Fluvial thermal erosion investigations along a rapidly eroding river bank: application to the Lena River (central Siberia)

In Central Yakutia, frozen river banks are affected by a combination of thermal and mechanical erosion. Exceptional bank retreat of up to 40 m per year is observed. This results from ground thawing produced by heat transfer from the ?ow of water through the frozen ground, followed by mechanical transport of the thawed sediments. A one‐dimensional model is proposed to estimate the thermal erosion ef?ciency. A test of this model is a comparison of results obtained from experiments carried out in a cold room. A hydraulic channel allows measurements of the thaw front propagation, as well as the thermal erosion rate, in simulated ground ice that is subjected to warm water ?ow. Various laboratory simulations demonstrate the validity of the mathematical model for the range of laboratory conditions. A hierarchy of parameters (Reynolds number, water and ground ice temperatures) is proposed to explain the present ef?ciency of thermal erosion along the Siberian rivers. From the characteristics of the Lena River (geometry, temperature and discharge) during the ?ood season, the erosion of banks with different ice content predicted by the model is in agreement with ?eld observations. Copyright © 2003 John Wiley & Sons, Ltd.     

River ice cover influence on sediment transportation at present and under projected hydroclimatic conditions

A large number of rivers are frozen annually, and the river ice cover has an influence on the geomorphological processes. These processes in cohesive sediment rivers are not fully understood. Therefore, this paper demonstrates the impact of river ice cover on sediment transport, i.e. turbidity, suspended sediment loads and erosion potential, compared with a river with ice‐free flow conditions. The present sediment transportation conditions during the annual cycle are analysed, and the implications of climate change on wintertime geomorphological processes are estimated. A one‐dimensional hydrodynamic model has been applied to the Kokemäenjoki River in Southwest Finland. The shear stress forces directed to the river bed are simulated with present and projected hydroclimatic conditions. The results of shear stress simulations indicate that a thermally formed smooth ice cover diminishes river bed erosion, compared with an ice‐free river with similar discharges. Based on long‐term field data, the river ice cover reduces turbidity statistically significantly. Furthermore, suspended sediment concentrations measured in ice‐free and ice‐covered river water reveal a diminishing effect of ice cover on riverine sediment load. The hydrodynamic simulations suggest that the influence of rippled ice cover on shear stress is varying. Climate change is projected to increase the winter discharges by 27–77% on average by 2070–2099. Thus, the increasing winter discharges and possible diminishing ice cover periods both increase the erosion potential of the river bed. Hence, the wintertime sediment load of the river is expected to become larger in the future. Copyright © 2015 John Wiley & Sons, Ltd.     

Improved discrimination of subglacial and periglacial erosion using 10Be concentration measurements in subglacial and supraglacial sediment load of the Bossons glacier (Mont Blanc massif,France)

Deciphering the complex interplays between climate, uplift and erosion is not straightforward and estimating present‐day erosion rates can provide useful insights. Glaciers are thought to be powerful erosional agents, but most published ‘glacial’ erosion rates combine periglacial, subglacial and proglacial erosion processes. Within a glaciated catchment, sediments found in subglacial streams originate either from glacial erosion of substratum or from the rock walls above the glacier that contribute to the supraglacial load. Terrestrial cosmogenic nuclides (TCN) are produced by interactions between cosmic ray particles and element targets at the surface of the Earth, but their concentration becomes negligible under 15 m of ice. Measuring TCN concentrations in quartz sand sampled in subglacial streams and in supraglacial channels is statistically compliant with stochastic processes (e.g. rockfalls) and may be used to discriminate subglacial and periglacial erosion. Results for two subglacial streams of the Bossons glacier (Mont Blanc massif, France) show that the proportion of sediments originating from glacially eroded bedrock is not constant: it varies from 50% to 90% (n = 6). The difference between the two streams is probably linked to the presence or absence of supraglacial channels and sinkholes, which are common features of alpine glaciers. Therefore, most of the published mean catchment glacial erosion rates should not be directly interpreted as subglacial erosion rates. In the case of catchments with efficient periglacial erosion and particularly rockfalls, the proportion of sediments in the subglacial stream originating from the supraglacial load could be considerable and the subglacial erosion rate overestimated. Here, we estimate warm‐based subglacial and periglacial erosion rates to be of the same order of magnitude: 0.39 ± 0.33 and 0.29 ± 0.17 mm a^?1, respectively. Copyright © 2015 John Wiley & Sons, Ltd.     

