The Laurentide Ice Sheet was the largest global ice mass to grow and decay during the last glacial cycle (~115 ka to ~10 ka). Despite its importance for driving major changes in global mean sea level, long-term landscape evolution, and atmospheric circulation patterns, the history of the Laurentide (and neighbouring Innuitian) Ice Sheet is poorly constrained owing to sporadic preservation of stratigraphic records prior to the Last Glacial Maximum (LGM; ~25 ka) and a case-study approach to the dating of available evidence. Here, we synthesize available geochronological data from the glaciated region, together with published stratigraphic and geomorphological data, as well as numerical modelling output, to derive 19 hypothesised reconstructions of the Laurentide and Innuitian ice sheets from 115 ka to 25 ka at 5-kyr intervals, with uncertainties quantified to include best, minimum, and maximum ice extent estimates at each time-step. Our work suggests that, between 115 ka and 25 ka, some areas of North America experienced multiple cycles of rapid ice sheet growth and decay, while others remained largely ice-free, and others were continuously glaciated. Key findings include: (i) the growth and recession of the Laurentide Ice Sheet from 115 ka through 80 ka; (ii) significant build-up of ice to almost LGM extent at ~60 ka; (iii) a potentially dramatic reduction in North American ice at ~45 ka; (iv) a rapid expansion of the Labrador Dome at ~38 ka; and (v) gradual growth toward the LGM starting at ~35 ka. Some reconstructions are only loosely constrained and are therefore speculative (especially prior to 45 ka). Nevertheless, this work represents our most up-to-date understanding of the build-up of the Laurentide and Innuitian ice sheets during the last glacial cycle to the LGM based on the available evidence. We consider these ice configurations as a series of testable hypotheses for future work to address and refine. These results are important for use across a range of disciplines including ice sheet modelling, palaeoclimatology and archaeology and are available digitally.

Laurentide 冰盖是最后一个冰川周期（~115 ka 到~10 ka）期间生长和衰变的最大的全球冰块。尽管它对推动全球平均海平面、长期景观演变和大气环流模式的重大变化具有重要意义，但由于最后一次之前地层记录的零星保存，劳伦泰德（和邻近的因纽特）冰盖的历史受到很大限制。冰川最大值 (LGM；~25 ka) 和对可用证据进行年代测定的案例研究方法。在这里，我们综合了冰川地区的可用地质年代学数据，连同已发表的地层和地貌数据，以及数值建模输出，以 5 kyr 为间隔推导出 19 种假设的劳伦泰德和因纽特冰盖重建，从 115 ka 到 25 ka , 将不确定性量化为包括每个时间步长的最佳、最小和最大冰范围估计。我们的工作表明，在 115 ka 到 25 ka 之间，北美的一些地区经历了多次冰盖快速增长和衰退的循环，而其他地区则基本保持无冰状态，而其他地区则不断被冰川覆盖。主要发现包括：(i) Laurentide 冰盖从 115 ka 到 80 ka 的增长和衰退；(ii) 在~60 ka 时，冰的显着积聚几乎达到 LGM 程度；(iii) 大约 45 ka 时北美冰层可能急剧减少；(iv) 拉布拉多穹顶在~38 ka 时迅速扩张；(v) 从~35 ka 开始逐渐向 LGM 增长。一些重建只是松散约束，因此是推测性的（尤其是在 45 ka 之前）。尽管如此，这项工作代表了我们根据现有证据对 LGM 的最后一个冰川周期期间劳伦泰德和因纽特冰盖的积聚的最新理解。我们将这些冰结构视为一系列可测试的假设，供未来解决和完善工作。这些结果对于冰盖建模、古气候学和考古学等一系列学科的使用非常重要，并且可以数字方式获得。