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Abstract We use digital elevation models (DEMs) and ICESat‐2 data to study the filling and outflow from a large subglacial lake under Manson Icefield in the Canadian Arctic. When full, the lake is ∼17 × 3 km with an area of 52 km2. Early in 2021 the ice surface over the center of the lake sank by >140 m implying a subglacial outburst flood of ∼4 km3. Rapid outflow occurred over ∼30 days at an average rate of ∼1,500 m3s−1 resulting in the formation of a single ∼15 km subglacial outflow path detectable from post‐outflow surface depression. The shape of the surface depression, 600–800 m wide by 2–4 m deep, reflects the shape of the subglacial channel prior to closure. Downstream ice movement appears unaffected by the outflow. After outflow ends the surface depression persisted over weeks, apparently dependent on the difference between water and overburden pressures.

We use digital elevation models (DEMs) and ICESat‐2 data to study the filling and outflow from a large subglacial lake under Manson Icefield in the Canadian Arctic. When full, the lake is ∼17 × 3 km with an area of 52 km2. Early in 2021 the ice surface over the center of the lake sank by >140 m implying a subglacial outburst flood of ∼4 km3. Rapid outflow occurred over ∼30 days at an average rate of ∼1,500 m3s−1 resulting in the formation of a single ∼15 km subglacial outflow path detectable from post‐outflow surface depression. The shape of the surface depression, 600–800 m wide by 2–4 m deep, reflects the shape of the subglacial channel prior to closure. Downstream ice movement appears unaffected by the outflow. After outflow ends the surface depression persisted over weeks, apparently dependent on the difference between water and overburden pressures. Plain Language Summary: Using satellite observations, we discovered a large lake under the Manson Icefield in the Canadian Arctic. Early in 2021 the ice surface over the center of the lake sank by around 140 m implying a total subglacial water outflow of around 4 km3, the largest reported outside of Iceland and Antarctica. Most of this water drained from the subglacial lake within 30 days melting some of the ice along the outflow path. For the first time we map the position and size of the subglacial output channel between the downstream end of the lake and the ocean using post‐outflow surface depression as the ice sank downward to close the channel after the water outflow. These results help in understanding the ways in which the presence, movement, and volume of water beneath glaciers influence ice movement and climate related glacial ice loss. Key Points: Using satellite height change data we document the discovery of a 52 km2 subglacial lake under the Manson Icefield, Nunavut, CanadaThe lake filled for around 14 years until early 2021 when the level in the center of the lake dropped by 130 m over 30 daysThe outflow volume was around 4 cubic kilometers and created a wide and shallow subglacial channel that could be tracked for over 15 km [ABSTRACT FROM AUTHOR]

We describe and model the evolution of a recent landslide, tsunami, outburst flood, and sediment plume in the southern Coast Mountains, British Columbia, Canada. On November 28, 2020, about 18 million m3 of rock descended 1,000 m from a steep valley wall and traveled across the toe of a glacier before entering a 0.6 km2 glacier lake and producing >100‐m high run‐up. Water overtopped the lake outlet and scoured a 10‐km long channel before depositing debris on a 2‐km2 fan below the lake outlet. Floodwater, organic debris, and fine sediment entered a fjord where it produced a 60+km long sediment plume and altered turbidity, water temperature, and water chemistry for weeks. The outburst flood destroyed forest and salmon spawning habitat. Physically based models of the landslide, tsunami, and flood provide real‐time simulations of the event and can improve understanding of similar hazard cascades and the risk they pose. Plain Language Summary: Glacier retreat exposes unstable slopes that can suddenly fail. We describe and model one such event with far‐reaching consequences. The landslide mass (50 million tonnes, equivalent to the combined mass of all Canadian automobiles) entered and suddenly drained a 0.6‐km2 alpine lake in the southern Coast Mountains of British Columbia. Displaced water destroyed salmon‐spawning habitat over a distance of 8.5 km and created a plume of sediment and organic matter more than 60 km from the head of the fjord into which the floodwaters discharged. Physically based models are able to simulate the hazard cascade, and such models could be used to improve hazard and risk assessments of these events under future climate change. Key Points: Rapid glacier retreat created conditions that allowed a geohazard cascade to occur in a steep mountain valleyWe describe and model a recent landslide, tsunami, and outburst flood that typifies a deglacial geohazard cascadeFuture work should predict new glacial lakes and use physically based models to simulate the slope, tsunami, and outburst flood hazards [ABSTRACT FROM AUTHOR]

