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Climate Change

2006 was the second-warmest year in UK coastal waters since 1870 with seven of the ten warmest years occurring in the last decade. More robust evidence relies on longer-term trends, but several impacts of climate change on the sea have been already noted1, including:

  • Sea surface temperature increases at up to 0.8oC per decade in some UK waters (Fig. 1)
  • Global and UK sea-level rise at around 1.8mm per year during the 20th century (Fig. 2)
  • The ocean is becoming more acidic, accompanied by declining carbonate concentrations (30% drop in pH and 16% decrease in carbonate since 1750)

 

Figure 1. Global Temperature Trends (Source: IPCC, 2007). Click image for enlarged version.

  

Fig 2. Global Sea Level Rise (Source: IPCC, 2007).  Click image for enlarged version.


As a result, climate change has already started to impact on marine ecosystems. Within the plankton community of the North Atlantic changes have been observed in the distribution of different species, the species composition of the plankton and the timing (phenology) of the growing season2. Edwards et al also highlight that warming may temporarily lead to greater biodiversity as warmer-water species expand Northwards faster than cold-water species retreat; however this could potentially have detrimental effects on an economically productive environment. Future climate impacts under all realistic models are expected to increase throughout this century3, so while sea level has risen 1 - 2 mm per year, the anticipated range of sea-level rise by the 2080s is estimated at 20 - 80 cm in south-west England. Arguably more important for the marine environment are projected changes in sea surface temperature and acidity. Sea surface temperatures closely reflect seasonal air temperatures, predicted to rise to around 1oC in the next 10 - 20 years and 3oC by 2100. At these levels the species composition of the Irish Sea is likely to change markedly due to Northward expansion of warm water species and the loss of some native species with vulnerable life stages.

The oceans soak up much of the CO2 we release in to the atmosphere where the carbon is sequestered into the deep via biological processes, the ‘biological pump’. Without this process atmospheric concentrations of CO2 would be higher and the climate much warmer as a result. However, some of the CO2 forms carbolic acid when dissolved in seawater, lowering the pH of the oceans while also removing some carbonate and aragonite ions from solution. As a consequence, species such as molluscs, crustaceans and corals which deposit carbonate into shells or skeletons will find it increasingly difficult to do so; leading to major negative impacts on shell-forming organisms within this century (Fig. 3).

Climate models also predict increased storm and wave intensity although the result is more uncertain. The impact on the Irish Sea will depend on how changing wind patterns and ocean currents combine to influence the route of storm tracks over the Atlantic. Another predicted effect of climate change is an increase in the strength and duration of the sea shelf stratification. By limiting the extent of vertical mixing in coastal regions, stratification reduces the availability of nutrients and thereby can bias competition among the phytoplankton in favour of the dinoflagellates, the group most frequently forming harmful algal blooms (HABs)4,5. The final outcome of these and other impacts of climate change within the Irish Sea will, to varying degrees, depend on the precise changes in oceanic currents that affect UK waters and the outcome of complex ecological interactions.




 

Figure 3. Change to ocean pH over the next 100 years.

 

  1. MCCIP. 2011. Marine Climate Change Impacts Annual Report Card 2010-2011 (J. M. Baxter, P. J. Buckley, & C. J. Wallace, Eds.). Lowestoft: MCCIP.
  2. Edwards, M., Johns, D. G., Beaugrand, G., Licandro, P., John, A. W. G., & Stevens, D. P. 2008. Ecological Status Report: results from the CPR survey 2006/2007. SAHFOS Technical Report 5: 1-8.
  3. IPCC, 2007: Summary for Policymakers. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
  4. Moore, S. K., Trainer, V. L., Mantua, N. J., Parker, M. S., Laws, E. A., Backer, L. C., & Fleming, L. E. 2008. Impacts of climate variability and future climate change on harmful algal blooms and human health. ENVIRONMENTAL HEALTH 7.
  5. Edwards, M., Johns, D. G., Leterme, S. C., Svendsen, E., & Richardson, A. J. 2006. Regional climate change and harmful algal blooms in the northeast Atlantic. LIMNOLOGY AND OCEANOGRAPHY 51: 820-829.