The retreat of mountain glaciers since the Little Ice Age: a spatially explicit global database

Most of the world’s mountain glaciers have been retreating for more than a century in response to climate change. Accurate, spatially explicit information on glacier retreat is pivotal to study the consequences of ice loss on both abiotic and biotic components of the environment. Here, we present a spatially explicit dataset showing positions of glacier fronts since the Little Ice Age (LIA) maxima. The dataset is based on multiple historical archival records including topographical maps; repeated photographs, paintings and aerial or satellite images with supplement of geochronology and our own field data. We provide ESRI shapefiles showing 728 past positions of 93 glacier fronts from all continents, except Antarctica, covering the period between the Little Ice Age maxima and the present. On average, the time series span the past 190 years. From 2 to 46 past positions per glacier are depicted (on average: 7.8).

Past positions of the glaciers have been obtained mostly on the basis of the literature, provided in a separate file, complemented with information obtained from topographical maps, historical, aerial or satellite pictures, and with our own field data, dating the position of geomorphological elements in the landscape on the basis of measurements taken in the field, signals and marks reporting the ancient position of the glacier front, and additional approaches for dating older moraines (lichenometry, dendrochronology, radiocarbon chronology).

NOTES TO THE DATABASE:

Database structure:
glacier: glacier name
GLIMS id: glacier id, according to the Global Land Ice Measurements from Space (GLIMS)
dating: calculated (or estimated) dating for a given line.
source: source followed to draw the lines.


Notes to fields of the database:
GLIMS id: the database version is glims_db_20200630 (downloaded on February 3rd 2021). Exceptions i) Maladeta: the glacier is not mapped in the GLIMS db, but it appears in the online viewer (https://www.glims.org/maps/glims); ii) Qamanaarsuup Sermia and Popocatepetl: the glacier is not mapped neither in the GLIMS db nor in the online viewer.
dating: in the cases a reference is cited in this field, it refers to the source we followed to estimate the age of the moraine ridge / position, sometimes by analogy with surrounding glaciers (cf. main text).

source: specifically, we used:
1) Articles / theses / maps: one or more figures from a given source were georeferenced, and the lines were redrawn following the original maps;
2) Satellite / orthophotogrammetric data: the glacier profile in the specific year was drawn interpreting the satellite / aerial images provided by the sources (i.e., Esri ArcGIS World Imagery, GN orthophotogrammetry, Google Earth, IGN orthophotogrammetry, Regional orthophotogrammetry - Lombardia, Regional orthophotogrammetry - Vallee d Aoste / Valle d Aosta);
3) Databases: lines were used as provided by the sources (i.e., GlaRiskAlp, GLIMS, OpenData Trentino);
4) unpublished data / field marks: the identification of the moraine / position occurred in the field or using sources not yet published.