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Sea chemistry & salinity

With increasing CO2 in the atmosphere, levels of ocean acidity area likely to increase and potentially double by 2100.

Projected changes in salinity vary with region but changes in rainfall will affect coastal salinities.


Observed change

  • Measurements of surface waters in the Rockall Trough to the west of Ireland between 1991 and 2013 indicate increasing levels of acidity.
  • Decadal changes in levels of salinity levels have taken place with an unprecedented reduction in salinity levels observed in recent years in the north-east Atlantic.


Projected change

  • Ocean acidification is a result of ocean chemistry changing in response to increasing CO2 concentrations. The average surface pH of the ocean will continue to see an unprecedented rate of change, potentially a doubling of acidity by 2100 under late action scenarios. Ocean acidification and warming will rapidly expose marine ecosystems to conditions they have not experienced over many millions of years, with the potential for catastrophic ecosystem collapse.
  • Salinity: changes in salinity will vary with region. Changes in rainfall patterns will affect coastal salinities with implications for amongst others coastal dynamics, water column stability, water quality.



Ireland’s Climate Change Assessment Volume 1: Climate Science- Ireland in a Changing World 2024, Noone et al.: climate observations & projections report

Climate status report for Ireland 2020, Camaro & Dwyer: climate observations & projections report