Agenda

The application of optical satellite remote sensing techniques was a major breakthrough in the seventies of the past century for monitoring oceans, seas and coastal areas. Dedicated ocean colour instruments have provided fundamental new insight in the dynamics and role of oceanic plankton. The observations now start to span multiple decades, allowing a first glimpse of long-term variations in the composition of the oceans. However, in order to characterize the role of the oceans in the climate debate, longer time series are required. 

In this presentation we show the latest results on an alternative ocean colour data set, the Forel-Ule time series, that pushes the measurement of ocean colour back to 1889, making it one of the longest time series of marine biological data. 

Towards the end of the nineteenth century, Forel and Ule proposed a method to classify the colour of the oceans, regional seas and coastal waters using a colour comparator scale. The scale became known as the Forel-Ule (FU) scale and since then scale observations have been performed, generating hundreds of thousands of data points over a globe-scale for more than a century.  Recently, it was shown (Wernand and Van der Woerd, 2010a) that the FU scale is can be used to characterize the colour of natural waters. More importantly, the analysis of FU colour variation in many oceans, especially the North Pacific since 1930, has revealed significant variations at decadal timescales (Wernand and Van der Woerd, 2010b).