Risk/opportunity:(from the Climate Change Risk Assessment for Scotland 2012):
MA1: Risk of harmful algal blooms due to changes in ocean stratification MA4a/b: Changes in fish catch latitude/centre of gravity MA6: Distribution of marine alien/invasive species MA23: Plankton blooms MA30: Damage to cultured aquatic species Mar1: Species migration (marine)

Narratives: Marine and coastal change

SCCAP theme: Natural environment

SCCAP objectives:
N2: Support a healthy and diverse natural environment with capacity to adapt
N3: Sustain and enhance the benefits, goods and services that the natural environment provides

Latest figures

Year

2008

2009

2010

2011

2012

Mean SST (oC)

10.18

10.38

10.50

10.28

10.00

Mean annual SST at the Fair Isle monitoring station to the east of Orkney for the 5 years leading up to 2012 (adapted from ICES Report on Ocean Climate, Beszczynska-Möller & Dye (2013)).

Trend
At a glance
  • General increase in sea surface temperatures during the 20th Century
  • Seas in all of the regions are predicted to continue warming
  • The global long term rise in sea surface temperature can be seen with a high degree of confidence. However, there is much more uncertainty over smaller temporal and spatial scales

Temperature change is a crucial risk associated with climate change and therefore sea surface temperature (SST) is an intuitive indicator for the high level monitoring of changes in the marine environment. Changes in temperature can lead to associated impacts such as the increased risk of harmful algal blooms, changes in the distribution and occurrence of key commercial fish species, changes in the distribution of marine non-native species, changes in the intensity, duration and geolocation of plankton blooms, damage to temperature sensitive aquaculture species and altered species migration. The risk of increases in SST and associated impacts pose a real threat to the Scottish marine environment. However, these must be considered in a broader context due to the variability seen at smaller temporal and spatial scales.

Sea-surface temperatures can be monitored through the use of satellite data and in-situ observations. The use of satellite data requires specialist knowledge and modification due to changes in atmospheric conditions; these adjustments can be made using the in-situ observations (Dye et al, 2013). Depending on the network, SST observations can allow the examination of long and short-term trends.

In the past 30 years the average sea surface temperature has risen in the North Atlantic, with 2000 - 2009 being the warmest on record (IPCC, 2013). Surface waters around Ireland and the UK have warmed quickly, increasing by between 0.1 and 0.5˚C decade-1 (Dye et al 2013). The most recent warming can be seen at more local scales in Scottish records for offshore stations monitoring the Fair Isle Current water (East of Orkney, water entering the North Sea from the Atlantic) (Fig. 1) and even the deeper water Faroe Shetland Channel (Shetland Shelf, North Atlantic water) (Fig. 2). The pattern is much more variable and less clear for more inshore locations.

There is a great deal of spatial variability in SST around the UK, with some regions showing temperature changes at different rates, but in general there is a similar long-term warming trend to the rest of the North Atlantic (Fig. 1 & 2). The UK also shows significant temporal variability relative to this warming trend which can be seen as a cooling phase between 1900 and 1930, warming from 1930 to 1960, cooling between the late 1960s and 1990 and then generally warming again from 1990 to present (Dye et al, 2013).

 

Figure 1. Mean annual SST at the Fair Isle monitoring station to the east of Orkney (solid line) with a 10 year running mean (dashed line) (adapted from ICES Report on Ocean Climate, Beszczynska-Möller & Dye (2013)).

 

Figure 2. Mean annual SST at the Faroe Shetland Channel monitoring station (solid line) with a 10 year running mean (dashed line) (adapted from ICES Report on Ocean Climate, Beszczynska-Möller & Dye (2013)).

The global long term rise in SST can be seen with a high degree of confidence (IPCC, 2013). However, there is much more uncertainty over smaller temporal and spatial scales (Hawkins and Sutton, 2009). The background warming trend in SST is superimposed upon natural variability which also occurs at varying temporal and spatial scales. Therefore, in the future some regions will continue to show warming while others show no change or even periodic cooling (Hawkins et al., 2011).

