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Silt-rich meltwater plume deposits (MPDs) analyzed from marine sediment cores have elucidated relationships that are clearly connected, yet difficult to constrain, between subglacial hydrology, ice-marginal landforms, and grounding-zone retreat patterns for several glacial catchments. Few attempts have been made to infer details of subglacial hydrology, such as flow regime, geometry of drainage pathways, and mode(s) of sediment transport through time, from grain-scale characteristics of MPDs. Using sediment samples from MPD, till, and grounding-zone proximal diamicton collected offshore of six modern and relict glacial catchments in both hemispheres, we examine grain shape distributions and microtextures (collectively, grain micromorphology) of the silt fraction to explore whether grains are measurably altered from their subglacial sources via meltwater action. We find that 75 % of all imaged grains (n = 9400) can be described by 25 % of the full range of measured shape morphometrics, indicating grain shape homogenization through widespread and efficient abrasive processes in subglacial environments. Although silt grains from MPDs exhibit edge rounding more often than silt grains from tills, grain surface textures indicative of fluvial transport (e.g., v-shaped percussions) occur in only a modest number of grains. Furthermore, MPD grain surfaces retain several textures consistent with transport beneath glacial ice (e.g., straight or arcuate steps, (sub)linear fractures) in comparable abundances to till grains. Significant grain shape alteration in MPDs compared to their till sources is observed in sediments from glacial regions where (1) high-magnitude, potentially catastrophic meltwater drainage events are inferred from marine sediment records and (2) submarine landforms suggest supraglacial melt contributed to the subglacial hydrological budget. This implies that quantifiable grain shape alteration in MPDs could reflect a combination of high-energy flow of subglac

Measurements of underwater sound are still scarce in the rapidly changing Arctic. Tele-seismically detectable glacial earthquakes caused by iceberg calving have been known for nearly two decades but their underwater sound levels remain undocumented. Here, we present near-source underwater sound records from a kilometer-scale iceberg calving associated with a glacial earthquake. Records were obtained using an ocean-bottom lander deployed near the calving front of a Greenlandic tidewater Bowdoin Glacier in July 2019. An underwater-detonation-like signal with an overall duration of 30 min and two major phases owing to iceberg detachment and disintegration corresponded to extreme source sound levels (225 +/- 10 dB(p2p)( )re 1 mu Pa) and acoustic energy on the order of 10(8-)(10) J or 0.1-7.6 tonnes TNT-equivalent. Our estimates and comparison with other anthropogenic and natural sources suggest that this type of geophysical event is among the loudest sounds in the Arctic. Such high sound levels are important for estimating the noise budget of the ocean and possible impacts on endemic Arctic species exposed to such sounds. The sound of calving may cause direct mechanical damage to the hearing of marine mammals such as narwhals and seals present in the glacial fjord. (C) 2022 Author(s).

Detecting structures within the continuous diving behavior of marine animals is challenging, and no universal framework is available. We captured such diverse structures using chaos theory. By applying time-delay embedding to exceptionally long dive records (83 d) from the narwhal, we reconstructed the state-space portrait. Using measures of chaos, we detected a diurnal pattern and its seasonal modulation, classified data, and found how sea-ice appearance shifts time budgets. There is more near-surface rest but deeper dives at solar noon, and more intense diving during twilight and at night but to shallower depths (likely following squid); sea-ice appearance reduces rest. The introduced geometrical approach is simple to implement and potentially helpful for mapping and labeling long-term behavioral data, identifying differences between individual animals and species, and detecting perturbations.

