Abstract Glaciers and ice caps (GICs) respond rapidly to changes in temperature and precipitation. Thus, records of their past fluctuations yield valuable information on past climate. However, relatively little is known about the long-term, Holocene history of Greenland’s local GICs, peripheral to the Greenland Ice Sheet. Here we report sediment records of Holocene glacier activity from two distally fed glacial lakes near Buksefjord, southwest Greenland. The two lakes’ watersheds host modern GICs of contrasting size. The Pers Lake (informal name) watershed drains part (3 km2) of a single small ice cap. In contrast, nearby Lake T3’s (informal name) watershed drains numerous GICs totaling 100 km2. At the time it emerged from the sea ∼8.6 ka BP, Pers Lake was receiving no glacial meltwater input. Sediment physical and geochemical properties indicate persistent meltwater input and regrowth of the ice cap within the Pers Lake catchment beginning at ∼1.4 ka BP, after almost 3000 years of sporadic meltwater input beginning ∼4.3 ka BP. The ice cap above Pers Lake reached a maximum late Holocene extent during the final phase of the Little Ice Age (LIA), ∼0.1 ka BP. The complementary Lake T3 sediment record suggests continued meltwater input from the larger suite of upstream GICs from the time of the lake’s isolation from the sea ∼8.4–7.5 ka BP through to the present. This indicates that some GICs here probably survived the Holocene Thermal Maximum (HTM), although were significantly reduced in size for an extended period (of unknown age and duration). Combined with evidence from Pers Lake and prior studies that show GICs at low and intermediate elevations in this region melted away completely during the HTM, and evidence for GIC presence at Lake T3, we provide lower and upper bounds on regional HTM equilibrium-line altitudes (ELAs). We estimate that regional ELAs were between ∼1370 and 1470 m above sea level in the early-to-middle Holocene. From the middle to late Holocene, our results, along with other regional GIC studies, indicate progressive lowering of regional glacier ELAs in response to Neoglacial summer cooling of ∼2.7 °C, assuming no change in precipitation.

中文翻译：

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从两个湖泊记录推断格陵兰岛西南部全新世冰川和冰盖波动

摘要 冰川和冰盖 (GIC) 对温度和降水的变化反应迅速。因此，它们过去波动的记录产生了关于过去气候的宝贵信息。然而，人们对格陵兰岛冰盖外围的格陵兰当地 GIC 的长期全新世历史知之甚少。在这里，我们报告了格陵兰西南部 Buksefjord 附近的两个远端冰川湖的全新世冰川活动的沉积物记录。这两个湖泊的流域拥有大小不同的现代 GIC。Pers 湖（非正式名称）分水岭排出单个小冰盖的一部分（3 平方公里）。相比之下，附近的 T3 湖（非正式名称）分水岭排放了大量总面积为 100 平方公里的 GIC。在大约 8.6 ka BP 出海时，Pers 湖没有接收到冰川融水输入。沉积物的物理和地球化学性质表明，在大约 3000 年的零星融水输入开始后，Pers Lake 流域内的冰盖在大约 1.4 ka BP 开始持续输入和再生长，大约 4.3 ka BP 开始。在小冰河时代 (LIA) 的最后阶段，Pers 湖上方的冰盖达到了全新世晚期的最大范围，约为 0.1 ka BP。互补的 T3 湖沉积物记录表明，从该湖与海洋隔绝的时间到 8.4-7.5 ka BP 到现在，来自上游 GIC 的更大套件的融水持续输入。这表明这里的一些 GIC 可能在全新世热最大值 (HTM) 中幸存下来，尽管在很长一段时间内（未知年龄和持续时间）尺寸显着减小。结合来自 Pers Lake 的证据和先前研究表明该地区中低海拔的 GIC 在 HTM 期间完全融化，以及 T3 湖存在 GIC 的证据，我们提供了区域 HTM 平衡线高度的下限和上限（ ELA）。我们估计，在全新世早期至中期，区域 ELA 位于海平面以上约 1370 至 1470 米之间。从全新世中期到晚期，我们的结果以及其他区域 GIC 研究表明，假设降水没有变化，区域冰川 ELA 会逐渐降低，以响应新冰期夏季降温约 2.7 °C。我们估计，在全新世早期至中期，区域 ELA 位于海平面以上约 1370 至 1470 米之间。从全新世中期到晚期，我们的结果以及其他区域 GIC 研究表明，假设降水没有变化，区域冰川 ELA 会逐渐降低，以响应新冰期夏季降温约 2.7 °C。我们估计，在全新世早期至中期，区域 ELA 位于海平面以上约 1370 至 1470 米之间。从全新世中期到晚期，我们的结果以及其他区域 GIC 研究表明，假设降水没有变化，区域冰川 ELA 会逐渐降低，以响应新冰期夏季降温约 2.7 °C。