3rd Apr, 2012

Contrast between 2011 and 2012

The temperature and salinity record at station E1 is one of the longest depth resolved oceanographic time-series in the world, dating back to 1903.  The notable warm periods during autumn and early to mid-winter, resulted in sea-surface temperatures in November – January being about 2 standard deviations above the long-term centennial mean (around about 1.5 °C).  A spell of cooler weather during February brought the temperatures in March closer to the mean, but still slightly above.  The surface salinity at E1 continues to be around 1.5 PSU above the mean, this due to a dry start to 2012; there is a possible link between the outflow of the western French rivers and salinity measured in the centre of the English Channel, a link that we are actively investigating.

The attached plots show the temperature, salinity, density and fluorescence profiles at station L4 during 2011 and early 2012. The influence of the River Tamar on the salinity profiles can clearly be seen during December 2011 with surface values of salinity below 35 PSU. This surface freshening is caused by high levels of rainfall, enhancing the river flow and influencing the coastal zone. The lack of rainfall in the early part of 2012 stands in contrast to the early part of 2011; the surface salinities are some 0.2 PSU more saline currently than this time last year. The temperature is also higher than after the cold winter of 2010/11; the intense cold not penetrating through the water column. The fluorescence profiles also clearly show the time evolution of the blooms at this coastal station, with a late summer / early autumn bloom at the surface during October 2011. The start of the spring bloom in 2012 is already evident.

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