Using a Web Map Service to map Little Ice Age glacier extents at regional scales

• Main Authors: Reinthaler, Johannes, Paul, Frank
• Format: Article in Journal/Newspaper
• Language: English
• Published: International Glaciological Society 2023
• Subjects: Institute of Geography; 910 Geography & travel; Earth-Surface Processes; Baffin Island; Annals of Glaciology; Baffin; glacier; glaciers; Novaya Zemlya; Alaska
• Online Access: https://www.zora.uzh.ch/id/eprint/259039/; https://www.zora.uzh.ch/id/eprint/259039/1/ZORA_div_class_title_using_a_web_map_service_to_map_little_ice_age_glacier_extents_at_regional_scales_div.pdf; https://doi.org/10.5167/uzh-259039; https://doi.org/10.1017/aog.2023.39

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 km$^{2}$, now 891 ice bodies with 3590 km$^{2}$) 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.