Gridmapping the northern plains of Mars: Geomorphological, Radar and Water-Equivalent Hydrogen results from Arcadia Plantia

A project of mapping ice-related landforms was undertaken to understand the role of sub-surface ice in the northern plains. This work is the first continuous regional mapping from CTX (“ConTeXt Camera”, 6 m/pixel; Malin et al., 2007) imagery in Arcadia Planitia along a strip 300 km across stretching from 30°N to 80°N centred on the 170° West line of longitude. The distribution and morphotypes of these landforms were used to understand the permafrost cryolithology. The mantled and textured signatures occur almost ubiquitously between 35° N and 78° N and have a positive spatial correlation with inferred ice stability based on thermal modelling, neutron spectroscopy and radar data. The degradational features into the LDM (Latitude Dependent Mantle) include pits, scallops and 100 m polygons and provide supporting evidence for sub-surface ice and volatile loss between 35-70° N in Arcadia with the mantle between 70-78° N appearing much more intact. Pitted terrain appears to be much more pervasive in Arcadia than in Acidalia and Utopia suggesting that the Arcadia study area had more wide-spread near-surface sub-surface ice, and thus was more susceptible to pitting, or that the ice was less well-buried by sediments. Correlations with ice stability models suggest that lack of pits north of 65-70° N could indicate a relatively young age (~1Ma), however this could also be explained through regional variations in degradation rates. The deposition of the LDM is consistent with an airfall hypothesis however there appears to be substantial evidence for fluvial processes in southern Arcadia with older, underlying processes being equally dominant with the LDM and degradation thereof in shaping the landscape

Formation and evolution of periglacial landforms under global warming : comparison Earth-Mars

