Thin Ice Research Articles

The Best of Both Worlds: Connecting Remote Sensing and Arctic Communities for Safe Sea Ice Travel


 Northern communities are increasingly interested in technology that provides information about the sea ice environment for travel purposes. Synthetic aperture radar (SAR) remote sensing is widely used to observe sea ice independently of sunlight and cloud cover, however, access to SAR in northern communities has been limited. This study 1) defines the sea ice features that influence travel for two communities in the Western Canadian Arctic, 2) identifies the utility of SAR for enhancing mobility and safety while traversing environments with these features, and 3) describes methods for sharing SAR-based maps. Three field seasons (spring and fall 2017 and spring 2018) were used to engage residents in locally guided research, where applied outputs were evaluated by community members. We found that SAR image data inform and improve sea ice safety, trafficability, and education. Information from technology is desired to complement Inuit knowledge-based understanding of sea ice features, including surface roughness, thin sea ice, early and late season conditions, slush and water on sea ice, sea ice encountered by boats, and ice discontinuities. Floe edge information was not a priority. Sea ice surface roughness was identified as the main condition where benefits to trafficability from SAR-based mapping were regarded as substantial. Classified roughness maps are designed using thresholds representing domains of sea ice surface roughness (smooth ice/maniqtuk hiku, moderately rough ice/maniilrulik hiku, rough ice/maniittuq hiku; dialect is Inuinnaqtun). These maps show excellent agreement with local observations. Overall, SAR-based maps tailored for on-ice use are beneficial for and desired by northern community residents, and we recommend that high-resolution products be routinely made available in communities.

Fracture formation due to differential compaction under glacial load: a poro-elastoplastic simulation of the Hugin Fracture

The Hugin Fracture, discovered in 2011, is an approximately 3.5 km long seafloor fracture in the North Sea. This fracture was unexpected and, due to the geology in the North Sea no obvious explanation could be found. In our study, we adopt the hypothesis that the Hugin fracture was formed by differential compaction controlled by glacial load. We construct a simplified 2D geomechanical model partly covered by top load (ice sheet) and test this hypothesis. We employ transient poro-elastoplastic simulation with a finite element method. For the simulations, we had to make assumptions regarding the material properties, because the fracture is located in-between well locations. We used descriptions from drilling site survey reports and literature values and performed seismic matching form well paths to the Hugin Fracture. Nearby well data were only partly useful due to incomplete logging in the first 400 m below seafloor. To overcome this problem, we introduced a mixing k-value which allows us to easily change the material properties from pure clay to sand. Changing the mixing k-value for each simulation provided information about the limits and robustness of the simulation results. Simulation results show isotropic stress and strain distribution in the horizontally layered, isotropic part of the model that is totally covered by the ice. In the central, channelized part of the model a composite stress and strain pattern develops with sub-vertical focus areas tangential to channel edges. Low stress, strain and deformation values under total load increase drastically soon after the load starts to decrease, resulting in the development of fractures along the focussed zones. Surface deformation such as formation of compaction ridges above stiff clay-filled channels and depression associated with plastic deformation is observed. A fracture and associated surface deformation develop above the shallowest sand-filled channel, very much resembling the observed geometry at the Hugin Fracture. The simulation supports the formation hypothesis for the Hugin Fracture as a compaction fracture and suggests that thin ice sheets may induce differential compaction to a depth of several hundred meters.

