Relative Sea Level

We are aware that the Irish coast is under threat from relative sea-level rise. It is also important to remember that relative sea-level rise is linked to global sea-level rise. The rivers of Ireland are connected to the oceans of the world therefore we should be concerned when these oceans rise too. Firstly, we will establish the differences between global sea-level rise and relative sea-level rise. Then we will focus on the numerous mechanisms of sea-level rise. Firstly we will discuss tectonic movements (for example, glacio-eustatic movements); secondly we will focus on the affects of sedimentation and it’s movements and finally the role humans have in relative sea-level rise on our coasts. When we consider all these factors, we will

It does however rise because of global temperature changes just like global sea-level rise. However, tectonic activities have an impact on relative sea-level changes and an absolute change in sea-level isn’t necessarily needed in order for the sea to rise to a level relative to the land. Bird (2008) explains that it is difficult to establish how relative sea-level rise has occurred. Bird (2008) explains that it is often extremely difficult to establish if relative sea level (RSL) has been caused by ‘an actual rise or fall in the level of the sea’ or possible a combination of both. These changes in the land are called tectonic movements. We also need to consider the contribution of processes from the hydrological cycle like the balance of evaporation and precipitation. This water contributes to sea-level rise. We’ll now discuss the numerous mechanisms of sea-level rise in more

Pethick (1984) states that glacio-eustatic movements are caused by the transfer of water into ice ‘onto the land surface during glacial periods’. The volume of the ocean water changes because of this. He explains that tectonic lifts are ‘the steady uplift of the land surface relative to the sea’ and hydro-isostasy is formed from ‘the variation in the weight of water in the oceans during the Quaternary caused isostatic depression and rebound of the ocean floor’. We are aware there is a vast variation of elevations all over the island of Ireland in relation to glacio-eustatic movements. Lambeck and Purcell (2001) explain that in Dundalk they predict ‘elevated shorelines of about 30 m elevation’ developed when there was an ice margin at the Main Drumlin Moraine. For well elevated shorelines to be formed in Wicklow, ‘a three-fold increase’ was needed. In Wexford ‘the requisite increase’ was a lot bigger. In Donaghadee there is a prediction that the raised shorelines were formed in late-glacial times. However, there are lowstands predicted within the Counties of Antrim and Down towards ‘the end of the Pleistocene and earliest Holocene (Carter, 1982)’. In Donegal there were ‘models with increased ice thickness’. These contributed to the ‘elevated Holocene highstands’ that do not correspond with the evidence that was