Climate change and underwater noise
Climate change may affect levels of underwater noise, and the impact of noise on marine environments, in various ways. Changes in human activities resulting from climate change, or from policies to address climate change, can change the levels and / or distribution of underwater noise. Effects on the physical environment may also influence natural levels of ambient sound, or the extent to which noise is transmitted.
Reduction in Arctic ice may lead to increased noise from shipping activity. For example, a United Kingdom Government study noted that the Arctic shipping season could triple in length by mid-century, potentially saving 10-12 days on routes from East Asia to Europe. The scale of any increase remains uncertain, as there will be a trade-off between gains from the shorter distance and the higher costs of Arctic shipping. The impacts of increased Arctic shipping could extend beyond Arctic Waters, for example if new routes from European ports to the Arctic crossed areas currently less affected by shipping noise, such as the central North Sea. Changes in the Arctic environment may also allow tourism vessels to operate in more months of the year.
The major expansion of offshore wind energy referred to above will lead to increased piling and survey activity generating impulsive noise as well as continuous noise from the operation of the turbines themselves and from service vessels. The noise effects of other offshore energy sources, such as tidal energy, are unknown, although all human activities will cause extra underwater noise.
Changes to the spatial distribution of fish stocks and other marine organisms due to climate change may cause changes in the noise associated with fishing activity as well as, more generally, in the impact of underwater noise on different parts of the marine environment.
Effects on the physical environment which could influence natural levels of sound, or transmission of sound, include changes in ice coverage, temperature change (including stratification), sea-level rise and changes in weather, such as storminess.
Ocean acidification is a perturbation of the physicochemical environment of the world’s oceans that changes the acidity of the water (pH). The way ocean acidification is influencing or could be influenced by underwater noise was considered when drafting this assessment, however no clear links were described at this time.
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