This data collection is the result of a Secchi depth data mining
study for the North Sea – Baltic Sea region carried out by Thorkild
Aarup. It covers the period from 1902 to 1999. The
study was completed in 2002.
40,829 measurements of Secchi depth were compiled from the area
as a result of this study. 4.3% of the observations were found in the
international data centers [ICES Oceanographic Data Centre and the
World Ocean Data Center A (WDC–A) in the USA], while 95.7% of the data
were provided by individuals and ocean research institutions from the
surrounding North Sea and Baltic Sea countries. Inquiries made at the
World Ocean Data Center B (WDC–B) in Russia suggested that there could
be significant additional holdings in that archive but, unfortunately,
no data could be made available.
The earliest Secchi depth measurement retrieved in this study
dates back to 1902 for the Baltic Sea, while the bulk of the
measurements were gathered after 1970. The spatial distribution of
Secchi depth measurements in the North Sea is very uneven with
surprisingly large sampling gaps in the Western North Sea. Quarterly and
annual Secchi depth maps with a 0.5.×0.5. spatial resolution are
provided for the transition area between the North Sea and the Baltic
Sea (4.E–16.E, 53.N–60.N).
Downloads available from this site are:
Secchi data archive – ships
Secchi data archive - buoys
Data set description
- Reprint of article “Transparency of the North Sea and Baltic Sea – a
Secchi Depth data mining study” by Thorkild Aarup (Oceanologia 44(3)
2002).
