DOI: 10.25923/f47r-hd76

G. Wolken^1,2, D. Burgess³, B. Wouters⁴, L. M. Andreassen⁵, J. Kohler⁶, B. Luks⁷, F. Pálsson⁸, L. Thomson⁹, and T. Thorsteinsson¹⁰

¹University of Alaska Fairbanks, Fairbanks, AK, USA
²Alaska Division of Geological and Geophysical Surveys, Fairbanks, AK, USA
³Geological Survey of Canada, Ottawa, ON, Canada
⁴Department of Geoscience and Remote Sensing, Delft University of Technology, Delft, The Netherlands
⁵Section for Glaciers, Ice and Snow, Norwegian Water Resources and Energy Directorate, Oslo, Norway
⁶Norwegian Polar Institute, Tromsø, Norway
⁷Institute of Geophysics, Polish Academy of Sciences, Warsaw, Poland
⁸Institute of Earth Sciences, University of Iceland, Reykjavík, Iceland
⁹Queen’s University, Kingston, ON, Canada
¹⁰Icelandic Meteorological Office, Reykjavík, Iceland

Headlines

• During the 2022/23 and 2023/24 mass balance years, Arctic glaciers and ice caps continued their widespread mass loss. Glaciers in Arctic Scandinavia and Svalbard experienced their most negative mass balance year on record in 2023/24.
• Since the mid-20th century, Arctic glaciers and ice caps have undergone relentless thinning, with long-term measurements on glaciers in Alaska showing an average of over 38 meters of water equivalent thinning, which is contributing steadily to global sea level rise.
• Ongoing glacier loss threatens Arctic communities by reducing water supplies, driving destructive floods, and increasing landslide and tsunami hazards that endanger people, infrastructure, and coastlines.

Introduction

The Arctic contains 60% of the world’s mountain glaciers and ice caps by area, excluding the Greenland and Antarctic ice sheets (RGI Consortium 2023) (Fig. 1). While Arctic glaciers and ice caps’ potential long-term sea level contribution is smaller than that of the Greenland and Antarctic ice sheets, they are more responsive to climate variability and have been a leading contributor to recent sea level rise due to persistent atmospheric warming (The GlaMBIE Team 2025; Hugonnet et al. 2021; Wouters et al. 2019; Box et al. 2019).

With amplified warming at high northern latitudes (see essay Surface Air Temperature; Masson-Delmotte et al. 2021), the annual mass loss of Arctic glaciers and ice caps has tripled since the mid-1990s (Zemp et al. 2019). While observations of Arctic glaciers and ice caps from balance year 2024/25 are not yet available, observations from mass balance years 2022/23 and 2023/24 highlight both regional and interannual variability, yet the overall trajectory remains one of widespread and significant ice loss.

Recent observations and regional contrasts

Mass changes in glaciers and ice caps result from the balance between inputs, primarily snow accumulation, and outputs, which include surface melt and runoff, as well as iceberg calving for tidewater- or lake-terminating glaciers. The net, or total, mass balance reflects the difference between these processes. Our analysis of the 27 monitored Arctic glaciers excludes losses from iceberg calving, which occurs only at Kongsvegen, Hansbreen, and Devon Ice Cap (Table 1; Fig. 1). Accordingly, we report the climatic mass balance (B_clim), the difference between annual snow accumulation and annual runoff, expressed as the mean annual thickness change (mm water equivalent, w.e.) averaged over the glacier or ice cap surface.

In the 2023/24 balance year (October 2023 to September 2024), all 25 of the monitored glaciers for which we have data (i.e., data were not available for 2 of the 27) recorded negative mass balances, consistent with the 2022/23 balance year (Table 1; WGMS 2025). This decline was most severe in Arctic Scandinavia and Svalbard, which experienced a precipitous drop in land ice since 2021. Both regions had their most negative mass balance year on record in 2023/24 (Kjøllmoen et al. 2025; Schuler et al. 2025), with melt increasing by an average of 1486% in Arctic Scandinavia and 482% in Svalbard relative to the 1991-2020 mean. This enhanced melt coincided with a persistent warm air mass over northern Scandinavia and the Barents Sea that produced record high seasonal temperatures since 1950 (Ballinger et al. 2024).

This dramatic thinning is underscored by data from monitored Arctic glaciers. For example, Arctic Scandinavia’s Langfjordjokelen and Engabreen saw their climatic mass balances decrease, respectively, from -1651 and -1101 mm w.e. in 2022/23 to -4060 and -3855 mm w.e. in 2023/24. Similarly, Svalbard’s Midre Lovenbreen and Austre Broggerbreen went from -972 and -948 mm w.e. to -1955 and -2048 mm w.e. during the same period. While Alaska, Arctic Canada, and Iceland also showed negative anomalies in 2022/23, with melt increases of 30%, 112%, and 115%, respectively, they experienced less melt (i.e., positive anomalies) in 2023/24 relative to the 1991-2020 mean.

Long-term mass loss and global contribution

Observations from the 2023/24 balance year confirm the ongoing multi-decadal trend of surface mass loss for glaciers and ice caps across the Arctic (Fig. 2). Since the mid-20th century, long-term records show that Alaska’s glaciers have experienced the greatest thinning, exceeding 38 m w.e. by 2024. Arctic Scandinavia follows with over 32 m w.e. of loss, while Iceland and Svalbard have also undergone significant cumulative thinning of 29 m w.e. and 27 m w.e., respectively. Arctic Canada has lost 16 m w.e. These widespread negative balances further demonstrate that these glaciers are highly sensitive to climate warming and are significant contributors to sea-level rise (Box et al. 2018).

