The Rockall Trough Mooring Data – NERC National Capability Programme: Climate Linked Atlantic Sector Science
The Rockall Trough mooring array consists of five moorings with the following objectives: Rockall Trough Western Boundary 1 (RTWB1) & Rockall Trough Eastern Boundary 1 (RTEB1) are end-point density moorings measuring the baroclinic circulation across the width of the Rockall Trough using CTDs distributed in the vertical; RTWB1 & RTWB2 measure the Wyville-Thomson Ridge overflow current along the Feni Ridge using current meters; RTEB1 measures the eastern Rockall Trough and outer Shelf Edge Current (Figure 1). RTWB1 and RTEB1 include bottom pressure recorders to determine the barotropic variability across the Rockall Trough. The Shelf Edge Current is also surveyed by glider, at roughly weekly intervals, for continuous durations of up to 5 months.
Figure 1. Figure taken from Fraser et al., 2022. Bathymetry (a) and meridional velocity structure (b) of the Rockall Trough (RT) region west of Scotland, along with the positions of the Overturning in the Subpolar North Atlantic observing network. In each panel, green triangles show the locations of (from west to east) the WB1, WB2, and EB1 moorings, the blue square marks the acoustic Doppler current profiler location, and red circles show the nominal endpoints of the RT cross section. In panel (b), solid vertical black lines show mooring locations and the dotted vertical line at −12.5°E marks the partition between the western wedge and mid-basin regions, defined as the midway point between WB1 and WB2. Black cross-hatching in the upper 1,000 m of the eastern wedge denotes the region monitored by gliders. The color scale shows mean meridional (positive northward) velocity in the RT from 17 repeat lowered acoustic Doppler current profiler sections along the Extended Ellett Line in the period 1996–2017, while black contours show the corresponding potential density values.
Table of Contents
2.1 Gridded Temperature, Salinity, and Pressure (Microcats)
2.2 Gridded Velocity data (Aquadopp current meters)
5.2 List of published papers using these data
1. Data access
Data are availabe for direct download as nectCDF files from SAMS data servers.
NetCDF Climate and Forecast (CF) Metadata Conventions Version 1.8 are used to describe the data.
2. Mooring data
Rockall-Trough-Mooring-Time-Series-2022.nc is composed of conservative temperature, absolute salinity, and velocity data from either the western or eastern boundary mapped on to a regular depth and time grid. Data from the eastern boundary (e.g. TG_EAST, SG_EAST) is from a single mooring array east of the Rockall Trough. The western boundary data (e.g. TG_WEST,SG_WEST) comes as a merged profile from two mooring arrays west of the Rockall trough for temperature and salinity, and individual moored profiles for the velocity data (e.g. U_WEST_1,U_WEST_2).
Table 1. Variable names from T_S_gridded.nc
| Variable | Description | Unit |
|---|---|---|
| TIME | Time | days since 1st January 1950 |
| PRES | Sea water pressure | Decibar |
| TG_EAST | Sea water temperature at eastern boundary | o C |
| TG_WEST | Sea water temperature at western boundary | o C |
| SG_EAST | Sea water salinity at eastern boundary | g kg-1 |
| SG_WEST | Sea water salinity at western boundary | g kg-1 |
| U_WEST_1 | current speed u-direction at western boundary (0-1600 m) | cm s-1 |
| V_WEST_1 | current speed v-direction at western boundary (0-1600 m) | cm s-1 |
| W_WEST_1 | current speed w-direction at western boundary (0-1600 m) | cm s-1 |
| U_WEST_2 | current speed u-direction at western boundary (1000-1800 m) | cm s-1 |
| V_WEST_2 | current speed v-direction at western boundary (1000-1800 m) | cm s-1 |
| W_WEST_2 | current speed w-direction at western boundary (1000-1800 m) | cm s-1 |
