10,000 years of centennially-resolved climate and sea-level change archived in Svalbard beach ridge system

Over the last 10,000 years, no fewer than 178 beach ridges were formed and preserved at Bjonasletta in central Spitsbergen, recording shifts in relative sea level and fluctuations in glacier- and sea ice extent. Shell-based dating of beach-ridge crests combined with a centimetre-scale photogrammetry-based digital elevation model reveal that the formation of this beach sequence progressed through three major phases of relative sea-level fall. In line with other records from the central part of the archipelago, we observe a rapid (0.9 m per century) fall in sea level during the Early Holocene, followed by a gradual deceleration (0.45 m per century) during the Middle Holocene, until near-modern levels were reached around 2.2 ka. Ground-penetrating radar surveying of the internal sedimentary architecture of the beach ridges suggests that plain progradation and ridge formation were dominated by continuous swash accretion under fair-weather conditions. We argue that climate changes are recorded by the geometry and formation rate of individual ridges. Correlations of the beach-ridge record with independent climate proxy data suggest that warmer conditions at 10–6 ka were favourable for supplying the beach-ridge plain with sediments from nearby slopes and reworked glacial landforms, allowing ridges to form at a relatively rapid rate of ~ 45 yrs per ridge. Climate cooling, particularly after 4 ka during the Neoglacial period, allowed for the expansion of sea-ice coverage in the fjords and the advance of tidewater glaciers, which reduced fetch in the fjord and limited the transfer of wave energy onto the Bjonasletta beach. This led to a reduction in sediment supply to the beach-ridge plain and an attendant slowing of progradation to ~ 100 yrs per ridge. The Neoglacial was further characterized by the development of coastal permafrost across the beach-ridge plain, which creeped down from extensive talus slopes and dissected ridges through frost fissure and ice-wedge polygons. Our findings suggest that the morphology and growth patterns of beach-ridge plains, common throughout global high latitudes, can archive signals not only of sea-ice and sea-level fluctuations, but also of glacial advance and retreat, opening a new avenue for paleo-environmental reconstructions in the planet’s most sensitive and rapidly changing regions.