Quantification and implications of change in organic carbon bearing coastal dune cliffs: A multiscale analysis from the Northumberland coast, UK

Michael Lim,Stuart A Dunning,Matthew Burke,Helen King,Nigel King

doi:10.1016/j.rse.2015.01.034

Michael Lim, Stuart A Dunning + Show 3 more

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https://doi.org/10.1016/j.rse.2015.01.034

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Abstract

Eroding coastlines composed of sequences of till, carbon rich peat and sand layers are characteristic of many formerly glaciated coastlines due to the interplay of relative land and sea levels. Dune cliffs cut into these materials represent one of the most sensitive systems to the processes of coastal change. Establishing appropriate scales for the quantification and analysis of change in coastal dune cliffs remains limited by the speed and nature of change, the intensity of environmental processes and the challenges of achieving adequate survey control. This paper presents the results from multi-scale analyses into the behaviour of dune cliffs on the northeast coast, UK, over a 118year period. Repeat unmanned aerial vehicle (UAV) survey differences have been used to identify and quantify system behaviour, set in context with historic map comparisons. At the landform scale, monthly dune cliff dynamics have been analysed over the course of a year with terrestrial laser scanning (TLS) in order to gain insights into the drivers of contemporary dune cliff behaviour. Finally, pseudo three-dimensional ground-penetrating radar (GPR) data are used to trace subsurface stratigraphy from which the potential extent of stored carbon (in excess of 100t over 50m of monitored dune cliff) at risk of release by coastal erosion over the next 50years can be calculated. The consideration of multi-scale changes over time periods relevant to well-constrained sea level change has revealed a complex combination of failure mechanisms that have resulted in an acceleration in dune cliff recession (particularly over the last decade) and a form change to shallower, divergent profiles. This potential acceleration in contemporary dune cliff response holds significant implications for both coastal management and the contribution of this poorly quantified input to the coastal carbon flux.

Highlights

The interplay of glacial–interglacial environments has left many modern mid- to high-latitude coastlines dominated by interleaved deposits of till, peat and sand (Holocene accumulations)
The dynamism associated with dune systems means that few datasets achieve sufficient accuracy, spatial coverage and temporal frequency to adequately quantify dune cliff behaviour
This study combines historic map analyses with airborne and ground based remote sensing approaches to quantify over a century of dune cliff changes

Summary

Introduction

The interplay of glacial–interglacial environments has left many modern mid- to high-latitude coastlines dominated by interleaved deposits of till (glacial), peat (interglacial) and sand (Holocene accumulations). The beach and dune systems that result from erosion and reworking of these deposits are thought to account for 34% of ice-free coastlines globally (Hardisty, 1994) They are widely distributed, occurring at every latitude (Barbier et al, 2011), and dominate shorelines throughout Northern Europe (de Ceunynck, 1985; Wilson, Orford, Knight, Braley, & Wintle, 2001), the coastal lowlands of Australia (Taffs, Logan, Parr, & Jacobsen, 2012; Whinam et al, 2003) and even the Great Lakes of North America (Hill, 1974) for example. The benefits of dune systems, both direct and indirect, remain poorly quantified and often specific aspects are considered individually rather than collectively (Brown & McLachlan, 2002; Zarnetske, Seabloom, & Hacker, 2010) and are fixed both spatially and over time (Koch et al, 2009)

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