Russian Dialects as a Resource for Finniс Historical Lexicology

This article proposes a reconstruction of a number of Vepsian and Ludic Karelian derivatives of lexemes, referring to the dialectal vocabulary of the Russian dialects of Obonezhye region. Having been lost from the aforementioned Finnic languages due to the Russification of the population living along the transit waterways used for the development of Obonezhye region since the time of Veliky Novgorod, they have survived as substratum or borrowed units in geographically adjacent Russian dialects. Vepsian and Karelian language data are traditionally used for the etymological interpretation of the Russian dialect lexicon. The reverse approach, i.e. the involvement of Russian dialects as a resource for Finnic etymological studies has not been widely used. When reconstructing, it is important to consider such parameters as the area of the Russian word, aiming at a well-defined Finnic language etymon; patterns of phonetic substitution and adaptation of specific Finnic sounds and sound combinations into Russian dialects; the existence of a word and its semantics in related languages. Additional opportunities are provided by the use of toponymic data due to the massive character and good preservation of toponyms. The article reconstructs several Vepsian and Ludic derived lexemes which have not been recorded in dictionaries or other sources. Among them, there are lexemes with suffixes -(e)k and -(e)h (*katek ‘thin ice’, *torek ‘noise, crackling, rumbling’, *čapek ‘overgrown undercut’, räbeh ‘damp low place in the forest’), Vepsian verbal name *kütm <* kütkim ‘leash for cattle’ with the -im suffix, Ludic term *hörpäk ‘stake with branches for drying hay’ with the suffix -äk and Vepsian landscape term *pugend ~ *pugond ‘swift with a narrow bed on the river’, in which the suffix -nd (< -nto) is embodied. The source of Russian dialectal data is the monumental publication Russian Dialect Etymological Dictionary. Vocabulary of Contact Regions (2019) prepared by S. А. Myznikov. A lot of work was done in it to find Finnic roots for Russian lexemes. The author of the dictionary had natural difficulties in attributing Russian dialect lexemes, for which their Vepsian or Karelian etymon did not survive. The interpretations presented in the article, along the way, clarify, supplement, and sometimes correct the etymology of the Russian Dialect Etymological Dictionary.

Joaquín Ortega: Pan-Americanism at the University of New Mexico by Russ Davidson

Reviewed by: Joaquín Ortega: Pan-Americanism at the University of New Mexico by Russ Davidson Cynthia E. Orozco Joaquín Ortega: Pan-Americanism at the University of New Mexico. By Russ Davidson. ( Albuquerque: University of New Mexico Press, 2020. Pp. 248. Illustrations, appendix, notes, bibliography, index.) Russ Davidson highlights Spaniard Joaquín Ortega's role in developing Pan-Americanism at the University of New Mexico (UNM). This is not a narrow biography focused on one man's greatness in creating a university program; rather, it is a comprehensive study of UNM's uneven development of its Latin American and Hispanic studies programs. The author addresses what specific university presidents, faculty members, and community leaders thought about New Mexico's place in the United States and Latin America and how they did or did not support Pan Americanism at UNM from the 1890s to the 1950s. One result of Davidson's placing the university and the state in a hemispheric setting is that Pan-Americanism can be seen as a response to a famous question from University of California historian Herbert Eugene Bolton: "Do the Americas share a common history?" Following the rise of Euro-American interest in New Mexico's Spanish past and politician Octaviano Larrazolo's long fight for the Hispano cause, UNM first developed a keen interest in Latin American and Hispano studies in the 1920s. The 1930s saw UNM president James F. Zimmerman support these interests by hiring Joaquín Ortega, whom he saw as an "insider" (125) due to his Spanish origin but as an "outsider" (88) [End Page 114] thanks to a century of debate about race that assumed Anglo superiority. The president gave Ortega carte blanche, but when Zimmerman died, Ortega encountered the whims of other presidents and faculty members who cared less about Latin America and the "little Latin America" (80) found in New Mexico. By 1951 UNM had thirty-four courses on Latin America and Hispanos. The United States' global reach into Asia in the 1950s, competing academic interests, and White disinterest in Hispanics led to a declining focus on Pan Americanism. At the national level, high interest in Pan Americanism arose from President Franklin Delano Roosevelt's Good Neighbor policy during World War II. The Institute of Inter-American Affairs was created at UNM in 1941, and Ortega was its director from its founding to 1948. U.S. commitment to Pan Americanism reflected short-term strategic goals and not a true commitment to racial equality or empowerment of Latin American nations or its peoples. Nonetheless, Ortega championed Pan Americanism, and established academic excellence at UNM, even creating an artistin-residence program that hosted renowned artist Jesús Guerrero Galván of Mexico. Ortega admired George I. Sánchez's book Forgotten People: A Study of New Mexicans (Calvin Horn Publishers, 1940) about Taos Hispanos that "laid the ideological foundation" (11) for Ortega's institute and its goal of serving both local and state Hispano communities. Ortega advocated Spanish-language instruction in the state's public schools, edited the New Mexico Quarterly, and oversaw one of the first Hispanic studies bibliographies in the United States. Davidson chides Ortega for his "silence" (152) at UNM faculty meetings, but Ortega was walking on thin ice as a foreigner, likely with an accent, and a man of color. Further, there was hardly a cohort of Hispano colleagues. Faculty members Aurelio Espinosa, Arturo Campa, and George I. Sánchez were treated unfairly by UNM, Davidson noted, and there were only a few Hispana professors, such as Anita Osuna Carr in the 1920s and Mela Sedillo Brewster in the 1930s. In Texas, scholars have identified similar barriers confronting Carlos E. Castañeda and Sánchez at the University of Texas at Austin, but both were still prolific writers and activists. Instead of writing an epilogue about several commissioned Pan American artworks at UNM that addresses the continuing, perplexing question of ethnic identities, Davidson might have turned his attention to the rise of Chicano Studies in the 1970s, the Southwest Hispanic Research Institute in the 1980s, and the Center for Regional Studies in the 1990s, all of which showed a continuation of at least some aspects of...

