Open AccessAbsolute sea levels and isostatic changes of the eastern N orth S ea to central B altic region during the last 900 years
Author(s) -
Hansen Jens Morten,
Aagaard Troels,
Binderup Merete
Publication year - 2012
Publication title -
boreas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.95
H-Index - 74
eISSN - 1502-3885
pISSN - 0300-9483
DOI - 10.1111/j.1502-3885.2011.00229.x
Subject(s) - geology , sea level , sea level change , tide gauge , tectonics , archipelago , period (music) , noise (video) , oceanography , paleontology , physics , acoustics , artificial intelligence , computer science , image (mathematics)
Most studies of late H olocene sea‐level changes generally assume stable tectonic conditions. However, unrecognized neotectonic ‘noise’, even the small rates of passive continental margins, can severely distort sea‐level reconstructions of the late H olocene. The detailed sea‐level curve proposed here is reconstructed by identification of an area ( L æsø archipelago in the K attegat S ea) where small neotectonic level changes and other kinds of ‘background noise’ can be precisely quantified by advanced L i DAR techniques. We show that the absolute (‘eustatic’) sea level of K attegat has risen by 110±14 cm since AD 1300 and that the L ittle I ce A ge lowstand occurred between 1250 and 1750. Thereafter, four oscillations with a cyclicity of ∼ 70 years peaked around 1790, 1860, 1920–1950 (double peak), and at the present. We discuss the global implications of the curve, for example that the acceleration in the present sea‐level rise may be part of this 70‐year cyclicity, and that the non‐anthropogenic sea‐level rise between 1700 and 1790 seems faster than the present and projected sea‐level rise for the 21st century. Moreover, the conspicuous sea‐level fall at the beginning of the L ittle I ce A ge confirms that ice‐cap growth can be faster than ice‐cap melting. By comparison with 29 long‐term tide gauge measurements of the region we show that the isostatic implications of the sea‐level curve are in nearly perfect agreement with P eltier's global isostatic VM 2 model (applied by IPCC and PSMSL ) and yield a 3–4 times smaller spread of isostatic rates. Owing to this higher precision it is possible to produce a reliable isostatic map of SW S candinavia, D enmark, N G ermany and NW P oland. This new map identifies an isostatic jump by ∼ 0.6 mm a −1 at the R ingkøbing‐ F yn B asement H igh, separating the isostatic pattern of the N orth G erman B asin from the isostatic pattern of the D anish B asin and the S candinavian P eninsula.