EPA - Ireland's Environment, An Integrated Assessment - 2020

Ireland’s Environment – An Integrated Assessment 2020 Ocean Warming, Sea Level Rise and Coastal Erosion Evidence of warming waters and sea level rise has been recorded around Ireland’s coasts and poses a serious risk to Ireland’s coastal areas, particularly major coastal cities. Global sea surface temperature has been increasing consistently over the last three decades and the world’s oceans were the warmest in recorded human history in 2019 (Cheng et al. , 2020; von Schuckmann et al. , 2020;). Since 1994, temperatures in Irish coastal waters have increased at a rate of 0.6°C per decade (Nolan et al. , 2010), which is unprecedented in the 158 years of observational records available. Warm water organisms, such as certain species of zooplankton, jellyfish and comb jellies, have been more evident since 1997, particularly in warm years (Nolan et al. , 2010). A number of warm water fish species have also become more abundant around the northern-most coasts of Ireland and in the Celtic Sea. This phenomenon is expected to continue as temperatures increase. Increasing temperatures have also been shown to alter kelp forests globally (Krumhansl et al. , 2016). At the warmest edges of their range, some of these forests are decreasing in size, while in Arctic regions the geographical distribution of certain species has increased (Filbee-Dexter et al. , 2019). Estimates based on seabed type indicate Ireland has abundant kelp forests (Werner and Kraan, 2004). These are not only an important food source and habitat for many types of flora and fauna but also capture and store carbon. While no large-scale changes have been recorded thus far, a southern European kelp species ( Laminaria ochroleuca , Bachelot de pylaie) was recently identified in Béal an Mhuirthead, County Mayo, suggesting the possible movement of the species northwards (Schoenrock et al. , 2019). A possible threat to Ireland’s kelp forest from changes in geographical range due to increasing temperatures has not yet been identified but may need to be considered in future scenarios. Future warming is expected to increase the intensity of storms (Desmond et al. , 2017). Coupled with this, sea level rise has been recorded globally (3.3 ± 0.4 mm per year since 1993, Von Schuckmann et al. , 2020), in Ireland (2-3 mm per year since the early 1990s) using satellite data 15 and in the south-west of England (3.8 mm per year since 1993) using tide gauges (Bradshaw et al. , 2016). Under current scenarios, the sea level will continue to rise (Flood and Sweeney, 2012). According to the latest report from the Intergovernmental Panel on Climate Change, the sea level is predicted to rise by between 0.43 metres and 0.84 metres by the end of the century, based on emission scenarios compatible with achieving the long-term temperature goal set out in the Paris Agreement (IPCC, 2019). Incidents of coastal erosion and flooding from increased storm activity will be magnified by sea level rise and pose a serious risk to Ireland’s coastal areas, particularly major coastal cities. Increasing annual mean river flows have also been recorded (DCCAE, 2018). If this continues, it could exacerbate the transport of nutrients from soil and anthropogenic sources to coastal and marine areas, as well as increasing the risk of flooding. Ocean Acidification Increasing seawater acidity, caused by carbon emissions, could particularly impact Ireland’s shellfish industry. The oceans currently absorb a quarter of anthropogenic carbon dioxide emissions, resulting in them becoming more acidic. This progressive acidification can make it difficult for organisms such as corals, shellfish and crabs to build their outer calcium carbonate shells. This in turn can impact the functioning of the food web, including structural changes in phytoplankton communities and keystone species, alteration of fish populations through habitat modification, and the potential to disrupt nutrient and carbon cycles (Mostofa et al. , 2016). Seawater acidity increased in the Labrador Sea waters of the Rockall Trough between 1991 and 2010 at a rate of 0.02 pH units per decade (McGrath et al. , 2012). If this rate continues it could have an impact on the Irish shellfish aquaculture industry, particularly on high-value rope mussels and Pacific oysters. A recent study of Irish coastal and transitional (estuarine) systems indicates that local vulnerability to future acidification will be dependent on geology, freshwater discharge and biological activity (McGrath et al. , 2019). 15 Information and data from the European Space Agency’s Climate Change Initiative, the Sea Level project, are available at http://www. esa-sealevel-cci.org/. 202