Ketil Isaksen

• Dr. scient
• Senior Researcher at Norwegian Meteorological Institute

Mountain permafrost, constituting 30% of the global permafrost area, is sensitive to climate change and strongly impacts mountain ecosystems and communities. This study examines 21st century permafrost warming in European mountains using decadal ground temperature data from sixty-four boreholes in the Alps, Scandinavia, Iceland, Sierra Nevada and S...

The effect of climate change on mountain vegetation is influenced by environmental factors and site effects. To monitor the effect of climate change we therefore need to understand species' sensitivity to microclimate and environmental gradients. The objective of this study is to study widespread plant species' temporal and spatial variation along...

Arctic observations in 2023 provided clear evidence of rapid and pronounced climate and environmental change, shaped by past and ongoing human activities that release greenhouse gases into the atmosphere and push the broader Earth system into uncharted territory. This chapter provides a snapshot of 2023 and summarizes decades-long trends observed a...

The dataset includes abundance data of seven widespread plant species across environmental and microclimate gradients in Norwegian mountains. The widespread species are Salix herbacea, Phyllodoce caerulea, Carex bigelowii, Juncus trifidus, Vaccinium myrtillus, Avenella flexuosa, and Empetrum nigrum. The environmental variables include altitude (met...

The Arctic region is warming at over twice the mean rate of the Northern Hemisphere and nearly four times faster than the globe since 1979. The local rate of warming is even higher in the European archipelago of Svalbard. This warming is transforming the terrestrial snow cover, which modulates surface energy exchanges with the atmosphere, accounts...

With the EU-funded PACE (Permafrost and Climate in Europe) project at the turn of this century, several deep boreholes (100 m+) were drilled in European mountain sites, including in mainland Norway, Svalbard and Sweden. During other projects from 2004 and the International Polar Year (IPY) period in 2006–2007, several additional boreholes were dril...

This article presents a comprehensive documentation and analysis of long-term observations of year-round groundwater occurrences in rivers and various types of taliks under continuous permafrost conditions on Svalbard. Previously thought to be nonexistent, the existence of these taliks has been confirmed through rigorous field observations, geotech...

Rapid warming due to human-caused climate change is reshaping the Arctic, enhanced by physical processes that cause the Arctic to warm more quickly than the global average, collectively called Arctic amplification. Observations over the past 40+ years show a transition to a wetter Arctic, with seasonal shifts and widespread disturbances influencing...

The ground thermal regime and permafrost development have an important influence on geomorphological processes in periglacial regions and ultimately landscape development. About 10 % of unstable rock slopes in Norway are potentially underlain by widespread permafrost. Permafrost thaw and degradation may play a role in slope destabilisation, and mor...

With the EU-funded PACE project in the turn of this century, several deep boreholes (100 m +) were drilled in European mountain sites, including mainland Norway, Svalbard and Sweden. During other projects from c. 2004 and the International Polar Year (IPY) period in 2006/07, several additional boreholes were drilled in different sites in both Norwa...

Meteorologiens samfunnsbetydning er økende, ikke bare gjennom værvarslene, men også grunnet energiomstillingen og tilpasningen til klimaendringene. Høstingen av energi fra fossile reserver under bakken må erstattes av vind-, sol- og vannkraft på jordens overflate. Denne omstillingen vil kreve store arealressurser, og de lokale meteorologiske forhol...

Meteorologiens samfunnsbetydning er økende, ikke bare gjennom værvarslene, men også grunnet energiomstillingen og tilpasningen til klimaendringene. Høstingen av energi fra fossile reserver under bakken må erstattes av vind-, sol- og vannkraft på jordens overflate. Denne omstillingen vil kreve store arealressurser, og de lokale meteorologiske forhol...

Ground temperatures in coarse, blocky deposits such as mountain blockfields and rock glaciers have long been observed to be lower in comparison with other (sub)surface material. One of the reasons for this negative temperature anomaly is the lower soil moisture content in blocky terrain, which decreases the duration of the zero curtain in autumn. H...

The cryosphere web portal maintained by the Norwegian Meteorological Institute (MET Norway), https://cryo.met.no, provides access to the latest operational data and the current state of sea ice, snow, and permafrost in Norway, the Arctic, and the Antarctic. We present the latest addition to this portal: the operational permafrost monitoring at MET...

Ground temperatures in coarse, blocky deposits such as mountain blockfields and rock glaciers have long been observed to be lower in comparison with other (sub)surface material. One of the reasons for this negative temperature anomaly is the lower soil moisture content in blocky terrain, which decreases the duration of the zero curtain in autumn. H...

