Assessment summary

The summary table below shows the status of ocean process, in both the UK atmosphere and the UK seas. The first column shows the trend in the variable assessed, with representing an upward trend and representing no significant trend. The central column describes the timescales over which change has occurred. The assessments in the Feeder Report prepared by the Ocean Processes Evidence Group provide valuable additional information that can be used to give context to the findings given in the summary table.

Trend in variable assessed	Status in UK atmosphere and seas	Influencing factors and significance for UK seas
Air temperature	Rising in all regions UK annual mean temperature has risen by about 1 °C since the beginning of the 20th century. 2006 was the warmest year in central England since records began in the 17th century	Influencing factors Global climate change mostly resulting from anthropogenic greenhouse gas emissions Significance Raises sea temperature
Sea temperature	Rising in all regions Sea-surface temperature has risen by between 0.5 and 1 °C from 1870 to 2007. Warming since the mid-1980s has been more pronounced in Regions 2, 5 and 6 (Southern North Sea, Irish Sea, Minches and Western Scotland)	Influencing factors Air temperature Significance Reduces the ability of the oceans to take up CO₂, affects certain species, e.g. forcing them to move or adapt, and contributes to rising sea level. Shifts in plankton populations on which most marine animals feed are associated with temperature rise
Sea level	Rising in all regions Mean sea level around the UK coast rose by about 1.4 mm per year during the 20th century	Influencing factors Temperature (the greater effect to date) and melting land-based ice (potentially more important in future) Significance Intertidal habitats and groundwater regimes are affected, and the flooding risk for vulnerable coastal populations will increase, notably in Region 2 (Southern North Sea), if upward trends continue
Carbon dioxide and ocean acidification	Acidification in all regions Oceans are acidifying (pH decreasing) as CO₂ is absorbed. In UK waters we have no baseline measurements of pH against which changes can be judged, and it will be some time before we can make accurate judgements about the rate of acidification relative to natural annual and interannual cycles of pH	Influencing factors CO₂ which is present naturally and released from anthropogenic sources (e.g. combustion of fossil fuel). Various climatic factors influence its concentration in the sea Significance There are potential threats to marine species and ecosystems if acidification continues
Circulation, suspended particulate matter, turbidity,salinity and waves	Variable These processes vary on daily to interannual timescales but show no significant trend over the past decade, except for a slight salinity decrease in Region 2 (Southern North Sea) and a slight increase in salinity in the northern Regions 1, 7 and 8	Influencing factors Circulation: tides and weather, especially winds Salinity: rainfall near the surface and near river outflows; adjacent Atlantic salinity Significance Suspended particles: can reduce light availability and inhibit plant growth Waves: the main cause of damage to offshore and coastal structures

Trend in variable assessed

Status in UK atmosphere and seas

Influencing factors and significance for UK seas

Air temperature

Upward Trend

Rising in all regions

UK annual mean temperature has risen by about 1 °C since the beginning of the 20th century. 2006 was the warmest year in central England since records began in the 17th century

Influencing factors

Global climate change mostly resulting from anthropogenic greenhouse gas emissions

Significance

Raises sea temperature

Sea temperature

Upward Trend

Rising in all regions

Sea-surface temperature has risen by between 0.5 and 1 °C from 1870 to 2007. Warming since the mid-1980s has been more pronounced in Regions 2, 5 and 6 (Southern North Sea, Irish Sea, Minches and Western Scotland)

Influencing factors

Air temperature

Significance

Reduces the ability of the oceans to take up CO₂, affects certain species, e.g. forcing them to move or adapt, and contributes to rising sea level. Shifts in plankton populations on which most marine animals feed are associated with temperature rise

Sea level

Upward Trend

Rising in all regions

Mean sea level around the UK coast rose by about 1.4 mm per year during the 20th century

Influencing factors

Temperature (the greater effect to date) and melting land-based ice (potentially more important in future)

Significance

Intertidal habitats and groundwater regimes are affected, and the flooding risk for vulnerable coastal populations will increase, notably in Region 2 (Southern North Sea), if upward trends continue

Carbon dioxide and ocean acidification

Upward Trend

Acidification in all regions

Oceans are acidifying (pH decreasing) as CO₂ is absorbed. In UK waters we have no baseline measurements of pH against which changes can be judged, and it will be some time before we can make accurate judgements about the rate of acidification relative to natural annual and interannual cycles of pH

Influencing factors

CO₂ which is present naturally and released from anthropogenic sources (e.g. combustion of fossil fuel). Various climatic factors influence its concentration in the sea

Significance

There are potential threats to marine species and ecosystems if acidification continues

Circulation, suspended particulate matter, turbidity,salinity and waves

No Trend

Variable

These processes vary on daily to interannual timescales but show no significant trend over the past decade, except for a slight salinity decrease in Region 2 (Southern North Sea) and a slight increase in salinity in the northern Regions 1, 7 and 8

Influencing factors

Circulation: tides and weather, especially winds Salinity: rainfall near the surface and near river outflows; adjacent Atlantic salinity

Significance

Suspended particles: can reduce light availability and inhibit plant growth

Waves: the main cause of damage to offshore and coastal structures

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