Sub-arctic river bank dynamics and driving processes during the open-channel flow period

There is growing concern that rapidly changing climate in high latitudes may generate significant geomorphological changes that could mobilise floodplain sediments and carbon; however detailed investigations into the bank erosion process regimes of high latitude rivers remain lacking. Here we employ a combination of thermal and RGB colour time-lapse photos in concert with water level, flow characteristics, bank sediment moisture and temperature, and topographical data to analyse river bank dynamics during the open-channel flow period (the period from the rise of the spring snowmelt flood until the autumn low flow period) for a subarctic river in northern Finland (Pulmanki River). We show how variations of bank sediment temperature and moisture affect bank erosion rates and locations, how bank collapses relate to fluvial processes, and elucidate the seasonal variations and interlinkages between the different driving processes. We find that areas with high levels of groundwater content and loose sand layers were the most prone areas for bank erosion. Groundwater seeping caused continuous erosion throughout the study period, whereas erosion by flowing river water occurred during the peak of snowmelt flood. However, erosion also occurred during the falling phase of the spring flood, mainly due to mass failures. The rising phase of the spring flood therefore did not affect the river bank as much as its peak or receding phases. This is explained because the bank is resistant to erosion due to the prevalence of still frozen and drier sediments at the beginning of the spring flood. Overall, most bank erosion and deposition occurrences were observed during the low flow period after the spring flood. This highlights that spring melt, while often delivering the highest discharges, may not be the main driver of bank erosion in sub-arctic meandering rivers. © 2019 John Wiley & Sons, Ltd.     

Hysteretic freezing characteristics of riparian peatlands in the Western Boreal Forest of Canada

Freezing characteristics were investigated for a sedge covered floating fen and spruce covered swamp located beside a shallow lake in the Western Boreal Forest of Canada. Thermal properties were measured in situ for one freeze‐thaw cycle, and for two freeze‐thaw cycles in laboratory columns. Thermal conductivity and liquid water content were related to a range of subsurface temperatures above and below the freezing thresholds, and clearly illustrate hysteresis between the freezing and thawing process. Thermal hysteresis occurs because of the large change in thermal conductivity between water and ice, high water content of the peat, and wide variation in pore sizes that govern ice formation. Field and laboratory results were combined to develop linear freezing functions, which were tested in a heat transfer model. For surface temperature boundary conditions, subsurface temperatures were simulated for the over‐winter period and compared with field measurements. Replication of the transient subsurface thermal regime required that freezing functions transition gradually from thawed to frozen state (spanning the ?0·25 to ?2 °C range) as opposed to a more abrupt step function. Subsurface temperatures indicate that the floating fen underwent complete phase change (from water to ice) and froze to approximately the same depth as lake ice thickness. Therefore, the floating fen peatland froze as a ‘shelf’ adjacent to the lake, whereas the spruce covered swamp had a higher capacity for thermal buffering, and subsurface freezing was both more gradual and limited in depth. These thermal properties, and the timing and duration of frozen state, are expected to control the interaction of water and nutrients between surface water and groundwater, which will be affected by changes in air temperature associated with global climate change. Copyright © 2009 John Wiley & Sons, Ltd.     

Quantifying glacial erosion on a limestone bed and the relevance for landscape development in the Alps

Glacial erosion is the basic process that has shaped the landscapes of the Alps. Despite intense research over centuries, and the use of various techniques, determination of glacial erosion rates remains challenging. This is not only because the location where the process occurs is almost inaccessible, but also because it is dependent on many different factors, including ice thickness and velocity, glacier thermal regime and lithology. Reported glacial erosion rates range over several orders of magnitude (0.01 to >10 mm a⁻¹). Most studies focus on crystalline bedrock, whereas few researchers have investigated glacial erosion on limestone. Here we analyse glacially polished bedrock surfaces at the recently deglaciated forefield of the Tsanfleuron glacier, Swiss Alps. The nearly horizontally bedded limestone hosts a well-developed karst system. Meltwater from the glacier drains into the subsurface within a few metres of the ice margin. By combining geomorphological mapping, measurement of cosmogenic ³⁶Cl concentrations of glacially eroded bedrock surfaces and a numerical model (MECED), we quantify at each sample location the amount of rock removed during glacier occupation. The glacial erosion rates calculated from these values range from 0 to 0.08 mm a⁻¹. These are orders of magnitude lower than values measured at comparable sites on crystalline bedrock. The high ³⁶Cl concentrations we measured show that the Tsanfleuron glacier was unable to effectively erode the gently dipping, strongly karstified limestone. We suggest that this effect may play a key role in formation and preservation over many glacial cycles of high-elevation, low-relief limestone plateaus in the Alps. © 2020 John Wiley & Sons Ltd.     

