Ice Worm Glacier Disappears in 2023, North Cascade Range, WA

On February 16, 2025February 28, 2025 By mspeltoIn climate change glacier retreat, Glacier Observations, North Cascade Glaciers

**Ice Worm Glacier from the same location in 1986 and 2023, Bill Prater in 1986 image.**

Ice Worm Glacier is an east-facing cirque glacier on the east flank of Mount Daniel, WA. Mount Daniel is on the crest of the North Cascade Range of Washington, the crest separates the dry east side that drains to the Columbia River and the wet west side that drains to Puget Sound. The glacier is at the headwaters of Hyas Creek, which drains into the Cle Elum River and the Cle Elum Reservoir. The Cle Elum Reservoir has a storage volume of 538,900,000 m³ and is primarily used for flood control in spring, and agricultural irrigation in summer. This reservoir is the largest in the Yakima River Basin and provides irrigation to 180,000 hectares of agricultural land. The glacier is located in the Alpine Lakes Wilderness area which prohibits the use of mechanized equipment. The Ice Worm Glacier cirque floor is at 1940 m and the headwall at 2050 m. There is a bench at 2150–2300 m that held a glacier/perennial icefield prior to 2015. The glacier is accessed by backpacking 8 km from the Cathedral Rock trailhead with the same base camp used each year at 1700 m on the bank of Hyas Creek. Detailed publication by Mauri and Jill Pelto at: Loss of Ice Worm Glacier, North Cascade Range, WA USA, 2025.

The glacier is fed by wind drift accumulation along the ridge that was just above the top of the glacier during the 1944-2000 period. Avalanching from the slopes below the East Peak of Mount Daniel and from the ridges extending along the north and south flank of the glacier have also been significant. The glacier is part of the Mount Daniel-Mount Hinman Glacier Complex just south of Highway 2 and sits astride the Cascade Divide. This complexcomprised of 9 glaciers covering 3.8 km² in 1984. This was the biggest cocentration of glaciers between Mount Rainer and Glacier Peak. At the end of the summer 2023 melt season only three of these remain as glaciers, Daniels, Foss and Lynch Glacier. We began monitoring these glaciers along with Ice Worm Glacier in 1984.

Ice Worm Glacier Evolution

**Ice Worm Glacier field sketch by Jill Pelto in 2023.**

In 1986 William (Bill) Prater, who had made many first ascents in the area between 1944 and 1960, joined us in the field. Bill also had invented and patented (1973) the first snowshoe with a claw attached to its binding, the Sherpa Snowshoe. Comparing images from these early visits with the current margin of Ice Worm Glacier indicated that there had little change in this glacier from 1944-1986. The mapped area in 1958 was 0.19 km²(GLIMS, 2023), in 1986 we mapped the area at 0.18 km².

Each summer during the third week in August we measure the mass balance of this glacier. Because the glacier lacks crevasses we simply grid the glaciers with measurements made 50 m apart along transects running up the glacier and across the glacier along the margins. We also completed a longitudinal profile running up the glacier from a fixed location on the bedrock at the below and at the top of the glacier. The surface elevation was determined at the specific 50 m points to identify thinning of the glacier. During the first decade the glacier extended to within 10 m of the ridge on the south side of the glacier, allowing us to ski off of the ridge, see 1990 image below.

Glacier Area Change

**View of the south ridge across Ice Worm Glacier in 1990 above and 2006 below, note recession of the top of the glacier from this ridge.**

