Coastal evolution and sedimentary mobility of Brøgger Peninsula, northwest Spitsbergen

Since the end of the Little Ice Age (LIA), Svalbard glaciers have undergone a net retreat in response to changing meteorological conditions. Located between 76°N and 80°N, western Spitsbergen has seen a climatic transition from a glacial to a paraglacial system. On the northern shore of the Brogger Peninsula (northwest Spitsbergen), the average temperature increased by 3°C between 1965 and 2015, and cold-based valley glaciers have retreated more than 1 km from their LIA limits. This rapid deglaciation has exposed large areas of glacigenic sediments being easily reworked by runoff. This has led to the formation of extensive glacier-river delta systems and coastal progradation. Post-LIA coastal progradation and formation of new landforms in Kongsfjorden have been controlled predominantly by substantial availability of glacial sediment. A combination of aerial photographic and field data has been employed to estimate the post-LIA evolution of coastal sandur deltas and their submarine parts (named here ‘‘prodeltas’’). The data set reveals that delta shoreline advance could have reached around 5m/year between 1966 and 1990 for the most energetic delta of Austre Lovenbreen, and around 4 m/year between 2011 and 2014 for the most energetic delta of Midtre Lovenbreen. The prodeltas registered a net growth from 2009 to 2012: the biggest, located in the prolongation of deltas of Austre Lovenbreen, measured 1033 m in length in 2009 and 1180 m in length in 2012. This substantial amount of sediment supplied in the fjord has an impact on the fjord ecology, especially on the benthic ecosystem.