Numerous small alpine glaciers occupy the high elevation regions of the central and southern Siena Nevada, California. These glaciers change size in response to variations in climate and are therefore important indicators of climate change. An inventory based on USGS topographic maps (l :24,000) revealed 1719 glaciers and perennial snow and ice features for a total area of 39.l5 ±7.52 km2. The number of 'true' glaciers, versus non-moving ice, is estimated to be 118, covering 15.87 ± 1.69 Km2. All glaciers were located on north to northeast aspects, at elevations >3000 m. Historical photographs, geologic evidence, and field mapping were used to determine the magnitude of area loss over the past century at 14 glaciers. These glaciers decreased in area by 31% to 78%, averaging 55%. The rate of area change was determined for multiple time periods for a subset of seven glaciers. Rapid retreat occurred over the first half of the twentieth century beginning in the 1920s in response to warm/dry conditions and continued through the mid-1970s. Recession ceased during the early 1980s, when some glaciers advanced. Since the 1980s each of the seven study glaciers resumed retreat. The uniform timing of changes in area amongst study glaciers suggests a response to regional climate, while the magnitude of change is influenced by local topographic effects. Glacier area changes correlate with changes in spring and summer air temperatures. Winter precipitation is statistically unrelated to changes in glacier area. Headwall cliffs above the glaciers alter the glacier responses by reducing incoming shortwave radiation and enhancing snow accumulation via avalanching.

Mountain glaciers have influenced the surface of our planet throughout geologic time. These large reservoirs of water ice sculpt alpine landscapes, regulate downstream river flows, perturb climate-tectonic feedbacks, contribute to sea level change, and guide human migration and settlement patterns. Glaciers are especially relevant in modern times, acting as buffers which supply seasonal meltwater to densely populated downstream communities and support economies via hydropower generation. Anthropogenic warming is accelerating ice loss in most glacierized regions of the world. This has sparked concerns regarding water resources and natural hazards, and placed glaciers at the forefront of climate research. Here we provide new observations of glacier change in key mountain regions to quantify rates of ice loss, better understand climate drivers, and help establish a more unified framework for studying glacier change across timescales. In Chapter 1 we use seismic observations, numerical modeling, and geomorphic analysis to investigate a destructive glacial lake outburst flood (GLOF) which occurred in Bhutan. GLOFs are a substantial hazard for downstream communities in many vulnerable regions. Yet key aspects of GLOF dynamics remain difficult to quantify, as in situ measurements are scarce due to the unpredictability and remote source locations of these events. Here we apply cross-correlation based seismic analyses to track the evolution of the GLOF remotely (~100 km from the source region), use the seismic observations along with eyewitness reports and a downstream gauge station to constrain a numerical flood model, then assess geomorphic change and current state of the unstable lakes via satellite imagery. Coherent seismic energy is evident from 1 to 5 Hz beginning approximately 5 hours before the flood impacted Punakha village, which originated at the source lake and advanced down the valley during the GLOF duration. Our analysis highlights potential benefits of using real-time seismic monitoring to improve early warning systems. The next two chapters in this work focus on quantifying multi-decadal glacier ice loss in the Himalayas. Himalayan glaciers supply meltwater to densely populated catchments in South Asia, and regional observations of glacier change are needed to understand climate drivers and assess impacts on glacier-fed rivers. Here we utilize a set of digital elevation models derived from cold war–era spy satellite film and modern stereo satellite imagery to evaluate glacier responses to changing climate over the last four decades. In Chapter 2 we focus on the eastern Himalayas, centered on the Bhutan–China border. The wide range of glacier types allows for the first mass balance comparison between clean, debris, and lake-terminating (calving) glaciers in the area. Measured glaciers show significant ice loss, with statistically similar mass balance values for both clean-ice and debris-covered glacier groups. Chapter 3 extends the same methodology to quantify glacier change across the entire Himalayan range during 1975–2000 and 2000–2016. We observe consistent ice loss along the entire 