From 1984 to 1992, the glacier extended to within 15 m of the ridge on the south side of the basin. By 1995 this was no longer possible as the top of the glacier was retreating as fast as the bottom of the glacier. In 2006, the recession from this ridge was greater than the recession at the terminus. The glacier perimeter was surveyed in the low snow years of 2005 and 2015, identifying the glacier area to be 0.15 km² and 0.110 km², respectively. In 2015, the inventory for RGI noted an area of 0.106 km². Annually, from 2021 to 2024, low snow cover allowed for mapping of the glacier perimeter during a rapid decline from 0.09 km² to 0.03 km². The area loss from 1986 to 2015 was 0.07 km², which is less than the area loss from 2015 to 2023 of 0.08 km². provides a photo comparison of the change from 1986 to 2023, with the people standing in the same location in each case. The observed area determined in the field from the GPS position locations closely matches the RGI inventory area in 2015 and the area derived from overlaying the points on Sentinel 2 imagery from August 2021 to 2024, which have a 10–30 m resolutionThis summer we observed a dozen holes that reached the bottom of the glacier 4-6 m below, indicating how thin the ice is. There is no movement, the size and thickness are too low to generate future movement, hence this is no longer a glacier. A glacier is a body of snow and ice that is moving, this requires a persistent thickness of 20-30 m, which is typically associated with snow/ice areas of ~50,000 m² or larger. As a glacier becomes thinner or smaller than this movement will not be sustained.

Table 1. The observed area of Ice Worm Glacier from field measurements. The area of Ice Worm Glacier from previous inventories and Sentinel 2 imagery.

Year	Field Mapped Area (m²)	Validating Aerial/Satellite Image Area (m²)
1958		190,000 (GLIMS)
1986	180,000 (±10,000)	Field Observation only
1992	170,000 (±10,000)	Field Observation only
2005	150,000 (±5000)	Field Observation only
2015	110,000 (±5000)	106,000 (RGI)
2021	88,000 (±2000)	90,000 (Sentinel)
2022	68,000 (±2000)	Field Observation only
2023	41,000 (±2000)	40,000 (Sentinel)
2024	32,000 (±2000)	30,000 (Sentinel)

We have measured discharge at a natrual weir below Ice Worm Glacier since 1986. Average August daily runoff has declined 60% by 2022.

Glacier Base Observations

**Ice Cave in 2024 that extended from top to the end of the glacier.**

Beginning in 2015, we routinely assessed how deep each moulin, crevasse or supraglacial stream channel was on the glacier. One measure of a glacier no longer being a glacier is when crevasse features and stream channels consistently reach the bedrock below the glacier. In 2023, we examined 24 of these features and each reached bedrock at depths of 2–10 m. These features were distributed widely across the glacier. There are undoubtedly limited areas of thicker ice. In 2024, we explored an ice cave that extended 250 m from the top of the glacier to the end of the glacier. The cave roof was 1–4 m above bedrock, and the roof was consistently less than 2 m thick allowing light to penetrate from the glacier surface into the cave. An extensive ice cave transecting the entire glacier such as this cannot exist in a current glacier because ice movement would lead to ice cave closure.

Streams channel reaching bedrock at base of Ice Worm Glacier.

Each year in mid-August, stream discharge has been observed immediately below the 1986 terminus position of Ice Worm Glacier at 11 a.m., 2 p.m. and 5 p.m. during the field visit. This stream is also fed by perennial snowfields and, before 2015, a small glacier. These observations are insufficient to quantify daily runoff, but because of the consistent timing and methods, do allow for comparison. The glacier is located on the dry side of the range and has not experienced rainfall during any of our field observation periods, which would contribute to stream discharge. From 1985 to 2002, streamflow was observed on 36 days, with the average discharge being 0.12 m³ s⁻¹. From 2021 to 2024, discharge was observed on 6 days with the average discharge being 0.03 m³ s⁻¹. This roughly 75% decline in August runoff is similar to the 60% loss in runoff modeled for the loss of small glaciers in basins in the Alps and observed when the Lewis Glacier, North Cascade Range was lost. The change in summer streamflow in Hyas Creek near our base camp is apparent, as it had been a challenging stream crossing to keep your feet dry until 2013, and now is a simple step across. There has also been a marked increase in algae coating the substrate of the stream with the lower flow, clearer and warmer water, which is expected.

Climate Drivers

Trends in summer temperature at Western Cascade weather stations for the 1896 to 2024 period indicate that seven of the ten warmest melt seasons (June–September) have occurred since 2013. Melt season temperatures from 2014 to 2024 were 1.3 °C above the 1896 to 2022 mean. The long-term winter temperature trend from 1896 to 2024 has been 1.2 °C. From 2014 to 2024 winter temperatures were 0.9 °C above the long-term average, the warmest decadal period of the record.

