Collapse of the Icelandic ice sheet controlled by sea-level rise?

Abstract

The deglaciation of the Late Weichselian Icelandic ice sheet was extremely rapid, and marked by a collapse of its marine-based sections between 15.0 and 14.7 ka BP. We present a conceptual two-dimensional glacio-isostatic equilibrium model that describes the effect of simultaneous glacio-isostatic responses to changes in glacier load on the crust and relative eustatic sea level changes during the deglaciation of the Icelandic ice sheet. The deglaciation was characterized by three main steps: (1) slow deglaciation of the outer shelf, progressing between about 18.6–15.0 ka BP, mainly driven by sea-level rise and grounding line retreat on a retrograde slope; (2) an extremely rapid retreat from the shelf areas between 15.0 and 14.7 ka BP, mainly driven by rapid sea-level rise and large-scale calving; (3) a slower retreat driven by North Atlantic warming once the ice sheet was inside the coast, between 14.7 and 13.8 ka BP. The very rapid deglaciation of the Iceland shelf areas between 15.0 and 14.7 ka BP does not confirm with linear response to warming, but rather describes a non-linear response, where the ice sheet experiences an abrupt collapse once a threshold defined by relative eustatic sea-level rise is crossed. We propose that rapid eustatic sea-level rise that peaked during Mwp-1A being coeval with the collapse of the marine-based part of the Icelandic ice sheet suggests a causal relationship between the two events.