Blog

The NSERC PermafrostNet blog for long-form updates and stories.

Brief communication: Reanalyses underperform in cold regions, raising concerns for climate services and research

Many changes in cold regions are amplified by nonlinear processes involving ice and have important consequences locally and globally.

The climate-driven changes in cold regions have an outsized importance for local resilient communities and for global climate through teleconnections. Bin Cao and Stephan Gruber show that reanalyses are less accurate in cold regions compared to other more populated regions, coincident with the low density of observations. Our findings likely point to similar gaps in our knowledge and capabilities of climate research and services in cold regions.

 
The 1991–2020 average ensemble spread of (a) mean annual air temperature (MAAT) and (b) relative maximum snow water equivalent (maxSWE) among different reanalyses. 

The ensemble spread in the mean annual maximum snow water equivalent is found to be greater than the ensemble mean. The reduced quality of reanalyses in cold regions, coinciding with sparse in situ observations and low population, points to challenges in how we represent cold-region phenomena in simulation systems and limits our ability to support climate research and services.

The 1991–2020 average ensemble spread of mean annual air temperature (MAATs) and relative spread of maximum snow water equivalent (maxSWEs).

Cao, B. and Gruber, S.: Brief communication: Reanalyses underperform in cold regions, raising concerns for climate services and research, The Cryosphere, 19, 4525–4532, https://doi.org/10.5194/tc-19-4525-2025, 2025.

By Tristan MacLean, ago

Glossary of Permafrost Science and Engineering

The new Glossary of Permafrost Science and Engineering has been launched.

With accelerated climatic warming and announcements of important investments in northern infrastructure, the need for a comprehensive and up-to-date glossary of permafrost was more pressing than ever.

The new Glossary is the culmination of multiple years of consensus-based work by a Canadian-led team of multidisciplinary experts in permafrost science and engineering.

This exhaustive reference work (355 entries) will facilitate effective communication between the communities of experts and practitioners of the permafrost world.

You can download an electronic, hyperlinked version on the website of the Canadian Permafrost Association for free – Glossary of Permafrost Science and Engineering.

The project was led by Antoni Lewkowicz and co-authors included Brendan O’Neill, Steve Wolfe, Pascale Roy-Leveillee, Vladislav Roujanski, Ed hove, Stephan Gruber, Heather Brooks, Ashley Rudy, Cassandra Koenig, Nicholas Brown, and Philip Bonaventure, but many other contributed to reviewing the entries, providing equivalent French terms, or giving expert advice.

By Tristan MacLean, ago

Parameter optimization for global soil carbon simulations: Not a simple problem

Soils store large amounts of organic carbon that could be released into the atmosphere due to climate change, but future projections from numerical models of soil organic carbon dynamics remain highly uncertain. 

Une étude récente de Charles Gauthier used Bayesian optimization techniques and global sensitivity analysis to better constrain the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC) model’s soil organic carbon parameters.

Getting a handle on how soil stores and releases carbon is critical for modeling climate change, yet global simulations face many challenges due to uncertain parameters and sparse data. The team explored different sets of parameters and tested two types of loss functions, finding that this choice can greatly influence model outcomes.

Schematic representation of the optimization workflow.

The best parameter set resulted in a 12% improvement when compared to observations and matched well with global estimates of soil carbon stocks, particularly at high latitudes. However, the study also points out that certain regions—like the vast needle-leaf forests of Siberia—remain poorly observed and contribute to ongoing uncertainty. By flagging these gaps, the research not only offers a more accurate model but also calls for more targeted data collection and optimization approaches going forward, aiming to close the loop on carbon-climate feedbacks for better future predictions.

Top meter soil organic carbon (SOC) content across the Northern Circumpolar Soil Carbon Database domain obtain with the default parameterization (SDEF) and the two optimized parameter sets (S2EO and SPMO). SOC content is averaged over the 1950–2000 period.

Gauthier, C. B.,  Melton, J. R.,  Meyer, G.,  Raj Deepak, S. N., &  Sonnentag, O. (2025).  Parameter optimization for global soil carbon simulations: Not a simple problem. Journal of Advances in Modeling Earth Systems,  17, e2024MS004577. https://doi.org/10.1029/2024MS004577

By Tristan MacLean, ago

Beyond MAGT: learning more from permafrost thermal monitoring data with additional metrics.

Ground temperature is the most common variable in permafrost monitoring and one of three products used to characterize the permafrost Essential Climate Variable by the World Meteorological Organization.

PermafrostNet’s data scientist, Nicholas Brown, has conducted an investigation into the metrics used to assess indicators of permafrost and heat changes in the ground.

Based on this investigation, recommendations are provided for a set of five metrics that offer a more comprehensive picture of permafrost thaw.

Metrics such as the mean annual ground temperature (MAGT) and active layer thickness (ALT) are used to monitor and quantify permafrost change. However, these have limitations including those arising from the effects of latent heat, which reduce their sensitivity.

