Post-Little Ice Age development of a High Arctic paraglacial beach complex

Abstract

We reconstruct the behaviour of a High Arctic gravel-dominated beach complex that has developed in central Spitsbergen, Svalbard, since the end of the Little Ice Age (LIA). The studied coastal environment in northern Billefjorden (Petuniabukta) is characterised by limited wave action and ephemeral sediment delivery from non-glaciated, mainly snow-fed fans and talus slopes. Aerial photographic evidence and morpho-sedimentological observations of a beach-ridge plain and spit complex in northern Billefjorden reveal a dynamic coastal system. During the post-LIA period, a prominent coastal barrier at the mouth of the Ebbaelva migrated seawards several tens of metres and prograded northwards to form new spit systems, each > 150 m in length. The post-LIA coastal evolution occurred in two main phases. In the first half of the 20th century, increased paraglacial sediment released by retreating land-based glaciers led to the development of a subaqueous spit platform and the progradation of an ebb-tide delta into the mouth of the Ebbaelva, diverting its mouth to the northwest. In the second half of the 20th century, the barrier prograded onto this platform, promoting the development of three massive spits. Sedimentological data suggest that changes in beach-ridge composition that occurred during the 20th century are linked to episodic sediment delivery from an adjacent permafrost and snow-fed alluvial fan and delta system. Our work provides a basis for a new model of paraglacial barrier development that recognises the fundamental role of climate and sediment supply as two intimately connected processes that control coastal development in the High Arctic over decadal to centennial timescales.