6 Climate change and ocean acidification
The average global temperature is expected to rise as a result of emissions of greenhouse gases. Possible consequences of global warming include rising sea levels and changes in ocean currents, ice cover and salinity. These changes may have a dramatic impact on the marine environment and marine biological diversity. Elevated levels of CO2 in the atmosphere also lead to higher CO2 uptake in seawater, which in turn increases the acidity of the seawater. Only a few years ago, ocean acidification was almost unheard of. Today, this is considered to be one of the most serious threats to the marine environment.
Textbox 6.1 New challenges for marine environment conventions
Climate change and ocean acidification have generated new problems that must also be addressed within the framework of the international marine environment conventions. Regional cooperation under the Convention for the Protection of the Marine Environment in the North-East Atlantic (the OSPAR Convention) is particularly important for Norway. The Convention has assumed an active role with regard to
assessing and monitoring the impacts of climate change and ocean acidification on the marine environment, and
encouraging appropriate measures for climate change mitigation and regulating them to prevent negative impacts on the marine environment
Ocean acidification was included in the work of the OSPAR Commission, on Norway’s initiative, as early as 2004. As a result, the OSPAR report Effects on the marine environment of ocean acidification resulting from elevated levels of CO2in the atmosphere was published in 2006. This report has subsequently been presented in a range of international forums, including the global Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter of 1972 (the London Convention) and its 1996 Protocol (the London Protocol). Climate change and ocean acidification, including an assessment of impacts, possible measures to mitigate climate change that may influence the marine environment and strategies for adaptation to a changed environment, will also be central topics in the Quality Status Report for the North-East Atlantic (QSR 2010) that is to be presented at OSPAR’s ministerial meeting in 2010.
Measures to reduce atmospheric greenhouse gas levels, including new forms of energy production, may lead to new ways of using the oceans. These developments may in turn generate a need for adjustments and new forms of regulation under the conventions. Amendments to the OSPAR Convention were adopted in 2007 to allow the storage of carbon dioxide in geological formations under the seabed, which was previously prohibited unless the storage was an integral part of petroleum activities. The amendments will enter into force as soon as at least seven parties to the Convention have ratified them. Guidelines and reporting requirements to ensure environmentally safe storage were also adopted. Similar amendments to the London Protocol were adopted in 2006 and entered into force in 2007. The London Protocol has also adopted guidelines and reporting requirements for CO2 storage.
Another example of new developments is OSPAR’s work on offshore wind power. The Commission has adopted guidelines for assessing the environmental impact of offshore wind farms. Harnessing the ocean in new forms of energy production such as wind farms and wave power is also relevant in connection with marine spatial planning, which is a priority area for cooperation under the Convention.
In its annual resolutions on oceans and the law of the sea, the UN General Assembly has expressed concern about the impacts of climate change and ocean acidification. Heightened interest in these issues has resulted in a focus on knowledge building and research into adaptation measures in recent years, both internationally and nationally.
The rise in temperature, other forms of climate change and ocean acidification are expected to progress more quickly at our latitudes than further south. According to the Intergovernmental Panel on Climate Change (IPCC), ocean acidification may damage marine ecosystems in the course of only a few decades.
The Government’s targets and measures for reductions of greenhouse gas emissions are not the subject of this white paper. However, a reduction in global greenhouse gas emissions will be of crucial importance for the state of the Norwegian Sea environment in the future.
6.1 Expected developments
Developments in climate change and ocean acidification are difficult to predict on a regional scale, for example for the Norwegian Sea. Models used to predict changes on a global scale cannot be applied directly to a limited sea area, and there is substantial uncertainty in the results from the regional models that have been developed, particularly with regard to climate change.
However, northern sea areas are known to be early indicators of the impacts of global warming and ocean acidification. Very little is known about how climate change and ocean acidification will interact, but it is possible that the negative impacts will reinforce one another.
Climate change
The rising temperature is expected to lead to changes in precipitation, winds, solar and UV radiation, ocean currents, melting of ice, salinity and sea level. However, it is very uncertain how quickly and in what way climate change will become apparent and affect the marine environment of the Norwegian Sea. It is particularly difficult to model brief extreme weather periods that can have implications for emergency response systems. A reduction in ice cover, a higher frequency of extreme weather events and a displacement in the distribution of some species towards the north are, however, expected in the relatively near term. The impacts of climate change in the Norwegian Sea may be partially masked over the next few years by natural fluctuations.
Warming in the Arctic is taking place at about twice the global average rate, and the Arctic is expected to be ice-free in summer before the end of this century. Ice reflects sunlight, and with a loss of sea ice, less energy is reflected, causing the Arctic seawater temperature to rise more quickly. Global warming may reduce surface-water cooling and inhibit the «conveyor belt» process whereby the cold water sinks to the depths. This may in turn affect ocean circulation and currents in the Atlantic.