Polythermal glaciers can trap considerable volumes of liquid water with the potential to generate devastating outburst floods. This study aims to identify water‐filled subglacial reservoirs from ambient seismic noise collected by moderate‐cost surveys. The horizontal‐to‐vertical spectral ratio technique is highly sensitive to impedance contrasts at interfaces, thus commonly used to estimate glacier thickness. Here, we focus on the inverse ratio, that is, the V/H spectral ratio (VHSR), whose high values indicate a low impedance volume beneath the surface, suggesting subglacial cavities. We analyze VHSR peaks from a seismic array of 60 nodes installed on the Tête‐Rousse Glacier (Mont Blanc massif, French Alps); data were gathered over 15 days. Mapping the VHSR amplitude over the free surface reveals the main cavity locations and the basal areas affected by melting within the glacier. Results obtained in the field are supported by a conceptual model based on 3D finite‐element simulations. Plain Language Summary: Considerable volumes of liquid water may be trapped within cavities in polythermal glaciers. If these cavities rupture, the resulting outburst flood has the potential to cause devastation in populated mountain areas. With the aim of testing methods to locate such cavities, we installed 60 small 3‐component seismic sensors on the Tête‐Rousse Glacier (Mont Blanc massif, French Alps), which is known to contain such cavities. We used these sensors to test a detection method based on ambient seismic noise. For 3 weeks, the sensors recorded vibrations within the glacier. On a glacier without cavities, these vibrations ought to be predominantly in the horizontal direction. In the presence of a cavity, we expect the ice above the cavity to vibrate mostly vertically—like a bridge. In this paper, we highlight areas on the glacier where vertical vibrations were stronger than horizontal vibrations. These areas fit well with the locations of the main known cavities in this glacier, and with areas affected by basal melting. We supported our field observations with modeling based on 3D simulations, paving the way to a new method to locate water‐filled cavities within glaciers. Key Points: Spectral analysis from ambient seismic noise is complementary to other geophysical methods for investigating glaciers at depthResults suggest that the vertical‐to‐horizontal spectral ratio is a reliable proxy to locate subglacial cavitiesExperimental results were confirmed using a simplified numerical model [ABSTRACT FROM AUTHOR]

The development of hummocky topography is a poorly understood aspect of down‐wasting on debris‐covered glaciers that is often attributed to variable debris thickness. Thousands of enclosed depressions pit the hummocky topography. To better understand depression growth, we examined the size distribution and geometry of depressions on the Ngozumpa Glacier, in the Everest Region of Nepal. The depressions exhibited a power‐law size distribution, fractal perimeters, and power‐law depth‐area scaling, which suggest positive feedback growth. With a simple model, we showed that positive feedback growth produces similar power‐law size distributions. Based on these findings, we propose a "sinkhole" hypothesis for the development of depressions. Drainage into englacial sink points removes debris from the depressions and inhibits ponds from overflowing, thereby enabling positive feedback growth via incision, increased sub‐debris melt rates, and ice cliff retreat. By facilitating sustained depression growth, englacial drainage preconditions the ablation zone for the rapid growth of glacial lakes. Plain Language Summary: As debris‐covered glaciers melt, they develop a complex, "hummocky" surface that is often attributed to variable thickness debris. Thousands of enclosed depressions pit the hummocky topography. An enigmatic quality of the depressions is that most do not contain meltwater ponds. To better understand how depressions form and grow, we examined the size distribution and geometry of depressions on the Ngozumpa glacier, located in the Everest Region of Nepal. These analyses suggest that the depressions undergo positive feedback growth. With a simple model, we demonstrated that positive feedback growth produces distributions of depressions similar to the Ngozumpa Glacier. Variable thickness debris cannot explain positive feedback depression growth because downhill debris movement and pond overflows would inhibit growth. However, englacial drainage is widespread on debris‐covered glaciers, and karst sinkholes undergoing positive feedback growth develop distributions similar to the depressions. Englacial drainage makes positive feedback depression growth possible by focusing incision and debris removal within the depression, limiting the influence of negative feedbacks. Sustained depression growth primes the glacier for the rapid development of glacial lakes, which increase melt rates and can pose outburst flood hazards. Our results show that englacial drainage is an important driver of hummocky topography development on debris‐covered glaciers. Key Points: Power‐law size distribution and geometric scaling relationships suggest positive feedback depression growth on the Ngozumpa GlacierSimulations showed that only strong positive feedback growth produces comparable power‐law size distributionsEnglacial drainage enables positive feedback growth by regulating water storage in ponds and removing debris from depressions [ABSTRACT FROM AUTHOR]