2000-km transect for both intervals and find a doubling of the average loss rate during 2000–2016 compared to 1975–2000. The similar magnitude and acceleration of ice loss across the Himalayas suggests a regionally coherent climate forcing, consistent with atmospheric warming and associated energy fluxes as the dominant drivers of glacier change. Chapter 4 investigates millennial-scale glacier changes during the Late Glacial period (15-11 ka). Here we present a high-precision beryllium-10 chronology and geomorphic map from a sequence of well-preserved moraines in the Nendaz valley of the western European Alps, with the goal to shed light on the timing and magnitude of glacier responses during an interval of dramatic natural climate variability. Our chronology brackets a coherent glacier recession through the Younger Dryas stadial into the early Holocene, similar to glacier records from the southern hemisphere and a new chronology from Arctic Norway. These results highlight a general agreement between mountain glacier changes and atmospheric greenhouse gas records during the Late Glacial. In Chapter 5 we use a numerical glacier model to simulate glacier change across a typical alpine region in the European Alps. Model results suggest that shorter observational timespans focused on modern periods (when glaciers are far from equilibrium and undergoing rapid change) exhibit greater spatial variability of mean annual ice thickness changes, compared to intervals which extend further back in time (to include decades when climate was more stable). The model agrees with multi-decadal satellite observations of glacier change, and clarifies the positive correlation between glacier disequilibrium and spatial variability of glacier mass balance. This relationship should be taken into account in regional glacier studies, particularly when analyzing recent spatial patterns of ice loss. Advances made in this work are of practical value for societies vulnerable to glacier change. This includes potential improvements to GLOF early warning systems via seismic monitoring, better constraints on glacier-sourced water scenarios in South Asia, strengthened understanding of long-term glacier responses to baseline natural climate variability, and a clarified relationship between glacier disequilibrium and spatial variability of ice loss. When placed within a global context, our observations highlight the correlation between regional mountain glacier change and greenhouse gas forcing through time.

Effective coastal adaptation to sea-level rise requires an understanding of how much and how fast glaciers and ice sheets will melt in the coming decades, together with an understanding of the provenance of that ice melt. When land ice is lost to the oceans, sea-levels do not rise uniformly across the globe, but exhibit a “sea-level fingerprint” specific to the source of ice melt, posing an important question motivating this thesis: Which ice mass(es) will contribute the first 1m/3 feet of sea-level rise? The glacial-geologic record archives the vulnerability of ice sheets and their sub-sectors to past warming. To analyze this record of past glacial change, I develop and apply cosmogenic-nuclide techniques for investigating the climate sensitivity of four key ice sheets. The novel geochemical techniques described here also allow me to investigate processes of landscape evolution, including subglacial and subaerial erosion. Subglacial erosion dictates landscape development in glaciated and formerly glaciated settings, which in turn influences ice-flow dynamics and the climate sensitivity of ice masses, making it an important input in ice-sheet models. In Chapter 1, I use 10Be measurements in surficial bedrock and a 4-m-long bedrock near Jakobshavn Isbræ, to constrain the erosion rate beneath the Greenland Ice Sheet (GrIS) on historical and orbital timescales. 10Be concentrations measured below ~2 m depth in a 4-m-long bedrock core are greater than what is predicted by an idealized production-rate depth profile and I develop a model to utilize this excess 10Be at depth to constrain orbital-scale erosion rates. I find that erosion rates beneath GrIS were 0.4–0.8 mm yr-1 during historical times and 0.1–0.3 mm yr-1 on Pleistocene timescales. The broad similarity between centennial- and orbital-scale erosion rates suggests that subglacial erosion rates adjacent to Jakobshavn Isbræ have remained relatively uniform throughout the Pleistocene. In Chapter 2, I present cosmogenic 10Be and 3He data from Ferrar dolerite pyroxenes in surficial rock samples and a bedrock core from the McMurdo Dry Valleys, Antarctica, opening new opportunities for exposure dating in mafic rocks. I describe scalable laboratory methods for isolating beryllium from pyroxene, estimate a spallation production