep basins (Rockall Trough and Iceland Basin) contain southward flowing dense northern overflow waters, and Labrador Sea Water in the intermediate layers.

The specific objectives of cruise DY031 were:

To complete the annual Extended Ellett Line CTD section
To collect water samples for measuring biogeochemical properties including dissolved oxygen, nutrients, carbon and trace metals.
To collect underway measurements of surface currents, surface temperature and salinity, bathymetry, surface meteorology.
To complete epibenthic sled tows at a deep location in the central Rockall Trough.
To launch a seaglider for a related research programme (near Rockall) which will stay in UK or international waters.
To launch a second seaglider for a related research programme (near Iceland) which will operate in Iceland and Greenland waters.
To deploy 2 Met Office Argo floats along the CTD section

We successfully completed all of these objectives.

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