Sporting Organisations on Thin Ice: Speed Skating, Arbitration and the Competition Rules (T-93/18 International Skating Union)

Sporting Organisations on Thin Ice: Speed Skating, Arbitration and the Competition Rules (T-93/18 International Skating Union)

Stress Promotion of the 1958 Mw∼7.8 Fairweather Fault Earthquake and Others in Southeast Alaska by Glacial Isostatic Adjustment and Inter‐earthquake Stress Transfer

AbstractWe assess how recent glacial isostatic adjustment (GIA) and inter‐earthquake stress transfer modulated the state of stress on major faults in Southeast Alaska, and how these effects may have influenced recent large and moderate earthquakes. The Glacier Bay Icefield has lost >3,000 km3 of ice since ca. 1770, with ice thinning up to 1.5 km, and the rest of southeast Alaska has been deglaciating since ca. 1900. The resulting GIA response in the solid earth produces present‐day surface uplift rates of up to ∼4 cm/yr, among the fastest on Earth. This rapid deformation occurs directly alongside and atop the Fairweather Fault, which accommodates 4–5 cm/yr of right‐lateral motion through slip in frequent large earthquakes, recently including a Mw∼7.8 earthquake in 1958. We find that the 1958 earthquake nucleated very close to the location of maximum GIA‐induced Coulomb stress increase on the Fairweather Fault between 1770 and 1958 (estimated at ∼0.2–0.6 MPa), on the only section of fault where GIA‐induced stress changes had involved both right‐lateral shearing and unclamping. The September 10, 1899 Mw∼8.1 Yakutat Bay earthquake also promoted failure on at least the northwest part of the eventual 1958 rupture. In turn, the 1899 and 1958 earthquakes and GIA promoted failure along the St. Elias compressional margin, the site of a Mw∼7.4 event in 1979. While rapid tectonic loading is very likely the main driver of earthquakes in southeast Alaska, we estimate that 23 of 30 instrumentally constrained Mw ≥ 5.0 earthquakes in this region were also promoted by post‐1770 GIA.