Understanding the long‐term streamflow variability of the Yarlung Tsangpo (called the Brahmaputra River in downstream) is critical for water resources management due to its provision of freshwater for millions of people and its flood risk. However, previous streamflow reconstructions, based on dendrochronology and palaeo‐flood sediments, are either discontinuous or cover only a few hundred years. Here, we provide a continuous palaeolimnological record of the streamflow of the Yarlung Tsangpo upstream. Our results reveal an unexpected streamflow rise after 6,000 years ago, indicating the Westerlies and glacier meltwater replaced Indian Summer Monsoon as the dominant driver of runoff. Furthermore, the relatively frequent palaeo‐flood events during the early and late Holocene may be attributed to El Niño‐Southern Oscillation (ENSO) variance. These findings suggest the future occurrence of unsustainable streamflow and an increased flooding risk, as a result of weakening Westerlies, reduced glaciers, and strengthened ENSO activity under climatic warming. Plain Language Summary: Yarlung Tsangpo (the upper reaches of the Brahmaputra River) is one of the most important transboundary rivers in South Asia, providing crucial freshwater resources for over 60 million people, while also experiencing frequent hazardous floods. To improve water resources management with goal of improving the public's lives, it's important to understand long‐term changes in streamflow and to determine underlying mechanisms. Here, we provide a continuous Holocene streamflow record using a river‐connected lake in the upstream of the Yarlung Tsangpo. Our results reveal that the streamflow was primarily controlled by the Indian Summer Monsoon before 6,000 years ago, which is consistent with modern observations. Later, however, the streamflow increased continuously despite the weakened monsoon. This increased streamflow was caused by the enhancement of the Westerlies and increased glacial meltwater. Palaeo‐floods, identified using Rate of Change analysis, show a relatively high frequency during the early and late Holocene, possibly linked to the variability of the El Niño‐Southern Oscillation (ENSO). If correct, our findings suggest that future warming may weaken the Westerlies and accelerate glacier melting, thereby threatening the long‐term sustainability of the streamflow of the Yarlung Tsangpo. Additionally, climatic warming leading to an intensified ENSO would result in an increased flood risk. Key Points: Continuous streamflow and palaeo‐flood records in the upstream of Yarlung Tsangpo during the HoloceneThe Westerlies and meltwater have replaced Indian Summer Monsoon as key factors influencing the streamflow since 6,000 years agoThe frequency of palaeo‐flood is regulated by the variability of El Niño‐Southern Oscillation [ABSTRACT FROM AUTHOR]

Glacial lake‐moraine dam systems are widespread in cold alpine environments such as the Qinghai‐Tibet Plateau (QTP). Without climate change, the lake‐dam system exhibits stably dynamic evolution on a hydrological annual cycle. However, climate change may drive subtle alterations in the system's evolution. We developed a fully coupled Thermal‐Hydraulic‐Mechanical simulation platform considering ice‐water phase change, showing robust performance under CMIP6‐derived boundary conditions. Using this platform, we simulated climate warming‐driven multiphysics responses and dam stability evolutions of a homogeneous, simplified conceptual model of the lake‐dam system. We identified critical temperature thresholds for permanently frozen area thawing and abrupt changes in dam stability of this lake‐dam system. Considering the current slope stability situations on the QTP, the SSP 5–8.5 climate warming scenario is conservatively anticipated to pose significant geological safety risks due to potential disaster chains from glacial lake failures. Our study provides insights into profound geological process evolutions driven by climate change. Plain Language Summary: Sizable and numerous moraine‐dammed glacial lakes in cold alpine regions are increasingly threatened by climate change. This study simulated the long‐term (2020–2140) Thermal‐Hydraulic‐Mechanical coupling and stability evolution of a homogeneous conceptualized glacial lake‐moraine dam system under climate warming on the Qinghai‐Tibet Plateau (QTP). Two types of critical state‐transition points were identified in this conceptual model, marking shifts from quantitative to qualitative changes. A temperature rise threshold of 5.89°C indicates the onset of rapid shrinkage in permanently frozen area of the conceptual lake‐dam system. Another type of transition points occurs at 1.92°C and 4.48°C, corresponding to sharp year‐over‐year declines in spring and winter stability, respectively. A conservative estimation suggests that, if evaluated using stability reduction rate of the conceptualized model, moraine dams on the QTP with current stability factors below 1.19 in summer or 1.81 in winter, could fail after 120 years of intense climate warming. Considering the current stability situations on the QTP and geohazard chains resulting from glacial lake failure, uncontrolled global climate change would pose a severe threat to regional geological safety of QTP. The study has significant implications for assessing geological safety in periglacial environments and supports investigating coupling issues of climate change, geological processes, and human activities. Key Points: Climate change‐driven multiphysics responses and stability evolution of a conceptual glacial lake‐moraine dam are depicted over the next 120 yearsFrozen area would rapidly retreat for nearly 10 years once the temperature rise crosses a certain threshold (5.89°C for the conceptual model)Spring and winter stability would rapidly deteriorate after surpassing certain temperature thresholds (1.92°C and 4.48°C, respectively, for the model) [ABSTRACT FROM AUTHOR]

Addressing impacts of flash droughts (FDs) on the water‐food nexus requires a understanding of FD mechanisms and drivers at the watershed level. Examining climatic drivers, dry and wet spell lengths from 1980 to 2019, we analyzed FD spatial and temporal characteristics, emphasizing areal extent, onset time, and duration. Our findings reveal substantial variations in FDs among different watersheds. Notably, watersheds in the Southern Hemisphere are witnessing expanding, faster‐developing, and longer‐lasting FDs, aligning with climate variations in precipitation and temperature. Additionally, at the watershed scale, the onset and duration of FDs are more influenced by the intensity (magnitude and variability) of climatic drivers than the average length of wet and dry periods. FD‐extents, however, correlate with both climatic conditions and wet and dry periods, underscoring watershed connectivity. Ultimately, our results underscore the necessity for research to comprehend the interplay between FDs and watershed characteristics and how it manifests in overall water resource management. Plain Language Summary: Flash droughts (FDs), which are sudden and severe dry periods, are causing problems for our water and food systems and making it harder to prepare for disasters. To address these challenges effectively, it is crucial to gain a thorough understanding of the underlying mechanisms and factors driving FDs at the watershed level. In this study, we looked at climatic patterns alongside the lengths of dry and wet periods spanning from 1980 to 2019. Our primary focus was on three key aspects: the extent of FDs, when they begin, and how long they persist. Our research findings demonstrate considerable variations in FDs occurrences across different regions. Notably, in the Southern Hemisphere, FDs are expanding rapidly, developing more swiftly, and enduring for extended periods, closely mirroring shifts in precipitation and temperature patterns. Interestingly, the onset and duration of FDs seem to depend more on the intensity of climatic factors than on how long it's been dry or wet. The expansion of FDs in a region is linked to both the climatic and dry/wet periods, emphasizing the geophysical connectivity within a watershed. Key Points: Watersheds in tropical, temperate climates, and with savanna and grassland land cover are more susceptible to flash droughts (FDs)FDs extents are affected by intraannual precipitation variability, but not by intraannual air temperature variabilityThe onset and duration of FD at the watershed scale are influenced more by climate variables, than average wet/dry spell periods [ABSTRACT FROM AUTHOR]

