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RRS Discovery Cruise D365 salinity from CTD bottles

Originator's Protocol for Data Acquisition and Analysis

Sampling Strategy

The Extended Ellett Line is a full-depth hydrographic section between Iceland, 60°N 20°W, Rockall and Scotland. The original Ellett Line across the Rockall Trough was first occupied in 1975 when measurements were attempted four times a year. In 1996 the line was extended to Iceland and since then has been occupied approximately annually. The data form a 35 year time series of the oceanic conditions west of the British Isles. The section monitors the characteristics of the warm water inflow into the Nordic Seas and thence to the Arctic, and observes part of the returning cold water outflow with measurements of the Iceland-Scotland Overflow and the overflow of the Wyville-Thomson Ridge into the Rockall Trough. In total, 55 CTD casts were completed during the cruise along the original and extended Ellett line, with nutrient samples being taken from the majority of bottles fired during the casts.

Salinity samples were drawn from Ocean Test Equipment 10 litre Niskin bottles (S/N 1-24) mounted on the rosette of a NOC Seabird 9plus unit with stainless steel frame system (S/N 09P-46253-0869) from a selection of depths spanning the salinity range and wherever a weak salinity stratification was observed.

Analysis

The salinometer for on-board salinity determination sited in the stable laboratory (set at 21°C) was a Autosal 8400B salinometer fitted with a peristaltic pump. Samples were taken using 200 mL glass sample bottles that were rinsed three times in the sample water, filled to the shoulder and sealed with a disposable plastic insert and the bottle's own screw cap. Once a crate of sample bottles had been filled they were moved into the constant temperature laboratory to stand for 12-24 hours prior to analysis. Standardisation was performed using IAPSO Standard Seawater batch P152 before the analysis of each crate. For further details please see the cruise report .

BODC Data Processing Procedures

Data arrived at BODC in the form of Pstar sample files (sam365***), one for each CTD cast. In total, 212 salinity samples were provided from all 55 CTD casts. Data received were loaded into the BODC database using established BODC data banking procedures. The following table shows how the variable supplied was mapped to BODC parameter code.

Data Quality Report

None (BODC assessment).

Problem Report

None (BODC assessment).