Ice cap erosion patterns from bedrock 10Be and 26Al,southeastern Tibetan Plateau

Quantifying glacial erosion contributes to our understanding of landscape evolution and topographic relief production in high altitude and high latitude areas. Combining in situ ¹⁰Be and ²⁶Al analysis of bedrock, boulder, and river sand samples, geomorphological mapping, and field investigations, we examine glacial erosion patterns of former ice caps in the Shaluli Shan of the southeastern Tibetan Plateau. The general landform pattern shows a zonal pattern of landscape modification produced by ice caps of up to 4000 km² during pre-LGM (Last Glacial Maximum) glaciations, while the dating results and landforms on the plateau surface imply that the LGM ice cap further modified the scoured terrain into different zones. Modeled glacial erosion depth of 0–0.38 m per 100 ka bedrock sample located close to the western margin of the LGM ice cap, indicates limited erosion prior to LGM and Late Glacial moraine deposition. A strong erosion zone exists proximal to the LGM ice cap marginal zone, indicated by modeled glacial erosion depth >2.23 m per 100 ka from bedrock samples. Modeled glacial erosion depths of 0–1.77 m per 100 ka from samples collected along the edge of a central upland, confirm the presence of a zone of intermediate erosion in-between the central upland and the strong erosion zone. Significant nuclide inheritance in river sand samples from basins on the scoured plateau surface also indicate restricted glacial erosion during the last glaciation. Our study, for the first time, shows clear evidence for preservation of glacial landforms formed during previous glaciations under non-erosive ice on the Tibetan Plateau. As patterns of glacial erosion intensity are largely driven by the basal thermal regime, our results confirm earlier inferences from geomorphology for a concentric basal thermal pattern for the Haizishan ice cap during the LGM. © 2018 John Wiley & Sons, Ltd.     

Modeling the Development of Ice Phenomena in Rivers as Applied to the Assessment of Probable Changes in Ice Conditions at Various Scenarios of the Future Climate

The results of investigations of the alteration in river ice regime associated with the global climate warming are presented. It is shown that a simple model based on the relationship between the dates of ice phenomena and the average air temperature for the preceding month can be used for the assessment of probable changes in ice phenomena at various scenarios of the future climate. It is found that as a rule, the allowance made for the rate of streamflow in autumn does not improve the assessment of the probable dates of river freeze-up, whereas the model of the process of river breakup allows improving the estimates of the relevant shifts in the dates.     

Interrogating the time and processes of development of the Las Liebres rock glacier,central Chilean Andes,using a numerical flow model

The Las Liebres rock glacier is a large (~2.2 km long) Andean rock glacier whose internal composition and kinematics are known from previous studies. We investigate its development by posing and testing the following null hypothesis: the rock glacier has developed from a constant supply of debris and ground ice in periglacial conditions and resulting creep of the ice‐rock mixture. A rheological model was formulated based on recent advances in the study of ice‐rock mixture rheology, and calibrated on the known surface velocities and internal composition of the rock glacier. We show that the rock glacier viscosity is inversely related to both water and debris fractions, in agreement with recent field and theoretical studies of ice‐rock mixture rheology. Taking into account the possible variations in water fraction, the model was used to estimate the time spans of development (0.91–7.11 ka), rates of rock wall retreat (0.44–4.18 mm/a), and rates of ground ice formation (0.004–0.026 m/a) for the rock glacier. These results support the null hypothesis of a periglacial origin of the Las Liebres rock glacier. Copyright © 2016 John Wiley & Sons, Ltd.     

The effect of varied dam release mechanisms and storage volume on downstream river thermal regimes

Temperature plays an essential role in the ecology and biology of aquatic ecosystems. The use of dams to store and subsequently re-regulate river flows can have a negative impact on the natural thermal regime of rivers, causing thermal pollution of downstream river ecosystems. Autonomous thermal loggers were used to measure temperature changes downstream of a large dam on the Macquarie River, in Australia’s Murray-Darling Basin to quantify the effect of release mechanisms and dam storage volume on the downstream thermal regime. The magnitude of thermal pollution in the downstream river was affected by different release mechanisms, including bottom-level outlet releases, a thermal curtain (which draws water from above the hypolimnion), and spill-way release. Dam storage volume was linked to the magnitude of thermal pollution downstream; high storage volumes were related to severe thermal suppressions, with an approximate 10 °C difference occurring when water originated from high and low storage volumes. Downstream temperatures were 8 ̶ 10 °C higher when surface releases were used via a thermal curtain and the spillway to mitigate cold water pollution that frequently occurs in the river. Demonstrating the effectiveness of engineering and operational strategies used to mitigate cold water pollution highlight their potential contribution to fish conservation, threatened species recovery and environmental remediation of aquatic ecosystems.     