Sur Terre, les régions périglaciaires ayant un pergélisol riche en glace peuvent enregistrer les changements climatiques globaux. Ce pergélisol contenant 50-80 % de glace en volume s'est formé lors des grandes périodes glaciaires du Pléistocène. Par la suite, ce pergélisol riche en glace a subi une dégradation intense lors de réchauffements climatiques globaux au début de la période interglaciaire de l'Holocène.La planète Mars comporte un pergélisol à l'échelle planétaire dont la formation serait associée à des changements climatiques globaux provoqués par des variations chaotiques de son orbite durant les derniers millions d'années. La région d'Utopia Planitia située dans les moyennes latitudes nord de Mars présente différents modelés de surface (“ scalloped depressions ”, polygones, cavités à la jonction des polygones) interprétés comme s'étant formés à partir d'un pergélisol contenant potentiellement une grande quantité de glace. De la même manière que sur Terre, ce pergélisol a pu enregistrer les derniers changements climatiques globaux survenus sur Mars.Cette thèse propose d'étudier comparativement l'impact des changements climatiques sur le paysage des régions périglaciaires sur Terre et sur Mars. Dans ce but, nous avons conduit des études sur le terrain des processus et des modelés périglaciaires en Yakoutie Centrale (Sibérie) et dans le delta du Mackenzie (Canada) associées à une étude géomorphologique à haute résolution des modelés d'Utopia Planitia.Notre étude montre que l'ensemble des modelés d'Utopia Planitia est similaire en morphologie, taille et association spatiale à celui de la Yakoutie Centrale et du delta du Mackenzie (lacs thermokarstiques, polygones, mares à la jonction des polygones) indiquant que la région présenterait un pergélisol riche en glace. Le pergélisol serait composé de sédiments stratifiés et dont l'âge de formation minimale est estimé entre ~ 5 et 100 Ma. Le pergélisol contiendrait un volume de glace important (≥ 50 % en volume) sur une épaisseur de ~ 70 m.De part ses caractéristiques, ce pergélisol aurait une origine syngénétique : sa formation serait le résultat d'une accumulation importante de sédiments au sein du bassin d'Utopia Planitia sous des conditions froides permettant le gel in-situ des sédiments. Les sédiments peuvent avoir été déposés par des vallées de débâcles provenant d'Elysium Mons et/ou par une activité éolienne importante. Par ailleurs, la formation synchrone d'une calotte de glace régionale près d'Utopia Planitia lors de périodes de moyenne obliquité (~ 35°) de Mars pourrait avoir induit un dépôt éolien préférentiel dans Utopia Planitia.Par la suite, le pergélisol riche en glace aurait subi une dégradation régionale importante entre ~ 5 et 10 Ma. Ce thermokarst aurait été déclenché par une insolation accrue lors de périodes de haute obliquité (~ 45°) de Mars. L'augmentation des températures aurait provoqué une déstabilisation thermique du pergélisol entraînant une sublimation de la glace, modifiant profondément le paysage de la région.Ainsi, les variations importantes de l'obliquité de Mars ont généré des changements climatiques globaux qui ont permis la formation et la dégradation du pergélisol riche en glace d'Utopia Planitia entre ~ 5 et 10 Ma.On Earth, periglacial regions where an ice-rich permafrost is present provide a record of global climate changes. For example, the ice-rich permafrost (50-80 % of ice by volume) that occurs in Central Yakutia (Siberia) and in the Mackenzie River Delta (Canada) was formed during the glacial periods of the Pleistocene. This permafrost was subsequently degraded during global warming at the early Holocene interglacial period.Global and possibly ice-rich permafrost occurs on Mars as well. It is thought to be the product of obliquity-driven and relatively recent global climate change (i.e. dozens of Ma). Utopia Planitia, situated in the northern mid-latitudes, is dotted with possible periglacial landforms (scalloped depressions, polygons and polygon-junction pits) that could indicate the presence of an ice-rich permafrost. Similarly to Earth, this permafrost could be marker of recent global climate changes.This thesis focuses on the impact of global climate changes on the periglacial regions of Earth and Mars. With this aim in view, we conducted (i) field studies of the periglacial processes and landforms in the Central Yakutia (Siberia) and in the Mackenzie River Delta (Canada) and, (ii) a geomorphological study (based on high-resolution images) of the putative-periglacial landforms of Utopia Planitia.Our study shows that the assemblage of landforms in Utopia Planitia share traits of form, scale and spatial association with the landforms of the Central Yakutia and of the Mackenzie Delta (thermokarst lakes, polygons and polygon-junction ponds) indicating that Utopia Planitia has an ice-rich permafrost. The permafrost is composed of stratified sediments ~ 70 m thick with a high ice-content (possibly ≥ 50 % by volume).The permafrost appears to have a syngenetic origin: it was formed by an accumulation of sediments in the basin of Utopia Planitia under cold climate conditions that leaded to the in-situ freezing of the sediments. The sediments could have been deposited by outflow valleys from Elysium Mons and/or by an eolian activity. With regard to the latter, the synchronous formation of a possible regional ice-sheet near Utopia Planitia during medium-obliquity (~ 35°) periods of Mars could have induced a preferential eolian deposition in Utopia Planitia.Subsequently, the ice-rich permafrost was regionally degraded between ~ 5 and 10 Ma. The thermokarst was triggered by an increase of insolation during high-obliquity (~ 45°) periods of Mars. The increase of temperature caused the thermal destabilization of the permafrost inducing the sublimation of ground-ice, deeply modifying the landscape.Thus, important obliquity variations of Mars caused global climate changes that could have induced the formation and the degradation of the ice-rich permafrost of Utopia Planitia between ~ 5 and 10 Ma

Formation et évolution des structures périglaciaires en contexte de réchauffement climatique : comparaison Terre-Mars

