Ice margin oscillations during deglaciation of the northern Irish Sea basin

We present a new chronology to constrain ice-margin retreat in the northern Irish Sea Basin. Estimates on the timing of ice thinning derived from CN ages for boulders from the summits of the Isle of Man and southwest Cumbria suggest that ice thinning was commensurate with the rapid retreat that followed the short-lived advance of the Irish Sea Ice Stream (ISIS) to maximum limits in the Celtic Sea. This ice retreat in the northern ISB was fastest at 20 ka in response to a wider calving margin, but slowed as ice stabilised and oscillated against the Isle of Man. We provide the first age constraints for the Scottish Readvance (19.2-18.2 ka) and demonstrate that it was potentially regional event across the Isle of Man and Cumbrian lowlands not linked with Heinrich event 1. After the Scottish Readvance ca. 19 ka, the ice front retreated northwards towards the Southern Uplands at the same time as climate north of ~45 °N warmed in response to summer insolation. This sequence demonstrates the importance of internal dynamics in controlling ice retreat rates in the Irish Sea, but also that deglaciation of the northern ISB was a response to climate warming