Long‐term records of the flow patterns and dynamics of surge‐type glaciers improve our understanding of their underlying dynamic processes, and are critical to better resolve their contribution to a changing cryosphere. We adapt a modeling approach designed to emulate glacier surging and fold kinematics using the full Stokes ice‐flow model Elmer/Ice to simulate surging of the Dusty Glacier, located in the St. Elias Mountains, Canada. We combine distributed mass‐balance and numerical ice‐flow models to reconstruct the fold kinematics of the 2001–2003 surge of the Dusty Glacier by comparing model results to Landsat‐7 and Sentinel‐2 imagery, and assess the sensitivity of centennial‐scale modeled glacier structure to different mass balance and sliding parameterizations. This study demonstrates the feasibility of using the approach to reconstruct the surface structure kinematics of a surge‐type glacier in nature, highlighting its potential application to other surge‐type glaciers and regions. Plain Language Summary: Glaciers can exhibit irregular flow patterns that complicate predictions of their evolution over the coming decades and centuries. We present a method for reproducing iconic surface structures known as folded medial moraines using glaciological modeling. These moraines are wavy flow patterns found on surge‐type glaciers, highlighted by sediment deposited onto the ice that traces their path. By reconstructing these patterns, the underlying climate and sliding conditions that contributed to the glacier's past flow can be identified. Improving our knowledge of these conditions can help improve glacier flow models. We demonstrate that our methodology successfully reconstructs the flow patterns present on a large surge‐type glacier in Yukon, Canada, and explore its past flow history, and possible future, based on these results. Key Points: We use a distributed mass‐balance model and Elmer/Ice to reconstruct the 2001–2003 surge kinematics of the Dusty Glacier, Yukon, CanadaWe explore the centennial‐scale sensitivity of glacier surface fold geometry to mass balance and sliding parameterizationsThis study is a proof‐of‐concept for further model reconstructions of the past dynamics of surge‐type glaciers [ABSTRACT FROM AUTHOR]

Cryospheric responses to climate warming include glacier retreat, altitude‐dependent thermal instability, and abundant meltwater, which increase the frequency of catastrophic glacier hazard chain (CGHC) events. Here we investigated the formation mechanism of a special CGHC event in 2018, in the Sedongpu Glacier, Eastern Himalayas, China. Based on the multi‐source remote sensing, seismic signal analysis, and numerical simulation, we conducted long‐term retrospective analysis and co‐event process reconstruction. The results show that the event could be divided into two phases. First, the hanging glacier with a volume of 8.5 × 106 m3 collapsed onto the downstream trunk glacier. Next, ∼1.17 × 108 m3 eroded materials from the impacted glacier transformed into debris flow and traveled downstream 8 km. During the cascading process, ice‐rock avalanche momentum and glacier velocity are key factors in determining CGHC formation and eventual volume. Our study helps better understand the domino effects of the CGHC disaster. Plain Language Summary: Glacier instability in cryosphere is significantly influenced by global warming. The glacial lake outburst floods are the most widely studied and catastrophic events resulting from this instability, but they are not the only ones. In recent years, increasing catastrophic glacier hazard chain (CGHC) events have reminded us of disasters during climate warming, especially in the Himalayas region. Here, we report a typical CGHC event in the Eastern Himalayas, where the retreated glaciers are widely distributed. Based on our observations and simulations, we completed the retrospective analysis of CGHC through its formation conditions, evolution process, and specific kinematic process. These analyses help us understand the driving mechanism, the volume‐increasing effect, and the super‐fluidity of CGHC. Our findings help improve such hazard chain identification and mitigation in the Eastern Himalayas and glacierized environments elsewhere in the world. Key Points: New insights of Ice‐rock avalanche hazard chain on retreated hanging glacier in Eastern HimalayaErosion process on the trunk glacier led to a volume‐increasing and super‐fluidity of catastrophic glacier hazard chain (CGHC)The pre‐evolution and formation of CGHC were closely related to climate warming [ABSTRACT FROM AUTHOR]

