Glaciers on active volcanoes are subject to changes in both climate fluctuations and volcanic activity. Whereas many studies analysed changes on individual volcanoes, this study presents for the first time a comparison of glacier changes on active volcanoes on a continental scale. Glacier areas were mapped for 59 volcanoes across Latin America around 1986, 1999 and 2015 using a semi-automated band ratio method combined with manual editing using satellite images from Landsat 4/5/7/8 and Sentinel-2. Area changes were compared with the Smithsonian volcano database to analyse possible glacier–volcano interactions. Over the full period, the mapped area changed from 1399.3 ± 80 km2to 1016.1 ± 34 km2(−383.2 km2) or −27.4% (−0.92% a−1) in relative terms. Small glaciers, especially in tropical regions lost more of their area compared to large and extra–tropical glaciers. Interestingly, 46 out of 59 analysed glaciers (78%) showed a decelerating shrinkage rate in the second period (−1.20% a−1before 1999 and −0.70% a−1after 1999). We found a slightly higher (but statistically not significant) area loss rate (−1.03% a−1) for glaciers on volcanoes with eruptions than without (−0.86% a−1).
Abstract. Glacier fronts are retreating across the globe in response to climate warming, revealing valleys, fjords, and proglacial lakes. The piedmont lobe of San Quintín, the largest glacier of the Northern Patagonia Icefield, in southern Chile, has recently entered a phase of frontal retreat, where its terminus is rapidly disintegrating into large tabular icebergs calving into a new proglacial lake. We present results of a new airborne GPR survey of the terminus of this large Patagonian glacier (763 km2 in 2017), complemented with an analysis of ice flow velocity, satellite imagery, and ice elevation change to show that the ongoing retreat is caused by recent detachment of a floating terminus from the glacier bed and may shortly lead to the disappearance of the last existing piedmont lobe in Patagonia. Finally, we discuss how the observations of San Quintín’s ongoing collapse may give insights into processes governing frontal retreat of fast-flowing temperate glaciers and the quasi-stability of the floating termini.
Extending the record of glacier area changes into the past improves our understanding of climate change impacts. Although analogue maps showing historic glacier extents are abundant, digital outlines from before the satellite era are sparse as the digitisation of moraines and trimlines on freely available satellite images is challenging. With the now available very high-resolution images provided by Web Map Services (WMS), new doors are open for the precise digitisation. Here, we used the ESRI WMS to digitise Little Ice Age (LIA) glacier extents and present area changes since the LIA in four selected regions along with a detailed uncertainty analysis. We used modern glacier outlines as a starting point and additionally consulted Sentinel-2 images, the ArcticDEM and historic maps for interpretation. Dating records from the literature allowed calculating area change rates. In total, 493 LIA glaciers (4640 km2, now 891 ice bodies with 3590 km2) were digitised, yielding relative area changes of −20% (−0.14% a−1), −15% (−0.10% a−1), −26% (−0.16% a−1) and −61% (−0.19% a−1) for Alaska, Baffin Island, Novaya Zemlya and the tropics, respectively. The ESRI WMS images are a great asset to precisely map moraines and trimlines, but information about the timing of the related extents requires further sources.
<p>Glacier fronts are retreating across the globe in response to climate warming, revealing valleys, fiords, and proglacial lakes. The piedmont lobe of San Quint&#237;n, the largest glacier of the Northern Patagonia Icefield, in southern Chile, has recently entered a catastrophic phase of frontal retreat, where its terminus is rapidly disintegrating into large tabular icebergs calving into a new proglacial lake. We present results of a unique airborne GPR survey of the terminus of this large Patagonian glacier (763 km<sup>2 </sup>in 2017), complemented with an analysis of ice flow velocity, satellite imagery, and ice elevation change to show that the ongoing retreat is caused by recent detachment of a floating terminus from the glacier bed and may shortly lead to the disappearance of the last existing piedmont lobe in Patagonia. Finally, we discuss how the observations of San Quint&#237;n&#8217;s ongoing collapse may give insights into processes governing frontal retreat of fast-flowing temperate glaciers and the quasi-stability of the floating termini.</p>
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