Location and physical characteristics
Figure 1: Solway Scottish Marine Region. The thicker white line delineates the extent of the Solway SMR. For a map of all SMRs and OMRs, see Figure 5 here
Coastline length (km): 777
Sea area (km2): 3,724
Deepest point (m): 314
Shallowest point (m): coastline
Average depth (m): 52
Tides (m): 2.1 – 6.6
Salinity: 33.46 – 34.04
Sea surface temperature (°C): 7.9 – 14.9
The Solway SMR is the most south-western Scottish SMR; it borders the marine regions of England and Northern Ireland and the outer boundary extends into the North Channel of the Irish Sea (Figure 1). The SMR has large tidal ranges due to the complex tidal interactions in the Irish Sea. The inner Solway Firth has a mean spring tidal range of 7-8 m (not included in the data product used in this assessment). The coastal waters in the Solway SMR are greatly influenced by the freshwater input: the region’s salinities are much lower than in many other Scottish regions and salinity changes are dominated by this freshwater input. The Solway SMR is exposed to waves from the south west, but wave heights in the coastal zone are generally small.
Holocene (current geological epoch) sea-bed sediments
The sea bed is covered by a wide range of mobile sediments, largely affected by the strength of the local tidal streams and the effects of the rise in sea level during the early Holocene. The sea bed of the North Channel, between Northern Ireland and the Scottish coast, is covered by a thin layer of sand and gravel, with extensive areas of exposed bedrock.
There was extensive deposition during the last (Devensian or Weichselian) Pleistocene glaciation, and there is evidence of deposition from an earlier (Saalian) glaciation in parts of the SMR. During the last glaciation an ice sheet flowed down the western Irish Sea and spilt over eastwards into the shallower, eastern part. This ice sheet interfingered with the ice sheets flowing off the surrounding massifs to deposit a complex sequence of sediments across coastal fringes of the region. Much of the north-eastern Irish Sea is underlain by till, which may be over 100 m thick in the over-deepened valleys off the Cumbrian coast. These muds were deposited soon after the retreat of the ice sheet from the region, when turbid water from a distant, melting ice sheet entered the area. The variations in sea level across the region since the last glacial maximum are complex, owing to the combination of a global rise in sea level and more local isostatic changes. The latter are due to the depression and subsequent uplift of the land as a result of the changing load imposed by the ice sheet.
Solid (pre-Quaternary) geology
The Solway Firth Basin, which occupies an NE-SW syncline, is infilled largely with Permo-Triassic sediments and is less well known than the intensively-investigated East Irish Sea Basin.
The Productive Assessment has been undertaken, with a focus on 2014 – 2018, on a sectoral basis. For a number of Sectors, including aquaculture, oil and gas, carbon capture and storage, and aggregates, there was no activity within the Solway SMR during the period 2014 – 2018. However, for many sectors, there were changes over the period 2041 – 2018. For example, there has been a large decrease in the fixed engine catch of salmon and sea trout, but an increase in the value of the fishing catch (Figure 2).