| U_EAST | current speed u-direction at eastern boundary | cm s-1 |
| V_EAST | current speed v-direction at eastern boundary | cm s-1 |
| W_EAST | current speed w-direction at eastern boundary | cm s-1 |
2.1 Gridded Temperature, Salinity, and Pressure (Microcats)
The microcat data were made up of Conductivity, Temperature (° C), and Pressure (db) records, which were calibrated using seawater samples and in-situ CTD profiles and corrected for sensor drift. The instrument data was fitted on to a regular 2-hour time grid using linear interpolation. Conductivity data were converted first to Practical Salinity (PSU) then Absolute Salinity, SA (g kg-1). Temperature (° C) were converted to Conservative Temperature, CT (° C). Salinity data were de-spiked for each instrument by excluding data outside of a cut-off of deployment-median salinity ± 10 g kg-1. Remaining data were further de-spiked up to n(=5) times through a loop where the cut off is one standard deviation from the deployment median, calculated during each pass. Contemporaneous temperature data to the spikes in salinity were also excluded. SA, CT, and P were then low-pass filtered with MATLABs zero-phase digital filtering function; filtfilt, using a Butterworth filter design, 6th order, with cut-off frequency of ½(days). Gaps in the filtered data of more than 10 days were populated with fill values. The resulting data were fitted to a regular 2-hour time grid using linear interpolation. SA, CT, and P from all deployments were concatenated and then fitted to a regular 12-hour horizontal time grid and 20 db vertical pressure grid using linear interpolation. Salinity data were de-spiked n(=5) times through a loop where the cut off was 3.5 standard deviations from the time-series median during each pass. Contemporaneous temperatures were also excluded. Linear Interpolation across vertical pressure grid of data values since de-spiking.
Figure 2. Gridded and merged temperature, salinity, and density from the eastern boundary
Figure 3. Gridded and merged temperature, salinity, and density from the western boundary
2.2 Gridded Velocity data (Aquadopp current meters)
Velocity data (from Nortek current meters) were corrected for sound and magnetic deviation. The data were low-pass filtered with MATLABs zero-phase digital filtering function; filtfilt, using a Butterworth filter design, 6th order, with a cut off frequency of [fs/(1/fs*2)], where the fs is the median time between samples. The velocity data from each deployment were fitted to a regular (12 hr) horizontal time and 20 db vertical pressure grid by linear interpolation. Missing data between the shallowest instrument and the surface were extrapolated in the same manner. The velocity data from each deployment were concatenated and de-spiked. Vertical differences between velocity values that exceed 10 m s-1 were excluded. Missing data resulting from de-spiking were re-fitted to the 12-hour grid along each depth using linear interpolation.
Figure 4. Gridded current in u direction from the eastern boundary
Figure 5. Gridded current in v direction from the eastern boundary
Figure 6. Gridded current in u direction from the western boundary upper elements (WB1)
Figure 7. Gridded current in v direction from the western boundary upper elements (WB1)
Figure 8. Gridded current in u direction from the western boundary deep elements (WB2)
Figure 9. Gridded current in v direction from the western boundary deep elements (WB2)
3. Volume transport
The calculation of the Rockall Trough transport timeseries is decribed in Fraser et al. (2022, https://doi.org/10.1029/2022JC019291). Rockall-Trough-Transport-Time-Series-2020.nc is the 6 years timeseries published in Fraser et al. (2022). Rockall-Trough-Transport-Time-Series-2022_v0.nc extends the timeseries of Fraser et al. (2022) to 8 years.