On Earth, periglacial regions where an ice-rich permafrost is present provide a record of global climate changes. For example, the ice-rich permafrost (50-80 % of ice by volume) that occurs in Central Yakutia (Siberia) and in the Mackenzie River Delta (Canada) was formed during the glacial periods of the Pleistocene. This permafrost was subsequently degraded during global warming at the early Holocene interglacial period.Global and possibly ice-rich permafrost occurs on Mars as well. It is thought to be the product of obliquity-driven and relatively recent global climate change (i.e. dozens of Ma). Utopia Planitia, situated in the northern mid-latitudes, is dotted with possible periglacial landforms (scalloped depressions, polygons and polygon-junction pits) that could indicate the presence of an ice-rich permafrost. Similarly to Earth, this permafrost could be marker of recent global climate changes.This thesis focuses on the impact of global climate changes on the periglacial regions of Earth and Mars. With this aim in view, we conducted (i) field studies of the periglacial processes and landforms in the Central Yakutia (Siberia) and in the Mackenzie River Delta (Canada) and, (ii) a geomorphological study (based on high-resolution images) of the putative-periglacial landforms of Utopia Planitia.Our study shows that the assemblage of landforms in Utopia Planitia share traits of form, scale and spatial association with the landforms of the Central Yakutia and of the Mackenzie Delta (thermokarst lakes, polygons and polygon-junction ponds) indicating that Utopia Planitia has an ice-rich permafrost. The permafrost is composed of stratified sediments ~ 70 m thick with a high ice-content (possibly ≥ 50 % by volume).The permafrost appears to have a syngenetic origin: it was formed by an accumulation of sediments in the basin of Utopia Planitia under cold climate conditions that leaded to the in-situ freezing of the sediments. The sediments could have been deposited by outflow valleys from Elysium Mons and/or by an eolian activity. With regard to the latter, the synchronous formation of a possible regional ice-sheet near Utopia Planitia during medium-obliquity (~ 35°) periods of Mars could have induced a preferential eolian deposition in Utopia Planitia.Subsequently, the ice-rich permafrost was regionally degraded between ~ 5 and 10 Ma. The thermokarst was triggered by an increase of insolation during high-obliquity (~ 45°) periods of Mars. The increase of temperature caused the thermal destabilization of the permafrost inducing the sublimation of ground-ice, deeply modifying the landscape.Thus, important obliquity variations of Mars caused global climate changes that could have induced the formation and the degradation of the ice-rich permafrost of Utopia Planitia between ~ 5 and 10 Ma.Sur Terre, les régions périglaciaires ayant un pergélisol riche en glace peuvent enregistrer les changements climatiques globaux. Ce pergélisol contenant 50-80 % de glace en volume s'est formé lors des grandes périodes glaciaires du Pléistocène. Par la suite, ce pergélisol riche en glace a subi une dégradation intense lors de réchauffements climatiques globaux au début de la période interglaciaire de l'Holocène.La planète Mars comporte un pergélisol à l'échelle planétaire dont la formation serait associée à des changements climatiques globaux provoqués par des variations chaotiques de son orbite durant les derniers millions d'années. La région d'Utopia Planitia située dans les moyennes latitudes nord de Mars présente différents modelés de surface (“ scalloped depressions ”, polygones, cavités à la jonction des polygones) interprétés comme s'étant formés à partir d'un pergélisol contenant potentiellement une grande quantité de glace. De la même manière que sur Terre, ce pergélisol a pu enregistrer les derniers changements climatiques globaux survenus sur Mars.Cette thèse propose d'étudier comparativement l'impact des changements climatiques sur le paysage des régions périglaciaires sur Terre et sur Mars. Dans ce but, nous avons conduit des études sur le terrain des processus et des modelés périglaciaires en Yakoutie Centrale (Sibérie) et dans le delta du Mackenzie (Canada) associées à une étude géomorphologique à haute résolution des modelés d'Utopia Planitia.Notre étude montre que l'ensemble des modelés d'Utopia Planitia est similaire en morphologie, taille et association spatiale à celui de la Yakoutie Centrale et du delta du Mackenzie (lacs thermokarstiques, polygones, mares à la jonction des polygones) indiquant que la région présenterait un pergélisol riche en glace. Le pergélisol serait composé de sédiments stratifiés et dont l'âge de formation minimale est estimé entre ~ 5 et 100 Ma. Le pergélisol contiendrait un volume de glace important (≥ 50 % en volume) sur une épaisseur de ~ 70 m.De part ses caractéristiques, ce pergélisol aurait une origine syngénétique : sa formation serait le résultat d'une accumulation importante de sédiments au sein du bassin d'Utopia Planitia sous des conditions froides permettant le gel in-situ des sédiments. Les sédiments peuvent avoir été déposés par des vallées de débâcles provenant d'Elysium Mons et/ou par une activité éolienne importante. Par ailleurs, la formation synchrone d'une calotte de glace régionale près d'Utopia Planitia lors de périodes de moyenne obliquité (~ 35°) de Mars pourrait avoir induit un dépôt éolien préférentiel dans Utopia Planitia.Par la suite, le pergélisol riche en glace aurait subi une dégradation régionale importante entre ~ 5 et 10 Ma. Ce thermokarst aurait été déclenché par une insolation accrue lors de périodes de haute obliquité (~ 45°) de Mars. L'augmentation des températures aurait provoqué une déstabilisation thermique du pergélisol entraînant une sublimation de la glace, modifiant profondément le paysage de la région.Ainsi, les variations importantes de l'obliquité de Mars ont généré des changements climatiques globaux qui ont permis la formation et la dégradation du pergélisol riche en glace d'Utopia Planitia entre ~ 5 et 10 Ma

