Sea Surface Temperature Trends in the Coastal Zone of Southern England

Sea surface temperature (SST) trends along the south coast of England (northern English Channel) were examined based on data from systematic buoy measurements deployed by the National Network of Regional Coastal Monitoring Programmes of England (NNRCMP) since 2003. These data were supplemented with: (1) long-term, coastal SST measurements by the Centre for Environment, Fisheries and Aquaculture Science (CEFAS); (2) global data sets compiled by the Hadley Centre since 1900, and (3) satellite-derived observations from Moderate Resolution Imaging Spectroradiometer (MODIS) (Aqua) since 2002. These data sets were used to evaluate de-seasoned nearshore trends in SST along the south coast of England and examine links to regional ocean-atmosphere teleconnections. The analyses of long-term, CEFAS data support the proposal that prior to the mid-1980s there were no de-seasoned trends in SST and conditions from year to year were relatively stable. Subsequently, interannual fluctuations appear to have increased, associated with a period of warming between 1985 and 2003 (0.28 degrees C/decade). Post 2003, interannual fluctuations in SST monitored by the NNRCMP buoys continued, and the warming trend appears to be greater (0.42 degrees C/decade). This trend in SST is greatest in the nearshore and decreases with distance offshore. The warming in SST also varied greatly from month to month. The greatest warming took place from December to March, whilst the least heating (and sometimes cooling) occurred between September and November. Analysis of Hadley (HadSST1.1) and MODIS data sets substantiated these trends. The greatest warming (post 2003) was found west of Portland Bill (up to 0.76 degrees C/decade) and decreased towards the Strait of Dover. Despite this west-to-east trend, all 12 NNRCMP stations between Penzance and Folkestone showed remarkably similar results, suggesting regional and global sources of heat rather than local sources. This is corroborated through wavelet coherence analysis linking SST anomalies to regional/global ocean-atmosphere teleconnection indices at seasonal scales.