Ocean melting of the Zachariae Isstrøm and Nioghalvfjerdsfjorden glaciers, northeast Greenland

Zachariae Isstrøm (ZI) and Nioghalvfjerdsfjorden (79N) are marine-terminating glaciers in northeast Greenland that hold an ice volume equivalent to a 1.1-m global sea level rise. ZI lost its floating ice shelf, sped up, retreated at 650 m/y, and experienced a 5-gigaton/y mass loss. Glacier 79N has been more stable despite its exposure to the same climate forcing. We analyze the impact of ocean thermal forcing on the glaciers. A three-dimensional inversion of airborne gravity data reveals an 800-m-deep, broad channel that allows subsurface, warm, Atlantic Intermediate Water (AIW) (+1.[Formula: see text]C) to reach the front of ZI via two sills at 350-m depth. Subsurface ocean temperature in that channel has warmed by 1.3[Formula: see text]C since 1979. Using an ocean model, we calculate a rate of ice removal at the grounding line by the ocean that increased from 108 m/y to 185 m/y in 1979-2019. Observed ice thinning caused a retreat of its flotation line to increase from 105 m/y to 217 m/y, for a combined grounding line retreat of 13 km in 41 y that matches independent observations within 14%. In contrast, the limited access of AIW to 79N via a narrower passage yields lower grounded ice removal (53 m/y to 99 m/y) and thinning-induced retreat (27 m/y to 50 m/y) for a combined retreat of 4.4 km, also within 12% of observations. Ocean-induced removal of ice at the grounding line, modulated by bathymetric barriers, is therefore a main driver of ice sheet retreat, but it is not incorporated in most ice sheet models.

Latitudinal variation of methane mole fraction above clouds in Neptune's atmosphere from VLT/MUSE-NFM: Limb-darkening reanalysis

We present a reanalysis of visible/near-infrared (480–930 nm) observations of Neptune, made in 2018 with the Multi Unit Spectroscopic Explorer (MUSE) instrument at the Very Large Telescope (VLT) in Narrow Field Adaptive Optics mode, reported by Irwin et al., Icarus, 311, 2019. We find that the inferred variation of methane abundance with latitude in our previous analysis, which was based on central meridian observations only, underestimated the retrieval errors when compared with a more complete assessment of Neptune's limb darkening. In addition, our previous analysis introduced spurious latitudinal variability of both the abundance and its uncertainty, which we reassess here. Our reanalysis of these data incorporates the effects of limb-darkening based upon the Minnaert approximation model, which provides a much stronger constraint on the cloud structure and methane mole fraction, makes better use of the available data and is also more computationally efficient. We find that away from discrete cloud features, the observed reflectivity spectrum from 800 to 900 nm is very well approximated by a background cloud model that is latitudinally varying, but zonally symmetric, consisting of a H2S cloud layer, based at 3.6–4.7 bar with variable opacity and scale height, and a stratospheric haze. The background cloud model matches the observed limb darkening seen at all wavelengths and latitudes and we find that the mole fraction of methane at 2–4 bar, above the H2S cloud, but below the methane condensation level, varies from 4–---6% at the equator to 2–4% at south polar latitudes, consistent with previous analyses, with a equator/pole ratio of 1.9 ± 0.2 for our assumed cloud/methane vertical distribution model. The spectra of discrete cloudy regions are fitted, to a very good approximation, by the addition of a single vertically thin methane ice cloud with opacity ranging from 0 to 0.75 and pressure less than ~0.4 bar.

Walking on thin ice: How cancer survivors manage disclosure at work

Purpose: Work issues for cancer survivors are often not addressed, although many individuals are diagnosed during central years of employment. To examine the impact of dynamic factors on how survivors navigate disclosure about cancer at work, a semi-structured focus group study was conducted with 27 survivors. Method: Grounded theory was implemented to develop a disclosure model. Results: The disclosure model illustrates pre-disclosure processes, processes during disclosing, and potential outcomes of disclosure, including how perceptions of safety and choice affect the outlet, structure, and the emotional, cognitive, social, and behavioral effects of disclosure. Conclusions: Survivors’ disclosure experiences are influenced by a complex interaction of factors at the level of the individual, social support system, work environment, and healthcare system, with perceptions of choice as key points of intervention by psycho-oncology providers.

Does the science criterion rest on thin ice?