The team investigated the behaviour of existing and novel metrics derived from temperature observations (TSP metrics) using an ensemble of more than seventy 120-year simulations. They evaluated which TSP metrics provide new insight into permafrost change and evaluated how reliably each one indicates changes in sensible, latent, and total heat contents for different levels of sensor quality. They also quantified the effect of sensor placement on the magnitude of observed MAGT trends.

Brown, N. and Gruber, S. (2025). Beyond MAGT: learning more from permafrost thermal monitoring data with additional metrics, EGUSphere [preprint], DOI: https://doi.org/10.5194/egusphere-2025-2658

By Tristan MacLean, ago

Modelling the temporal dynamics of subarctic surface temperature inversions from atmospheric reanalysis for producing point-scale multi-decade meteorological time series in mountains

The vertical profile of air temperatures in subarctic regions is difficult to quantify, especially in areas with mountainous terrain subject to strong and lasting inversion events. 

Relying on observational data is not possible in most places due to sparse weather stations.

Une étude récente de Victor Pozsgay tackles the challenge of developing a model that leverages atmospheric reanalysis data and calibrates it using data from five weather stations in the Yukon, Canada.

Map of the study area showing the five sites around Dawson City, Yukon Territory, Canada. The basemap is composed of the Esri World Terrain Base and Esri World Hillshade layers, and is projected in the WGS 1984 Web Mercator projection.

Accurately tracking air temperatures in subarctic mountainous regions is a challenging task, especially due to the prevalence of strong and frequent temperature inversions. These inversions play a critical role in shaping permafrost distribution and regional climate dynamics, yet traditional observations are sparse because of the lack of weather stations in rugged terrain. Victor’s study tackles this challenge by developing a model that leverages atmospheric reanalysis data and calibrates it using actual data from the Yukon. The calibrated model successfully reflects the trends in inversion frequency, strength, and depth that have been evolving since 1948, departing from typical warming patterns seen elsewhere. This approach makes it possible to produce reliable, point-scale meteorological time series for even the most inaccessible locations—an essential advance for studies of permafrost and the broader climate system. The model’s reliance on global reanalysis data and minimal location-specific calibration means it is poised to be both future-proof and widely applicable for regional climate applications, offering a much-needed solution for addressing data gaps in complex, mountainous terrains.

Mean daily pressure-level temperatures for several altitudes at and above the Dawson Airport (ERA5 data on 1 February 2007). The dependence with altitude is linear above 2300 m, where the linear lapse rate can be fitted. Below this, a ‘‘lapse’’ temperature is extrapolated at the grid and station levels. In the grey band, the altitudinal temperature behaviour is inverted, increasing with elevation. The elevation of the five stations used is reported on the right-hand side. The reanalysis data appear in blue, with points representing the pressure level air temperature Tpl and a triangle at the grid level for the surface temperature Tsur. Finally, the observed temperature Tobs is a green diamond at the station’s elevation.

Victor Pozsgay and Stephan Gruber. 2025. Modelling the temporal dynamics of subarctic surface temperature inversions from atmospheric reanalysis for producing point-scale multi-decade meteorological time series in mountains. Arctic Science. 11: 1-16. https://doi.org/10.1139/as-2025-0027

By Tristan MacLean, ago

Detecting ground ice in warm permafrost with the dielectric relaxation time from SIP observations.

Conventional geophysical techniques like electrical resistivity, seismic surveys, or ground-penetrating radar alone often produce ambiguous results due to the overlap of material characteristics between frozen and unfrozen ground.

Detecting ground ice in permafrost is crucial for climate research and infrastructure, but traditional methods often struggle to distinguish it. This study by Hosein Fereydooni examines the dielectric properties of ground ice as a unique fingerprint. Field measurements were taken at two Yukon permafrost sites: a retrogressive thaw slump and a pingo. Comparing these with electrical resistivity and impedance results, he found relaxation time is a more reliable indicator for ground ice detection.


(a) The retrogressive thaw slump, headwall, (b) long and (c) short SIP survey.

Hosein’s team developed a method to quantify relaxation time from Spectral Induced Polarization (SIP) data measured by the FUCHS III device. The method’s effectiveness was demonstrated through synthetic data and two field surveys. SIP field measurements, ranging from 1.46 Hz to 40 kHz, were conducted on a retrogressive thaw slump and a pingo in Yukon, Canada. The extracted relaxation times were mapped to pseudo-depths obtained from single-frequency inversion. This study proposes a relaxation time range from 10 to 400 μs for ground ice, and the results demonstrate that this range can detect ground ice spectra in field studies. Comparison with observations in a borehole and an exposure of permafrost indicate that relaxation time is less ambiguous in detecting ground ice in warm permafrost than conventional methods such as electrical resistivity tomography.


(a) The pingo site and (b) the survey line with the FUCHS device.