As the world's glaciers recede in response to a warming atmosphere, a change in the magnitude and frequency of related hazards is expected. Among the most destructive hazards are glacier lake outburst floods (GLOFs), and their future evolution is concerning for local populations and sustainable development policy. Central to this is a better understanding of triggers. There is a long‐standing assumption that earthquakes are a major GLOF trigger, and seismic activity is consistently included as a key hazard assessment criterion. Here, we provide the first empirical evidence that this assumption is largely incorrect. Focusing on the Tropical Andes, we show that, of 59 earthquakes (1900–2021) the effects of which intersect with known glacier lakes, only one has triggered GLOFs. We argue that, to help develop climate resilient protocols, the focus for future assessments should be on understanding other key GLOF drivers, such as thawing permafrost and underlying structural geology. Plain Language Summary: Climate change is increasing glacier melt in high mountains and increasing the size and number of glacial lakes. Over time, these lakes may drain catastrophically to generate glacier lake outburst floods (GLOFs), which can devastate downstream communities and destroy valuable infrastructure such as roads, bridges, and hydroelectric power facilities. As a result, many risk assessments have been carried out to understand what the triggers of GLOFs might be, in order to better predict their occurrence. One of the main triggers has been assumed to be earthquakes, but this association has not been properly tested. In this paper, we use earthquake and GLOF data from the Peruvian and Bolivian Andes to test this and find that there is little association between earthquakes and GLOFs. We conclude by arguing that focus needs to be on other GLOF triggers, and earthquake activity should be used as a secondary – not primary – indicator in GLOF susceptibility studies. Key Points: Glacier lake outburst floods (GLOFs) are a major risk concern, with earthquakes being commonly considered effective triggers in hazard assessmentsOf 59 earthquakes (1900–2021), the effects of which intersect lakes in the Tropical Andes, only one triggered GLOFsWe suggest that earthquake activity should be used as a secondary – not primary – susceptibility indicator for GLOFs [ABSTRACT FROM AUTHOR]

Pore‐fluid pressure (PP) plays an important role in bed erosion, but the mechanisms that control PP evolution and the resulting feedbacks on flow dynamics are unclear. Here, we develop a general formulation, allowing quantification of the propensity for PP evolution of saturated and unsaturated bed sediments. We conduct erosion experiments by systematically varying grain composition and water content of beds, for investigating effects of PP evolution on flow erosion. With increasing water content, PP shows a slight rise in deforming beds with drained behavior but significant larger rise in undrained beds. Regardless of bed composition, the erosion rate of beds presents a synchronous change tendency with PP evolution due to the loss in basal friction. PP instigates positive feedback that induces a remarkable gain of flow velocity and momentum on wet beds with undrained behavior. Our results help explain observations of volume growth and long run out of debris flows. Plain Language Summary: Debris flows are common geophysical flows consisting of debris grains and muddy water. Debris flows can grow significantly in volume and mobility as they pick up loose sediment from gully bed and banks. The destructive potential of debris flows increases with increasing flow volume and run out. This brings about great challenges for effective early warning of debris flows, design of prevention measures and mapping of hazard zones related to human settlements. It is commonly believed that flow momentum is consumed by carrying static bed sediments. However, flows can gain momentum by overriding wet bed sediments. This can be explained by pore‐pressure generation as debris flows move across wet beds. The increase of measured pore‐fluid pressure is limited for beds with a low water content, but substantial for beds with a higher water content, which strongly affects the erosion rates of bed sediments. Flow velocity and momentum on wet beds are observed to increase significantly but slightly for dryer beds as a result of the pore‐pressure feedback. These findings indicate that the debris composition of the catchment, the water content of bed sediment and the pore‐pressure development should be evaluated when making predictions on debris‐flow hazard. Key Points: Propensity for pore pressure evolution of bed sediments during debris‐flow erosion is evaluated by a Deborah numberSignificant pore pressure and accompanying intense erosion occur for wet bed sediments with undrained behaviorEnhanced pore pressure of wet bed sediments reduces flow basal friction, increasing flow mobility and runout [ABSTRACT FROM AUTHOR]

High‐resolution present‐day earth surface deformation maps from satellites provide important data constraints, which help us better understand tectonic processes and analyze seismic hazards. Here, we use Sentinel‐1 Radar images (2014–2020) and accurate positioning measurements (2009–2019) to get a high‐resolution three‐dimensional earth surface velocity map for the northeastern Tibetan Plateau, and we invert the slip rate and coupling ratio of major regional faults. We find ∼4 mm/yr uplift along an arc from the Qilianshan to Lajishan, relative to the neighboring low‐elevation area to the east, which indicates ongoing rapid orogeny. We find transient deformation along the Laohushan and 1920 M8.5 Haiyuan rupture segments of the Haiyuan fault, whereas the western Haiyuan, southern Liupanshan, central Lajishan and central‐western West Qinling faults are essentially locked above 15–20 km, suggesting a potentially high seismic hazard. Plain Language Summary: The northeast Tibetan Plateau, which is impeded by the tectonically stable Ordos block, continues to grow in response to the far‐field India‐Eurasia collision. This region has several large‐scale active faults that hosted some destructive earthquakes in the last 100 years. Although intensively studied, the fault kinematics of those seismogenic faults are still not clear, mainly because of poor observational constraints. Hence, high‐resolution present‐day deformation maps are essential to answering this question, either of scientific or societal concern. We provide satellite‐based ground deformation rate maps with mm‐accuracy for this region. They show shallow fault creep along some segments of the Haiyuan fault which is better constrained than previous results, active tectonic uplift in the Lajishan. Our work gives new constraints for the seismic hazard for the Northeastern Tibetan Plateau case. Key Points: We derive a new high‐resolution three‐dimensional present‐day deformation map for the Northeastern Tibetan PlateauGeodetic data reveals ongoing rapid uplift along an accurate orogenic belt from the eastern Qilianshan and LajishanNew constraints for the seismic hazard analysis for the Northeastern Tibetan Plateau [ABSTRACT FROM AUTHOR]