This paper explores whether a central plank of the Antarctic Treaty System (ATS) - the science criterion - is threatened by anthropogenic climate change. It begins by situating the origins of the ATS within the context of the International Geophysical Year (IGY), and the privileged position that science obtained within first the IGY and later the ATS. This extends to science functioning as the dominant currency through which states may ascend to the level of consultative parties (CPs), the highest level of authority within the ATS. Within this model Antarctica functions as a laboratory, a metaphor with a long history in Antarctica, reinforced by the Madrid Protocol and its strong focus on maintaining environmental boundaries and by a perception that Antarctica otherwise plays a minimal role in global affairs. Much of the research in Antarctica focuses on climate change and indeed has been important in establishing its scope and magnitude. But climate change also threatens both Antarctica itself and - by extension - the many low-lying areas of the world that would be affected by rising sea levels caused by melting Antarctic ice. Given Antarctica may no longer be so removed from the rest of the world, is this sufficient reason to revisit the centrality of science to legitimate participation in Antarctic governance? The paper considers alternatives to the current system, including assigning authority within the ATS to states affected by climate change. It concludes that while the science criterion remains viable, it rests on a moral as well as practical foundation that could be undermined if the right to authority over Antarctica remains disconnected from the actions that cause changes to the continent.

GERALDINE (Google Earth Engine supRaglAciaL Debris INput dEtector): a new tool for identifying and monitoring supraglacial landslide inputs

Abstract. Landslides in glacial environments are high-magnitude, long-runout events, believed to be increasing in frequency as a paraglacial response to ice retreat and thinning and, arguably, due to warming temperatures and degrading permafrost above current glaciers. However, our ability to test these assumptions by quantifying the temporal sequencing of debris inputs over large spatial and temporal extents is limited in areas with glacier ice. Discrete landslide debris inputs, particularly in accumulation areas, are rapidly “lost”, being reworked by motion and icefalls and/or covered by snowfall. Although large landslides can be detected and located using their seismic signature, smaller (M≤5.0) landslides frequently go undetected because their seismic signature is less than the noise floor, particularly supraglacially deposited landslides, which feature a “quiet” runout over snow. Here, we present GERALDINE (Google Earth Engine supRaglAciaL Debris INput dEtector): a new free-to-use tool leveraging Landsat 4–8 satellite imagery and Google Earth Engine. GERALDINE outputs maps of new supraglacial debris additions within user-defined areas and time ranges, providing a user with a reference map, from which large debris inputs such as supraglacial landslides (>0.05 km2) can be rapidly identified. We validate the effectiveness of GERALDINE outputs using published supraglacial rock avalanche inventories, and then demonstrate its potential by identifying two previously unknown, large (>2 km2) landslide-derived supraglacial debris inputs onto glaciers in the Hayes Range, Alaska, one of which was not detected seismically. GERALDINE is a first step towards a complete global magnitude–frequency of landslide inputs onto glaciers over the 38 years of Landsat Thematic Mapper imagery.

Interaction of flexural gravity wave in ice cover with a pair of bottom-mounted rectangular barriers

This paper considers the reflection and transmission of flexural gravity waves by a pair of bottom-mounted rectangular barriers of arbitrary height and width. Depth of the fluid considered here is finite but not necessarily uniform. The fluid region is bounded by an infinite long thin ice sheet of homogeneous properties. Using linearized water wave theory the velocity potential associated with the motion is formulated. Eigenfunction matching technique is used to convert the boundary value problem to a set of integral equations which are solved by using multi-term Galerkin method. The reflection and transmission coefficients are calculated and represented graphically. An expression for the energy balance relation is given and checked carefully. A model of the problem in which the fluid is bounded by a free surface is recovered. For a set of physical parameters the results are analyzed through a number of figures. The convergence and correctness of the method is confirmed by comparing the results with the one available in the literature. It is shown that a pair of thick bottom-mounted barriers have significant impact on reflected and transmitted flexural gravity waves. Resonance effects are observed and verified for different parameters of the current problem.

Estimating Arctic Sea Ice Thickness with CryoSat-2 Altimetry Data Using the Least Squares Adjustment Method.

