描述热带安第斯山脉的冰川变化很重要,因为热带冰川对气候变化很敏感。我们对冰川动力学以及热带冰川如何应对全球气候扰动的理解很少受到限制。对热带安第斯山脉过去冰川作用的研究集中在冰川仍然存在或最近在高海拔地区腾空的地方。很少有研究关注低海拔地区,因为人们认为冰川不存在或没有那么广泛。我们提出了秘鲁北部 Lagunas de Las Huaringas 过去冰川作用的第一个地貌证据,海拔 3,900-2,600 m asl 使用遥感光学图像和新创建的高分辨率(~2.5 m)数字高程进行测绘模型(DEM)。该地区有大量冰川作用的证据,包括冰碛、冰川圆环、丘陵地形、冰川线条和冰雕基岩。假设有两种潜在的冰川作用模型:1)高原冰盖,或 2)山谷冰川作用。假设冰川在局部末次盛冰期(LLGM)期间达到最大范围,在 23.5 ± 0.5 和 21.2 ± 0.8 ka 之间,最大重建冰川面积为 75.6 km2. 计算出的平均平衡线高度 (ELA) 为 3,422 ± 30 m,表明与现代雪线高度相比,ELA 变化为 -1,178 ± 10 m。有一个东西向的 ELA 海拔梯度,东低西高,与现代水分转移一致。与目前相比,采用 5.5 至 7.5°C/km 之间的递减率可提供 6.5-8.8°C 之间的 LLGM 温度冷却。这些值与北部热带安第斯山脉其他研究和冰芯重建的估计值相当。Lagunas de las Huaringas 冰川地貌的测绘首次证明了秘鲁北部低海拔地区广泛的冰川作用,这对我们了解亚热带过去的气候具有重要意义。观察和重建支持山谷,而不是冰盖冰川作用。需要进一步的工作来限制冰川作用的时间,有证据表明冰碛比最大冰川范围的 LLGM 上谷更年轻。数值模型还将有助于了解该地区的冰川控制。
"点击查看英文标题和摘要"
Palaeoglaciation in the Low Latitude, Low Elevation Tropical Andes, Northern Peru
Characterising glaciological change within the tropical Andes is important because tropical glaciers are sensitive to climate change. Our understanding of glacier dynamics and how tropical glaciers respond to global climate perturbations is poorly constrained. Studies of past glaciation in the tropical Andes have focused on locations where glaciers are still present or recently vacated cirques at high elevations. Few studies focused on lower elevation localities because it was assumed glaciers did not exist or were not as extensive. We present the first geomorphological evidence for past glaciations of the Lagunas de Las Huaringas, northern Peru, at elevations of 3,900–2,600 m a.s.l. Mapping was conducted using remotely-sensed optical imagery and a newly created high-resolution (∼2.5 m) digital elevation model (DEM). The area has abundant evidence for glaciation, including moraines, glacial cirques, hummocky terrain, glacial lineations and ice-sculpted bedrock. Two potential models for glaciation are hypothesised: 1) plateau-fed ice cap, or 2) valley glaciation. Assuming glaciers reached their maximum extent during the Local Last Glacial Maximum (LLGM), between 23.5 ± 0.5 and 21.2 ± 0.8 ka, the maximum reconstructed glacial area was 75.6 km2. A mean equilibrium line altitude (ELA) of 3,422 ± 30 m was calculated, indicating an ELA change of −1,178 ± 10 m compared to modern snowline elevation. There is an east to west ELA elevation gradient, lower in the east and higher in the west, in-line with modern day transfer of moisture. Applying lapse rates between 5.5 and 7.5°C/km provides a LLGM temperature cooling of between 6.5–8.8°C compared to present. These values are comparable to upper estimates from other studies within the northern tropical Andes and from ice-core reconstructions. The mapping of glacial geomorphology within the Lagunas de las Huaringas, evidences, for the first time, extensive glaciation in a low elevation region of northern Peru, with implications for our understanding of past climate in the sub-tropics. Observations and reconstructions support a valley, rather than ice cap glaciation. Further work is required to constrain the timing of glaciations, with evidence of moraines younger than the LLGM up-valley of maximum glacier extents. Numerical modelling will also enable an understanding of the controls of glaciation within the region.