1. Tiree Passage (1981 – 2006) and Ellett Line Shelf Stations (1975 – 2005): Tides, Seasonality and Climatology Mark Inall, Phil Gillibrand, Colin Griffiths Neil MacDougal, Kimberly Blackwell, Graham Walkden

2. Outline Oceanographic context: NW UK Shelf The “Observatory” Tiree Passage “continuous” time series –Variability: tidal to inter-decadal –Forcing of residual flow Ellett Line shelf stations: shelf-wide context Where do we go from here?

3. Circulation Ellett and Edwards schematic circulation of the NW UK Shelf Based on a variety of sources, including 137Cs distributions

4. Surface Salinity

5. Semi-diurnal tides ( POLCOMS )

6. Moorings Met. Stations Tide gauges CTD Section SST/SSS Station (Port Erin) The “Observatory” plus satellite imagery, model products and ‘foul weather CTD opportunities’

7. AVHRR 11 May 2000. Peter Miller PML

8. POLCOMS

9. Ellett Line 75 occupations since 1975 SAMS 1975 – 1992 NOC 1992-1995 SAMS/NOC Joint 1996 - present No occupations in 1986 and 2002 SAMS Northern Seas Programme Occupations in 2001 (partial) 2003 (full), 2005 (partial), 2006 (happening now!) Tiree Passage: Longest temperature and flow time series on the NW European continental shelf June 1981: Hourly current and temperature (11 m a.b.) November 1987 2 nd meter added at 22 m a.b. Ended in September 1997 at both depths. Restarted June 1999 to February 2000 and then May 2002 until the present with RCMs at 11m and 22 m a.b. Seabird salinity added in August 2002 at 22 m above bed. A total of 61 deployments.

10. Raw Tiree time series Inevitable gaps, but tidal to inter-annual (decadal?) variability captured Temperature Velocity

11. Tiree Variability Temperature: SA dominant, weak tidal Along channel velocity: tides dominate, SA significant X-channel velocity: tides and broad SA dominate

12. Northward residual flow Residual flow for full time series = 10.8 cms -1 northwards Equating to 6.7  10 4 m 3 s -1 SA clear in monthly means

13. Moorings Met. Stations Tide gauges CTD Section SST/SSS Station (Port Erin) The “Observatory” plus satellite imagery, model products and ‘foul weather CTD opportunities’

14. Tiree Passage Barotropic dynamics Correlation Coefficients = 0.11 = 0.46 = 0.53 = 0.83 = 0.08 = 0.12 = 0.03 (local only)

15. Atmospheric forcing of residual flow: NAO Index r = 0.59

16. Tiree temperature anomalies Irish Sea vs. NE Atlantic TIME SERIESr2r2 SIGNIFICANT Tiree and Port Erin0.5047Yes Tiree and Rockall0.1674Yes Port Erin and Rockall0.1117Yes Tiree and Q net 0.0005No Port Erin and Q net 0.0423Yes Rockall and Q net 0.0071No

17. Port Erin vs. Tiree Passage

18. Coastal warming trend 0.57 C per decade. Note broad cooling in late 1980s and early 1990s, and peaked warm episodes of late 1980s and 1990s.

19. Seasonal shifts Advance of date of maximum temperature by 9 days/decade: clearly not sustainable. No significant trend in date of minimum temperature

20. Reliable salinity - only recently: seasonality? Probably not (Ellett Line) – too early to tell

21. Shelf-wide Context

22. Ellett Shelf Stations

23. Seasonally adjusted bottom and surface (10m) temperature.

24. Salinity Climatology Salinity trend –Surface (10m) +0.044 psu/decade –Bottom +0.036 psu/decade

25. Where do we go from here? Modeling context for –Process studies of cross shelf exchange –30 year Hindcasts of inter-annual variability X-shelf surface elevation data Acoustics Time to work on the data !

26. Predictive Capability ? Karemia mikimotoi bloom during summer 2005 Progression of bloom from Mull – Lewis – Orkney - Shetland MODIS Aqua image, 31 July 2005 (RSDAS)