Satellite altimeters can be used to derive long-term and large-scale sea ice thickness changes. Sea ice thickness retrieval is based on measurements of freeboard, and the conversion of freeboard to thickness requires knowledge of the snow depth and snow, sea ice, and sea water densities. However, these parameters are difficult to be observed concurrently with altimeter measurements. The uncertainties in these parameters inevitably cause uncertainties in sea ice thickness estimations. This paper introduces a new method based on least squares adjustment (LSA) to estimate Arctic sea ice thickness with CryoSat-2 measurements. A model between the sea ice freeboard and thickness is established within a 5 km × 5 km grid, and the model coefficients and sea ice thickness are calculated using the LSA method. Based on the newly developed method, we are able to derive estimates of the Arctic sea ice thickness for 2010 through 2019 using CryoSat-2 altimetry data. Spatial and temporal variations of the Arctic sea ice thickness are analyzed, and comparisons between sea ice thickness estimates using the LSA method and three CryoSat-2 sea ice thickness products (Alfred Wegener Institute (AWI), Centre for Polar Observation and Modelling (CPOM), and NASA Goddard Space Flight Centre (GSFC)) are performed for the 2018–2019 Arctic sea ice growth season. The overall differences of sea ice thickness estimated in this study between AWI, CPOM, and GSFC are 0.025 ± 0.640 m, 0.143 ± 0.640 m, and −0.274 ± 0.628 m, respectively. Large differences between the LSA and three products tend to appear in areas covered with thin ice due to the limited accuracy of CryoSat-2 over thin ice. Spatiotemporally coincident Operation IceBridge (OIB) thickness values are also used for validation. Good agreement with a difference of 0.065 ± 0.187 m is found between our estimates and the OIB results.

The Antarctic sea ice cover from ICESat-2 and CryoSat-2: freeboard, snow depth, and ice thickness

Abstract. We offer a view of the Antarctic sea ice cover from lidar (ICESat-2) and radar (CryoSat-2) altimetry, with retrievals of freeboard, snow depth, and ice thickness that span an 8-month winter between 1 April and 16 November 2019. Snow depths are from freeboard differences. The multiyear ice observed in the West Weddell sector is the thickest, with a mean sector thickness > 2 m. The thinnest ice is found near polynyas (Ross Sea and Ronne Ice Shelf) where new ice areas are exported seaward and entrained in the surrounding ice cover. For all months, the results suggest that ∼ 65 %–70 % of the total freeboard is comprised of snow. The remarkable mechanical convergence in coastal Amundsen Sea, associated with onshore winds, was captured by ICESat-2 and CryoSat-2. We observe a corresponding correlated increase in freeboards, snow depth, and ice thickness. While the spatial patterns in the freeboard, snow depth, and thickness composites are as expected, the observed seasonality in these variables is rather weak. This most likely results from competing processes (snowfall, snow redistribution, snow and ice formation, ice deformation, and basal growth and melt) that contribute to uncorrelated changes in the total and radar freeboards. Evidence points to biases in CryoSat-2 estimates of ice freeboard of at least a few centimeters from high salinity snow (> 10) in the basal layer resulting in lower or higher snow depth and ice thickness retrievals, although the extent of these areas cannot be established in the current data set. Adjusting CryoSat-2 freeboards by 3–6 cm gives a circumpolar ice volume of 17 900–15 600 km3 in October, for an average thickness of ∼ 1.29–1.13 m. Validation of Antarctic sea ice parameters remains a challenge, as there are no seasonally and regionally diverse data sets that could be used to assess these large-scale satellite retrievals.

The 2017 Reversal of the Beaufort Gyre: Can Dynamic Thickening of a Seasonal Ice Cover During a Reversal Limit Summer Ice Melt in the Beaufort Sea?

