Department of Atmospheric and Environmental Sciences, University at Albany, Albany, New York, 12222, USA.
Department of Geosciences, University of Massachusetts Amherst, Massachusetts, USA.
Sci Rep. 2018 Oct 22;8(1):15564. doi: 10.1038/s41598-018-33698-z.
We analyze the future state of Quelccaya Ice Cap (QIC), the world's largest tropical ice cap with a summit elevation of 5680 m a.s.l., which, in terms of its elevation range (~5300-5680 m a.s.l.), is representative of many low-elevation glacierized sites in the tropical Andes. CMIP5 model projections of air temperature (Ta) at QIC indicate a warming of about 2.4 °C and 5.4 °C (respectively) for RCP4.5 and RCP8.5 scenarios by the end of the 21 century, resulting in a pronounced increase in freezing level height (FLH). The impact of this warming on the QIC was quantified using equilibrium-line altitude (ELA) projections. The change in the ELA was quantified based on an empirical ELA-FLH relationship, and calibrated with observations of the highest annual snowline altitude (SLA) derived from LANDSAT data. Results show that from the mid-2050s onwards, the ELA will be located above the QIC summit in the RCP8.5 scenario. At that time, surface mass balance at QIC and most tropical glaciers at similar elevations will become increasingly negative, leading to their eventual complete disappearance. Our analysis further corroborates that elevation-dependent warming (EDW) contributes significantly to the enhanced warming over the QIC, and that EDW at Quelccaya depends on the rate of anthropogenic forcing.
我们分析了 Quelccaya 冰帽（QIC）的未来状态，QIC 是世界上最大的热带冰帽，其山顶海拔为 5680 米，就其海拔范围（~5300-5680 米）而言，它代表了安第斯山脉热带地区许多低海拔冰川化地区。在 QIC 上，CMIP5 模式对空气温度（Ta）的预测表明，到 21 世纪末，RCP4.5 和 RCP8.5 情景下的气温将分别升高约 2.4°C 和 5.4°C，导致冻结层高度（FLH）显著升高。利用平衡线高度（ELA）预测来量化这种变暖对 QIC 的影响。通过经验 ELA-FLH 关系来量化 ELA 的变化，并根据从 LANDSAT 数据得出的最高年雪线高度（SLA）观测值进行校准。结果表明，从中期 2050 年代开始，在 RCP8.5 情景下，ELA 将位于 QIC 山顶之上。此时，QIC 和类似海拔的大多数热带冰川的表面质量平衡将变得越来越负，最终导致它们完全消失。我们的分析进一步证实，海拔依赖性变暖（EDW）对 QIC 之上的变暖有很大贡献，而且 Quelccaya 的 EDW 取决于人为强迫的速度。