rate for 10Be in this mineral phase, referenced to 3He, of 3.6 ± 0.2 atoms g-1 yr-1, and present initial estimates for parameters associated with 10Be and 3He production by negative muon capture. I also demonstrate that the 10Be-3He pair in pyroxene can be used to simultaneously resolve exposure ages and subaerial erosion rates, and that the precision of my 10Be measurements in pyroxene enable exposure dating on Last Glacial Maximum to Late Holocene surfaces, including moraines, on a global scale. In Chapter 3, I apply exposure dating locally to investigate the Last Glacial Maximum (LGM) and initial deglaciation of the Laurentide Ice Sheet (LIS), the most dynamic continental ice sheet, in southern New England and New York City. I synthesize new and existing exposure age chronologies from moraines and other glacial deposits that span ~26 to 20.5 ka, and quantify retreat rates for the southeastern LIS margin. Initial retreat at <5 to 30 m yr-1 started within the canonical LGM period, representing the slowest LIS retreat rates of the entire New England deglacial record, which I relate to a slow rise in modeled local summer temperatures through the LGM. Employing similar exposure dating techniques in Chapter 4, I describe the first 10Be ages from nunataks of the Juneau Icefield (JIF), Alaska, that I collected through the Juneau Icefield Research Program (JIRP) in order to evaluate icefield thinning during the Late Glacial and Holocene. I find that the JIF was smaller-than-present under warm climate conditions during the early-to-mid Holocene, elucidating the sensitivity of the icefield to warming. Tackling the climate crisis more broadly and in turn, addressing pressing Earth science questions like those posed in this dissertation, requires diverse perspectives. Yet, the Earth sciences have historically been among the least diverse of the STEM disciplines. As one contribution to a comprehensive effort through JIRP to increase diversity in the geosciences pipeline, Chapter 5 details the curriculum for a two-week course titled ‘A Virtual Expedition to the Juneau Icefield’ that I co-designed and co-taught in 2021 to bring accessible polar science experiences to high school students.

Regional paleoclimatic proxies and current local climate variables and were analyzed to reconstruct paleoglaciers in an effort to assess glacier change On Mount Rainier. Despite the dry and generally warm conditions (sea surface temperatures (SST) -0.15°C to +1.8°C relative to current temperatures), the previously documented McNeeley II advance (10,900 - 9,950 cal yr B.P.) was likely produced by air temperature fluctuations. The average SST record and the terrestrial climate proxies show cooling temperatures with continued dryness between McNeeley II and the Burroughs Mountain advance (3,442 - 2,153 cal yr B.P.). The paleoclimate during the Burroughs Mountain advance was both cool and warm (SST temperatures -0.55°C to +0.5°C) and was the wettest of the Holocene. A combination of statistical and deterministic equilibrium line altitude (ELA) models was used to produce Holocene ELAs between 1,735 -2,980 m. Glacial advances were predicted 10,990, 10,170, 9,260, 8,200, 6,490, 3,450 and 550 - 160 cal yr. B.P. Two glacier flow models were produced simultaneously to constrain glacial extent through the Holocene. Model I is based on current mass balance parameters and produced lengths for the Nisqually and Emmons glaciers 3.7 - 14.2 km and 4.2 - 17.1 km respectively. Glaciated area ranged from 26 to 327 km2. Model 2 is tuned to the Garda advance and produced lengths 2.6-10.6 km and 2.3-13.9 km. Glaciated area ranged from 11 to 303 km2. The first two advances were similar in elevation and GIS-modeled extent to McNeely II moraines. The following three advances were not detected in the geologic record. The 3,450 cal yr. B.P. advance was the largest of the late-Holocene (ELA 1,800 - 1,817 m) and was ~200 m lower than the geologic record. The ELAs of the Garda advance were modeled (1,944 - 1,983 m) and are similar to previous reconstructions. North-south spatial variations in glacial extent increase during periods of recession as the southern glaciers receive more ablation than northern glaciers. Early humans could have accessed the alpine environments as high as 1,730-2,980 m. The early Holocene glacial extent allowed the highest (2,980 m) 11,150 cal yr. B.P. and lowest (1,730 m) 10,990 cal yr. B.P. alpine access. Glacial retreat (2,727 m 10,400 cal yr. B.P.) was followed by an advance (1,929 m 10,170 cal yr. B.P.) and another retreat (2,951 m 10,050 cal yr. B.P.). Ice gradually descended and limited access to 1,820 m 6,490 cal yr. B.P. Glacial extents remained largely unchanged until the historic era when paleohumans would have had access to alpine environments at 2,000 m.

