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Surging and streaming of glaciers are modulated by meltwater availability and pressure which controls mechanical coupling at their beds. Using laboratory-scale experimental modelling and palaeoglaciological mapping, we explore how subglacial drainage landsystems control meltwater drainage efficiency and ice flow velocities for terrestrial-based ice lobes resting on flat horizontal and permeable beds. Two end-members regimes, surging and streaming, appear in our experiments. The surge regime is characterised by a rapid increase of drainage efficiency through development of tunnel valleys and their tributaries, thus reducing the duration of ice flow speed-up events by lowering water pressures and increasing ice-bed coupling. Tunnel valleys connected to ice lobe margins, submarginal thrust moraines, reduced ice lobe extensions and ephemeral shear margins are the most distinctive characteristics of this regime. The stream regime is characterised by disconnected channels of smaller dimensions unable to evacuate all the meltwater: this prolonged drainage inefficiency leads to sustained high ice flow velocity and steady shear margins. Small and rectilinear meltwater channels devoid of tributaries, often disconnected from ice lobe margins, and lineation swarms are diagnostic of this regime.

We report on measurements of dissipation and frequency noise at millikelvin temperatures of nanomechanical devices covered with aluminum. A clear excess damping is observed after switching the metallic layer from superconducting to the normal state with a magnetic field. Beyond the standard model of internal tunneling systems coupled to the phonon bath, here we consider the relaxation to the conduction electrons together with the nature of the mechanical dispersion laws for stressed/unstressed devices. With these key ingredients, a model describing the relaxation of two-level systems inside the structure due to interactions with electrons and phonons with well separated timescales captures the data. In addition, we measure an excess 1/f-type frequency noise in the normal state, which further emphasizes the impact of conduction electrons., 7 pages (main text) + 9 pages (SI), same as published version

Introduction: Louth Crater is a 36 km diameter located at 70 °N, 103.2 °E (Fig. 1) less than 1000 km from the Martian North Polar Cap. At the center of Louth crater a perennial water ice cap ~10 km in diameter, ~250 m in width (Fig. 1) that undergoes phase changes (condensation / sublimation cycles) during the Martian year [1 - 4]. Some periodic structure at the surface of its perennial water ice cap have been observed [2]. The presence of smaller ice undulations superimposed on this periodic structure, comparable to the sublimation waves on the Martian North Polar Cap [5] could be formed during sublimation and condensation period of the water ice. The characterization of this ice waves could make it possible to specify environmental conditions favorable to their formation. The first part of the study consists of identifying these ice waves using orbital topography and imaging data, and then associating these results with data from the Martian Database [6-7] and with the scaling laws inherent to the formation of sublimation and condensation waves. Fig. 1: Louth crater in summer. CTX product J02_045439_2504_XN_70N256W Ls = 133.2° Geomorphological analysis: Methods: Digital Elevation Model (DEM) at ~100 m/pixel and MOLA elevation data at ~128 m/pixel have been coupled with imagery data from HRSC ~10 m/pixel, CTX at ~6 m/pixel and HiRISE images for more precise areas for up to 25 cm/pixel. Data were georeferenced in ESRI’s ArcMap GIS software to produce geomorphological map and analyzed to evaluate ice waves shape and spatial organization. Observations: Louth presents two units (Fig. 2). (a) Lower unit with dark stucco texture and stratifications (Fig. 3a). (b) Fresh ice overlies this older, stratified structure (Fig 3.a). This fresh ice is distributed in a non-uniform manner as shown by the kilometrics waves of about 560 m wavelength on which are superimposed decametrics waves of about 55 m wavelength which are both perpendicular to the prevailing wind (Fig 3.b). The crests of both wave populations