Ocean circulation in the Atlantic is expected to be weakened, resulting in lower inflow of Atlantic water to the Norwegian Sea. In spite of this, the temperature will rise due to global warming. Changes in wind fields are of great importance to the climate in the Norwegian Sea. If westerly winds become more prevalent over the Nordic seas, the westerly extent of warm Atlantic water in the Norwegian Sea will be reduced, and transport of cold Arctic water to its western parts will increase. However, it is very uncertain how the low pressure activity will actually change. In addition, as already mentioned, the climate of the Norwegian Sea is highly variable, and this may in the short term mask the effects of global warming.
Textbox 6.2 The Monaco Declaration
In October 2008, 155 scientists from 26 countries issued a declaration from an international symposium in Monaco on ocean acidification. In the declaration, the scientists express deep concern about rapid ocean acidification and its potential, within decades, to severely affect marine ecosystems and fisheries. The declaration calls for research into the effects of ocean acidification on ecosystems and socioeconomic conditions, improved dialogue between policymakers and scientists, and the development of ambitious, urgent plans to cut greenhouse gas emissions.
Ocean acidification
In the period since the industrial revolution, the ocean has absorbed just over half of the CO2 emitted to the atmosphere. This has reduced the atmospheric concentration of CO2, but has at the same time resulted in ocean acidification. A slight increase in the acidity of the deep water in the Norwegian Sea has already been detected, and marked changes are expected in the decades ahead. Greater changes are expected towards the end of the century, and forecasts for the next 100 years suggest that seawater will become more acidic than it has been for the past 20 million years.
Textbox 6.3 Higher concentration of CO2 increases ocean acidity
According to the laws on the solubility of gases in liquids, CO2 dissolved in surface sea water will always be in equilibrium with atmospheric CO2. When CO2 dissolves in water, it forms carbonic acid, increasing ocean acidity. Since the industrial revolution, global surface ocean acidity has increased by 30 %. This means that the concentration of positive, acidic hydrogen ions (H+) has risen by 30 %. Acidity is expressed as pH, which is defined as the negative logarithm of the hydrogen ion (H+) concentration. A pH of 7 is neutral, solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic or alkaline. The 30 % increase in the hydrogen ion concentration means that the average surface-water pH has dropped from 8.2 to 8.1. The water is still on the basic side of neutral, but has become more acidic. In the decades ahead, a further reduction of 0.1–0.2 pH units is expected.
Due to the oceanographic features of the Norwegian Sea, ocean acidification will occur rapidly here. As individual species and populations are affected, changes at ecosystem level can also be expected. Damage to ecosystems is expected as early as 2025, and severe damage by the end of this century.
Figure 6-1.EPS pH and carbonate concentration (global mean values) in surface ocean waters between 1800 and 2100. The values for 1800 are to close to those for pre-industrial conditions. Projected values are based on continued greenhouse gas emissions. The dotted lines show the projected levels in 2025
Source Norwegian Institute for Water Research. Based on Brewer (1997)
The global warming of surface water may reduce the capacity of seawater to absorb CO2, which may curb acidification in deep water. If the capacity of seawater to absorb CO2 is reduced as a result of global warming and lower buffering capacity, this may in turn lead to a more rapid increase in atmospheric greenhouse gas levels and thereby in global warming. There is limited knowledge about how the interaction of climate change and increased ocean uptake of CO2 will affect the marine environment. It is therefore essential to strengthen research on these processes.
6.2 Impacts of climate change and ocean acidification on ecosystems
Climate change
There is considerable uncertainty as to how and how quickly climate change will affect ecosystems in the Norwegian Sea. However, impacts on distribution, density and reproduction for a number of fish, seabird and marine mammal stocks in the area covered by the management plan can be expected. Warming of the Norwegian Sea is expected to lead to a northward and westward shift of the front zone between Atlantic and Arctic water, where biological production is high and feeding conditions for fish, seabirds and marine mammals are good. New species may expand their distribution northwards towards Norwegian waters. Southerly species along the Norwegian coast are expected to move northwards along the coast towards Svalbard and the eastern part of the Barents Sea. Northerly coastal species may disappear from the Norwegian Sea, shifting northwards to the Barents Sea. Some alien species may more easily gain a foothold in a warmer marine environment. Climate change can also lead to changes in health status, including an increase in parasitic disease, for example in fish and marine mammal populations.
In isolation, a somewhat warmer ocean is expected to result in increased growth in fish stocks. The expected impacts of climate change on certain important fish and seabird populations have therefore been assessed as positive, although these assessments are highly uncertain. At worst, climate change may result in the collapse of food chains and major changes in for example fish, seabird and marine mammal populations. For coral reefs, the impacts of climate change have been assessed as clearly negative.