Ice sheets and mountain glaciers are critically important components of Earth'sclimate system due to societal and ecological risks associated with sea-level change, ocean freshening, ice-albedo feedback, glacial outburst floods, and freshwater availability. As Earth warms, increasing volumes of surface meltwater will access subglacial environments, potentially lubricating the base of the ice sheets and causing enhanced ice discharge into the ocean. Since subglacial water is effectively hidden beneath the ice, the primary ways to study subglacial hydrological systems are through mathematical modelling and interpreting indirect observations. Glaciers often host subglacial or ice-dammed lakes that respond to changes in subglacial water flow, thereby providing indirect information about the evolution of subglacial hydrological systems. While monitoring subaerial ice-dammed lakes is straightforward, the evolution of subglacial lakes must be inferred from the displacement of the overlying ice surface, posing additional challenges in modelling and interpretation. This dissertation addresses these challenges by developing and analyzing a series of mathematical models that focus on relating subglacial hydrology with observable quantities such as lake level or ice-surface elevation. The dissertation is divided into five chapters. Chapter 1 demonstrates how ageneralization of Nye's (1976) canonical model for subglacial water flow admits a wide class of solitary-wave solutions---localized regions of excess fluid that travel downstream with constant speed and permanent form---when melting at the ice-water interface is negligible. Solitary wave solutions are proven to exist for a wide range of material parameter values that are shown to influence the wave speed and wave profile. Melting at the ice-water interface is shown to cause growth and acceleration of the waves. To relate dynamics like these to observable quantities, Chapter 2 focuses on modelling water-volume oscillations in ice-dammed lakes during outburst flood cycles while accounting for the potential influence of neighboring lakes. Hydraulic connection between neighboring lakes is shown to produce a wide variety of new lake-level oscillations that depend primarily on the relative sizes and proximity of the lakes. In particular, the model produces lake-level time series that mirror ice-elevation changes above a well-known system of Antarctic subglacial lakes beneath the Whillans and Mercer ice streams even though the modelled ice-dammed lakes are not buried beneath the ice. The stability of lake systems with respect to variations in meltwater input is characterized by a transition from oscillatory to steady drainage at high water supply. To create a framework for extending these models of ice-dammed lakes to thesubglacial setting, variational methods for simulating the dynamics of subglacial lakes and subglacial shorelines are derived in Chapter 3. By realizing a direct analogy with the classical Signorini problem from elasticity theory, this chapter also furnishes a new, rigorous computational method for simulating the migration of oceanic subglacial shorelines, which are strongly tied to ice-sheet stability in response to climatic forcings. In Chapter 4, this newly developed model is used to highlight the challenge of accurately interpreting ice-surface elevation changes above subglacial lakes without relying on ice-flow models. The surface expression of subglacial lake activity is shown to depend strongly on the effects of viscous ice flow and basal drag, causing altimetry-derived estimates of subglacial lake size, water-volume change, and apparent highstand or lowstand timing to deviate considerably from their true values under many realistic conditions. To address this challenge, Chapter 5 introduces inverse methods for inferring time-varying subglacial lake activity or basal drag perturbations from altimetry data while accounting for the effects of viscous ice flow. Incorporating horizontal surface velocity data as additional constraints in the inversion is shown to facilitate reconstruction of multiple parameter fields or refinement of altimetry-based estimates. In sum, this dissertation constitutes several novel approaches to understanding ice-water interaction beneath glaciers while laying the foundation for future work seeking to elucidate the role of subglacial processes in the changing climate.