show similar NW-SE. The main wind direction was assessed from barkhane field on the sand mound. Fig. 2: Louth’s geomorphological map in summer. CTX product J02_045439_2504_XN_70N256W Ls = 133.2°. Fig. 3: Boxes from Fig. 2. (a) East side of the Louth crater ice cap. Green lines represents stratifications, HiRISE product EPS_045439_2505, Ls = 133.2°. (b) decametric waves on the ice waves. Black dashes represent leeside foot of each kilometric waves. Blue lines emphasize decametric waves, same HiRISE product from (a). Transport hypothesis: Preliminary experiments studied the threshold velocity necessary to initiate a transport of ice grains in Martian Simulation Wind Tunnel [8]. These experiments were carried out for grains from a few hundred micrometers to 2 mm in diameter under atmospheric pressures of 40 to 1000 mbar. To transport ice particles under near-Martian condition is hard because the threshold velocity is ten times higher than Earth. The wind speeds estimated from the Martian Database [6-7] in Louth crater are much lower than those needed to transport ice grains at Martian pressure. We support the hypothesis of diffusion by sublimation/condensation rather than the transport of icy particles by the wind. Mass transfer hypothesis: In a recent theoretical model [5] scaling laws explain the formation of sublimation waves and have been validated on terrestrial bedforms and on the Martian North Polar Cap. These waves are periodic and oriented in accordance with a turbulent boundary layer flow that diffuse the sublimated vapor. These laws, which are superimposed on the two ice waves studied, make these waves suitable geomorphological markers for climatic predictions. This model has been adapted to study similar waves created by condensation [9] and results indicate that condensation waves would be larger with one order gap than sublimation waves. Discussion: From the wind tunnel experimentation of ice particles transport in Martian-Like environment [8], wind necessary to initiate transport of ice particles is unlikely in Louth. Friction velocities of 3 m.s-1 would be required, compared to 0.6 m.s-1 deduced from scaling laws, to transport the most mobilizable 0.3 mm ice particles [8]. Wind speed in Louth is too weak for initiating particles transport. From the scaling laws, we extract values of friction velocity and flow velocity at a given altitude that can be compared with those extracted from the Martian Data Base over two Martian periods: a period of sublimation (during the summer in the northern hemisphere) at the origin of the formation of decametric waves and a period of condensation at the end of the summer, beginning of the autumn favorable for the kilometric waves formation. Scaling laws are in agreement with the predicted ratio velocity between sublimation and condensation period from the Martian Data Base values. From the Martian Data Base, independent velocity values are larger. This can be explained by the gridding of the database which takes place on a global scale larger than the crater. Conclusion: The observations indicate kilometric bedforms on the ice cap of Louth Crater, on which decametric bedforms appear with an order of magnitude gap. Comparison with numerical results suggests that the kilometric bedforms are formed by condensation and the smaller ones by sublimation. These condensation and sublimation waves are suitable markers to constrain mesoscale climate modelling in small, complex regions such as this type of crater, where topographic and/or seasonal effects can affect climate data. These waves can also be used as geomarkers on other planetary bodies where climatic conditions are not well constrained. Acknowledgments: We acknowledge PNP (Plan National de Planétologie) for founding the project “sublimation and condensation waves”. We used Planetary Data System (PDS) for observational data. References: [1] Conway et al. (2012) Icarus. [2] Brown et al. (2008) Icarus. [3] Hofstader & Murray (1990) Icarus. [4] Appéré et al. (2011) Journal of Geophysical Research. [5] Bordiec M. et al. (2020) Earth-Science Reviews, 211, 103350.[6] Forget et al. (1999). [7] Millour et al. (2018). [8] Herny et al. (2020). 7th Mars Polar Science Conf. Abstract #2099. [9] Carpy S. et al. (2022). EGU, Abstract #5998.