Stochastic erosion of composite banks in alluvial river bends

The erosion of composite river banks is a complex process involving a number of factors including fluvial erosion, seepage erosion, and cantilever mass failure. To predict the rate of bank erosion with these complexities, a stochastic bank erosion model is suitable to define the probability distribution of the controlling variables. In this study, a bank erosion model in a river bend is developed by coupling several bank erosion processes with an existing hydrodynamic and morphological model. The soil erodibility of cohesive bank layers was measured using a submerged jet test apparatus. Seasonal bank erosion rates for four consecutive years at a bend in the Brahmaputra River, India, were measured by repeated bankline surveys. The ability of the model to predict erosion was evaluated in the river bend that displayed active bank erosion. In this study, different monsoon conditions and the distribution functions of two variables were considered in estimating the stochastic bank erosion rate: the probability of the soil erodibility and stochastic stage hydrographs for the nth return period river stage. Additionally, the influences of the deflection angle of the streamflow, longitudinal slope of river channel, and bed material size on bank erosion rate were also investigated. The obtained stochastic erosion predictions were compared with the observed distribution of the annual‐average bank erosion rate of 45 river bends in the Brahmaputra River. The developed model appropriately predicted the short‐term morphological dynamics of sand‐bed river bends with composite banks. Copyright © 2014 John Wiley & Sons, Ltd.     

Quantifying periglacial erosion: insights on a glacial sediment budget,Matanuska Glacier,Alaska

Glacial erosion rates are estimated to be among the highest in the world. Few studies have attempted, however, to quantify the flux of sediment from the periglacial landscape to a glacier. Here, erosion rates from the nonglacial landscape above the Matanuska Glacier, Alaska are presented and compare with an 8‐yr record of proglacial suspended sediment yield. Non‐glacial lowering rates range from 1·8 ± 0·5 mm yr^?1 to 8·5 ± 3·4 mm yr^?1 from estimates of rock fall and debris‐flow fan volumes. An average erosion rate of 0·08 ± 0·04 mm yr^?1 from eight convex‐up ridge crests was determined using in situ produced cosmogenic ¹⁰Be. Extrapolating these rates, based on landscape morphometry, to the Matanuska basin (58% ice‐cover), it was found that nonglacial processes account for an annual sediment flux of 2·3 ± 1·0 × 10⁶ t. Suspended sediment data for 8 years and an assumed bedload to estimate the annual sediment yield at the Matanuska terminus to be 2·9 ± 1·0 × 10⁶ t, corresponding to an erosion rate of 1·8 ± 0·6 mm yr^?1: nonglacial sources therefore account for 80 ± 45% of the proglacial yield. A similar set of analyses were used for a small tributary sub‐basin (32% ice‐cover) to determine an erosion rate of 12·1 ± 6·9 mm yr^?1, based on proglacial sediment yield, with the nonglacial sediment flux equal to 10 ± 7% of the proglacial yield. It is suggested that erosion rates by nonglacial processes are similar to inferred subglacial rates, such that the ice‐free regions of a glaciated landscape contribute significantly to the glacial sediment budget. The similar magnitude of nonglacial and glacial rates implies that partially glaciated landscapes will respond rapidly to changes in climate and base level through a rapid nonglacial response to glacially driven incision. Copyright © 2009 John Wiley & Sons, Ltd.     