From the moment a snowflake touches down on the surface of a glacier, it begins a process of transformation. Fresh snow, made up of single-grained snowflakes is compacted into glacial ice by the weight of subsequent snowfall and by sintering, grain boundary sliding and diffusion. At first, snow grains accommodate the stress through mechanical failure and by changing their shapes and positions. Fragile, dendritic structures on the edges of snowflakes break off, and grains round into lower free energy configurations. Rounded grains slip into air pockets. As time passes, increasing overburden of a load to bear, and it is, for a single snowflake. But it is precisely this stress that creates a glacier. Stress, in this case, is a catalyst for transformation. But don't worry. I am not going to make an overly forced metaphor for what happens during a doctorate program.} Pressure causes the grains to merge, large grains absorbing small ones. As ice grains squeeze and grow into all the available pore space, grains trap air bubbles and cut them off from the atmosphere, preserving records of climate conditions. Eventually, these processes densify the snow so thoroughly that it metamorphoses into glacial ice, and from a crumbly collection of snowflakes emerges a cohesive crystalline matrix. This process, firn densification, is the subject of my first chapter. From measurements of englacial strain rates by repeat phase-sensitive radar deployments, we show it is possible to extract densification rates that match modeled predictions. The formation of ice is just the beginning of the story of a glacier. As and after ice forms, gravity pulls on the body of the glacier; ice flows under its own weight, becoming a viscous river that meanders from high elevations toward the sea level. Along the way, various other forces act on the ice (e.g., friction at the ice-bed causes ice to shear, narrowing valley walls create compressive stresses, etc.). This history can be written into the ice in the orientation and configuration of its molecular structure. Ice is made of a regular crystal matrix of water molecules. Covalently bonded oxygen and hydrogen molecules assemble into sheets of hexagons, held to each other by hydrogen bonds. The relative orientation of these hexagonal sheets is called the "ice fabric”, and its importance lies in the fact that ice’s asymmetric molecular structure gives rise to asymmetric properties. For example, ice is softer—more deformable—when stress is applied parallel to the hexagonal planes, like playing cards sliding over one another. Over hundreds or thousands of years, this asymmetric response to stress causes the hexagonal planes to rotate so that they lie perpendicular to the direction of compressive stress. This, in turn, changes which relative direction a glacier is the “softest”. In short, the history of the glacier is written into its fabric. Ice remembers the stress it has undergone, and that memory changes its resistance to (or accommodation of) stress in the present and future. In chapter two, I use an autonomous phase-sensitive radar to measure the ice fabric along a central transect of Thwaites Glacier. Thwaites drains ice from West Antarctica and is one of the fastest changing glaciers on the continent. Locked up in Thwaites is at least half a meter of sea level rise, as well as much of the buttressing that holds back WAIS. Measurements of the fabric of Thwaites tell us about the history of stress undergone by the glacier, as well as any change in relative direction of the "softest" ice. As a glaciologist, I have dedicated my life to studying how glaciers form, flow, and disappear. As an artist and writer, I am interested in material memory, with a particular orientation toward ice itself and in the way the language and mathematics used to describe ice mimic processes that happen in body, mind, and society. My fourth chapter is centered on the creative research and art produced during my dissertation, particularly focused on a visual autoethnography of my body I created during my first field season in Antarctica in 2022-2023. In it, I try to grapple with whether/how, even as positivist science demands I remove as much of myself as possible from my scientific research, my body/myself show up in small ways in my data. I consider how ice's response to stress—to soften or harden, to flow or crack—is in many ways, a mirror for how we as humans respond to stress. Other work in Chapter 4 was created in direct response to the beauty of glaciated landscapes and the grief I struggle to manage in response to their rapid change. Biome I is a short zine that uses faux-color satellite imagery overlain with text and meshes of glaciers from Grand Teton National Park (GRTE). In 2021, I spent six months as a Scientists-in-Parks fellow through AmeriCorps, joining the park's physical science team in Wyoming to expand their glacier monitoring program. From this work emerged Chapter 3 a history of glacial change in the park over the last 70 years from in situ and remotely sensed observations. This work, while quite different from my previous scientific output, allowed me to learn and explore other glaciological techniques