Sublimation combined with wind: Volatiles (N2, CH4, CO2, H20, NH3) are very common in the solar system (Fig 1). The average pressure and temperature conditions at the surface of many bodies suggest that volatile ices are stable and we thus expect that solid bedforms may form on these surfaces by either sublimation and/or condensation. These mass transfers between ice and overlying atmospheres are already known as landforms-shaping processes at different scales. These processes are very effective on the Martian North Polar Cap [2], whose spirals of the MNPC are known to be the result of sublimation on one side and condensation on the other [3-4], and as Pluto, where the Bladed Terrain Deposits are associated with sublimation of N2 and condensation of CH4 [5]. FIGURE 1 – Superimposed phase diagrams of the predominantly represented species (N2, CH4, CO2, NH3, H2O) in the Solar System in (p,T), using the Clausius-Clapeyron relationship. Scientific goal: To understand the process of material redistribution by the wind on icy planetary surfaces subject to phase changes, we propose a theoretical model coupling of flow dynamics and mass transfer and perform a linear stability analysis [6]. As done for loose bedforms, we use solid transverse bedforms as geomarkers to identify sublimation zones and to deduce erosion rate. We aim to physically and morphologically characterise these periodic waves perpendicular to the main flow over icy substrates and we are looking for analogues to assess the validity of our model before interpreting the observations on other bodies. On Earth, field analogues could be found in extreme cold and icy environment. Similar laboratory experiments are also suggested to complete the dataset. Sublimation waves analogues: We have identified two possible analogues for sublimation patterns from the literature: in the Blue Ice areas (Fig 2a) of the Antarctic ice sheets [1] and in ice caves such as the Eisriesenwelt cave (Fig 2b) in Austria [7]. We also use new measurements made in a laboratory experiment on the sublimation of CO2 ice in an atmospheric wind tunnel (Fig 2c). FIGURE 2 – Sublimation waves analogues [6]: (left: a) Blue Ice areas (middle: b) the Eisriesenwelt ice cave (right: c) CO2 ice in an atmospheric wind tunnel. In all these environments, linear and transverse bedforms appear. However, there are quite different in scales and involve different compositions of the icy substrate and the atmosphere. Despite those differences, the winds that flow on these surfaces are always turbulent and of infinite height and the environmental conditions are favorable to sublimation of ice: the surface temperatures are lower than the triple point and the partial pressure of the species is far from pressure at saturation. These sublimation waves have been classified as net ablation areas from surface energy balance. Theoretical model for redistribution processes: We consider a simple 2D case of a wavy surface of wavelength l and small amplitude with an overlying turbulent atmospheric boundary layer, of height H much larger that the wavelength. The mass transfer rate varies along the profile and has a maximum somewhere in the troughs, shifted from the crests by a phase lag. This effect allows the growth of a range of wavelengths and their migration, depending on the location of the maximum. The flow is perturbed by the topography and modify the mass transfer in turn, which may lead to the instability of such bedforms. From the stability analysis [6] we obtain 3 scaling laws: (1) the first law can predict either the friction velocity or the wind speed from a measure of the wavelength and if the viscosity is known, (2) the second law show that the migration velocity is found to scale linearly with the average value of the sublimation rates and thus depends on the kinetics of the phase transition, (3) the third law links the characteristic time of formation with the viscous length and the sublimation rate. FIGURE 3 – Model (black line), measurements (symbols) and prediction (MNPC) for sublimation waves [6]. Sublimation bedforms as geomorphic markers: The model prediction, black line (Fig 3), is superimposed on the natural terrestrial and the experimental model. This allows us to predict either the friction velocity or the wind speed from a measurement of the wavelength for the Martian Northern Polar Cap. The values predicted are in good agreement with those obtained by the martian climate database at the same place where these sublimation waves have been detected, and those both for the frictional velocities and the wind speeds. Conclusion: We propose a formation model for the sublimation waves by coupling mass waste with the hydrodynamic instability of the overlaying turbulent flow, in the case where the flow heigh is larger than the wavelength. The subjacent objective was to determine if terrestrial analogues exist or some experimental facilities could be used. We show it is possible to link the dimension of the sublimation waves to their environment and produce three scaling laws that links the geomorphological characteristics of these bedforms (wavelengths, migration, formation time) and the flow (velocity, viscosity, flow height). The adequacy between the observations/experiments and our model allows us to validate these environments as terrestrial/experimental analogues of sublimation waves. New experiments could thus be designed in controlled atmospheric wind tunnel like Aarhus wind tunnel, Denmark to explore controlling parameters. Acknowledgments: Plan National de Planétologie. References: [1] Bintanja R. (1999) Reviews of Geophysics, 37(3) :337–359 [2] Herny C. et al. (2014) EPSL, 4013, 56-66. [3] Howard A. D. (2000)Icarus, 144(2) :267–288. [4] Smith I. et al (2010) Nature, 465(7297). [5] Moore et al (2017) Icarus, 287 :320–333, 2017. [6] Bordiec M. et al. (2020) Earth & Sci. Reviews. Sci., 103350. [7] Obleitner and Spötl, (2011) Cryosphere, 5(1) :245–25.