In recent decades, surface air temperature (SAT) data from Global reanalyses points to maximum warming over the northern Barents area. However, a scarcity of observations hampers the confidence of reanalyses in this Arctic hotspot region. Here, we study the warming over the past 20–40 years based on new available SAT observations and a quality cont...

Around 10 % of unstable rock slopes in Norway are possibly underlain by widespread permafrost. Permafrost thaw and degradation may play a role in slope destabilization and more knowledge about rock wall permafrost in Norway is needed to investigate possible links between ground thermal regime, geomorphological activity and natural hazards. Here, we...

Permafrost temperatures have increased in polar and high-elevation regions, affecting the climate system and the integrity of natural and built environments. In this Review, we outline changes in the thermal state of permafrost, focusing on permafrost temperatures and active-layer thickness. Increases in permafrost temperature vary spatially owing...

Knowledge about how weather conditions affect travel behavior in different user groups and contexts is relevant for planners and policymakers to facilitate sustainable transportation systems. We aimed to assess the influence of day-to-day weather on cycling for transportation among parents of young children with access to different bike types (e-bi...

Cryosphere is the collective term for places on Earth with frozen water or permanently frozen ground, like snow, ice, and permafrost. The Norwegian Meteorological Institute (MET Norway) has long experience in monitoring the cryosphere through remote sensing and surface-based automatic and manual observations, and providing data in near-real-time an...

Electronic archives of data from standard meteorological observations (mean daily/monthly surface air temperatures - SAT) at the meteorological stations at Bukhta Tikhaya (Hooker Island, 1929-1960) and Krenkel Observatory (Hayes Island, 1957-2017) on Franz Josef Land (FJL) are presented. Parallel data series of SAT made in 1958 and 1959 on both met...

The Arctic is warming rapidly, and the rate of warming is twice as fast in winter as in summer. More frequent extreme warm spells and associated rain-on-snow events in winter can dramatically alter snowpack conditions, ultimately encapsulating the tundra vegetation in ‘basal ice’ for several months. As most tundra vegetation studies have focused on...

This paper reviews and analyses the past 20 years of change and variability of European mountain permafrost in response to climate change based on time series of ground temperatures along a south–north transect of deep boreholes from Sierra Nevada in Spain (37°N) to Svalbard (78°N), established between 1998 and 2000 during the EU-funded PACE (Perma...

A number of seaside communities in Troms, northern Norway, are vulnerable to sudden weather-induced access disruptions due to high-impact weather and dependency on one or few roads. In this paper we study changes in winter weather known to potentially cause access disruptions in Troms, for the present climate (1958–2017) and two future periods (204...

A number of seaside communities in Troms, northern Norway, are vulnerable to sudden weather-induced access disruptions due to high-impact weather and dependency on one or few roads. In this paper we study changes in winter weather known to potentially cause access disruptions in Troms, for the present climate (1958–2017) and two future periods (204...

The Svalbard Airport composite series spanning the period from 1898 to the present represents one of very few long-term instrumental temperature series from the High Arctic. A homogenized monthly temperature series is available since 2014. Here we increase the resolution from a monthly to daily basis, and further digitization of historical data has...

Precipitation plays an important role in the Arctic hydrological cycle, affecting different areas like the surface energy budget and the mass balance of glaciers. Thus, accurate measurements of precipitation are crucial for physical process studies; but gauge measurements in the Arctic are sparse and subject to relocations and several gauge issues....

Overview of the Climate-Ecological Observatory for Arctic Tundra (COAT) for Svalbard. COAT is a response to the urgent international calls for establishment of observation systems that make it possible to gain insight into how climate impacts Arctic tundra. COAT Svalbard is an essential component of the Svalbard Integrated Arctic Earth Observing Sy...

This report follows up on the report published in the SESS Report 2018 (Christiansen et al. 2019). Since 2018, the Norwegian Environment Agency has released the Climate in Svalbard 2100 report summarizing observed trends in permafrost conditions over the period of field measurements and a forecast for the future, based on recent climate and permafr...

Permafrost in steep rock slopes has been increasingly studied since the early 2000s in conjunction with a growing number of rock slope failures, which likely resulted from permafrost degradation. In Norway, rock slope destabilization is a widespread phenomenon and a major source of risk for the population and infrastructure. However, a lack of prec...

