Reconstructing middle to late Holocene sea-level change: A methodological review with particular reference to ‘A new Holocene sea-level curve for the southern North Sea’ presented by K.-E. Behre

A number of disciplines are involved in the collection and interpretation of Holocene palaeoenvironmental data from coastal lowlands. For stratigraphic frameworks and the assessment of relative sea-level (RSL) change, many non-specialists rely on existing regional models. It is, however, important that they are aware of major developments in our understanding of the factors controlling coastal change and of the potential sources of error in sea-level reconstructions. These issues are explored through a critical evaluation of a new sea-level curve presented by Behre (2003, 2007) for the southern North Sea. In contrast to most sea-level curves published from this region over the last 20 years, the curve shows strong fluctuations that are interpreted as representing vertical movements of sea level. We present a detailed examination of the data used by Behre. From this analysis it is clear that many of the data points used are unsuitable for high-resolution (centimetre or decimetre) sea-level reconstruction. This paper also gives an overview of possible sources of error with respect to the age and altitude of sea-level index points and of changes in our understanding of the processes that underpin the interpretation of the organic and occupation levels used as index points. The constraints on the spatial scale over which sea-level reconstructions can be applied (changes in palaeotidal range and crustal movements) are also considered. Finally, we discuss whether the large-amplitude centennial-scale sea-level fluctuations proposed by Behre can be reconciled with the known mechanisms of sea-level change and other recent high-resolution studies from this region. We conclude that such fluctuations are highly unlikely to be real features of the sea-level history of the southern North Sea