During the 1896 to 2024 period from June to September, precipitation exhibited no significant trend. For the November–April (winter season) there was a 3% increase in precipitation from 1896 to 2024. From 2014 to 2024 winter precipitation averaged 1.68 m vs. the long-term average of 1.65 m. April 1 SWE from six long-term SNOTEL stations where April 1 SWE has a declining trend of 30% from 1946 to 2023, with a 10% decline since 1984. The April 1 SWE loss reflects increased melting of the snowpack or rain events during the winter season.This indicates that it is temperature rise that is driving the glacier mass balance loss, retreat and eventual disappearance of Ice Worm Glacier.

**Washington State Division 5 -Cascade West-Temperature trends.**

**Washington State Division 5 -Cascade West-Precipitation trends.**

How A Glacier Disappears- Lewis, Milk Lake and Colonial Glacier North Cascade Range?

On November 29, 2021April 22, 2024 By mspeltoIn North Cascade Glaciers

Colonial Glacier in late summer false color Sentinel 2 images from 2019, 2020 and 2021. Yellow arrow indicates step that calves in 2020. Notice the ~10% of snowcover (bright white) remaining on glacier surface with more melt to come.

An alpine glacier disappears when it no longer has a persistent accumulation zone (Pelto, 2010). When this occurs the glacier is typically limited in size, but still can have significant ice thickness that takes time to melt away. Here we look at three glaciers I have worked on, where two disappeared and the third is disappearing in the North Cascade Range, Washington.

Lewis Glacier was a small cirque glacier in the drier part of the range, near Rainy Pass. In 1985 during my second visit to the Lewis Glacier, was the first time I confronted the idea of a glacier disappearing. We were able to peer down several crevasses and see the bottom of the Lewis Glacier, measurements indicated a maximum depth of 12 meters over an area the size of a football field/soccer pitch. This glacier had been selected for the North Cascade Glacier Climate Projects’s mass balance program assessing mass balance on 10 glaciers across the mountain range. This size made it attractive to observe in terms of response to climate change. The USGS map indicated a significant glacier with an area of 0.12 km² in the 1950’s. By 1985 (top image) the glacier had lost half of its mapped area, there were still some significant blue ice areas, and areas of firn, snow several years old that is not yet glacier ice. Return visits each summer over the next few years chronicled the demise of the glacier. By 1988 (middle image) the glacier had shrunk dramatically even since 1985, the thickest ice measured was 5-6 meters. By 1990 the glacier was gone (bottom image), no blue ice left in the basin, the blue arrows indicate the lateral moraine above the now empty glacier basin. At the time I had not developed the model for forecasting glacier survival (Pelto, 2010). At bottom is 2021 image of the cirque basin with no glacier.

Milk Lake Glacier was a small glacier on the north flank of Glacier Peak in the North Cascades, Washington. The flat topography over the lake indicated a very thin unstable glacier area. In the USGS map for Glacier Peak in the based on 1979 aerial photographs, Milk Lake Glacier fills most of the Milk Lake Basin, had an area of 0.24 km² with just a fringe of lake visible. Thw flat topography indicates the thin unstable nature of this part of the glacier. By 1988, Milk Lake had formed, a notably circular new alpine lake, the former glacier ice still filled part of the lake as ice bergs. The glacier had retreated to the margins of the lake fringing the west side of the lake. The fringing ice was clearly thin, we found several crevasses that reached bedrock 5-10 m down. In 1994 on a return visit in miserable weather (camera got too wet to function), there was no longer any icebergs in the lake and the lake was more of a jade to turquoise color. The fringing ice had lost about half of its area since 1988. This glacier remnant was not going to last long. By the end of 2005 the glacier had disappeared. The lake retains a beautiful jade color that will slowly become more azure as glacier flour settles. In 2021, see image bottom, the basin does not look like a recently glaciated basin.