Higher water temperature can in isolation be expected to result in an increase in the biomass of phytoplankton, seaweed and kelp, which may in turn provide richer food supplies for organisms higher up the food chain, for example some fish populations. However, a rise in temperature can also lead to changes in which species of plankton, seaweed and kelp thrive best. In the Skagerrak, for example, an overall assessment concluded that high seawater temperature is probably the most important single factor behind a regionwide loss of sugar kelp.
Textbox 6.4 Frozen subsea gas
Subsea gas hydrates in frozen form (ice) occur in vast amounts all over the world. Under high pressure and/or at low temperatures, methane gas is trapped in a lattice of ice. Total global carbon reserves bound in frozen gas hydrates are roughly estimated to equal the combined oil, gas and coal reserves worldwide.
Gas hydrates are believed to occur in large quantities on the Norwegian continental shelf. The first gas hydrate samples on the Norwegian continental shelf were taken ten years ago at the Håkon Mosby mud volcano. In summer 2006 and 2008, gas hydrates were recovered in the Nyegga area of the Norwegian Sea. There are also believed to be large volumes of gas hydrates in the Barents Sea. Research into the quantities and formation of gas hydrates is being conducted by the GANS project (Gas Hydrates on the Norway – Barents Sea – Svalbard margin), which is partly financed by the Research Council of Norway.
Gas hydrates are regarded as a potential energy resource, and international pilot projects to assess extraction are being developed. However, extraction is challenging as gas hydrates readily decompose if pressure is reduced or the temperature rises. In addition, it will be necessary to ensure that the use of gas hydrates does not result in higher greenhouse gas emissions.
Methane may also be released from gas hydrates as a result of anthropogenic global warming. Initially, frozen methane gas in permafrost on land (particularly in Siberia) is most likely to be affected. An increase in the methane content of seawater above the Siberian continental shelf has already been recorded, and as global warming spreads to deep water, gas hydrates in seabed surface sediments may be affected. Methane is 25 times more potent as a greenhouse gas than CO2. Methane emissions to the atmosphere from thawing gas hydrates will in turn boost global warming, resulting in a positive feedback mechanism.
Ocean acidification
The projected impacts of ocean acidification are more clearly negative. Higher levels of CO2 and lower pH in the ocean are expected to have particularly severe impacts on living organisms that build calcium carbonate shells and skeletons. Calcifying phyto- and zooplankton species, corals and molluscs are among the organisms expected to be adversely affected.
There are particularly large coldwater coral reef complexes in the Norwegian Sea, and the deepest reefs are already being affected by acidification. Most corals in Norway grow at depths of 200–600 metres. At greater depths, the temperature is too low and the pressure too high in Norwegian waters for corals to produce calcium carbonate for reef-building. As the water becomes more acidic, the depth at which calcification is possible shifts upwards towards shallower water. When corals are no longer able to build calcium carbonate skeletons, they will stop growing. Their coral skeletons will gradually dissolve. Recent studies indicate that most coral reefs in Norwegian waters will have stopped growing in 100 years’ time and will be negatively affected much earlier.
Other animal groups that are particularly dependent on calcareous structures and are therefore sensitive to ocean acidification include some plankton species, crustaceans, molluscs and echinoderms such as starfish and sea urchins. Acidification and higher CO2 levels can also affect other physiological and biochemical parameters. Thus, it is not only calcifying organisms that may suffer the negative impacts of acidification. In general, it appears that the early development stages of animals (eggs, larvae, spawn) are more sensitive to ocean acidification than adults. Recent results have shown that cephalopods are also sensitive to ocean acidification. Impacts on marine mammals and seabirds are mainly expected to be indirect, and will depend on the extent to which their food supplies are affected by acidification.
Overall, the adverse impacts of ocean acidification on phyto- and zooplankton, fish eggs, coral reefs and herring are expected to be moderate in the period up to 2025. By 2080, these groups are expected to suffer major negative impacts, while the impacts on other fish stocks, fish larvae, benthic communities and marine mammals that have been evaluated are expected to be moderately negative. Some species can be expected to disappear within decades.
Climate change and ocean acidification interact
Separately and together, climate change and ocean acidification may result in changes in ecosystems, so that previously less important species take on a key role. Such changes at low levels in food chains may have a greater impact at higher trophic levels. Together, the loss of species or changes in the relative proportions of species at different levels of the food chains and in their temporal distribution may disrupt the structure and functioning of ecosystems, with unprecedented consequences. Such developments would probably be impossible to reverse in a controlled manner. For management purposes, it will be of crucial importance to be able to predict change as early as possible.
Knowledge about how climate change and ocean acidification will affect species and ecosystems is limited, and almost nothing is known about how they will interact. Change is taking place so rapidly that ecosystems have little time to adapt.
It is very important both for the marine environment and for business interests in the management plan area to focus on these issues in research and in the development of adaptation strategies in the time ahead.