Infrequent, large‐magnitude discharge (>106 m3/s) outburst floods—megafloods—can play a major role in landscape evolution. Prehistoric glacial lake outburst megafloods transported and deposited large boulders (≥4 m), yet few studies consider their potential lasting impact on river processes and form. We use a numerical model, constrained by observed boulder size distributions, to investigate the fluvial response to boulder deposition by megaflooding in the Yarlung‐Siang River, eastern Himalaya. Results show that boulder deposition changes local channel steepness (ksn) up to ∼180% compared to simulations without boulder bars, introducing >100 meter‐scale knickpoints to the channel that can be sustained for >20 kyr. Simulations demonstrate that deposition of boulders in a single megaflood can have a greater influence on ksn than another common source of fluvial boulders: incision‐rate‐dependent delivery of boulders from hillslopes. Through widespread boulder deposition, megafloods leave a lasting legacy of channel disequilibrium that compounds over multiple floods and persists for millennia. Plain Language Summary: Megafloods (discharge equivalent to ≥400 instantaneously draining Olympic‐sized swimming pools per second) can transport a lot of material, including car‐ to house‐sized boulders. Because these boulders are so big, they remain in the channel until the next megaflood or until they weather into smaller pieces. We use a computer model to understand the impact of these megaflood deposited boulders on mountain river processes. We find that megaflood boulders can protect the river from being eroded, causing other processes, like tectonic uplift, to outcompete erosion. Megaflood boulders cause small steps to form within the river. Our modeling shows that these effects can be felt for >20,000 yrs after a single flood. We suggest that megaflood deposition (in addition to erosion) can cause a significant, unique change in mountain river processes. Key Points: We studied channel response to megaflood boulder deposition in the eastern Himalaya using a numerical modelMegaflood boulder deposition locally changes channel steepness up to 180%, creating >100 knickpointsThe compounding effect from multiple megaflood boulder deposits in rapid succession perturbs channel form for many thousands of years [ABSTRACT FROM AUTHOR]

Permafrost warming and degradation is well documented across the Arctic. However, observation‐ and model‐based studies typically consider thaw to occur at 0°C, neglecting the widespread occurrence of saline permafrost in coastal plain regions. In this study, we document rapid saline permafrost thaw below a shallow arctic lake. Over the 15‐year period, the lakebed subsided by 0.6 m as ice‐rich, saline permafrost thawed. Repeat transient electromagnetic measurements show that near‐surface bulk sediment electrical conductivity increased by 198% between 2016 and 2022. Analysis of wintertime Synthetic Aperture Radar satellite imagery indicates a transition from a bedfast to a floating ice lake with brackish water due to saline permafrost thaw. The regime shift likely contributed to the 65% increase in thermokarst lake lateral expansion rates. Our results indicate that thawing saline permafrost may be contributing to an increase in landscape change rates in the Arctic faster than anticipated. Plain Language Summary: In this study, we combine direct field measurements, near‐surface geophysical studies, and remote sensing change detection to document the rapid thaw of saline permafrost below a shallow thermokarst lake on the Arctic Coastal Plain of northern Alaska. Thaw of ice‐rich saline permafrost resulted in an increase in the lake depth by 0.6 m over a 15‐year period. The transition from a bedfast ice lake to a floating ice lake with brackish water is responsible for the increase near‐surface bulk sediment electrical conductivity and likely contributed to an increase in the lateral expansion rate of the lake. Our findings indicate that active permafrost thaw is likely occurring below shallow arctic lakes at temperatures below 0°C. Key Points: We document the rapid thaw and subsidence of saline permafrost below a shallow thermokarst lake in Arctic AlaskaWe hypothesize that rapid saline permafrost degradation is occurring below shallow arctic lakes at sub‐zero temperaturesThawing saline permafrost may be contributing to an increase in landscape change rates in the Arctic [ABSTRACT FROM AUTHOR]

