Comment on essd-2022-56

Mauri Pelto

doi:10.5194/essd-2022-56-rc1

Abstract

Glacier monitoring in Switzerland has resulted in some of the longest and most complete data series globally. Mass balance observations at individual locations, starting in the 19th century, are the backbone of the monitoring as they represent the raw and original glaciological data demonstrating the response of snow accumulation and snow/ice melt to changes in climate forcing. So far, however, the variety of sources of historic measurements has not been systematically processed and documented. Here, we present a new complete and extensive point glacier mass balance dataset for the Swiss Alps that provides attributes for data quality and corresponding uncertainties. Original sources were digitized or re-assessed to validate or to correct existing entries and to identify metadata. The sources of data are highly diverse and stem from almost 140 years of records, originating from handwritten field notes, unpublished project documents, various digital sources, published reports, as well as meta-knowledge of the observers. The project resulted in data series with metadata for 63 individual Swiss glaciers, including more than 60'000 point observations of mass balance. Data were systematically analyzed and homogenized, e.g. by supplementing partly missing information based on correlations inferred from direct measurements. A system to estimate uncertainty in all individual observations was developed indicating that annual point balance is measured with a typical error of 0.07 m water equivalent (w.e.), while the average error in winter snow measurements is 0.20 m w.e. Our dataset permits further investigating the climate change impacts on Swiss glaciers. Results show an absence of long-term trends in snow accumulation over glaciers, while melt rates have substantially increased over the last three decades.

Highlights

Mass balance observations at individual locations, starting in the 19th century, are the backbone of the monitoring as they represent the raw and original glaciological data demonstrating the response of snow accumulation and snow/ice melt to changes in climate forcing
Data mass balance is measured with the glaciological method, i.e. ablation stakes and snow pits distributed across the glacier surface 25 (Cogley et al, 2011; Zemp et al, 2013; Sold et al, 2016; McGrath et al, 2018; Andreassen et al, 2020). These measurements require access to the glacier, they can be performed by relatively limited and simple technical equipment (Østrem and Stanley, 1969). This is the reason why some point observations have already been performed since the very beginning of glaciological research in the late 19th century based on consistent methodology (Mercanton, 1916)
320 A complete and documented dataset comprising all currently accessible point mass balance measurements that were acquired on Swiss Glaciers since 1884 has been compiled

Summary

Introduction

Mass loss of mountain glaciers in the Alps and worldwide in response to a changing climate is rapid and accelerating (Zemp et al, 2019; Hugonnet et al, 2021). Data mass balance is measured with the glaciological method, i.e. ablation stakes and snow pits distributed across the glacier surface 25 (Cogley et al, 2011; Zemp et al, 2013; Sold et al, 2016; McGrath et al, 2018; Andreassen et al, 2020). These measurements require access to the glacier, they can be performed by relatively limited and simple technical equipment (Østrem and Stanley, 1969). The World Glacier Monitoring Service (WGMS) collects this data from contributors over all continents, merging national datasets into a global database

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Conclusion