Final deglaciation of the Scandinavian Ice Sheet and implications for the Holocene global sea-level budget

The last deglaciation of the Scandinavian Ice Sheet (SIS) from ~21, 000 to 13,000 yr ago is well-constrained by several hundred ¹⁰Be and ¹⁴C ages. The subsequent retreat history, however, is established primarily from minimum-limiting ¹⁴C ages and incomplete Baltic-Sea varve records, leaving a substantial fraction of final SIS retreat history poorly constrained. Here we develop a high-resolution chronology for the final deglaciation of the SIS based on 79 ¹⁰Be cosmogenic exposure dates sampled along three transects spanning southern to northern Sweden and Finland. Combining this new chronology with existing ¹⁰Be ages on deglaciation since the Last Glacial Maximum shows that rates of SIS margin retreat were strongly influenced by deglacial millennial-scale climate variability and its effect on surface mass balance, with regional modulation of retreat associated with dynamical controls. Ice-volume estimates constrained by our new chronology suggest that the SIS contributed ~8 m sea-level equivalent to global sea-level rise between ~14.5 ka and 10 ka. Final deglaciation was largely complete by ~10.5 ka, with highest rates of sea-level rise occurring during the Bølling-Allerød, a 50% decrease during the Younger Dryas, and a rapid increase during the early Holocene. Combining our SIS volume estimates with estimated contributions from other remaining Northern Hemisphere ice sheets suggests that the Antarctic Ice Sheet (AIS) contributed 14.4±5.9 m to global sea-level rise since ~13 ka. This new constraint supports those studies that indicate that an ice volume of 15 m or more of equivalent sea-level rise was lost from the AIS during the last deglaciation.