Holocene land‐ and sea‐level changes in Great Britain

Abstract

Analysis of more than 1200 radiocarbon dated samples that constrain relative sealevels in Great Britain over the past 16 000 yr provides estimates of current land-level changes (negative of relative sea-level change). Maximum relative land uplift occurs in central and western Scotland, ca. 1.6 mm yr −1 , and maximum subsidence is in southwest England, ca. 1.2 mm yr −1 . Sediment consolidation, arising from autocompaction as the sediment accumulates and from land drainage, increases the subsidence in areas with thick sequences of Holocene sediments, with an average effect equivalent to at least an extra ca. 0.2 mm yr −1 land subsidence, but more in parts of southeast England, 0.5-1.1 mm yr −1 . Modelled changes in tidal range during the mid-to late Holocene in eastern England suggest that the calculated rate of land subsidence is overestimated unless such changes are quantified. The effect is most significant for large coastal lowlands, the Fenland and Humber (ca. 0.5 and 0.6 mm yr −1 ), that were tidal embayments during the mid-to late Holocene.

Observed mean sea level changes around the North Sea coastline from 1800 to present

“…One way of correcting the observed RMSL records is using predictions of RMSL changes from geological information (e.g. Shennan and Woodworth, 1992;Shennan and Horton, 2002;Gehrels and Woodworth, 2012) or models capable of simulating glacial isostatic adjustment, the rebound effect resulting from the last de-glaciation (e.g. Peltier, 2004;Bradley et al, 2009;Hansen et al, 2011;Shennan et al, 2012).…”

Mangrove pollen of Indonesia and its suitability as a sea-level indicator

“…However, when the index points are plotted against a western Atlantic coral based sea-level curve presented by Lighty et al (1982), the index points do not plot significantly below the coral based curve. Shennan and Horton (2002) prefer the use of basal soils and peats above Pleistocene substrate as it is less prone to compaction than intercalated sediments and this may explain the good general fit between these points. Gischler also highlights that the rates of sedimentation are not able to keep pace with the Holocene rise in sea-level and thus highlights a large potential error in using cycle thickness as a proxy for eustatic sea-level change.…”

“…Geophysical Model of Clarke et al ( 1978) splitting the globe into six regions based on the theoretical response to sea-level rise since the LGM Relative sea-level curves for four sites from Greenland, presented in Long et al (2003) Sea-level data for Northwest Scotland from Shennan and Horton (2002) Misfit between the geophysical model of Lambeck (1995) Chapter 5 Table 5.1 Table 5.2 Table 5.3 Table 5.4…”

“…The subsidence and uplift of the oceanic crust due to water loading, changes in the shape of the geoid, tectonic processes on land, isostatic uplift and depression due to the melting of ice-sheets and gravitational changes due to the change in size of the polar ice sheets can all have the effect of changing RSL. Shennan and Horton (2002) express the interplay between eustatic, isostatic and local scale processes on RSL change as a function of:…”

“…Scotland, presented by Shennan and Horton (2002), identifies an initial drop in RSL due to rapid isostatic uplift (figure 2.3). This is in turn replaced by a temporary increase in RSL due to the decrease in the rate of isostatic uplift in the early to mid-Holocene, allowing the eustatic increase to overtake the isostatic uplift.…”