Location and physical characteristics
Figure 1: Argyll Scottish Marine Region. The thicker white line delineates the extent of the Argyll SMR. For a map of all SMRs and OMRs, see Figure 5 here
|Coastline length (km)||2,918|
|Sea area (km2)||12,044|
|Deepest point (m)||320|
|Shallowest point (m)||coastline|
|Average depth (m)||66|
|Tides (m)||0.3 – 4.2|
|Sea surface salinity||34.30 – 34.74|
|Sea surface temperature (°C)||8.0 – 14.3|
The Argyll SMR, located on the south-west coast of Scotland, has a complex and indented coastline with multiple sea lochs and islands. It includes Loch Linnhe and Loch Etive, two large sea lochs. This SMR extends out into the deeper regions of the Malin Shelf (150 – 200 m). Many of the sea lochs have one or multiple sills that restrict water exchange between the coastal area and surrounding sea. There are also areas with strong tidal currents such as the Great Race of the Gulf of Corryvreckan. Current speeds in this narrow strait can be greater than 4 m/s and set-up a whirlpool at certain times in the tide. Between Islay and the Mull of Kintrye there is an amphidromic point where the tidal range is at a minimum, but where strong tidal currents occur.
The Argyll SMR also experiences large freshwater inflow in places, with Loch Eil (which flows into Loch Linnhe) being one of the main contributors. Salinity changes are influenced by land runoff and small rivers. They display a large variability in space and time. Surface layer currents generally flow seaward in sea lochs and northwards in the more open sea.
The complex and indented coastline also means that wave exposure is variable with more exposed areas in the outer reaches and more sheltered in the inner reaches of the sea lochs, sounds and bays.
Seabed sediments in the Argyll SMR are highly variable in both geological characteristics and thickness. Thin gravels and sands predominate in the North Channel (between Scotland and Northern Ireland), where tidal currents are strongest. These gravels are locally shell-rich, and in places shell-gravel pavements may develop on bedrock. Sand is predominant near the coast, leading to a profusion of small, sandy beaches including Ganavan Sands (Oban) and Lossit Bay and Machir Bay (Islay). Within the glacially deepened sea lochs, tidal currents are weak and thick sequences of mud accumulate. Cemented calcareous dunes are found on Coll, the cementation locally picking out ‘fossilised’ hoof prints.
The major north-east/south-west faults, which divide the onshore geology into distinct sectors, formed before the Quaternary period (i.e. more than 2.6 million years ago) and continue across the offshore part of the Argyll SMR. The Great Glen Fault may be traced as a series of faults, along Loch Linnhe to the north-western part of Islay and further to Donegal in Ireland. These faults were most active during Precambrian (4.6 billion to 541 million years ago) and Paleozoic (541 to 252 million years ago) times, but later tensions in the Earth’s crust reactivated these faults. Thick basaltic lavas from igneous complexes in the Tertiary period (66 million to 2.6 million years ago) can be found on Mull, extending offshore to the west of the island and form the island of Staffa, including the world famous columnar jointing basalt at Fingal’s Cave.
The Productive Assessment for the Argyll SMR has been undertaken on a sectoral basis, with a focus on 2014 – 2018. The Argyll SMR provides important opportunities for fisheries, aquaculture and passenger transport. Figure 2 highlights the key economic statistics for the various productive sectors from SMA2020 for the period 2014 – 2018. Of the 11 SMRS, Argyll provides the median gross value added, at £34.7 million, for tourism in 2018.
Argyll and Clyde SMRs are especially important for aquaculture, especially oyster production. Argyll accounted for 41% of pacific oyster production in 2018. Military activity also provides an important source of employment in Argyll and Bute, with 4,840 MOD personnel based there, 36% of all MOD personnel in Scotland. In 2018, Argyll had the second busiest maritime passenger transport, accounting for 15% of all passenger numbers.
For a number of Sectors, including renewables, oil and gas, carbon capture and storage and aggregates, there was no activity within the Argyll SMR during the period 2014 – 2018. However, for many sectors, there were changes over the defined period (Figure 2).