Glacial areas, lake areas, and snow lines from 1975 to 2012: status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru

摘要

Glaciers in the tropical Andes of southern Peru have received limitedattention compared to glaciers in other regions (both near and far), yetremain of vital importance to agriculture, fresh water, and hydropowersupplies of downstream communities. Little is known about recent glacial-areachanges and how the glaciers in this region respond to climate changes, and,ultimately, how these changes will affect lake and water supplies. To remedythis, we have used 158 multi-spectral satellite images spanning almost 4decades, from 1975 to 2012, to obtain glacial- and lake-area outlines for theunderstudied Cordillera Vilcanota region, including the Quelccaya Ice Cap.Additionally, we have estimated the snow-line altitude of the Quelccaya IceCap using spectral unmixing methods. We have made the following four key observations: first, since 1988 glacial areas throughout the CordilleraVilcanota (1988 glacial area: 361 km2) have been declining at a rate of3.99 ± 1.15 km2 yr?1 (22 year average, 1988–2010, with95% confidence interval (CI), n = 8 images). Since 1980, the QuelccayaIce Cap (1980 glacial area: 63.1 km2) has been declining at a rate of0.57 ± 0.10 km2 yr?1 (30 year average, 1980–2010, with95% CI, n = 14). Second, decline rates for individual glacierizedregions have been accelerating during the past decade (2000–2010) ascompared to the preceding decade (1988–1999) with an average increase from37.5 to 42.3 × 10?3 km2 yr?1 km?2 (13%).Third, glaciers with lower median elevations are declining at higher ratesthan those with higher median elevations. Specifically, glaciers with medianelevations around 5200 m a.s.l. are retreating to higher elevations at arate of ~1 m yr?1 faster than glaciers with median elevationsaround 5400 m a.s.l. Fourth, as glacial regions have decreased, 77% oflakes connected to glacial watersheds have either remained stable or shown aroughly synchronous increase in lake area, while 42% of lakes notconnected to glacial watersheds have declined in area (58% have remainedstable). Our new and detailed data on glacial and lake areas over 37 yearsprovide an important spatiotemporal assessment of climate variability in thisarea. These data can be integrated into further studies to analyzeinter-annual glacial and lake-area changes and assess hydrologic dependenceand consequences for downstream populations.