Past, Present and Future Perspectives of Sediment Compaction as a Driver of Relative Sea Level and Coastal Change

Matthew J. Brain

doi:10.1007/s40641-016-0038-6

Abstract

Compaction describes a range of natural syn- and post-depositional processes that reduce the volume of sediments deposited in low-lying coastal areas, causing land-level lowering and a distortion of stratigraphic sequences. Compaction affects our reconstructions and understanding of historic sea levels, influences how relative sea level changes in the future and can act as a catalyst for rapid, widespread changes in coastal geomorphology. Rates of compaction-induced relative sea-level rise vary across space and through time in response to a range of natural and anthropogenically accelerated processes and conditions. This paper provides a summary of our understanding of the causes and effects of compaction, considering findings from key palaeoenvironmental and stratigraphic studies, sea-level reconstructions and recent observational data. It then considers the implications of these findings for our ability to project compaction-induced relative sea-level and associated coastal changes into the future.

Highlights

Sea-level rise is arguably the most damaging and disruptive effect of climate change, with potentially widespread andThis article is part of the Topical Collection on Sea Level Projections significant impacts on coastal populations, infrastructure, landforms and ecosystems [1,2,3,4,5,6,7]
To assess the extent to which this scatter could be explained by sediment compaction and to estimate magnitudes and average rates thereof, Horton and Shennan [66] used a combination of basal sea-level index points (SLIs) and glacio-isostatic adjustment model results [68] to develop regionally specific compaction-free relative sea level (RSL) records for the late Holocene
The results suggest that the magnitude of compaction-induced lowering of SLIs is generally positively related to the thickness of overlying sediment and the overall thickness of the sediment column but negatively related to the depth to the incompressible pre-Holocene basement (Fig. 3)

Summary

Introduction

Sea-level rise is arguably the most damaging and disruptive effect of climate change, with potentially widespread and. To assess the extent to which this scatter could be explained by sediment compaction and to estimate magnitudes and average rates thereof, Horton and Shennan [66] used a combination of basal SLIs and glacio-isostatic adjustment model results [68] to develop regionally specific compaction-free RSL records for the late Holocene They noted that intercalated SLIs are located at elevations lower than their isochronous basal equivalents due to compaction-induced PDL. By considering the differences in elevation (i.e. the residuals) between compaction-prone (non-basal, intercalated) SLIs from and the modelled RSL curve, Horton and Shennan [66] calculated rates of calculated millennially averaged compaction-induced subsidence rates of 0.4 ± 0.3 mm year−1 They noted considerable spatial variation between regions, notably in relation to macro-scale coastal geomorphology. Horton and Shennan [66] determined that the inclusion of non-basal samples when calculating late Holocene rates of a

Sea level index point at altitude of deposition

Conclusions