Nematodes of the genera Elaphostrongylus and Dictyocaulus are associated with disease in semi-domesticated tundra reindeer and farmed red deer whereas less knowledge exists in the wild. Their first stage larvae (L1) develop to the infective third stage (L3) in the environment; Elaphostrongylus spp. within intermediate gastropod hosts and Dictyocaul...

Permafrost in steep slopes has been increasingly studied since the early 2000s in conjunction with a growing number of rock-slope failures, which likely resulted from permafrost degradation. In Norway, rock-slope destabilization is a widespread phenomenon and a major source of risk for the population and infrastructure. However, the lack of precise...

This report was commissioned by the Norwegian Environment Agency in order to provide basic information for use in climate change adaptation in Svalbard. It includes descriptions of historical, as well as projections for the future climate development in the atmosphere, hydrosphere, cryosphere and ocean, and it includes effects on the physical natur...

Permafrost warming has the potential to amplify global climate change, because when frozen sediments thaw it unlocks soil organic carbon. Yet to date, no globally consistent assessment of permafrost temperature change has been compiled. Here we use a global data set of permafrost temperature time series from the Global Terrestrial Network for Perma...

Arctic winters have become increasingly warmer and rainier. Where permafrost prevails, winter rain (or rain-on-snow) is known to occasionally cause extensive ice layers at the snow/ground interface, i.e. ‘basal ice’ or ‘ground ice’, with potentially large ecological and socio-economic implications. However, an overall lack of field data has so far...

Recent acceleration of rock glaciers is well recognized in the European Alps, but similar behavior is hardly documented elsewhere. Also, the controlling factors are not fully understood. Here we provide evidence for acceleration of a rock glacier complex in northern Norway, from 62 years of remote sensing data. Average annual horizontal velocity me...

In 2017, the dominant greenhouse gases released into Earth's atmosphere-carbon dioxide, methane, and nitrous oxide-reached new record highs. The annual global average carbon dioxide concentration at Earth's surface for 2017 was 405.0 ± 0.1 ppm, 2.2 ppm greater than for 2016 and the highest in the modern atmospheric measurement record and in ice cor...

On 26 June 2008, a rock avalanche detached in the northeast facing slope of Polvartinden, a high-alpine mountain in Signaldalen, northern Norway. Here, we report on the observed and modelled past and present near-surface temperature regime close to the failure zone, as well as on a subsequent simulation of the subsurface temperature regime, and on...

Chronicle about causes and consequences of the rapidly warming Arctic winter, in the Norwegian newspaper Aftenposten: https://www.aftenposten.no/viten/i/bKav85/-Vinteren-201718-er-den-varmeste-noensinne-registrert-i-Arktis

Weighing precipitation gauges are used widely for the measurement of all forms of precipitation, and are typically more accurate than tipping-bucket precipitation gauges. This is especially true for the measurement of solid precipitation; however, weighing precipitation gauge measurements must still be adjusted for undercatch in snowy, windy condit...

This paper presents selected results of the interdisciplinary research project Impacts of extreme weather events on infrastructure in Norway (InfraRisk) carried out between 2010 to 2013, as part of the program NORKLIMA (2004 2013) of the Research Council of Norway (RCN). The project has systematized large amounts of existing data and generated new...

Prosjektets mål har vært å utvikle datagrunnlaget for naturindeks for økosystem fjell. The overriding objective of this project is to develop indicators of biodiversity in alpine ecosystems to be included in The Norwegian Nature Index.

This update of findings on permafrost adds to the benchmark assessments on snow, water, ice and permafrost in the previous SWIPA assessment. It provides a synthesis of current knowledge across the circumpolar permafrost regions on the thermal state of permafrost (Section 4.2), permafrost modeling and projections of future permafrost states (Section...

Editor’s note: For easy download the posted pdf of the State of the Climate for 2017 is a low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.

Ch 7. Regional Climates: f. Europe and the Middle East

Although precipitation has been measured for many centuries, precipitation measurements are still beset with significant inaccuracies. Solid precipitation is particularly difficult to measure accurately, and wintertime precipitation measurement biases between different observing networks or different regions can exceed 100 %. Using precipitation ga...

Adjustments for the undercatch of solid precipitation caused by wind were developed for different weighing gauge/wind shield combinations tested in WMO-SPICE. These include several different manufacturer-provided unshielded and single-Alter shielded weighing gauges, a MRW500 precipitation gauge within a small, manufacturer-provided shield, and host...

Hydrologic measurements are important for both the short- and long-term management of water resources. Of the terms in the hydrologic budget, precipitation is typically the most important input; however, measurements of precipitation are subject to large errors and biases. For example, an all-weather unshielded weighing precipitation gauge can coll...