as well as template methodologies and provide information that is immediately useful for education and action in GRTE and other rapidly deglaciating landscapes. Much of the way I have come to understand glacial geophysics is by considering the ways they connect more broadly to our lived experiences. In the Tetons, this involved understanding how deglaciation affects the park's ecological systems and the evolving safety for visitors given the changing ice conditions. In pursuit of both expanding my own understanding and hoping to share with others the joy and beauty of the study of ice, I have developed numerous education efforts to make the study of glaciers, climate, and the earth physical, tangible, less abstract, emotional, joyful, and intuitive. Chapter 5 concludes the thesis by taking a step back to look at education and teaching, the thread that has carried through my doctorate, from prior to starting graduate school and, I hope, that will continue long after. I discuss the influences of teacher-philosophers like Shannon Mattern, Lynda Barry, and bell hooks, who have all, in their own way, striven to reshape the (idea of the) classroom into forms that better serve the learner. This work has taken place on the seat of a bicycle riding across the country, on an icefield in Juneau, Alaska, and in my own backyard, in classrooms across New York City. To conclude, I hope this thesis is not only a scientific effort, but one that draws the curtain back on the broader work we do as glaciologists. We are also artists and educators, caretakers, archivists, and public figures. Our work can be physically, mentally, and emotionally demanding, and it is as often full of grief as it is of awe.

Glacier National Park, in northwestern Montana, is a unique and awe-inspiring national treasure that is often used by the media and public-at-large as a window into the effects of climate change. An updated inventory of glaciers and perennial snowfields (G&PS) in the Park, along with an assessment of their change over time, is essential to understanding the role that glaciers are playing in the environment of this Park. Nine inventories between 1966 and 2015 were compiled to assess area changes of G&PS. Over that 49-year period, total area changed by nearly -34 ± 11% between 1966 and 2015. Volume change, determined from changes in surface topography for nine glaciers, totaling 8.61 km² in area, was +0.142 ± 0.02 km³, a specific volume loss of -16.3 ± 2.5m. Extrapolating to all G&PS in the Park in 1966 yields a park-wide loss of -0.660 ± 0.099 km³. G&PS have been receding in the Park due to warming air temperatures rather than changes in precipitation, which has not changed significantly. Since 1900, air temperatures in Glacier National Park have warmed by +1.3 C°, compared to +0.9 C° globally. Spatially, G&PS at lower elevations and on steeper slopes lost relatively more area than other G&PS.

Eight glaciers, covering an area of 1.63 km2, reside on the northern and northeastern slopes of the Goat Rocks tallest peaks in the Cascades of central Washington. At least three glacial stands occurred downstream from these glaciers. Closest to modern glacier termini are Little Ice Age (LIA) moraines that were deposited between 1870 and 1899 AD, according to the lichenometric analysis. They are characterized by sharp, minimally eroded crests, little to no soil cover, and minimal vegetation cover. Glacier reconstructions indicate that LIA glaciers covered 8.29 km2, 76% more area than modern ice coverage. The average LIA equilibrium line altitude (ELA) of 1995 ± 70 m is ~150 m below the average modern ELA of 2149 ± 76 m. To satisfy climate conditions at the LIA ELA, the winter snow accumulation must have been 8 to 43 cm greater and mean summer temperatures 0.2 to 1.3 ºC cooler than they are now. Late Pleistocene to early Holocene (LPEH) aged moraines are located between 100 and 400 m below the LIA deposits. They have degraded moraine crests, few surface boulders, and considerable vegetation and soil cover. Volcanic ashes indicate LPEH moraines were deposited before 1480 AD while morphometric data suggest deposition during the late Pleistocene or early Holocene. The average LPEH ELA of 1904 ± 110 m is ~ 240 m and ~90 m below the modern and LIA ELAs, respectively. The climate change necessary to maintain a glacier with an ELA at that elevation for LPEH conditions requires the winter accumulation to increase by 47 to 48 cm weq and the mean summer temperature to cool by 1.4 to 1.5 ºC. Last glacial maximum (LGM) moraines are located more than 30 km downstream from modern glacial termini. They are characterized by hummocky topography, rounded moraine crests, complete vegetation cover, and well developed soil cover. Moraine morphometry, soil characteristics, and distance from modern glacial termini indicate that deposition occurred at least 15 ka BP during an expansive cooling event, the last being the LGM. The LGM ELA of 1230 m is ~920 m below the modern ELA. The climate change necessary to maintain a glacier with an ELA at that elevation for LGM conditions requires the mean summer temperature to cool by 5.6 ºC with no change in precipitation.