The northeast Pacific Coastal Temperate Rainforest (NPCTR) extending from southeast Alaska to northern California is characterized by high precipitation and large stores of recently fixed biological carbon. We show that 3.5 Tg‐C yr−1 as dissolved organic carbon (DOC) is exported from the NPCTR drainage basin to the coastal ocean. More than 56% of this riverine DOC flux originates from thousands of small (mean = 118 km2), coastal watersheds comprising 22% of the NPCTR drainage basin. The average DOC yield from NPCTR coastal watersheds (6.20 g‐C m−2 yr−1) exceeds that from Earth's tropical regions by roughly a factor of three. The highest yields occur in small, coastal watersheds in the central NPCTR due to the balance of moderate temperature, high precipitation, and high soil organic carbon stocks. These findings indicate DOC export from NPCTR watersheds may play an important role in regional‐scale heterotrophy within near‐shore marine ecosystems in the northeast Pacific. Plain Language Summary: Carbon and water are dominant features within coastal temperate rainforests, which ring the Pacific coast of northeast America and Asia, the southern coast of Chile, and western New Zealand. The environmental conditions that support large stores of above ground forest biomass also facilitate the movement of organic carbon through soils and streams to coastal zones. Here we present the results of a large data synthesis to estimate the flux of dissolved organic carbon from the land to sea along the Northeast Pacific Coastal Temperate Rainforest region that extends from northern California through Southeast Alaska. We highlight that, although large rivers like the Fraser River in Canada and the Columbia River in the United States drain the majority of the region, the majority of the dissolved organic carbon entering coastal ecosystems originates from small, coastal watersheds, highlighting the direct connection in the carbon cycle between terrestrial and estuarine ecosystems within this region. Key Points: The Northeast Pacific Coastal Temperate Rainforest drainage basin exports 3.5 Tg‐C yr−1 of dissolved organic carbon (DOC) to the oceanMore than 50% of the land‐to‐ocean DOC flux is derived from small (median = 44 km2), coastal watershedsModeled watershed DOC yields peak in coastal British Columbia where climate and landcover combine to maximize terrestrial‐aquatic DOC fluxes [ABSTRACT FROM AUTHOR]

Climatic warming following the Last Glacial Maximum caused the southern Laurentide Ice Sheet (LIS) to begin ∼2,000‐year cycles of retreat and readvance whose cause remains ambiguous. By developing a marine‐calibrated chronology of southern LIS position, we counterintuitively demonstrate that between 17.6 and 11.3 ka, ice advanced during times of northern‐hemisphere warming and retreated during times of northern‐hemisphere cooling. Here we propose a cyclical feedback: Meltwater from ice retreat cooled the northern hemisphere by weakening the Atlantic Meridional Overturning Circulation (AMOC). This eventually lead to ice‐sheet readvance, which reduced and rerouted meltwater discharge, and thereby allowed the AMOC to strengthen and the northern hemisphere to warm. Our data suggest that this antiphased ice–climate interaction, paced by ice‐sheet response time, was initiated by synchronous warming and ice retreat ∼18.7–17.6 ka (corresponding to the Erie "Interstade") and reached its apex during the Younger Dryas. Plain Language Summary: Twenty thousand years ago, a colder climate allowed glacial ice to flow from northern and eastern Canada into the Great Lakes region. But when climate began to warm, instead of simply melting from south to north, the margin of this ice front repeatedly retreated and re‐advanced in 2,000‐year cycles. First, we track these advances and retreats using records of ancient Gulf of Mexico water, stored in plankton shells retrieved from a sediment cores. Ice advance redirected water bearing "light" oxygen, with fewer neutrons, from Canada and the Great Lakes into the Mississippi River. When ice retreated, these waters found other courses to the sea, shifting Gulf of Mexico chemistry toward heavier oxygen (carrying more neutrons). Next, we ask why these ice‐margin cycles occurred during a time of monotonically increasing solar radiation to the northern hemisphere. We propose that ice‐sheet melt (during retreat) slowed Atlantic Ocean circulation, causing the northern hemisphere to cool and the ice sheet to gradually regrow. However, this same regrowth reduced meltwater flow to the ocean, causing the northern hemisphere to re‐warm and eventually leading the ice margin to retreat once more. This cycle persisted from approximately 17,600 to 11,300 years ago, until North American ice became too small to sustain this feedback. Key Points: δ18O records from the Gulf of Mexico refine the chronology of Laurentide Ice Sheet advance and retreat through the Great LakesCounterintuitively, from 17.6 to 11.3 ka, ice advanced during times of warming and retreated during times of coolingA feedback between meltwater, Atlantic Meridional Overturning Circulation strength, and temperature—paced by ice‐sheet response time—may have set this anticorrelation [ABSTRACT FROM AUTHOR]