AbstractDuring winter 2017, the semipermanent Beaufort High collapsed and the anticyclonic Beaufort Gyre reversed. The reversal drove eastward ice motion through the Western Arctic, causing sea ice to converge against Banks Island, and halted the circulation of multiyear sea ice via the gyre, preventing its replenishment in the Beaufort Sea. Prior to the reversal, an anomalously thin seasonal ice cover had formed in the Beaufort following ice‐free conditions during September 2016. With the onset of the reversal in January 2017, convergence drove uncharacteristic dynamic thickening during winter. By the end of March, despite seasonal ice comprising 97% of the ice cover, the reversal created the thickest, roughest, and most voluminous regional ice cover of the CryoSat‐2 record. Within the Beaufort Sea, previous work has shown that winter ice export can precondition the region for increased summer ice melt, but that a short reversal during April 2013 contributed to a reduction in summer ice loss. Hence, the deformed ice cover at the end of winter 2017 could be expected to limit summer melt. In spite of this, the Beaufort ice cover fell to its fourth lowest September area as the gyre re‐established during April and divergent ice drift broke up the pack, negating the reversal's earlier preconditioning. Our work highlights that dynamic winter thickening of a regional sea ice cover, for instance during a gyre reversal, offers the potential to limit summer ice loss, but that dynamic forcing during spring dictates whether this conditioning carries through to the melt season.

How widespread is the usage of the Northern Sea Route as a commercially viable shipping route? A statistical analysis of ship transits from 2011 to 2018 based on empirical data

We critically examined the usage of Northern Sea Route (NSR) during the 8 year period from 2011 to 2018, using empirical data collected from the NSR Administration (NSRA), Center for High North Logistics (CHNL) and Equasis databases, together with scholarship available in the public domain to determine its commercial usage. We find that NSR transit numbers have generally been low (μ = 34 transits per year), varying between 71 transits per year (in 2013), 18 transits (in 2015, 2016), and 27 transits each in 2017 and 2018. On an aggregate basis, tankers and dry cargo ships have been the largest users of the NSR (123 and 122 transits respectively, accounting for 82% of all transits), followed by ice breakers, OSVs and SAR vessels (12% or 35 transits). Only 15 transits (5%) were by passenger, cruise and research ships followed by coastguard and fishing vessel (1%). Factors preventing its wider adoption include the comparatively lesser, but still existent presence of sea ice thus constituting a hazard to navigation, few cargo ports along the NSR, higher insurance premiums, inadequate coverage of charts, inadequate SAR facilities, the need for ice breaker assistance and resultant higher transit costs. Due to the presence of ice, NSR was open for navigation for < 155 days each year (132 days in 2018). Due to these pertinacious obstacles to safe navigation, the thinning of arctic ice has not resulted in waters sufficiently free of ice to enable safe commercially viable passage of commercial conventional cargo ships.

Polarimetric Behavior for the Derivation of Sea Ice Topographic Height From TanDEM-X Interferometric SAR Data

Single-pass interferometric synthetic aperture radar (InSAR) is an effective technique for sea ice topographic retrieval despite the inherent dynamics of sea ice. However, the penetration of microwaves into snow-covered thick ice and the achievable height sensitivity for tens-of-centimeters thin ice are two major issues, which limit the accuracy of InSAR-derived sea ice topography. Polarimetry provides scattering information concerning the sea ice properties and has the potential, in combination with interferometry, to achieve an accurate reconstruction of a sea ice digital elevation model (DEM). This article studies the relation between polarimetric signatures and sea ice topography, and explores the possibility to compensate the penetration bias by merging copolar coherence into InSAR processing. The newly generated topographic map has a root-mean-square error under 0.3 m. For thin ice below 1 m, a positive relation between copolar phase φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">coPol</sub> and surface height is observed, suggesting that φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">coPol</sub> can effectively characterize thin sea ice topography. For thick ice with ridges, the maximum polarimetric phase difference Δφ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">maxPol</sub> reveals a particular shape of the coherence region, which can be interpreted as oriented volume scattering. It suggests that the model-based approach using polarimetric SAR interferometry assuming an oriented volume scattering model is promising in measuring the scattering centers in thick and deformed sea ice. The study of polarimetric behavior for the InSAR DEM is, therefore, a step forward toward accurate modeling of sea ice topography from polarimetric single-pass InSAR data.

