A wind proxy based on migrating dunes at the Baltic coast: statistical analysis of the link between wind conditions and sand movement

Svenja E Bierstedt,Eduardo Zorita,Juliane Ludwig,Birgit Hünicke

doi:10.5194/esd-8-639-2017

Svenja E Bierstedt, Eduardo Zorita + Show 2 more

Open Access

https://doi.org/10.5194/esd-8-639-2017

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Abstract

Abstract. We statistically analyse the relationship between the structure of migrating dunes in the southern Baltic and the driving wind conditions over the past 26 years, with the long-term aim of using migrating dunes as a proxy for past wind conditions at an interannual resolution. The present analysis is based on the dune record derived from geo-radar measurements by Ludwig et al. (2017). The dune system is located at the Baltic Sea coast of Poland and is migrating from west to east along the coast. The dunes present layers with different thicknesses that can be assigned to absolute dates at interannual timescales and put in relation to seasonal wind conditions. To statistically analyse this record and calibrate it as a wind proxy, we used a gridded regional meteorological reanalysis data set (coastDat2) covering recent decades. The identified link between the dune annual layers and wind conditions was additionally supported by the co-variability between dune layers and observed sea level variations in the southern Baltic Sea. We include precipitation and temperature into our analysis, in addition to wind, to learn more about the dependency between these three atmospheric factors and their common influence on the dune system. We set up a statistical linear model based on the correlation between the frequency of days with specific wind conditions in a given season and dune migration velocities derived for that season. To some extent, the dune records can be seen as analogous to tree-ring width records, and hence we use a proxy validation method usually applied in dendrochronology, cross-validation with the leave-one-out method, when the observational record is short. The revealed correlations between the wind record from the reanalysis and the wind record derived from the dune structure is in the range between 0.28 and 0.63, yielding similar statistical validation skill as dendroclimatological records.

Highlights

Climate change may induce changes in wind conditions at all timescales, ranging from multi-decadal trends to changes in the daily and seasonal variability including wind extremes
Before we applied the linear regression model to identify a relationship between dune migration and wind conditions, we analysed the connection between the dune movement and other atmospheric parameters
Our analysis provides more quantitative support for the migrating coastal dunes identified by the geological analysis of Ludwig et al (2017) as a wind proxy at interannual timescales

Summary

Introduction

Climate change may induce changes in wind conditions at all timescales, ranging from multi-decadal trends to changes in the daily and seasonal variability including wind extremes (see Christensen et al, 2015). It can lead to storm surges and high Baltic Sea levels, which can increase the damage potential (Rutgersson et al, 2015; Hünicke et al, 2015). To estimate future wind changes, it is essential to understand what and how wind conditions in the past were influenced (Feser et al, 2015; Rutgersson et al, 2015). Many studies have addressed past changes in wind climate (see review by Feser et al, 2015, and references therein) based on different approaches. Jaagus and Kull, 2011; Lehmann et al, 2011) on different timescales and with different data sets. These studies include analyses of observations derived from instrumental

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