This paper reconstructs the deglaciation of the Laurentide Ice Sheet (LIS; including the Innuitian IceSheet) from the Last Glacial Maximum (LGM), with a particular focus on the spatial and temporal var-iations in ice streaming and the associated changes in flow patterns and ice divides. We build on a recentinventory of Laurentide ice streams and use an existing ice margin chronology to produce the firstdetailed transient reconstruction of the ice stream drainage network in the LIS, which we depict in aseries of palaeogeographic maps. Results show that the drainage network at the LGM was similar tomodern-day Antarctica. The majority of the ice streams were ma rine terminating and topographically-controlled and many of these continued to function late into the deglaciation, unti l the ice sheet lostits marine margin. Ice streams with a terrestrial ice margin in the west and south were more transientand ice flow directions changed with the build-up, peak-phase and collapse of the Cordilleran-Laurentideice saddle. The south-eastern marine margin in Atlantic Canada started to retreat relatively early andsome of the ice streams in this region switched off at or shortly after the LGM. In contrast, the ice streamsdraining towards the north-western and north-eastern marine margins in the Beaufort Sea and in BaffinBay appear to have remained stable throughout most of the Late Glacial, and some of them continued tofunction until after the Younger Dryas (YD). The YD influenced the dynamics of the deglaciation, butthere remains uncertainty about the response of the ice sheet in several sectors. We tentatively ascribethe switching-on of some major ice streams during this period (e.g. M'Clintock Channel Ice Stream at thenorth-west margin), but for other large ice streams whose timing partially overlaps with the YD, thedrivers are less clear and ice-dynamical processes, rather than effects of climate and surface mass balanceare viewed as more likely drivers. Retreat rates markedly increased after the YD and the ice sheet beca melimited to the Canadian Shield. This hard-bed substrate brought a change in the character of icestreaming, which became less frequent but generated much broader terrestrial ice streams. The finalcollapse of the ice sheet saw a series of small ephemeral ice streams that resulted from the rapidlychanging ice sheet geometry in and around Hudson Bay. Our reconstruction indicates that the LIS un-derwent a transition from a topographically-controlled ice drainage network at the LGM to an icedrainage network characterised by less frequent, broad ice streams during the later stages of deglacia-tion. These deglacial ice streams are mostly interpreted as a reaction to localised ice-dynamical forcing(flotation and calving of the ice front in glacial lakes and transgressing sea; basal de-coupling due to largeamount of meltwater reaching the bed, debuttressing due to rapid changes in ice sheet geometry) ratherthan as conveyors of excess mass from the accumulation area of the ice sheet. At an ice sheet scale, theice stream drainage network became less widespread and less efficient with the decreasing size of thedeglaciating ice sheet, the final elimination of which was mostly driven by surface melt.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)