On the benefits of a multi-level monitoring strategy, some examples of the recent advances within the French GLACIOCLIM observatory

A multi-level monitoring combining in situ and remotely-sensed measurements within different climate regions constitutes the strategy recommended by the Global Terrestrial Network for Glaciers (GTN-G) to provide the basic data sets required for integrative studies and assessments of the distribution and changes of glaciers and ice caps. The French national observatory of glaciers “GLACIOCLIM”, in collaboration with local partners, has been developing such a strategy for several decades on glaciers in the French Alps, the tropical Andes, the Antarctic and the Himalayas. The policy supported by GLACIOCLIM in terms of data sharing relies on: (1) free access through an interactive database which has been recently redesigned; (2) a contribution to the World Glacier Monitoring Service database, sustained by an MoU; and (3) a contribution to the GLIMS initiative for multi-temporal glacier inventories.

This presentation will first present the GLACIOCLIM activities and data sets in the different regions where the observatory has been implemented. Secondly, we will focus on the case of the tropical Andes, showing the advantages of combining all the gathered information from "reference glaciers" (i.e. glaciers with in situ measurements of mass balance, surface energy balance and hydrological balance) and from glacier changes estimated from remote sensing data at the massif scale, to better understand the causes of the recent acceleration in glacier decrease over the last decades. Finally, we will present a promising method to retrieve annual mass balance data for individual glaciers at the massif scale on the basis of the end-of-summer snowline determined on satellite images, a highly relevant method to produce annual mass balance time-series allowing to spatially expand the information available on the small number "reference glaciers" benefiting of in situ monitoring.