The UK Climate Projections 2009 project that SST warming will continue in all regions of all seas (UKCP09; Lowe et al., 2009). Annual SST are predicted to rise by approximately 1.5-2.5oC in open ocean, shelf edge and the northern North Sea by 2070–2098 (relative to the 1961–1990 average) whereas larger rises are predicted for the shallower Irish, Celtic and southern North Seas (Dye et al, 2013). However, these predictions are based on a single model and need to be considered in the context of a wider range of models before a full assessment can be made (Dye et al, 2013).

Regional variation

Despite the underlying warming in SST, there is a great deal of regional variation. Scottish waters are no different and each region shows its own temporal and spatial patterns. Data HadISST1.1 data set (Rayner et al., 2003) shows that the east coast of Scotland has warmed at a slightly faster rate than the west coast over the past 30 years. The UK Climate Projections 2009 predict that SST warming will show a greater change on the east coast compared to the west coast of Scotland (UKCP09; Lowe et al., 2009).

Long term data shows the underlying warming trend in SST while on shorter timescales and at regional spatial scales there is a great deal of variability. This variability is caused by natural variation which has been described as the Atlantic Multi-decadal Oscillation (Knight et al., 2005).

Average SST was selected as it represents a consistent and long-term dataset in the marine environment. However, potentially the indicator could be improved by the use of multiple datasets (both inshore and offshore) in order to examine spatial variability. Further development of the indicator would analyse the rate of change, though in this initial analysis, average SST was considered as it removes much of the temporal variability and an examination of the long-term trend can itself be a measure of rate of change. Future developments will also consider maximum temperature effects on species and communities given that thermal stress is likely to be linked more to the maximum temperature than the average, or the latitude at which a particular temperature is reached.

Some of the data requires specialist knowledge or procedures to process and interpret. The MetOffice data in particular is in a file format that needs specialist software to open and requires specialist knowledge to be able to analyse and interpret. The SEPA data also requires specialised processing because of gaps in the data which make the calculation of broad scale annual means difficult.

Beszczynska-Möller, A. and Dye, S. R. (Eds.) 2013. ICES Report on Ocean Climate 2012. ICES Cooperative Research Report No. 321. 73 pp.

Dye, S.R., Hughes, S.L., Tinker, J., Berry, D.I., Holliday, N.P., Kent, E.C., Kennington, K., Inall, M., Smyth, T., Nolan, G., Lyons, K., Andres, O. & Beszczynska-Möller, A. (2013) Impacts of climate change on temperature (air and sea). MCCIP Science Review 2013, 1-12. doi:10.14465/2013.arc01.001-012

Hawkins, E. & Sutton, R. (2009) The potential to narrow uncertainty in regional climate predictions. Bull. Amer. Met. Soc., 90(8), 1095-1107

Hawkins, E., Robson, J., Sutton, R., Smith, D. & Keenlyside, N. (2011) Evaluating the potential for statistical decadal predictions of sea surface temperatures with a perfect model approach. Clim. Dyn., 37(11-12), 2495-2509.

Intergovernmental Panel for Climate Change (2013) Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex & P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Knight J.R., Allan, R.J., Folland, C.K., Vellinga, M. & Mann, M.E. (2005) A signature of persistent natural thermohaline circulation cycles in observed climate. Geophys. Res. Lett. 32, L20708

Lowe, J.A., Howard, T.P., Pardaens, A., Tinker, J., Holt, J., Wakelin, S., Milne, G., Leake, J., Wolf, J., Horsburgh, K., et al. (2009) UK Climate Projections science report: Marine and coastal projections. Met Office Hadley Centre, Exeter, UK.

Rayner, N. A., Parker, D. E., Horton, E. B., Folland, C. K., Alexander, L. V., Rowell, D. P., Kent, E. C. & Kaplan, A. (2003) Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J. Geophys. Res. 108, D14, 4407

Development of this indicator and primary author of this document: Andrew Blight (MASTS)

David Bailey (University of Glasgow) for document review and additional comments

Marine Scotland Policy and Marine Scotland Science for advice

Marine Climate Change Impacts Partnership (MCCIP)

Scottish Environment Protection Agency (SEPA)

International Council for the Exploration of the Sea (ICES) data collected by Marine Scotland Science (MSS)

Met-Office