Formation et évolution des structures périglaciaires en contexte de réchauffement climatique : comparaison Terre-Mars

On Earth, periglacial regions where an ice-rich permafrost is present provide a record of global climate changes. For example, the ice-rich permafrost (50-80 % of ice by volume) that occurs in Central Yakutia (Siberia) and in the Mackenzie River Delta (Canada) was formed during the glacial periods of the Pleistocene. This permafrost was subsequently degraded during global warming at the early Holocene interglacial period.Global and possibly ice-rich permafrost occurs on Mars as well. It is thought to be the product of obliquity-driven and relatively recent global climate change (i.e. dozens of Ma). Utopia Planitia, situated in the northern mid-latitudes, is dotted with possible periglacial landforms (scalloped depressions, polygons and polygon-junction pits) that could indicate the presence of an ice-rich permafrost. Similarly to Earth, this permafrost could be marker of recent global climate changes.This thesis focuses on the impact of global climate changes on the periglacial regions of Earth and Mars. With this aim in view, we conducted (i) field studies of the periglacial processes and landforms in the Central Yakutia (Siberia) and in the Mackenzie River Delta (Canada) and, (ii) a geomorphological study (based on high-resolution images) of the putative-periglacial landforms of Utopia Planitia.Our study shows that the assemblage of landforms in Utopia Planitia share traits of form, scale and spatial association with the landforms of the Central Yakutia and of the Mackenzie Delta (thermokarst lakes, polygons and polygon-junction ponds) indicating that Utopia Planitia has an ice-rich permafrost. The permafrost is composed of stratified sediments ~ 70 m thick with a high ice-content (possibly ≥ 50 % by volume).The permafrost appears to have a syngenetic origin: it was formed by an accumulation of sediments in the basin of Utopia Planitia under cold climate conditions that leaded to the in-situ freezing of the sediments. The sediments could have been deposited by outflow valleys from Elysium Mons and/or by an eolian activity. With regard to the latter, the synchronous formation of a possible regional ice-sheet near Utopia Planitia during medium-obliquity (~ 35°) periods of Mars could have induced a preferential eolian deposition in Utopia Planitia.Subsequently, the ice-rich permafrost was regionally degraded between ~ 5 and 10 Ma. The thermokarst was triggered by an increase of insolation during high-obliquity (~ 45°) periods of Mars. The increase of temperature caused the thermal destabilization of the permafrost inducing the sublimation of ground-ice, deeply modifying the landscape.Thus, important obliquity variations of Mars caused global climate changes that could have induced the formation and the degradation of the ice-rich permafrost of Utopia Planitia between ~ 5 and 10 Ma.Sur Terre, les régions périglaciaires ayant un pergélisol riche en glace peuvent enregistrer les changements climatiques globaux. Ce pergélisol contenant 50-80 % de glace en volume s'est formé lors des grandes périodes glaciaires du Pléistocène. Par la suite, ce pergélisol riche en glace a subi une dégradation intense lors de réchauffements climatiques globaux au début de la période interglaciaire de l'Holocène.La planète Mars comporte un pergélisol à l'échelle planétaire dont la formation serait associée à des changements climatiques globaux provoqués par des variations chaotiques de son orbite durant les derniers millions d'années. La région d'Utopia Planitia située dans les moyennes latitudes nord de Mars présente différents modelés de surface (“ scalloped depressions ”, polygones, cavités à la jonction des polygones) interprétés comme s'étant formés à partir d'un pergélisol contenant potentiellement une grande quantité de glace. De la même manière que sur Terre, ce pergélisol a pu