Gravity anomaly measurements from the combined GRACE (2002-16) and GRACE-FO (2018-25) satellite missions show that Pan-Arctic glaciers and ice caps lost mass at an average rate of -181 ± 21 Gt per year since 2002 (Figs. 1 and 3). This loss corresponds to a contribution of 0.55 ± 0.06 mm per year to global mean sea level rise. Although the magnitude of change varies by region, all records exhibit a persistent downward trend, highlighting the widespread and ongoing retreat of Arctic glaciers and ice caps outside Greenland.

During the 2023/24 balance year, Pan-Arctic glaciers and ice caps lost -151 ± 20 Gt of mass, contributing 0.42 ± 0.06 mm to global mean sea level rise. Regional differences were evident: while most areas continued to lose mass, Arctic Canada diverged from the broader Arctic pattern and recorded a slightly positive regional balance for the year. The overall Pan-Arctic losses were driven largely by sustained reductions in Alaska (36% of the Arctic total), Arctic Russia (31%), Svalbard (30%), and Iceland (7%), and countered by a small gain in Arctic Canada (5%). Mass balance data for 2024/25 and GRACE-derived regional anomalies are not yet available, but preliminary indicators suggest contrasting regional dynamics. In Alaska, the onset of summer melt was delayed in 2025 (see essays Surface Air Temperature and Terrestrial Snow Cover), potentially moderating annual losses. In contrast, Arctic Canada recorded only minimal mass gain during winter 2024/25, setting the stage for a strongly negative mass balance in 2024/25.

Direct societal impacts

Observations of the Arctic system, including glaciers and ice caps, support a multitude of societal impacts (see essay Assessing the State of the Arctic Observing Network). The societal dimensions of Arctic glacier mass loss are wide-ranging, from driving global sea level rise to having direct, regional effects in the Arctic. In the Arctic, this mass loss directly impacts communities and threatens public safety and infrastructure. At the local scale, a key impact is water availability. For example, the decline of ice in Ausuiktuq (Grise Fiord), Arctic Canada directly affects the local community’s water availability. Since the 1970s, this community has depended on an intermittent stream primarily fed by snowmelt and glacier runoff, supplemented by manually collected glacier ice. However, as glaciers and remnant ice patches disappear over the coming decades, a crucial mid- to late-summer water supply will be lost. This change will significantly shorten the already brief period during which meltwater is available, intensifying seasonal scarcity. In response, the community plans to temporarily relocate the water intake to a nearby catchment basin holding remnant glacier ice. Given the current warming trends across the Arctic, this new source, while initially more reliable, is anticipated to be short-lived. The community continues to blend traditional knowledge and modern technology to adapt to these escalating water challenges.

Another critical concern is geohazards associated with glacier-loss (Wolken et al. 2021). A notable example is the Mendenhall Glacier near Juneau in southeastern Alaska. Here, a retreating tributary glacier has created a basin for meltwater that is impounded by the larger Mendenhall Glacier. This has resulted in annual glacial lake outburst floods (GLOFs) since 2011 (Kienholz et al. 2020), which are becoming more frequent and severe, leading to widespread flooding resulting in property damage and loss of homes and infrastructure in Juneau, Alaska. Glacier mass loss is also contributing to slope destabilization and a rise in tsunamigenic landslides throughout the Arctic. The August 2025 landslide at South Sawyer Glacier in Alaska’s Tracy Arm fiord is a prime example of how these cascading hazards can pose a risk to people and infrastructure far from the initial slope failure. The unstable rock mass, with an estimated volume of ~100 million cubic meters (~130 million cubic yards), failed catastrophically and slid into the water near and onto the terminus of South Sawyer Glacier (USGS 2025). The resulting tsunami caused water to run-up slopes opposite the landslide to a height of nearly 500 meters (1600 feet) and was recorded as far away as Juneau, where a tide gauge measured a wave height of 36 cm (14 inches) above the tide.

Methods and data

Data were obtained from the World Glacier Monitoring Service (WGMS 2025) with updates from Norwegian Water Resources and Energy Directorate (NVE) and Geological Survey of Canada. Bias corrections were applied to B_clim for Hofsjökull glaciers (N, E, and SW), Iceland using methods outlined in Jóhannesson et al. (2013). Regional climatic mass balances were derived as arithmetic means for all monitored glaciers within each region for each year, and these means were summed over the period of record and interpreted as cumulative thickness changes.

Cumulative changes in regional total stored water (Gt) for 2002-25 were derived from GRACE and GRACE-FO satellite gravimetry for the five regions shown in Fig. 1 and for the total of these five regions (i.e., Pan-Arctic). A July 2017 to May 2018 data gap exists between retrieval periods. The data processing involved several steps. First, common post-corrections to the Level-2 data were applied, including the addition of degree-1 coefficients which are not directly observed by the satellites. To reduce correlated noise in the GRACE data, an adaptation of a method by Wouters and Schrama (2007) was used. This involved fitting a 3rd order polynomial to the monthly time series of all Stokes coefficients to preserve the long-term variability. After restoring this variability, a 150 km Gaussian smoothing filter was applied to the resulting Stokes coefficients to further reduce remaining noise. Finally, to retrieve the mass changes for the glacier regions, the processed coefficients were converted into maps of equivalent water height anomalies using a “mascon” (mass concentration) approach based on a global 0.5° × 0.5° grid.

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November 24, 2025