Although precipitation has been measured for many centuries, precipitation measurements are still beset with significant inaccuracies. Solid precipitation is particularly difficult to measure accurately, and differences between winter-time precipitation measurements from different measurement networks or different regions can exceed 100 %. Using pr...

Despite numerous spectacular archaeological discoveries worldwide related to melting ice patches and the emerging field of glacial archaeology, governing processes related to ice patch development during the Holocene and their sensitivity to climate change are still largely unexplored. Here we present new results from an extensive 6-year (2009–2015...

Comparative analysis of records of two gauges with different wind shields (Tretyakov gauge and Geonor T200-B) were done, based on time series of parallel measurement in Barentsburg settlement, Svalbard, during two winter times in period from September 2014 to July 2016. All collected data of solid precipitation were divided into two ranges with dif...

In June 2008, a rockslide detached in the northeast facing slope of Polvartinden, a high-alpine mountain in Signaldalen, Northern Norway. Here, we report on the observed and modelled past and present near-surface temperature regime close to the failure zone, as well as on a subsequent simulation of the subsurface temperature regime, and on initial...

A research-based understanding of permafrost distribution at a sufficient spatial resolution is important to meet the demands of science, education and society. We present a new permafrost map for Norway, Sweden and Finland that provides a more detailed and updated description of permafrost distribution in this area than previously available. We im...

Spitsbergen has experienced some of the most severe temperature changes in the Arctic during the last three decades. This study relates the recent warming to variations in large-scale atmospheric circulation (AC), air mass characteristics, and sea ice concentration (SIC), both regionally around Spitsbergen and locally in three fjords. We find subst...

Hydrologic measurements are becoming increasingly important for both the short and long term management of water resources. Of all the terms in the hydrologic budget, precipitation is the typically most important input. However, measurements of precipitation are still subject to large errors and biases. For example, a high-quality but unshielded we...

In recent years extreme winter warming events have been reported in arctic areas. These events are characterized as extraordinarily warm weather episodes, occasionally combined with intense rainfall, causing ecological disturbance and challenges for arctic societies and infrastructure. Ground-ice formation due to winter rain or melting prevents ung...

In the Arctic, the 2015 land surface temperature was 1.2°C above the 1981–2010 average, tying 2007 and 2011 for the highest annual temperature and representing a 2.8°C increase since the record began in 1900. Increasing temperatures have led to decreasing Arctic sea ice extent and thickness. On 25 February 2015, the lowest maximum sea ice extent in...

Daily temperature measurements from six meteorological stations along the coast and fjords of western Spitsbergen have been digitized and quality controlled in a Norwegian, Russian and Polish collaboration. Complete daily data series have been reconstructed back to 1948 for all of the stations. One of the station’s monthly temperature series has pr...

Despite numerous spectacular archaeological discoveries worldwide related to melting ice patches and the emerging field of glacial archaeology, governing processes related to ice patch development during Holocene and their sensitivity to climate change are still largely unexplored. Here we present new results from an extensive 6-year (2009–2015) fi...

We present an outlook for a number of climate parameters for temperature, precipitation, and storm statistics in the Barents region. Projected temperatures exhibited strongest increase over northern Fennoscandia and the high Arctic, exceeding 7 °C by 2099 for a typical 'warm winter' under the RCP4.5 scenario. More extreme temperatures may be expect...

Precipitation measurements exhibit large cold season biases due to under-catch in windy conditions. These uncertainties affect water balance calculations, snowpack monitoring and calibration of remote sensing algorithms and land surface models. More accurate data would improve the ability to predict future changes in water resources and mountain ha...

A 175 years long homogenized composite record of monthly mean temperatures is presented for Oslo, the capital of Norway. The early raw data have been digitised and quality controlled, and monthly means have been calculated. Some early original observations carried out in a Wild screen (1877–1936) were found to be spuriously high because of inapprop...

In permafrost environments exposed to strong winds, drifting snow can create a small-scale pattern of strongly variable snow heights, which has profound implications for the thermal regime of the ground. Arrays of 26 to more than 100 temperature loggers were installed to record the distribution of ground surface temperatures within three study area...

One predicted consequence of global warming is an increased frequency of extreme weather events, such as heat waves, droughts, or heavy rainfalls. In parts of the Arctic, extreme warm spells and heavy rain-on-snow (ROS) events in winter are already more frequent. How these weather events impact snow-pack and permafrost characteristics is rarely doc...