Ice cliff distribution plays a major role in determining the melt of debris‐covered glaciers but its controls are largely unknown. We assembled a data set of 37,537 ice cliffs and determined their characteristics across 86 debris‐covered glaciers within High Mountain Asia (HMA). We find that 38.9% of the cliffs are stream‐influenced, 19.5% pond‐influenced and 19.7% are crevasse‐originated. Surface velocity is the main predictor of cliff distribution at both local and glacier scale, indicating its dependence on the dynamic state and hence evolution stage of debris‐covered glacier tongues. Supraglacial ponds contribute to maintaining cliffs in areas of thicker debris, but this is only possible if water accumulates at the surface. Overall, total cliff density decreases exponentially with debris thickness as soon as the debris layer reaches a thickness of over 10 cm. Plain Language Summary: Debris‐covered glaciers are common throughout the world's mountain ranges and are characterized by the presence of steep ice cliffs among the debris‐covered ice. It is well‐known that the cliffs are responsible for a large portion of the melt of these glaciers but the controls on their formation, development and distribution across glaciers remains poorly understood. Novel mapping approaches combined with high‐resolution satellite and drone products enabled us to disentangle some of these controls and to show that the ice cliffs are generally formed and maintained by the surface hydrology (ponds or streams) or by the opening of crevasses. As a result, they depend both at the local and glacier scale on the dynamic state of the glaciers as well as the evolution stage of their debris cover. This provides a pathway to better represent their contribution to glacier melt in predictive glacier models. Key Points: We derived an unprecedented data set of 37,537 ice cliffs and their characteristics across 86 debris‐covered glaciers in High Mountain AsiaWe find that 38.9% of the cliffs are stream‐influenced, 19.5% pond‐influenced and 19.7% are crevasse‐originatedIce cliff distribution can be predicted by velocity, as an indicator of the dynamics and state of evolution of debris‐covered glaciers [ABSTRACT FROM AUTHOR]

Glaciers are commonly conceptualized as bodies composed of snow and ice. Yet, many glaciers contain a substantial amount of rock, especially those abutting steep mountains. Mountain slopes erode, depositing rocks on glaciers below. This loose rock (or debris) is buried in glaciers and melts out lower down creating a debris cover. Debris cover reduces ice melt, which changes the shape and movement of glaciers. Glacier movement, specifically basal sliding, efficiently sculpts landscapes. To date, we know little about the impacts of surface debris on conditions below glaciers. To help remedy this, we run numerical model simulations which show that debris‐covered glaciers erode slower than glaciers unaffected by debris. Reduced melt under surface debris lowers sliding speeds and causes sediment to accumulate at the bed, potentially establishing conditions for surging. The influence of surface debris cover on the subglacial environment may hold substantial implications for alpine sediment storage and landscape evolution. Plain Language Summary: Glaciers are imagined as bodies composed entirely of snow and ice. But many glaciers, especially those in steep mountains contain a substantial amount of rock as well. Rocks are deposited on glaciers from steep mountain slopes above them. This loose rock (or debris), buried by snow, can completely cover glaciers' lower reaches as it melts out of the ice. Debris reduces melt, which changes the glacier shape and in turn how glaciers move down valley. To test how debris‐covered glaciers erode and sculpt landscapes we use numerical models. Our simulations show that debris‐covered glaciers erode landscapes at lower rates than glaciers unaffected by debris. The reduced amount of melt from debris cover causes glaciers to slide slower and causes sediment to accumulate under debris‐covered ice, shielding bedrock from erosion. The tendency for debris‐covered glaciers to build sediment layers at their bed may lead to the rapid speed up and advancement of glaciers, also known as surges. The influence of surface debris cover on the subglacial environment may hold substantial implications for alpine sediment storage and landscape evolution. Key Points: Erosion is reduced under debris‐covered ice because of compounding effects between reduced surface melt and the subglacial environmentTill accumulates under debris‐covered ice because surface melt is suppressed by surface debris coverDebris cover on glaciers promotes subglacial fluvial conditions that can store sediment in alpine environments, altering erosional patterns [ABSTRACT FROM AUTHOR]

Much of the focus of global warming impacts on lakes have focused on changes in mean temperature. However, lakes are also highly vulnerable to thermal extremes. Such extremes occur, by definition, during lake heatwaves. Heatwaves in lakes have occurred globally in recent decades and have had severe negative impacts. However, unlike their atmospheric counterparts, it is currently unknown to what extent lake heatwaves are altered by human‐induced climate change. Here, we estimate the human contribution to lake heatwaves, specifically focusing on the most severe events. We demonstrate that the occurrence probabilities of severe lake heatwaves increase substantially due to human influence. Our analysis suggests that 94% of severe heatwaves observed during the satellite data‐taking period have an anthropogenic contribution. Globally, we suggest that severe heatwaves are 3 and 25‐ times more likely in a 1.5°C and 3.5°C warmer world, respectively, compared to a world without anthropogenic influence. Plain Language Summary: Lake heatwaves are occurring globally with severe negative impacts on lake ecosystems. However, it is currently unclear whether, and by how much, human‐induced global warming contributes to their occurrence. Here, we show that the occurrence probabilities of some of the most severe lake heatwaves observed are extremely sensitive to human influence. We estimated that 94% of severe heatwaves observed in recent decades have an anthropogenic contribution. Globally, severe heatwaves are 3 times more likely in a 1.5°C warmer world and 25 times more likely in a 3.5°C warmer world, compared to a world without anthropogenic warming. To prevent lake ecosystems being adversely affected by the projected increased occurrence of severe heatwaves, ambitious climate targets are of paramount importance. Key Points: Severe lake heatwaves have increased in our studied sites by sixfold since 1995Anthropogenic climate change made the severe heatwaves observed almost twice as likelyContinued anthropogenic warming will increase the likelihood occurrence of severe heatwaves this century [ABSTRACT FROM AUTHOR]