Plassche O van de ,
Edwards RJ ,
Wright AJ ,
Weber SL ,
Schrier G van der ,
Drijfhout SS ,
Gehrels WR
101 p
in Dutch
2002
Toon Nederlands
English Abstract We used reconstructed and model-simulated sea-level
variations during the past 1000-3000 years to investigate their cause(s) and
assess their suitability as proxy for ocean-related climate variations in
the North Atlantic region. We studied salt-marsh deposits in North
Carolina, Connecticut, Newfoundland, and Wales (UK). Sea-level
reconstructions obtained so far (for Connecticut) show that mean high water
varied on centennial and sub-centennial timescales on the order of cms-dms
during the past 3000 years. The mean high water fluctuations correlate more
or less positively with proxy records of temperature change, but this broad
correlation does not hold for the entire record. The most significant
correlation found is a consistent phase shift of ca. 125 years between
changes in solar activity (as expressed in variations in residual delta 14C)
and sea level, suggesting a linkage by one or more mechanisms with a
corresponding response time. The fact that sea level continued to fluctuate
during periods of low solar variability indicates, however, that other
factors are also involved.Sea-level change due to changes in the
thermohaline structure of the North Atlantic ocean has been calculated using
a coupled ocean-atmosphere model of intermediate complexity (ECBilt). Two
1000-yr simulations are made, one using a constant solar forcing and one
using an estimate of historic solar activity. In the solar forced
simulation, sea-level variations are a proxy for climate variations.
Anomalies in sea-surface temperature (SST) of the northern North Atlantic
are generated by the solar radiation changes. These SST anomalies modulate
the ocean thermohaline circulation, affecting surface salinities in the
northern North Atlantic which are subsequently advected to the deep ocean.
The associated deep ocean geopotential thickness anomalies dominate sea
level in the northern North Atlantic. Comparison of the simulated steric
sea-level variations in the Gulf Stream area for the past 1000 yr with the
corresponding part of the mean high water reconstruction for Connecticut
shows a satisfactory agreement, indicating that deep ocean salinity
anomalies in the northern North Atlantic, induced by changes in irradiance,
largely explains the timing of reconstructed mean high water variations.
This result has relevance for predictions of sea-level
change.