Colonial Glacier is a cirque glacier in the Skagit River Watershed, North Cascades of Washington. The North Cascade Glacier Climate Project has made six visits to this glacier since 1985. Meltwater from this glacier enters Diablo Lake above Diablo Dam and then flows through Gorge Lake and Gorge Dam. These two Seattle City Light hydropower projects yield 360 MW of power. In 1979 the glacier was clearly thinning, having a concave shape in the lower cirque, but still filled its cirque, there is no evidence of a lake in this image from Austin Post (USGS). In 1985 my first visit to the glacier there was no lake at the terminus. We measured the glacier area at 0.92 km². In 1991 the lake had begun to form, second image, but was less than 30 m across. The upper glacier was a smooth expanse of snow. By 1996 the lake was evident, and was 75 meters across. In 2001 the lake had expanded to a length of 125 meters. By 2006 the lake was 215 m in length, and had some thin icebergs broken off from the glacier front. From 2019-2021 a series of late summer Sentinel 2 images indicate the lack of retained snowcover necessary for survival. In 2019 15% of the glacier is snowcovered with three weeks left in the melt season. The terminus is just below a step in the glacier surface. In 2020 there is only 10% snowcover with two weeks left in the melt season. The portion of the glacier below the step has calved off and is now an iceberg in the lake. In 2021 the exceptional June heat wave took its toll and by the end of August the glacier only has 10% retained snowcover. The glacier area in 2021 is 0.26 km², a 70% decline in area. The glacier has retreated 440 m and now is 520 m long. The lake has an area of 0.1 km². The continued losses of Colonial Glacier are not being replenished by snowfall, this business model can only lead to the glacier disappearing. Colonial Glacier still has substantial area and thickness that will allow it to survive for a couple more decades. The continued loss of glacier area from Colonial and all other glaciers in the region reduce the mitigating affect of enhanced summer streamflow due to higher glacier runoff during warm dry periods.

Lewis Glacier cirque in Sentinel 2 image from 2021, Lewis Lake is lower right.

Milk Lake cirque in 2021, looking like a basin that was not recently glaciated.

36th Annual North Cascade Glacier Climate Project Field Season Begins

On July 29, 2019April 25, 2024 By mspeltoIn North Cascade Glaciers

Fieldwork includes terminus surveys, glacier runoff measurement and mass balance measurements

Field Season Begins August 1

Who we are? The North Cascade Glacier Climate Project (NCGCP) was founded in 1983 to identify the response of North Cascade glaciers to regional climate change, particularly changes in mass balance, glacier runoff and terminus behavior. This was prompted by the National Academy of Sciences listing this as a high priority and a personal appeal from Stephen Schneider. NCGCP is a field project that has a broader interdisciplinary scope and is the most extensive glacier mass balance field program in the United States. Two of the 41 reference glaciers in the world are in our network, and as of next year that will become three glaciers. We do this research cost effectively relying on no permanent camps, helicopter support or salary for the director. The field season includes no days off and each day is spent completing measurements on glaciers. The focus is on glacier mapping, mass balance measurement, terminus observations and glacier runoff monitoring. Each year we utilize several field assistants to complete the annual glacier surveys, with 2019 being the 36th field season. Our goal in choosing assistants is not to pick the most experienced, but the individuals who are capable and can benefit the most. We are a self-contained unit. Recently Hakai Magazine described our process well.

Why study glaciers in the North Cascades? Glaciers are one of the world’s best climate monitors and are a critical water resource to many populated glaciated regions. This is particularly true in the North Cascades where 700 glaciers yield 200 billion gallons of summer runoff and glaciers have lost 30 % of their area since 1980. These glaciers have lost 25-30% of their volume during the course of our study, three of our primary study glaciers have disappeared. We also monitor ice worms and mountain goats since we are in the same locations at the same time each year.