enregistrer les derniers changements climatiques globaux survenus sur Mars.Cette thèse propose d'étudier comparativement l'impact des changements climatiques sur le paysage des régions périglaciaires sur Terre et sur Mars. Dans ce but, nous avons conduit des études sur le terrain des processus et des modelés périglaciaires en Yakoutie Centrale (Sibérie) et dans le delta du Mackenzie (Canada) associées à une étude géomorphologique à haute résolution des modelés d'Utopia Planitia.Notre étude montre que l'ensemble des modelés d'Utopia Planitia est similaire en morphologie, taille et association spatiale à celui de la Yakoutie Centrale et du delta du Mackenzie (lacs thermokarstiques, polygones, mares à la jonction des polygones) indiquant que la région présenterait un pergélisol riche en glace. Le pergélisol serait composé de sédiments stratifiés et dont l'âge de formation minimale est estimé entre ~ 5 et 100 Ma. Le pergélisol contiendrait un volume de glace important (≥ 50 % en volume) sur une épaisseur de ~ 70 m.De part ses caractéristiques, ce pergélisol aurait une origine syngénétique : sa formation serait le résultat d'une accumulation importante de sédiments au sein du bassin d'Utopia Planitia sous des conditions froides permettant le gel in-situ des sédiments. Les sédiments peuvent avoir été déposés par des vallées de débâcles provenant d'Elysium Mons et/ou par une activité éolienne importante. Par ailleurs, la formation synchrone d'une calotte de glace régionale près d'Utopia Planitia lors de périodes de moyenne obliquité (~ 35°) de Mars pourrait avoir induit un dépôt éolien préférentiel dans Utopia Planitia.Par la suite, le pergélisol riche en glace aurait subi une dégradation régionale importante entre ~ 5 et 10 Ma. Ce thermokarst aurait été déclenché par une insolation accrue lors de périodes de haute obliquité (~ 45°) de Mars. L'augmentation des températures aurait provoqué une déstabilisation thermique du pergélisol entraînant une sublimation de la glace, modifiant profondément le paysage de la région.Ainsi, les variations importantes de l'obliquité de Mars ont généré des changements climatiques globaux qui ont permis la formation et la dégradation du pergélisol riche en glace d'Utopia Planitia entre ~ 5 et 10 Ma

Sub-kilometre (intra-crater) mounds in Utopia Planitia, Mars: character, occurrence and possible formation hypotheses

At the middle latitudes of Utopia Planitia (∼35–45°N; ∼65–101°E) hundreds of small-sized mounds located in sub-kilometre impact craters dot the landscape. Their shape varies from circular to crescentic and their height ranges from ∼10 to 50 m. Often, metre to decametre pitting is observed, as is metres-thick banding or stratification. Mound albedo is relatively high, i.e. ∼0.16. The plain’s terrain in the region, previously linked to the latitude-dependent mantle (LDM) of ice–dust, displays pitting and albedo similar to the small intra-crater mounds. Some workers have suggested that the mounds and the plain’s terrain share a common ice–dust origin. If so, then scrutinising the mounds could provide analogical insight on the key geological characteristics and spatial distribution of the LDM itself. Other workers have hypothesised that the mounds are eroded sedimentary landforms or periglacial mounds underlain by a perennial ice-core (closed-system pingos). In this article we develop and then discuss each of the three mound-hypotheses in a much more substantial manner than has been done hitherto. Towards this end we use high-resolution images, present a detailed regional-map of mound distribution and establish a regional platform of topographical analysis using MOLA data superposed on a large-scale CTX mosaic. Although the ice–dust hypothesis is consistent with some observations and measurements, we find that a (loess-based) sedimentary hypothesis shows greater plausibility. Of the three hypotheses evaluated, the pingo or periglacial one is the weakest