| Variable | Description | Unit |
|---|---|---|
| Q_EW | Transport for Eastern Wedge | Sv |
| Q_MB | Transport for Mid-Basin | Sv |
| Q_WW | Transport for Western Wedge | Sv |
| Q_tot | Total volume transport | Sv |
| Q_EW_lp | Low-passed filtered volume transport for Eastern Wedge | Sv |
| Q_WW_lp | Low-passed filtered volume transport for Western Wedge | Sv |
| Q_MB_lp | Low-passed filtered volume transport for Mid-Basin | Sv |
| Qh_tot_lp | Low-passed filtered total volume transport | Sv |
| Qh_EW | Heat transport Eastern Wedge | PW |
| Qh_MB | Heat transport Mid Basin | PW |
| Qh_WW | Heat transport Western Wedge | PW |
| Qh_tot | Total heat transport | PW |
| Qh_EW_lp | Low passed filtered heat transport Eastern Wedge | PW |
| Qh_MB_lp | Low passed filtered heat transport Mid Basin | PW |
| Qh_WW_lp | Low passed filtered heat transport Western Wedge | PW |
| Qh_tot_lp | Total Low passed filtered heat transport | PW |
| Qf_EW | Freshwater transport for Eastern Wedge | Sv |
| Qf_MB | Freshwater transport for Mid-Basin | Sv |
| Qf_WW | Freshwater transport for Western Wedge | Sv |
| Qf_tot | Total Freshwater transport | Sv |
| Qf_EW_lp | 90 days low-passed filtered Freshwater transport for Eastern Wedge | Sv |
| Qf_WW_lp | 90 days low-passed filtered Freshwater transport for Western Wedge | Sv |
| Qf_MB_lp | 90 days low-passed filtered Freshwater transport for Mid-Basin | Sv |
| Qf_tot_lp | 90 days low-passed filtered total Freshwater transport | Sv |
| SE_* | Variables with “SE_” as prefix are the standard error of the respected variable. E.g. SE_Qh_tot is the standard error of Qh_tot in Sv. Only available for Rockall-Trough-Transport-Time-Series-2022_v0.nc | Sv or PW, respectively |
Figure 3.1. Mean velocity, temperature and salinity sections recontructed from moored observations and model analysis and reanalysis from GLORYS12V1 for the western wedge (WW), the mid basin (MB) and the eastern wedge (EW) of the Rockall Trough. Red dots mark section endpoints, green triangles mark mooring positions, and the blue square marks the position of the ADCP which is simulated using GLORYS12V1 output. For more information see Fraser et al. (2022)
Figure 3.2. Extended Rockall Trough volume transport time series for the single sections (upper) and the sum of all three (lower).
Figure 3.3. Extended Rockall Trough heat transport time series for the single sections (upper) and the sum of all three (lower).
Figure 3.4. Extended Rockall Trough freshwater transport time series for the single sections (upper) and the sum of all three (lower).
Figure 3.5. Depth accumulated mean timeseries of volume (left), heat (middle) and freshwater transport (right) in the Rockall Trough temporal averaged between 2014 and 2022.
4. Glider data
SAMS glider missions
| Project | Mission | Start date | End date | Days in water | Months in water | Dives (down + up) | Approx. distance (km) | Glider name | Glider S/N | Glider mission |
|---|---|---|---|---|---|---|---|---|---|---|
| EEL | Extended Ellett Line #1 | 12-Oct-09 | 07-Mar-10 | 146 | 4.9 | 789 | 3020 | Talisker | SG156 | 1 |
| EEL | Extended Ellett Line #2 | 03-May-11 | 03-Sep-11 | 123 | 4.1 | 841 | 2292 | Talisker | SG156 | 2 |