Fereydooni, H., Gruber, S., Stillman, D., and Cronmiller, D.: Detecting ground ice in warm permafrost with the dielectric relaxation time from SIP observations, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-1801, 2025.

By Tristan MacLean, ago

Investigating the controls of ice-wedge initiation and growth using XFEM

A study of how climate, soil type and water saturation affect ice-wedge cracks

A new study by Gabriel Karam et al asks, how do climate and soil control the ice-wedge formation process?

Answering these questions can further our understanding of wedge-ice volume and distribution.

Ice wedge cracking simulation gif

Ice-wedges are periglacial landforms that develop as a result of thermal contraction-cracking in continuous permafrost regions, which appear as polygonal networks on the ground surface. Given their complex thermo- mechanical loading history, very few related numerical models have so far been developed. This study developed a new climate-driven model to show the fractures in soil that develop from thermal contraction in winter. The range of model results indicate how climate, soil type and water saturation of the soil affect the spacing, depth, and width of ice-wedge cracks. Estimating ice-wedge depth can help us make informed volume calculations which are otherwise difficult to measure in the field.

Karam, G., Pouragha, M. and Gruber, S. (2024). Investigating the controls of ice-wedge initiation and growth using XFEM, Computers and Geotechnics, Volume 173, DOI: 10.1016/j.compgeo.2024.106549

A typical simulation result showing multiple cracks.
A typical simulation result showing multiple cracks.

By Tristan MacLean, ago

A prototype field-to-publication data system for a multi-variable permafrost observation network.

A prototype field-to-publication data system for a multi-variable permafrost observation network.
Blog post by Nick Brown, NSERC PermafrostNet Data Scientist

Analysis and prediction of permafrost change are hampered by lack of observational data. In collaboration with Stephan Gruber, Peter Pulsifer, and Amos Hayes, we developed a permafrost data management system to support permafrost observation networks that involve many different kinds of permafrost data.

We identify five broad challenges for permafrost data management and publication: (1) existing data management strategies do not scale well, (2) data users have different skills and needs, (3) permafrost data are varied, (4) resources for permafrost data management are limited, and (5) existing permafrost data sources are difficult to integrate. Our prototype system supports a permafrost data workflow from observation to the distribution of interoperable data. The system simplifies data publication and management, although we identify and discuss several hurdles in adapting the CF conventions and ERDDAP for permafrost data. Our learning can inform organizations who collect, manage, or distribute permafrost data or those who manage large observation networks.

In summary:

  • Five broad challenges limit permafrost data management and publication.
  • We frame these challenges as requirements, and identify similarities with the FAIR principles.
  • We developed a prototype a permafrost data system to support field-to-publication workflows.
  • In this project, we use an “adopt and adapt” approach for standards and software.
  • Our data system supports more FAIR permafrost data.

Nicholas Brown, Stephan Gruber, Peter Pulsifer, Amos Hayes, A prototype field-to-publication data system for a multi-variable permafrost observation network, Environmental Modelling & Software, Volume 175, 2024, 106006, ISSN 1364-8152, doi:10.1016/j.envsoft.2024.106006

This research was enabled in part by support provided by Compute Ontario et du Digital Research Alliance of Canada.

By nick brown, ago

Enregistrement et résumé AI de la Conférence sur la politique scientifique canadienne 2023

A Vision for Permafrost Knowledge in Canada: From Strategy to Action

Permafrost Pathways et le PermafrostNet CRSNG ont organisé des tables rondes distinctes lors de la conférence 2022 du Centre canadien de la politique scientifique (CCPS). Cela a conduit à une collaboration pour organiser un panel unique pour la conférence du CCPS 2023 afin de faire avancer les discussions commencées en 2022, intitulée : A Vision for Permafrost Knowledge in Canada: From Strategy to Actionqui s'est tenue le lundi 13 novembre. Les panélistes comprenaient : John Holdren (Arctic Initiative, Harvard Kennedy School), Marc D'Iorio (SMA Sciences, ECCC), Sara Brown (Association des communautés des Territoires du Nord-Ouest) et Stephan Gruber (PermafrostNet CRSNG), sous la présidence de Janet King, présidente du conseil d'administration. Janet King moderating.
 

To enable more in-depth discussions and strategizing, Jennifer Spence (Carleton University; Arctic Initiative, Harvard Kennedy School) and Janet King organized a workshop that followed the panel titled: Advancing Canada’s role as a leader in permafrost knowledge and policy. The workshop featured representatives of ITK, NWT Association of Communities, ECCC, the federal government’s Working Group on permafrost,  Polar Knowledge Canada, the Geological Survey of Canada, the NWT Geological Survey, the Canadian Permafrost Association, NSERC PermafrostNet, Permafrost Pathways, ArcticNet, Woodwell Climate Research Centre, and the Cascade Institute.

Vous pouvez maintenant lire tous les détails du panel, obtenir un résumé AI de la discussion et écouter l'enregistrement audio du symposium sur le site web CSPC webpage for the session.

By Tristan MacLean, ago