About 70% of Earth's surface is covered by ocean, for which seismic observations are challenging. Seafloor seismology overcame this fundamental difficulty and radically transformed the earth sciences, as it expanded the coverage of seismic networks and revealed otherwise inaccessible features. At the same time, there has been a recent increase in the number of studies on cryoseismology. These have yielded multiple discoveries but are limited primarily to land and ice-surface receivers. Near ice calving fronts, such surface stations are noisy, primarily due to crevassing and wind, are hazardous to maintain, and can be lost due to iceberg calving. To circumvent these issues, we have applied ocean-bottom seismology to the calving front of a tidewater glacier in northwest Greenland. We present details of this experiment, and describe the technical challenges, noise analysis, and examples of recorded data. This includes tide-modulated seismicity with thousands of icequakes per day and the first near-source (similar to 200-640 m) underwater record of a major kilometer-scale calving event in Greenland, which generated a glacial earthquake that was detectable similar to 420 km away. We also identified a decrease in bottom-water temperature, presumably due to modified water stratification driven by extreme Greenland glacial melting, at the end of July 2019. Importantly, we identify glacial sediments as the key reason for the anomalously long (similar to 9.7 hr) delay in the sensor release from the fjord seafloor. Our study demonstrates a methodology to undertake innovative, interdisciplinary, near-source studies on glacier basal sliding, calving, and marine-mammal vocalizations.

Passive acoustic monitoring has revolutionized the characterization of industrial processes and the acoustic wavefield in various environments. However, cryospheric acoustic phenomena remain largely unknown, especially at medium and small scales. Furthermore, the englacial drainage system is poorly documented, even though it is fundamental for understanding water routing through the glacier body. Here I present the first-of-its-kind in situ records of periodic or sustained acoustic signals generated by water drainage through crevasses at the calving front of a glacier, in this case a Greenlandic tidewater glacier. The generative mechanisms of gurgling and bubbling noise are explained as flow-induced sounds that are excited by intermittent air-water two-phase flow and Helmholtz resonance, respectively. This paper demonstrates that there is the tremendous potential to study near-surface glacier systems using acoustic methods and detect different flow patterns in englacial conduits from their acoustic signatures, both of which can significantly advance our understanding of glaciological processes. Plain Language Summary The glacier surface is full of various audible sounds. While early polar explorers have documented this noisy glacier environment, these qualitative observations have never been supported by measurements. For example, Nansen (1897), wrote, "I can hear reports from the glacier... whenever it turns cold-it writhes horribly, and crevice after crevice appears in the huge body; there is a noise like the discharge of guns, and the sky and the earth tremble so that I can feel the ground that I am lying on quake" while wintering in Franz Josef Land, and Baldwin (1896) described his crossing of Bowdoin Glacier, which is the subject of this study, as follows: "...shrieking sounds frightful enough, came...to our ears, seeming to vibrate through...our very bodies, spitefully shouting in our ears: Why, presumptuous man, hast thou set disturbing foot upon my chaste b

We recorded the ice motion and icequakes on the floating part of Langhovde Glacier in East Antarctica to better understand the dynamic behavior of ice shelves and floating tongues. Diurnal and semi-diurnal variations in ice motion and seismicity were simultaneously observed at all four global navigation satellite system and three seismic stations over 2 weeks. The short-term along-flow ice motion is explained by the elastic response of the glacier to ocean tide-induced hydrostatic stress variations, which decayed at a rate of 0.8 km(-1) toward the grounding line. We observed a large number of icequakes during mid-rising and high tides that covered a broad frequency range and formed two major groups of events centered at 10 and 120 Hz, respectively. The hourly occurrence rates were similar to 500 events h(-1), with the observed seismicity consistent with fracture due to floating tongue bending. We also observed minor secondary peaks at high ice speeds, which could reflect surface cracking due to stretching or basal friction. Our observation demonstrates that tidal-modulation was the main factor to fracture the floating tongue of Langhovde Glacier.

Measuring glacier calving magnitude, frequency and location in high temporal resolution is necessary to understand mass loss mechanisms of ocean-terminating glaciers. We utilized calving-generated tsunami signals recorded with a pressure sensor for estimating the calving flux of Bowdoin Glacier in northwestern Greenland. We find a relationship between calving ice volume and wave amplitude. This relationship was used to compute calving flux variation. The calving flux showed large spatial and temporal fluctuations in July 2015 and in July 2016, with a mean flux of 2.3 ± 0.15 × 105 m3 d−1. Calving flux was greater during periods of fast ice flow, high air temperature, and at low/falling tide, indicating the importance of increased longitudinal strain due to glacier acceleration and/or submarine melting at the calving front. Long-term measurements with the method introduced here are promising for understanding the complex interplay of ice dynamics, melting and calving at glacier fronts.

