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

Abstract 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 marine-terminating 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 crept 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.