Limnological properties of thermokarst lakes in Central Yakutia sampled between 2018-2019

This dataset compiles selected limnological properties of a series of thermokarst (thaw) lakes in Central Yakutia (Eastern Siberia). These properties were measured during fall 2018 (September), winter 2019 (March-April), spring 2019 (May), and summer 2019 (August). These data span four seasons (Fall, Winter, Spring, and Summer) 2018-2019. The lake type designation is based on field observations, past radiocarbon dating of lake sediments, geochemical signatures of lake waters, and a multiple-stage development model of thermokarst lakes. Data were collected at the surface (~ 30 cm depth) from lake shores. Specific conductivity (accuracy ±1% of reading), temperature (accuracy ±0.2°C), dissolved oxygen (accuracy ±1% of reading or 1% saturation) and pH (accuracy ±0.2) were measured using a YSI Pro DSS multiprobe sensor. Water samples were collected to analyze dissolved organic carbon (DOC). Samples were filtered using baked glass fiber filters (Whatman GF/F, 0. 7µm), acidified to pH 2 with ultra-pure HCl and stored in baked glass vials. DOC concentration was measured using a TOC-5000A analyzer (Shimadzu, Japan). The quantification limit was 1 mg L-1. Above this value, the analytical uncertainty was estimated at ±0.1 mg L-1. Reference material included ION-915 ([DOC]= 1.37 ± 0.41mg C L-1) and ION 96.4 ([DOC]= 4.64 ± 0.70 mg C L-1) (Environment and Climate Change Canada, Canada)

Morphometric evidence of 3.6 Ga glacial valleys and glacial cirques in martian highlands: South of Terra Sabaea

International audienceThe climate of early Mars remains unclear and the debate is topical. Recently, climatic models have suggested a cold climate during the Noachian/Early Hesperian on Mars, which goes against the wet and warm climate often put forward. The purpose of this study is to seek geomorphologic evidence of this early cold climate. To achieve this, a step-by-step study of the geometry and morphology of several martian valleys has been done in the southern highlands. The analysis highlights the morphometric properties which enable the identification of martian glacial landscapes. We identified 100 cirques and 83 glacial valleys in two craters and on one mountain in the southern part of Terra Sabaea. The studied morphologies have the same morphometric characteristics and trends as terrestrial and martian glacial valleys and glacial cirques. In contrary, these trends are very different from those observed in fluvial valleys on Earth and on Mars. (1) The martian glacial valleys are U-shaped with a large flat floor and a V-index >0.20. While martian and terrestrial fluvial valleys are V-shaped with a V-index 1 while for fluvial valleys this ratio is ≫1. (3) Finally, the cross-sectional area and the elevation are higher for the glacial valleys compared to the fluvial ones. These glacial valleys often originate with a topographic hollow which have the same properties than terrestrial glacial cirque. The glacial landscapes identified in southern Terra Sabaea are restricted to elevations >1000 m and are dated by crater counting to be 3.6 Ga. This study strongly supports glacial processes as the origin of these valleys and cirques, and is the first morphometric evidence of glacial valleys associated with glacial cirques in the southern highlands in agreement with the climatic models. We propose that the martian climate during the late Noachian/early Hesperian was characterized by glaciated highlands at elevations >1500 m and at lower elevations where fluvial valley network has been identified (<1500 m) the climate was more temperate allowing liquid water to be stable and creating fluvial valley networks

Glacial landscape and paleoglaciation in Terra Sabaea: Evidence for a 3.6 Ga polythermal plateau ice cap

