Abstract Local glaciers and ice caps (GICs) respond sensitively and quickly, on the scale of decades to centuries, to climate variations. Continuous records of past fluctuations in GIC size provide information on the timing and magnitude of Holocene climate shifts, and a longer-term perspective on 21st century glacier retreat. Although there is broad-scale agreement on millennial-scale trends in Holocene climate variability and fluctuations in local GICs in Greenland, regional variations are only loosely constrained. Here we present three Holocene proglacial lake sediment records from South Greenland, an area with abundant local glaciers but few Holocene-length paleoclimate records. In addition, we use geospatial analysis to model past equilibrium-line altitudes (ELAs) and thereby constrain the magnitude of ablation-season temperature change during the warmest and coolest periods of the Holocene. Physical and geochemical sedimentary characteristics show that two of the proglacial lakes continued to receive glacial meltwater input until ∼7.3 and ∼7.1 ka BP. The survival of local glaciers implies that South Greenland remained relatively cool, and that summer temperatures gradually warmed, but did not warm well beyond 1.2 °C above present in the early Holocene. In the mid-Holocene, from ∼7.1 to 5.5 ka BP, organic sedimentation at these two sites indicates that local glaciers became very small, or more likely melted away completely. The glaciers within the third lake’s catchment melted away prior to ∼5.2 ka BP, as sediments deposited earlier in the Holocene could not be dated at this site. We estimate that summer temperatures increased by at least 1.2–1.8 °C above present by ∼7.3–7.1 ka BP. Our results are consistent with other observations that suggest a north-to-south gradient in the timing of Holocene thermal maximum conditions, with southern Greenland experiencing a delayed warming relative to other regions in Greenland. As summer temperatures cooled in the Neoglacial, our records show that sustained glacier regrowth began ∼3.1 ka BP with glaciers in the southernmost catchment, which at present, receive the most precipitation. In the other two catchments, which host smaller glaciers in a drier environment, regrowth began at ∼1.3 and ∼1.2 ka BP, the timing of which is in agreement with other glacial records from the Arctic Atlantic region. Local glaciers reached their maximum late Holocene extents during a cooler, second phase of the Little Ice Age (LIA) ∼0.2-0.1 ka BP, that we estimate was at least 0.4–0.9 °C cooler than present. Overall, these findings improve understanding of the spatio-temporal dynamics of Holocene glacier and climate change in Greenland, potentially yielding valuable information about their future response.

中文翻译：

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当地冰川记录了格陵兰南部全新世温暖高峰的延迟

摘要 当地冰川和冰盖 (GIC) 对气候变化的反应灵敏而迅速，范围从几十年到几百年不等。GIC 规模过去波动的连续记录提供了关于全新世气候变化的时间和幅度的信息，以及 21 世纪冰川退缩的长期前景。尽管在全新世气候变率和格陵兰当地 GIC 波动的千禧年尺度趋势方面存在广泛共识，但区域差异仅受到松散限制。在这里，我们展示了来自南格陵兰岛的三个全新世前冰湖沉积物记录，该地区当地冰川丰富，但很少有全新世长度的古气候记录。此外，我们使用地理空间分析来模拟过去的平衡线高度 (ELA)，从而限制全新世最暖和最冷时期的消融季节温度变化幅度。物理和地球化学沉积特征表明，两个前冰湖继续接收冰川融水输入，直到~7.3 和~7.1 ka BP。当地冰川的存留意味着南格陵兰岛保持相对凉爽，夏季气温逐渐变暖，但在全新世早期并没有超过 1.2°C。在全新世中期，从~7.1 到 5.5 ka BP，这两个地点的有机沉积表明当地冰川变得非常小，或者更有可能完全融化。第三湖流域内的冰川在~5.2 ka BP之前融化，因为在该地点无法确定早于全新世沉积的沉积物的年代。我们估计夏季温度比目前至少高出 1.2-1.8°C 约 7.3-7.1 ka BP。我们的结果与其他观察结果一致，这些观察表明全新世热最大条件的时间从北到南梯度，格陵兰南部相对于格陵兰的其他地区经历了延迟的变暖。随着夏季气温在新冰期变冷，我们的记录显示持续的冰川再生开始于约 3.1 ka BP，最南端的流域的冰川目前接收最多的降水。在其他两个流域中，在较干燥的环境中拥有较小的冰川，再生开始于约 1.3 和 1.2 ka BP，其时间与来自北大西洋地区的其他冰川记录一致。在小冰河时代 (LIA) 的第二阶段，当地冰川达到了其最大的全新世晚期范围，大约为 0.2-0.1 ka BP，我们估计至少比现在低 0.4-0.9 °C。总体而言，这些发现提高了对格陵兰全新世冰川和气候变化时空动态的理解，可能会提供有关其未来响应的宝贵信息。