The role of rapid glacial retreat and landscape transformation in controlling the post-Little Ice Age evolution of paraglacial coasts in central Spitsbergen (Billefjorden, Svalbard)

Abstract

In Svalbard, the rapid glacier retreat observed since the end of the Little Ice Age (LIA) has transformed the geomorphology and sediment budgets of glacial forelands, river valleys, and slope systems. To date, relatively little information exists regarding the impact of such a profound glacial landscape degradation on the evolution of coastal environment. This paper addresses this deficiency by detailing the post‐LIA sediment fluxes to the coastal zone in Billefjorden, central Spitsbergen (Svalbard). We analysed the response of the gravel‐dominated barrier coast to the decay of Ferdinandbreen, one of the fastest retreating glaciers in the region. Glacier retreat resulted in the development of paraglacial sediment cascade where eroded and reworked glacigenic sediments progressed through alluvial fans to the coast, thus feeding gravel‐dominated spit systems in Petuniabukta. We demonstrated that the coastal systems in central Spitsbergen responded abruptly to post‐LIA climatic changes. The acceleration of coastal erosion and associated spit development was coincident with rapid climate warming that dates from the 1980s and has been associated with longer ice‐free periods and activation of multiple sediment supply sources from the deglaciated landscape. In colder phases of post‐LIA period, coastal zone development was subdued and strongly dependent on the efficiency of sediment transport via in a longshore drift. Finally, we discuss the differences in the post‐LIA coastal responses between central Spitsbergen and western Spitsbergen highlighting the efficiency of paraglacial sediment delivery from land to the coast controlled by the state of glacial systems, bedrock topography, and development of river channels.