The specific heat of phonon cavities is investigated in order to analyze the effect of phonon confinement on thermodynamic properties. The specific heat of freestanding very thin SiN membranes in the low-dimensional limit is measured down to very low temperatures (from 6 K to 50 mK). In the whole temperature range, we measured an excess specific heat orders of magnitude bigger than the typical value observed in amorphous solids. Below 1 K, a crossover in cp to a lower power law is seen, and the value of the specific heat of thinner membranes becomes larger than that of thicker ones demonstrating a significant contribution coming from the surface. We show that this high value of the specific heat cannot be explained by the sole contribution of two-dimensional phonon modes (Lamb waves). The excess specific heat, being thickness dependent, could come from tunneling two-level systems that form in low-density regions of amorphous solids located on the surfaces. We also show that the specific heat is strongly tuned by the internal stress of the membrane by orders of magnitude, giving high values, making low-stress SiN very efficient for energy storage at very low temperature. peerReviewed

During the 20th century, the last glaciation in the Massif Central, France, was documented by several geomorphologists based on intensive field investigations. Seven paleoglaciers were identified, ranging from cirque glaciers in the Velay (4 km2) to coalescent ice caps (3500 km2) covering the Cantal, Cézallier and Monts Dore mountains. The associated glacial chronology relied mainly on morphostratigraphic observations and indirect age determination, such as radiocarbon ages from organic sediments in freshly deglaciated landscapes. Our study aims to improve this incomplete glacial chronology in order to reconstruct the paleoclimatic conditions that controlled these glaciations. We focused on the Cantal Mounts (45.0°N, 2.7°E) and Aubrac Mounts (44.6°N, 3.0°E) in the western Massif Central. Glacial landform assemblages and associated morphostratigraphy were re-investigated in the field and updated by new observations, e.g. the identification of end moraines. Three glacial stadials were recognized: the Local Last Glacier Maximum (LLGM) and two glacier re-advances. A final cirque glaciation was identified in the Cantal. We obtained an original set of exposure ages from erratic boulders and depth profiles in till at key sites using in situ produced Terrestrial Cosmogenic Nuclides 10Be, 26Al and 36Cl. Our results show comparable glacial chronologies for the Cantal ice cap and the Aubrac plateau icefield suggesting that the majority of glacial landforms and sediments were deposited during the global Last Glacial Maximum (LGM; 26.5 to 19.5 ka) and the Last Glacial-to-Interglacial Transition (LGIT; 19.5 to 11.7 ka). Advances and retreats of these two paleoglaciers were synchronous with regional climatic events reported from independant paleoclimatic proxies, especially the Heinrich Stadial 2 and the Heinrich Stadial 1. We combined two glacier modelling procedures, the theoretical glacier surface profiles and the Positive Degree-Day method, to constrain the paleoclimatic conditions (i.e. paleotemperatures and paleoprecipitations) that controlled these glacial fluctuations. The results showed changes between past and current climatic gradients with a probable enhancement of southerly moisture advection from the Mediterranean during the Heinrich Stadial 2 and drier conditions during the Heinrich Stadial 1.

Observation and modelling have long contributed to associate surging and streaming of glaciers with glacier thermal regime, variations in meltwater availability and pressure and mechanical coupling at their beds. Using experimental modelling and palaeoglaciological mapping, we explore how the development of subglacial drainage landsystems controls variations in drainage efficiency and ice flow velocities for terrestrial-based ice lobes on flat horizontal beds. We observe that the achievement or not of efficient subglacial drainage landsystems determines the fast-flow regime of these glaciers. In the surge regime, rapid increase of drainage efficiency through development of tunnel valleys and their tributaries reduces the duration of ice flow speed-up events by lowering water pressures and increasing ice-bed coupling. Tunnel valleys connected to ice lobe margins, submarginal thrust moraines, reduced ice lobe extensions and ephemeral shear margins are the most distinctive characteristics of this regime. In the stream regime, disconnected channels of smaller dimensions develop, but they are unable to evacuate all the meltwater: this prolonged drainage inefficiency leads to sustained high ice flow velocity and steady shear margins. Small and rectilinear meltwater channels devoid of tributaries, often disconnected from ice lobe margins and lineation swarms are diagnostic of this regime.

Aeolian processes are at the origin of a large number of bedforms, which are topographic patterns that are spatially organised in a periodic manner and that can be observed both on Earth and on other planetary bodies. Two main categories of bedforms can be distinguished: (i) "loose" bedforms, generated on a bed of mobilisable grains by erosion, transport and deposition and (ii) "solid" bedforms, not induced by grain transport but by mass transfers such as ice sublimation or condensation under turbulent winds. Although the mechanisms involved in the growth of some solid bedforms have been studied (penitents, sublimation ripples, …), the subject remains largely less treated to date than loose bedforms, partly because of the lack of terrestrial environments favourable to sublimation. Comparison with other planetary environments has opened up new horizons for understanding these objects and the aeolian environments in which they develop.Among these bedforms, sublimation waves are transverse linear waveforms: regular and parallel ridges oriented perpendicular to the main direction of the turbulent flow interacting with the ice surface. The height of the flow is greater than their wavelength. The emergence of the bedforms is due to a hydrodynamic instability mechanism of the band-pass type which allows their growth. Our theoretical linear stability study shows that this instability appears in the laminar-turbulent transition regime, based on the near-wall Reynolds number, only if the modulation of the viscous sublayer by an effective longitudinal pressure gradient is taken into account in the turbulence model enabling to reproduce the feedback of the topography on the flow.These sublimation waves have been observed in different environments [Bordiec et al, 2020], by sublimation and diffusion of (a) water ice in air, in Antarctica or Ice caves, (b) water ice in CO2 atmosphere, on some areas of the northern polar cap of Mars, (c) and experimentally with CO2 ice in air. They are also observed on a Martian H2O glacier near the northern polar cap of Mars [Collet et al, in prep.], however, in the latter case, these sublimation waves are observed on larger icy waves. How can this difference in scale between two wavelengths be explained? What is their size selection process? To answer these questions, we investigate in our theoretical study the dependence on environmental conditions through (i) the fluid properties (wind speed, fluid viscosity) (ii) the direction of the transfer (sublimation or condensation) and (iii) the height of the flow in front of the wavelength (infinite or finite).