A glacier responds to changes in climate by subsequent retreat and advance as a result of changes in snow inputs and outputs. Understanding these changes is important because shrinking glaciers limit and diminish local water resources. They contribute to alpine runoff in the late-summer months by delaying the maximum runoff until late in the melt season. A comprehensive glacier and perennial snowfield inventory has not been completed for the Three Sisters in Central Oregon. Using aerial photography, Digital Elevation Models (DEMs), previous studies, and historical ground based photographs these glacier and perennial snowfields were defined and their surface area change was quantified along with surface area and volume change for the 15 named glaciers for multiple years. The glaciers and perennial snowfields totaled 9.03 ± 1.65 km2 in 1949 and decreased to 7.1 ± 1.16 km2 in 2003 giving a total loss of -1.914 ± 0.974 km2 ( 21%). The 15 named glaciers totaled 12.43 ± 0.417 km2 in ~1900 and decreased to 5.65 ± 0.135 km2 in 2003 giving a total loss of -6.70 ± 0.439 km2 (54%) with more loss occurring in the early part of the century. It's estimated that the 15 named glaciers lost roughly 61% of volume from 1900 to 2010. From 1957 to 2010 their surface's dropped in elevation on average by -8.9m, losing an estimated 71.96 x 106 ± 2.87 x 106 m3 (53%) in total volume, seen across accumulation and ablation zones, with more loss happening from 1957 to 1990. There was no relationship found between topography and area. A small correlation was found between slope and increased volume change. Debris cover on glacier surfaces has increased and showed a correlation between decreasing area loss (no correlation with volume changes).

Glaciers respond to local climate changes making them important indicators of regional climate change. The North Cascades region of Washington is the most glaciated region in the lower-48 states with approximately 25% of all glaciers and 40% of the total ice-covered area. While there are many on-going investigations of specific glaciers, little research has addressed the entire glacier cover of the region. A reference inventory of glaciers was derived from a comparison of two different inventories dating to about 1958. The different inventories agree within 93% of total number of glaciers and 94% of total ice-covered area. To quantify glacier change over the past century aerial photographs, topographic maps, and geologic maps were used. In ~1900 total area was about 533.89 ± 22.77 km2 and by 2009 the area was reduced by -56% ± 3% to 236.20 ± 12.60 km2. Most of that change occurred in the first half of the 20th century, between 1900 and 1958, -245.59 ± 25.97 km2 (-46% ± 5%) was lost, followed by a period of stability/growth in mid-century (-1% ± 3% from 1958-1990) then decline since the 1990s (-9% ± 3% from 1990-2009). The century-scale loss is associated with increasing regional temperatures warming in winter and summer; precipitation shows no trend. On a decadal time scale winter precipitation and winter and summer temperatures are important factors correlated with area loss. Topographically, smaller glaciers at lower elevations with steeper slopes and higher mean insolation exhibited greater loss than higher, gentler more shaded glaciers.