Water temperature dynamics in High Arctic river basins

Despite the high sensitivity of polar regions to climate change and the strong influence of temperature upon ecosystem processes, contemporary understanding of water temperature dynamics in Arctic river systems is limited. This research gap was addressed by exploring high‐resolution water column thermal regimes for glacier‐fed and non‐glacial rivers at eight sites across Svalbard during the 2010 melt season. Mean water column temperatures in glacier‐fed rivers (0.3–3.2 °C) were lowest and least variable near the glacier terminus but increased downstream (0.7–2.3 °C km^–1). Non‐glacial rivers, where discharge was sourced primarily from snowmelt runoff, were warmer (mean: 2.9–5.7 °C) and more variable, indicating increased water residence times in shallow alluvial zones and increased potential for atmospheric influence. Mean summer water temperature and the magnitude of daily thermal variation were similar to those of some Alaskan Arctic rivers but low at all sites when compared with alpine glacierized environments at lower latitudes. Thermal regimes were correlated strongly (p < 0.01) with incoming short‐wave radiation, air temperature, and river discharge. Principal drivers of thermal variability were inferred to be (i) water source (i.e. glacier melt, snowmelt, groundwater); (ii) exposure time to the atmosphere; (iii) prevailing meteorological conditions; (iv) river discharge; (v) runoff interaction with permafrost and buried ice; and (vi) basin‐specific geomorphological features (e.g. channel morphology). These results provide insight into the potential changes in high‐latitude river systems in the context of projected warming in polar regions. We hypothesize that warmer and more variable temperature regimes may prevail in the future as the proportion of bulk discharge sourced from glacial meltwater declines and rivers undergo a progressive shift towards snow water and groundwater sources. Importantly, such changes could have implications for aquatic species diversity and abundance and influence rates of ecosystem functioning in high‐latitude river systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Slope failures and erosion rates on a glacierized high‐mountain face under climatic changes

In this study, rapid topographic changes and increased erosion rates caused by massive slope failures in a glacierized and permafrost‐affected high‐mountain face were investigated with respect to the current climatic change. The study was conducted at one of the highest periglacial rock faces in the European Alps, the east face of Monte Rosa, Italy. Pronounced changes in ice cover and repeated rock and ice avalanche events have been documented in this rock wall since around 1990. The performed multi‐temporal comparison of high‐resolution digital terrain models (DTMs) complemented by detailed analyses of repeat photography represents a unique assessment of topographic changes and slope failures over half a century and reveals a total volume loss in bedrock and steep glaciers in the central part of the face of around 25 × 10⁶ m³ between 1988 and 2007. The high rock and ice avalanche activity translates into an increase in erosion rates of about one order of magnitude during recent decades. The study indicates that changes in atmospheric temperatures and connected changes in ice cover can induce slope destabilization in high‐mountain faces. Analyses of temperature data show that the start of the intense mass movement activity coincided with increased mean annual temperatures in the region around 1990. However, once triggered, mass movement activity seems to be able to proceed in a self‐reinforcing cycle, whereby single mass movement events might be strongly influenced by short‐term extreme temperature events. The investigations suggest a strong stability coupling between steep glaciers and underlying bedrock, as most bedrock instabilities are located in areas where surface ice has disappeared recently and the failure zones are frequently spatially correlated and often develop from lower altitudes progressively upwards. Copyright © 2013 John Wiley & Sons, Ltd.     

Physical modelling of fault scarp degradation under freeze–thaw cycles

Physical modelling has been developed in order to simulate the effects of periglacial erosion processes on the degradation of slopes and scarps. Data from 41 experimental freeze–thaw cycles are presented. They attest to the efficiency of periglacial processes that control both erosion and changes in scarp morphology: (i) cryoexpulsion leads to an increase of scarp surface roughness and modifies significantly the internal structure of the active layer; (ii) combined effects of frost creep and gelifluction lead to slow and gradual downslope displacements of the active layer (0·3 cm/cycle); (iii) debris flows are associated with the most significant changes in scarp morphology and are responsible for the highest rate of scarp erosion; (iv) quantification of the erosion rate gives values close to 1 cm³ cm^?2 for 41 freeze–thaw cycles. These experimental results are consistent with field data acquired along the La Hague fault scarp (Normandy, France) where an erosion rate of 4·6 ± 1 m³ m^?2 per glacial stage has been computed from the volume of natural slope deposits stored during the Weichselian glacial stage. These results show that moist periglacial erosion processes could lead to an underestimation of Plio‐Quaternary deformation in the mid‐latitudes. Copyright © 2006 John Wiley & Sons, Ltd.     

A laboratory simulation of rock breakdown due to freeze-thaw in a maritime Antarctic environment

Results of freeze-thaw simulations on three large blocks of quartz-micaschist are presented. Three types of water to ice phase change were identified from temperature and ultrasonic measurements. It is suggested that the type of phase change results from a particular combination of rock moisture content, solute concentration, freeze amplitude, and rate of fall of temperature. The temperature at which ice thawed inside the rock (?0.7 to ?1.9°C) was also found, and this indicates the possibility of freeze-thaw effects without positive temperatures. Approximately 80 per cent of the water that will freeze under natural conditions, in the Maritime Antarctic environment under study, appears to have done so by ?6°.     

