Global Glacier mass balance – From a Glaciers Perspective

For the 14th year I had the opportunity to author the Alpine Glacier section of the State of the Climate 2022 report published in the Bulletin of the American Meteorolocial Society. Below is this report with additional images.

An increasing frequency of heat waves impacting glaciated mountain ranges continues to lead to large mass balance losses. In 2022 heat events in the European Alps, Svalbard, High Mountain Asia and the Central Andes of Argentina and Chile resulted in a mean annual mass balance of -1433 mm w.e., for all 108 reporting alpine glaciers, with data reported from 20 nations on five continents. In the hydrological year 2021/22 the preliminary regionally averaged annual mass balance based on the World Glacier Monitoring Service (WGMS, 2021) reference glaciers was -1179 mm w.e. compared to the 1970-2020 average -490 mm w.e.

In 2022, a negative annual mass balance was reported from 34 of the 37 reference glaciers reported to WGMS. The mean annual mass balance of thereference glaciers reporting was -1547 mm w.e.. Reference glaciers each years of observation are used to generate regional averages. Global values are calculated using a single value (averaged) for each of 19 mountain regions in order to avoid a bias to well observed regions. The regionally averaged annual mass balance was -1179 mm w.e., less negative than the general mean. This makes 2022 the 35^th consecutive year with a global alpine mass balance loss, and the 14^th consecutive year with a mean global mass balance below -500 mm w.e. This acceleration in mass loss from global alpine glaciers in the 21^st century matches the findings of Huggenet et al (2021).

The lack of retained snowpack is evident at glaciers around the world in 2022.

More frequent and intense heat waves impacting glaciated ranges continued to take a toll on alpine glaciers in 2022. Heat waves reduce snow cover extent earlier in the melt season, exposing ice surfaces earlier and enhancing surface darkening, both causing higher melt rates on alpine glaciers (Shaw et al. 2021; Pelto et al. 2022; Cremona et al., 2023).

All 32 reporting glaciers in the Alps, Pyrenees and Caucasus Mountains had a negative mass balance averaging –3100 mm w.e. in 2022. In the European Alps the combination of low winter snowpack and several summer heat waves generated unprecedented mass loss (BAMS, 2023?). In Switzerland the 25 days of heat waves in 2022 are estimated to have melted 1.27±0.10 km³ w.e., equivalent to 35 % of the overall glacier mass loss during the summer (Cremona et al, 2023).

In Norway and Sweden, the average balance of 11 reporting glaciers was -443 mm w.e., with three glaciers in Norway having a positive balance. Iceland completed surveys of nine glaciers, five had a positive balance and four a negative balance with a mean mass balance of -7 mm w.e., e.g. equilibrium.

Langjokulen (La), Kvitisen (Kv), Bergfonna (Be) and Blaisen (Bl) ice caps on Edgeøya in Sentinel image from 8-20-2022 illustrating the lack of snowcover, limited firn areas and numerous annual layers.

On Svalbard the mean loss of the four reporting glaciers was -1102 mm w.e.. The negative mass balances were due to several summer heat events (BAMS, 2023?), which led to many glaciers and ice caps losing all or most of their snow cover, further accelerating mass loss (Figure 2.c.3.1).

Helm Glacier BC with limited retained snowpack.

In Alberta and British Columbia, Canada and in Alaska and Washington, United States,19 glaciers had a negative mass balance, averaging -965 mm w.e.. The Alberta, British Columbia and Washington region again experienced several prolonged heat waves. Daily glacier ablation in this region was noted as increasing by 30-40% during heat wave periods (Pelto et al 2022).

Volcan Overo, Argentina with no retained snowpack

In South America, mass balance data, reported from five Andean glaciers in Ecuador, Argentina, and Chile, were negative with a mean of -1465 mm w.e.. The combination of drought and heat events left many central Andean glaciers snow free by mid-summer in 2022. Shaw et al. (2021) noted a significant decline in surface albedo (Section 2.h.1) due to decrease fractional snow cover that further enhances melt.

In the High Mountain Asia mass balance measurements were completed on glaciers in China, Kazakhstan, Kyrgyzstan, Russia, and Tajikistan. All twenty glaciers reported negative balances. The average mass balance was -1040 mm w.e.. The negative balances were driven by above average melting during the May-July period (BAMS, 2023?).

In New Zealand the mass balance assessed on Brewster and Rolleston Glacier was strongly negative at -1125 and -1065 mm w.e. respectively. This matched the end of year snowline observations on 50 glaciers that was one of the five highest of the last 45 years.

Annual mass balance is reported in mm water equivalent (w.e.). A value of -1000 m w.e. per year is representing a mass loss of 1,000 kg m^-2 of ice, or an annual glacier-wide thickness loss of about 1100 mm yr^-1

Cumulative glacier mass balance losses reported by WGMS by region, all glacier, reference glaciers and geodetic mass balance (Sholes Glacier, WA in background). The data set size, location and type changes but the story remains the same, mass loss resulting from global temperature increase.

The World Glacier Monitoring Service has released the second bulletin of Global Glacier Change. The bulletin provides detailed global and regional information on alpine glaciers particularly for 2014 and 2015. There is data reported from 621 glaciers. The glaciers vary in type and location, yet their response is the same retreat and mass balance loss as a result of the global temperature increases. There are currently 41 reference glaciers with at least 30 consecutive years of detailed field measurement of mass balance. Additionally mass balance is typically reported from 60-80 other glaciers. The graph below indicates that the reference glacier network mass balance losses parallels the losses of all glaciers and that of geodetic assessment of mass loss from remapping. The report indicates that alpine glaciers have lost 0.9 m w.e. per year. This continues the unprecedented trend of mass loss that is driving glacier retreat as well. In 2014 and 2015 316 mass balance observations are reported from 166 glaciers. There are 889 terminus change observations reported from 528 glaciers. The results in graph after graph illustrate that glaciers in all regions of the globe are experiencing mass loss and retreat. As the United States representative to the WGMS, helping pull together each strand of data, is a key task. The result unfortunately is a very strong line of data built of all these strands of glaciers losing mass. The report also contains preliminary data from 2016, which was the 37th consecutive year of mass loss as reported in BAMS State of the Climate 2016 (Pelto, 2017). The deadline for posting initial results on mass balance for reference glaciers in 2017 was Dec. 1 2017. Reporting on the US glaciers it is clear that 2017 will be another year of substantial losses in this region.

Annual glacier mass balance reported for each region. The coloration indicates the increase in mass balance loss in each region with global temperature increase.

There is a section of the bulletin on each region including graphs of terminus change and mass balance on selected glaciers. Below are examples from Western North America and Central Europe. For reference glaciers data is submitted that includes maps of the mass balance, and then charts are derived from WGMS illustrating mass balance changes and the relationships between mass balance and the equilibrium line altitude, and between mass balance and the accumulation area ratio.