Walking on Thin Ice: How and Why Frontline Officers Cope With Managerialism, Accountability, and Risk in Probation Services

Probation officers (POs) operate in a high-risk environment. They are vulnerable to mediatic and political backlash and are confronted with managerial innovations that can conflict with their values. A thematic analysis of 29 interviews with Belgian POs reveals that classical coping mechanisms caused by time shortages, such as rationing and prioritization, are amplified by managerialism. POs also break rules which present limited meaningfulness and routinize offender control to alleviate pressure from accountabilities to both managers and the general public. The study demonstrates that managerialism and accountabilities to the managers, the public, and the politicians model coping mechanisms in high-risk environments.

On thinning ice: Effects of atmospheric warming, changes in wind speed and rainfall on ice conditions in temperate lakes (Northern Poland)

Northern Hemisphere lakes are losing their ice cover due to climate change. Here we explored six decades of observational data (1961–2017) showing trends in air temperature, wind speed and precipitation over northern Poland, as well as changes in the ice conditions for five lakes with different morphometry. We evaluated whether and to what extent climatic effects, including atmospheric warming, changing wind speed and rainfall during fall and winter, influence ice conditions in morphometrically different lakes in Northern Poland. Our analysis demonstrated that ice cover duration and thickness decreased at rates of 5.4 days decade−1 and 2.5 cm decade−1, respectively. Ice conditions were influenced (65–75%) by the direct effects of air temperature change and to some extent by an interaction of warming with wind speed and precipitation (5–10%). While stronger autumnal winds result in longer ice cover duration, the effect of precipitation is bimodal with either an enhancement of ice formation by autumnal rain or accelerated ice loss during spring. To project future changes in ice conditions, we used a 1D hydrodynamic lake model forced with four climate model projections under low, medium and high Representative Concentration Pathway (RCP) scenarios. Our simulations demonstrate that current ice conditions will stabilize under the low emission scenario (RCP 2.6) but decrease under both the medium and high emission scenarios (RCP 6.0 and 8.5). During the 21st century, the lakes are projected to lose their ice at a rate between 4.5- and 10-days decade−1 and ice thickness will decrease by between 3.0 and 5.0 cm decade−1. The rate of change will be greater in smaller rather than larger lakes and more so for those situated further inland. The probability of ice-free winters will increase for all lakes and among all future scenarios by between 4 and 69% with the highest potential frequency of ice-free winters in smaller and deeper but relatively wind-exposed lakes.

Sea ice drift and arch evolution in the Robeson Channel using the daily coverage of Sentinel-1 SAR data for the 2016–2017 freezing season

Abstract. The Robeson Channel is a narrow sea water passage between Greenland and Ellesmere Island in the Arctic. It is a pathway of sea ice from the central Arctic and out to Baffin Bay. In this study, we used a set of daily synthetic aperture radar (SAR) images from the Sentinel-1A/1B satellites, acquired between September 2016 and April 2017, to study the kinematics of individual ice floes as they approach and then drift through the Robeson Channel. The tracking of 39 selected ice floes was visually performed in the image sequence, and their speed was calculated and linked to the reanalysis 10 m wind from ERA5. The results show that the drift of ice floes is very slow in the compact ice regime upstream of the Robeson Channel, unless the ice floe is surrounded by water or thin ice. In this case, the wind has more influence on the drift. On the other hand, the ice floe drift is found to be about 4–5 times faster in the open-drift regime within the Robeson Channel and is clearly influenced by wind. A linear trend is found between the change in wind and the change in ice drift speed components, along the length of the channel. Case studies are presented to reveal the role of wind in ice floe drift. This paper also addresses the development of the ice arch at the entry of the Robeson Channel, which started development on 24 January and matured on 1 February 2017. Details of the development, obtained using the sequential SAR images, are presented. It is found that the arch's shape continued to adjust by rupturing ice pieces at the locations of cracks under the influence of the southward wind (and hence the contour kept displacing northward). The findings of this study highlight the advantage of using the high-resolution daily SAR coverage in monitoring aspects of sea ice cover in narrow water passages where the ice cover is highly dynamic. The information will be particularly interesting for the possible applications of SAR constellation systems.