International audienceIn a previous study, we demonstrated with a comparative morphometrical analysis the first morphometric evidence of a glacial landscape composed of glacial cirques and glacial valleys in the south of Terra Sabaea at an elevation > 1000 m in two impact craters and one mountain. The purpose of this study is to use the same method to seek other geomorphologic evidence of glacial landscapes elsewhere in Terra Sabaea. Based on a comparison between current and old glacial landscapes on Earth and Mars, we identified 81 glacial valleys and possible evidence for a former plateau ice cap dated at 3.6 Ga at the highest elevation in Terra Sabaea. The identified glacial valleys have the same morphometric properties as terrestrial and martian glacial valleys with U-shaped cross-sectional profiles, a V-index >0.2, a length to with ratio >1 and a cross-sectional area to drainage area ratio four times higher than the fluvial ones. Moreover, these properties are different from terrestrial and martian fluvial valleys. We did not find well preserved glacial cirques in this area, this absence questions the origin of glacial valleys. However, the presence of an extensive flat plateau, from which the long valleys radiate, could have hosted an ancient plateau ice cap which was the source of these glacial valleys. A comparison with the Cantal and the Shaluli Shan in the southeastern Tibetan plateau on Earth reveals morphometrical similarities with our study area. In fact, long glacial valleys, originating radially from a plateau at higher elevation are characteristics of an ancient plateau ice cap. This analysis allowed us to propose a polythermal regime for martian glacial landscape, namely a cold-based ice cap except at the margin where the regime is warmed-based due to the steeper topography. This topography created shear stress which increased the heat at the base of the ice and created the outlet glacial valleys. Near the plateau, the radial valleys are U-shaped with a V-index >0.2 but downstream, to the low elevation area, these valleys become more V-shaped with a V-index around 0.1. This hypothesis is supported by the presence of an open-basin paleolake making the transition between inlet glacial valleys upstream and an outlet V-shaped valley downstream. So the morphometry of the radiating valleys suggests that liquid water played a role in the formation of this landscape

Automated Identification of Thermokarst Lakes Using Machine Learning in the Ice-Rich Permafrost Landscape of Central Yakutia (Eastern Siberia)

International audienceThe current rate and magnitude of temperature rise in the Arctic are disproportionately high compared to global averages. Along with other natural and anthropogenic disturbances, this warming has caused widespread permafrost degradation and soil subsidence, resulting in the formation of thermokarst (thaw) lakes in areas of ice-rich permafrost. These lakes are hotspots of greenhouse gas emissions (CO2 and CH4), but with substantial spatial and temporal heterogeneity across Arctic and sub-Arctic regions. In Central Yakutia (Eastern Siberia, Russia), nearly half of the landscape has been affected by thermokarst processes since the early Holocene, resulting in the formation of more than 10,000 partly drained lake depressions (alas lakes). It is not yet clear how recent changes in temperature and precipitation will affect existing lakes and the formation of new thermokarst lakes. A multi-decadal remote sensing analysis of lake formation and development was conducted for two large study areas (~1200 km2 each) in Central Yakutia. Mask Region-Based Convolutional Neural Networks (R-CNN) instance segmentation was used to semi-automate lake detection in Satellite pour l’Observation de la Terre (SPOT) and declassified US military (CORONA) images (1967–2019). Using these techniques, we quantified changes in lake surface area for three different lake types (unconnected alas lake, connected alas lake, and recent thermokarst lake) since the 1960s. Our results indicate that unconnected alas lakes are the dominant lake type, both in the number of lakes and total surface area coverage. Unconnected alas lakes appear to be more susceptible to changes in precipitation compared to the other two lake types. The majority of recent thermokarst lakes form within 1 km of observable human disturbance and their surface area is directly related to air temperature increases. These results suggest that climate change and human disturbances are having a strong impact on the landscape and hydrology of Central Yakutia. This will likely affect regional and global carbon cycles, with implications for positive feedback scenarios in a continued climate warming situation