The Irish Seafloor: Out of sight, out of mind?

In recent years, intensive marine mapping has provided unprecedented quantities of high quality data on Ireland’s offshore territories. Kieran Craven explains more.

It is said that we know more about the surface of the Moon, than we do about our own planet’s ocean floors.  Globally, the ocean floor has been mapped to a maximum resolution of around 5km, with less than 0.05% of the ocean floor being mapped to a level of detail useful for detecting items such as ariplane wreckage or the tops of undersea volcanic vents.  Compare this to the entire lunar surface being mapped to a resolution of seven metres, and we see the discrepency in our knowledge between these two places.  Hidden beneath kilometres of water, until quite recently the seabed has been out of sight and relatively inaccessible to humans.  The maps that have been produced have used few measurements with lots of guesswork added!

In recent years, helped by the activities of the fishing, petroleum exploration and telecommunication industries, the production of high resolution maps of the North Atlantic seafloor have become prioritisied.  To map it remotely (from the sea surface), multibeam sonar and other advanced geophysical techniques must be used.  Rapid advancements in ocean mapping techniques, in particular development of multibeam echosounders (MBES) and accurate global positioning systems (GPS) have now made this possible.  With these new tools, full coverage high resolution bathymetric mapping of the Irish seabed became feasible (Fig. 1).

Figure 1: The Real Map of Ireland

Started in 1999 with a €32m Irish investment, the Irish National Seabed Survey (INSS) and INFOMAR (INtegrated mapping FOr the sustainable development of the MArine Resources), both collaborations between the Geological Survey of Ireland (GSI) and the Irish Marine Institute (MI), have nearly completed the task of mapping the entire Irish sea bed (more than half a million square kilometres (Fig. 2).  The INSS mapped all areas deeper than 200m water depth, covering a total of 250,815 ship lines, while INFOMAR focuses on depths above this (Fig. 3).  All of this data is available to anyone free of charge from


Figure 3: Bathymetry of coastal zones above 300m: generated from INFOMAR data

This data has many uses.  First and foremost, geomorphological features, previously unmapped can be observed in great detail (Fig. 4).  Ireland’s shallow (<400m water depth) continental shelf is characterised by large submarine canyons, channels, seamounds, escarpments and carbonate mounds that form the architecture upon which diverse biological habitats form and which can become protected once identified.  Glacial features preserved on the continental shelf are also in abundance, including moraines and iceberg ploughmarks dating to the last ice age (>20 thousand years ago).  They contain footprints of the last ice sheets to have covered the island of Ireland; a history closely linked to past climate change.

Figure 4: Bathymetry of Porcupine Bank detailing bedrock ridges and iceberg ploughmarks on the seabed

In late 2015, following my PhD in Trinity (investigating coastal evidence of geologically-recent sea-level change) and a couple of years working in universities and industry, I was awarded an Irish Research Council (IRC) Enterprise Postdoctoral Scholarship based at Maynooth University (MU) and the Geological Survey of Ireland.  This started in February 2016 and the project continues the research collaboration between Dr Stephen McCarron (MU) and Xavier Monteys (INFOMAR, GSI), using the marine geophysical information to understand more about our current seafloor and recent glacial history.  Over the next two years, using the available INFOMAR data, along with other geophysical data available through the Petroluem Affairs Division and the British Geological Survey, I will be interpreting over 10,000km2 of Quaternary sediments on the Malin shelf, off northwest Ireland. The work aims to characterise seabed type (sand/mud/rock) along with the distribution, age and thickness of sediments. This work will help foster understanding, together with sustainable exploitation (e.g. renewable energy development), of our extensive marine resources.

No longer does the seafloor remain out of sight.

Blog Authored by: Kieran Craven, a former postgraduate student and lecturer in the School of Natural Sciences, Trinity College Dublin. He is now an IRC Postdoctoral Fellow in Maynooth University and the Geological Survey of Ireland.






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