Mountain permafrost dynamics within a recently exposed glacier forefield inferred by a combined geomorphological,geophysical and photogrammetrical approach

Geomorphological observations, geoelectrical soundings and photogrammetric measurements of surface movement on the Muragl glacier forefield were used to obtain an integrative analysis of a highly complex glacial and periglacial landform consisting of a push moraine, creeping permafrost and permafrost‐free glacial till in close proximity. Electrical resistivity tomography is considered as an important multifunctional geophysical method for research in periglacial permafrost related environments. Joint application with measurements of surface displacements offers a promising tool for investigating periglacial landforms related to ice‐rich permafrost for a more comprehensive characterization of permafrost characteristics and geomorphological interpretation of periglacial morphodynamics. The patchy permafrost distribution pattern described in this paper is determined by several factors, including the sediment characteristics, the snow cover distribution and duration, the aspect and the former glacier distribution and thermal regime. Recent and modern permafrost dynamics within the glacier forefield comprise aggradation, degradation and permafrost creep. Copyright © 2007 John Wiley & Sons, Ltd.     

Sensitivity of the multiannual thermal dynamics of a deep pre‐alpine lake to climatic change

The study of the multiannual thermal dynamics of Lake Iseo, a deep lake in the Italian pre‐alpine area, is presented. Interflow was found to be the dominant river entrance mode, suggesting future susceptibility of the lake thermal structure to the overall effects of climate change expected in the upstream alpine watershed. A lake model employed the results of a long‐term hydrologic model to simulate the effects of a climate change scenario on the lake's thermal evolution for the period 2012–2050. The model predicts an overall average increase in the lake water temperature of 0.012 °C/year and a reinforced Schmidt thermal stability of the water column in the winter up to 800 J/m². Both these effects may further hinder the deep circulation process, which is vital for the oxygenation of deep water. Copyright © 2014 John Wiley & Sons, Ltd.     

T‐NET,a dynamic model for simulating daily stream temperature at the regional scale based on a network topology

Currently, the distribution areas of aquatic species are studied by using air temperature as a proxy of water temperature, which is not available at a regional scale. To simulate water temperature at a regional scale, a physically based model using the equilibrium temperature concept and including upstream‐downstream propagation of the thermal signal is proposed. This model, called Temperature‐NETwork (T‐NET), is based on a hydrographical network topology and was tested at the Loire basin scale (10⁵ km²). The T‐NET model obtained a mean root mean square error of 1.6 °C at a daily time step on the basis of 128 water temperature stations (2008–2012). The model obtained excellent performance at stations located on small and medium rivers (distance from headwater <100 km) that are strongly influenced by headwater conditions (median root mean square error of 1.8 °C). The shading factor and the headwater temperature were the most important variables on the mean simulated temperature, while the river discharge influenced the daily temperature variation and diurnal amplitude. The T‐NET model simulates specific events, such as temperature of the Loire during the floods of June 1992 and the thermal regime response of streams during the heatwave of August 2003, much more efficiently than a simple point‐scale heat balance model. The T‐NET model is very consistent at a regional scale and could easily be transposed to changing forcing conditions and to other catchments. Copyright © 2016 John Wiley & Sons, Ltd.     

Cryologic continuum of a steep watershed

Ice processes taking place in steep channels are sensitive to the thermal and hydrological regimes of upstream reaches and tributaries as well as to the local channel morphology. This work presents freezeup, mid‐winter, and breakup data from four channels of increasing order located in a cold temperate watershed during the winter 2010–2011. From headwater channels to the main drainage system, water temperature, ice coverage, and ice processes are reported and related to weather conditions and to channel characteristics. Headwater channels only formed ephemeral ice features, and their water temperature reached as much as 4 °C in mid‐winter. On the other hand, larger channels formed impressively large ice dams, some of them reaching 2 m in height. The development of a suspended ice cover partially insulated the channels; as a result, water temperatures remained above 0 °C even for air temperatures well below freezing. This work presents steep channels ice processes that have not been described in previous publications. The concept of a watershed cryologic continuum (WCC) is developed from the data collected at each channel order. This concept emphasizes the feedback loops that exist between morphology, hydrology, heat, and ice processes in a given watershed and can lead to a better understanding of ice processes taking place at any channel location within that watershed. The WCC can also contribute in improving our understanding of the impacts of climate change on the cryologic and thermal regimes of steep channels. Copyright © 2012 John Wiley & Sons, Ltd.