| EEL | Extended Ellett Line #3 | 30-Apr-14 | 13-Jul-14 | 74 | 2.5 | 651 | 1423 | Bellatrix | SG532 | 5 |
| OSNAP | OSNAP #1 | 16-Jul-14 | 02-Feb-15 | 201 | 6.7 | 1864 | 3103 | Jura | SG604 | 1 |
| OSNAP | OSNAP #2 | 14-Oct-14 | 16-Apr-15 | 184 | 6.1 | 1597 | 2987 | Scapa | SG602 | 1 |
| EEL | Extended Ellett Line #4 | 06-Feb-15 | 18-Aug-15 | 193 | 6.4 | 1775 | 3753 | Ardbeg | SG545 | 3 |
| OSNAP | OSNAP #3 | 06-Feb-15 | 24-Jun-15 | 138 | 4.6 | 958 | 2607 | Bowmore | SG605 | 1 |
| OSNAP | OSNAP #4 | 08-Jun-15 | 01-Dec-15 | 176 | 5.9 | 886 | 2911 | Laphroaig | SG603 | 2 |
| EEL | Extended Ellett Line #5 | 11-Feb-16 | 29-May-16 | 108 | 3.6 | 758 | 2062 | Eltanin | SG156 | 1 |
| OSNAP | OSNAP #5 | 11-Feb-16 | 05-Jul-16 | 145 | 4.8 | 996 | 2298 | Bowmore | SG605 | 2 |
| OSNAP | OSNAP #6 | 23-Aug-16 | 09-Sep-16 | 17 | 0.6 | 427 | 420 | Ardbeg | SG545 | 4 |
| OSNAP | OSNAP #7 | 01-Oct-16 | 10-Feb-17 | 132 | 4.4 | 1685 | 2200 | Growler | u_408 | 1 |
| EEL | Extended Ellett Line #6 | 10-Feb-17 | 26-May-17 | 105 | 3.5 | 770 | 1674 | Bowmore | SG605 | 3 |
| OSNAP | OSNAP #8 | 10-Feb-17 | 04-Jul-17 | 144 | 4.8 | 1350 | 2410 | Scapa | SG602 | 2 |
| OSNAP | OSNAP #9 | 21-May-17 | 14-Nov-17 | 177 | 5.9 | 1618 | 2888 | Bellatrix | SG532 | 6 |
| OSNAP | OSNAP #10 | 14-Nov-17 | 30-Apr-18 | 167 | 5.6 | 1667 | 2923 | Jura | SG604 | 2 |
| OSNAP | OSNAP #11 | 30-Apr-18 | 13-Oct-18 | 166 | 5.5 | 1149 | 2209 | Kate Stansfield | SG616 | 1 |
| COMPASS | COMPASS #1 | 13-Aug-18 | 19-Oct-18 | 67 | 2.2 | 2052 | 735 | Corryvreckan | SG647 | 1 |
| EA | Ellett Array #1 | 09-Jan-19 | 27-Jun-19 | 169 | 5.6 | 1674 | 3074 | Bellatrix | SG532 | 7 |
| EA | Ellett Array #2 | 27-Jun-19 | 20-Nov-19 | 146 | 4.9 | 1030 | 1898 | Denebola | SG534 | 5 |
| EA | Ellett Array #3 | 20-Mar-20 | 30-Aug-20 | 163 | 5.4 | 1491 | 2544 | Bellatrix | SG532 | 8 |
| EA | Ellett Array #4 | 24-Sep-20 | 27-Feb-21 | 156 | 5.2 | 1959 | 2515 | Bowmore | SG605 | 5 |
| EA | Ellett Array #5 | 03-Mar-21 | 06-Jun-21 | 95 | 3.2 | 1330 | 1842 | Bellatrix | SG532 | 9 |
| EA | Ellett Array #6 | 15-Oct-21 | 24-Mar-22 | 160 | 5.3 | 1978 | 2942 | Artemis | SG671 | 1 |
| EA | Ellett Array #7 | 24-Mar-22 | 29-Apr-22 | 36 | 1.2 | 459 | 693 | Bellatrix | SG532 | 10 |
| C2 | C2 Ellett Array | 02-Jun-22 | 26-Aug-22 | 85 | 2.8 | 1514 | 1155 | Omura | SG637 | 5 |
| EA | Ellett Array #8 | 01-Jul-22 | 03-Nov-22 | 125 | 4.2 | 2185 | 2046 | Artemis | SG671 | 2 |
| EA | Ellett Array #9 | 17-Nov-22 | 02-Mar-23 | 105 | 3.5 | 1126 | 2127 | Denebola | SG534 | 6 |
Figure 1. Hovmöller plot of Rockall Trough linked glider missions.
5. References
5.1 List of cruise reports
A full repository of cruise reports for the UK-ONSAP programme is available through BODC.
5.2 List of published papers using these data
A full list of OSNAP publications and reports can be found here. Publications and reports using these data are being updated below.
Johnson, C., Fraser, N., Cunningham, S.A., Burmeister, K., Jones, S., Drysdale, L., Abell, R., Brown, P., Dumont, E., Fox, A., N. Holliday, N.P., Inall, M.A. and Reed, S., 2023. Carbon and nutrient transports in the eastern subpolar North Atlantic. Submitted to Journal of Geophysical Research: Oceans, August 2023.