During the last deglaciation, North Atlantic climate abruptly warmed at the Bølling (∼14.7 ka), cooled into the Younger Dryas (∼12.9 ka) and abruptly warmed again into the Holocene (∼11.7 ka). While these events are defined by Greenland ice cores, there is still considerable uncertainty on Greenland ice-sheet margin responses to abrupt climate change. To refine the ice sheet's deglacial history, we present new cosmogenic nuclide surface exposure ages from boulders on bedrock at five sites in southernmost Greenland fjords located midway between the coast and inland ice margin. We find ice-sheet thinning below three local topographic highs at 12.7 ± 0.3 ka (n = 3), 13.1 ± 0.4 ka (n = 1, 2 outliers), and 12.3 ± 0.2 ka (n = 3), with up-fjord retreat at 12.5 ± 0.3 ka (n = 3) and 12.7 ± 0.2 ka (n = 4) based on two sites just above the mid-fjord marine limit. These mid-fjord ¹⁰Be ages therefore show southernmost Greenland ice-sheet thinning and retreat during the Younger Dryas. We hypothesize that this thinning and retreat was a response to ocean warming prior to the Holocene and/or summer shortwave radiative forcing during the Younger Dryas due to peak boreal summer insolation. Our results also support a previously hypothesized winter bias in proxy records of Younger Dryas atmospheric cooling, since a large summer cooling during the Younger Dryas could have counteracted the effects of ocean warming and direct radiative forcing, inhibiting ice-sheet retreat.

在最后一次冰消期间，北大西洋气候在 Bølling（~14.7 ka）突然变暖，冷却到年轻的仙女木（~12.9 ka）并再次突然变暖到全新世（~11.7 ka）。虽然这些事件是由格陵兰冰芯定义的，但格陵兰冰盖边缘对突然气候变化的响应仍然存在相当大的不确定性。为了完善冰盖的冰川消融历史，我们在位于海岸和内陆冰缘中间的格陵兰岛最南端的五个地点的基岩上的巨石上展示了新的宇宙成因核素表面暴露年龄。我们发现冰盖在 12.7 ± 0.3 ka (n = 3)、13.1 ± 0.4 ka (n = 1, 2 个异常值) 和 12.3 ± 0.2 ka (n = 3) 的三个局部地形高点以下变薄，向上峡湾在 12.5 ± 0.3 ka (n = 3) 和 12.7 ± 0 撤退。2 ka (n = 4) 基于峡湾中部海洋极限上方的两个站点。这些中峡湾¹⁰ Be Ages 因此显示最南端的格陵兰冰盖在新仙女木期间变薄和退缩。我们假设这种变薄和后退是对全新世之前的海洋变暖和/或新仙女木期间由于北方夏季日照峰值引起的夏季短波辐射强迫的反应。我们的研究结果还支持先前假设的年轻仙女木大气冷却代理记录中的冬季偏差，因为新仙女木期间夏季的大规模冷却可能抵消了海洋变暖和直接辐射强迫的影响，从而抑制了冰盖退缩。