2019 Outlook: For North Cascade glaciers the accumulation season provides that layer of snow, that must then last through the melt season. A thin layer sets the glaciers up for a mass balance loss, much like a bear with a limited fat layer would lose more mass than ideal during hibernation. The 2019 winter season in the North Cascade Range, Washington has been unusual. On April 1 the retained snow water equivalent in snowpack across the range at the six long SNOTEL sites is 0.72 m, which is ~70% of average. This is the fifth lowest since 1984. The unusual part is that freezing levels were well above normal in January, in the 95% percentile at 1532 m, then were the lowest level, 372 m of any February since the freezing level record began in 1948. March returned to above normal freezing levels. As is typical periods of cold weather in the regions are associated with reduced snowfall in the mountains and more snowfall at low elevations. In the Seattle metropolitan area February was the snowiest month in 50 years, 0.51 m of snow fell, but in the North Cascades snowfall in the month was well below average. From Feb. 1 to April 1, snowpack SWE at Lyman Lake, the SNOTEL site closest to a North Cascade glacier, usually increases from 0.99 m to 1.47 m, this year SWE increased from 0.83 m to 1.01 m during this period. The melt season from May-Mid-July has also been warmer than average. This combination will lead to significant glacier mass loss in 2019, in one month we will report back on our measurements that will indicate just how negative.

2019 Field Team:

Clara Deck: is an earth scientist from Chicago with a passion for science communication, education, and outreach. She completed a B.A. in geology at the College of Wooster in Wooster, Ohio, where she began a journey in climatological research which led to a love for the cryosphere. In the summer of 2018, Clara contributed to glacial field work in the eastern Alaska Range, and was fascinated by the dynamic day-to-day changes in glacial features she was tasked with measuring. At the University of Maine, she is wrapping up her M.S. focused on numerical modeling of Antarctic ice shelf instabilities, but Clara’s favorite part of her college career has been sharing science with students as a teaching assistant. During her first visit to the North Cascades, she is excited to learn about ongoing glacial change and to explore accessible ways to share the findings with public audiences.

Abby Hudak is a native Floridian that has always had a deep calling to the mountains and frozen landscapes. Her passions revolve around understanding our changing climate and natural world which led her to attain a B.S. in Biological Sciences from the University of Central Florida. After starting her M.S. in Biological Sciences at Washington State University, she immediately indulged in snow sports and mountaineering in the Cascade Range. The beauty and vulnerability of these landscapes have driven her to expand her research interests to understanding aspects of the changing cryosphere. She is eager to intertwine her love for the Cascade Range and her desire to pursue scientific questions pertaining to climate impacts on alpine glaciers by working with the North Cascade Glacier Climate Project this summer.

Ann Hill, ever since she was a young child growing up in Minneapolis, Ann has been fascinated by ice and snow, however it wasn’t until her Sophomore year studying Geosciences at Skidmore College that she realized she could study ice as a career path. Consequently, during her junior year she traveled to Svalbard to gain hands-on experience studying and exploring glaciers. Determined to learn more, Ann spent a summer with the Juneau Icefield Research Program, which exposed her to glaciers that looked and behaved differently. In the fall, Ann will begin her M.S. in Earth and Climate Sciences at the University of Maine. Ann is thrilled to study the North Cascade glaciers to understand how their movement and characteristics compare to those she previously observed in Svalbard and Alaska.

Jill Pelto is an artist and scientist from New England who grew up loving winter sports and trips to the mountains. She incorporates scientific research and data into paintings and prints to communicate environmental changes. Her multi-disciplinary work weaves visual narratives that reveal the reality of human impacts on this planet. She completed both her B.A. degrees in Studio Art and Earth and Climate Sciences and her M.S. focused on studying the stability of the Antarctic Ice Sheet at the University of Maine. She spent two field seasons at a remote camp in the southern Transantarctic Mountains to map glacial deposits and collect samples from them for dating. Jill will be joining the project for her 11th field season. She is excited about continuing to document the change in North Cascade glaciers that she has witnessed each of the last ten years — through science and art.

Mauri Pelto has directed the project since its founding in 1984, spending more than 700 nights camped out adjacent to these glaciers. He is the United States representative to the World Glacier Monitoring Service, author of the AGU blog “From a Glacier’s Perspective”, and associate editor for three science journals. His primary job is Dean of Academic Affairs at Nichols College, where he has been a professor since 1989.