Recent observations suggest that the nocturnal thermal fracturing of ice occurs at relatively warm temperatures (above -15 degrees C) at a high-altitude Himalayan glacier system unless the ice is shielded by a debris mantle. Here we estimate the stresses induced by diurnal temperature variations using viscous, elastic, and two viscoelastic models, and various thicknesses of the debris mantle. Only the elastic and visco-elastic models are in agreement with the observations. The timing and amplitudes of the stresses in the upper 15 cm of the glacier are different among the models despite the ability of each approach to predict a diurnal increase in tension exceeding the critical threshold proposed for crevasse formation. For example, the elastic stress is several times larger than the viscous stress at the ice surface (650 vs. 250 kPa) and reaches its peak up to 5-6hr later in the night. The time lag is in line with the seismic records, suggesting that the viscous model is not appropriate. Furthermore, a debris layer of >= 50cm in thickness suppresses the diurnal fluctuations in thermal stress and therefore protects the ice from mechanical damage. We suggest that high-amplitude diurnal cooling and weak ice properties due to weathering are essential factors that influence thermal fracturing in the Himalayan environment. The ongoing expansion of seismic networks into cryospheric regions, which will be capable of detecting local thermal-contraction-induced cracks, in combination with the fact that such cracks can erode and weaken the ice, and thereby serve as meltwater and heat channels, warrants further research to better understand these near-surface processes and to monitor ice properties. Plain Language Summary Thermal fracturing is an important erosion process on the icy surfaces of solar system bodies, including Earth, Mars, and comets. However, the exact timing of this thermal fracturing process is poorly constrained, despite the need for this information to va

Calving plays a key role in the recent rapid retreat of glaciers around the world. However, many processes related to calving are poorly understood since direct observations are scarce and challenging to obtain. When calving occurs at a glacier front, surface-water waves arise over the ocean or a lake in front of glaciers. To study calving processes from these surface waves, we performed field observations at Glaciar Perito Moreno, Patagonia. We synchronized time-lapse photography and surface waves record to confirm that glacier calving produces distinct waves compared with local noise. A total of 1074 calving events were observed over the course of 39 d. During austral summer, calving occurred twice more frequently than in spring. The cumulative distribution of calving-interevent time interval followed exponential model, implying random occurrence of events in time. We further investigated wave properties and found that source-to-sensor distance can be estimated from wave dispersion within ∼20% error. We also found that waves produced by different calving types showed similar spectra in the same frequency range between 0.05–0.2 Hz, and that the amplitude of surface waves increased with the size of calving. This study demonstrates the potential of surface-wave monitoring for understanding calving processes.

Calving plays a key role in the recent rapid retreat of glaciers around the world. However, many processes related to calving are poorly understood since direct observations are scarce and challenging to obtain. When calving occurs at a glacier front, surface-water waves arise over the ocean or a lake in front of glaciers. To study calving processes from these surface waves, we performed field observations at Glaciar Perito Moreno, Patagonia. We synchronized time-lapse photography and surface waves record to confirm that glacier calving produces distinct waves compared with local noise. A total of 1074 calving events were observed over the course of 39 d. During austral summer, calving occurred twice more frequently than in spring. The cumulative distribution of calving-interevent time interval followed exponential model, implying random occurrence of events in time. We further investigated wave properties and found that source-to-sensor distance can be estimated from wave dispersion within ∼20% error. We also found that waves produced by different calving types showed similar spectra in the same frequency range between 0.05–0.2 Hz, and that the amplitude of surface waves increased with the size of calving. This study demonstrates the potential of surface-wave monitoring for understanding calving processes.