Ole Humlum

Bio: Ole Humlum is an academic researcher from University of Oslo. The author has contributed to research in topics: Permafrost & Glacier. The author has an hindex of 27, co-authored 59 publications receiving 3000 citations. Previous affiliations of Ole Humlum include University of Copenhagen & University Centre in Svalbard.

Permafrost creep and rock glacier dynamics

Abstract: This review paper examines thermal conditions (active layer and permafrost), internal composition (rock and ice components), kinematics and rheology of creeping perennially frozen slopes in cold mountain areas. The aim is to assemble current information about creep in permafrost and rock glaciers from diverse published sources into a single paper that will be useful in studies of the flow and deformation of subsurface ice and their surface manifestations not only on Earth, but also on Mars. Emphasis is placed on quantitative information from drilling, borehole measurements, geophysical soundings, photogrammetry, laboratory experiments, etc. It is evident that quantitative holistic treatment of permafrost creep and rock glaciers requires consideration of: (a) rock weathering, snow avalanches and rockfall, with grain-size sorting on scree slopes; (b) freezing processes and ice formation in scree at sub-zero temperatures containing abundant fine material as well as coarse-grained blocks; (c) coupled thermohydro-mechanical aspects of creep and failure processes in frozen rock debris; (d) kinematics of non-isotropic, heterogeneous and layered, ice-rich permafrost on slopes with long transport paths for coarse surface material from the headwall to the front and, in some cases, subsequent re-incorporation into an advancing rock glacier causing corresponding age inversion at

The Thermal State of Permafrost in the Nordic Area during the International Polar Year 2007-2009

Abstract: This paper provides a snapshot of the permafrost thermal state in the Nordic area obtained during the International Polar Year (IPY) 2007-2009 Several intensive research campaigns were undertaken within a variety of projects in the Nordic countries to obtain this snapshot We demonstrate for Scandinavia that both lowland permafrost in palsas and peat plateaus, and large areas of permafrost in the mountains are at temperatures close to 0 degrees C, which makes them sensitive to climatic changes In Svalbard and northeast Greenland, and also in the highest parts of the mountains in the rest of the Nordic area, the permafrost is somewhat colder, but still only a few degrees below the freezing point The observations presented from the network of boreholes, more than half of which were established during the IPY, provide an important baseline to assess how future predicted climatic changes may affect the permafrost thermal state in the Nordic area Time series of active-layer thickness and permafrost temperature conditions in the Nordic area, which are generally only 10 years in length, show generally increasing active-layer depths and risings permafrost temperatures Copyright (C) 2010 John Wiley & Sons, Ltd (Less)

The climatic significance of rock glaciers

Abstract: To obtain knowledge on the typical regional climate for rock glacier initiation and growth, a number of diagnostic geomorphological associations of normal glaciers and rock glaciers are analysed in selected regions of central west Greenland, north-east Greenland and Antarctica. In these study areas, active rock glaciers and normal glaciers occur in proximity, and meteorological data are at hand. In general, the overall climate at active rock glaciers is not significantly different from that at the equilibrium line of normal glaciers nearby; the mean annual air temperature at rock glaciers usually is only slightly higher, if at all, than at nearby ELAs, and also the annual regional precipitation is only slightly lower than at nearby glaciers. In a regional temperature–precipitation space, active rock glaciers therefore tend to plot close to ELAs for modern glaciers, although with a tendency towards somewhat drier environments. The typical rock glacier climate is not exactly continental as has often been argued; it is rather a dry to moderate humid climate with cool summers. An important difference appears to be that while glaciers typically are situated at sites with a local, high accumulation of snow in relation to the input of talus, the opposite is true for rock glaciers. The different locations of glaciers and rock glaciers are thus mainly controlled by topoclimatic differences, rather than being a result of regional climatic differences. The observational data are still geographically limited and require both quality improvement and testing from other regions with active rock glaciers, but the topographic position and altitudinal distribution of rock glaciers probably contain unique climatic information, much the same as normal glaciers do. Therefore, relict rock glaciers represent a potentially important source of palaeoclimatic information. © 1998 John Wiley & Sons, Ltd. Pour faire apparaotre le climat regional typique sous lequel se forment et grandissent les glaciers rocheux, un certain nombre de glaciers normaux et de glaciers rocheux ont ete analyses dans des regions selectionnees de l'Ouest et du Nord-Est du Groenland ainsi que dans l'Antarctique. Dans ces regions ou des glaciers normaux et des glaciers rocheux actifs existent les uns pres des autres, des donnees climatologiques sont disponibles. En general, le climat des glaciers rocheux actifs n'est pas significativement different de celui qui existe pres de la ligne d'equilibre des glaciers normaux proches; la temperature moyenne annuelle sur les glaciers rocheux est seulement legerement plus elevee qu'a proximite de la ligne d'equilibre proche tandis que la valeur annuelle des precipitations est un peu plus basse que sur les glaciers voisins. Dans un espace regional temperature/precipitations, les glaciers rocheux actifs ont tendance a se trouver pres de la limite d'equilibre des glaciers modernes, quoique avec une tendance vers un environnement plus sec. Le climat typique sous lequel existent les glaciers rocheux n'est pas exactement continental comme cela a ete souvent propose; il est plutot sec ou moderement humide avec des etes froids. Une difference importante semble etre que les glaciers sont typiquement situes dans des sites ou une grande accumulation locale de neige se produit en relation avec l'influence d'un talus, alors que l'inverse est vrai pour les glaciers rocheux. Les localisations differentes des glaciers et des glaciers rocheux sont donc principalement controlees par des differences topoclimatiques, plutot que par des differences climatiques regionales. Les donnees d'observations sont encore geographiquement limitees et demandent a la fois une amelioration de leur qualite et d'etre testees pour d'autres regions ou des glaciers rocheux actifs sont presents. Il est probable ainsi que la position topographique et la distribution en altitude des glaciers rocheux contiennent une information climatique unique, semblable a celle qui est attachee aux glaciers normaux. En consequence, les glaciers rocheux reliques sont potentiellement une importante source d'informations paleoclimatiques. Copyright © 1998 John Wiley & Sons, Ltd.

The role of biotic interactions in shaping distributions and realised assemblages of species: implications for species distribution modelling

Abstract: Predicting which species will occur together in the future, and where, remains one of the greatest challenges in ecology, and requires a sound understanding of how the abiotic and biotic environments interact with dispersal processes and history across scales. Biotic interactions and their dynamics influence species' relationships to climate, and this also has important implications for predicting future distributions of species. It is already well accepted that biotic interactions shape species' spatial distributions at local spatial extents, but the role of these interactions beyond local extents (e.g. 10 km2 to global extents) are usually dismissed as unimportant. In this review we consolidate evidence for how biotic interactions shape species distributions beyond local extents and review methods for integrating biotic interactions into species distribution modelling tools. Drawing upon evidence from contemporary and palaeoecological studies of individual species ranges, functional groups, and species richness patterns, we show that biotic interactions have clearly left their mark on species distributions and realised assemblages of species across all spatial extents. We demonstrate this with examples from within and across trophic groups. A range of species distribution modelling tools is available to quantify species environmental relationships and predict species occurrence, such as: (i) integrating pairwise dependencies, (ii) using integrative predictors, and (iii) hybridising species distribution models (SDMs) with dynamic models. These methods have typically only been applied to interacting pairs of species at a single time, require a priori ecological knowledge about which species interact, and due to data paucity must assume that biotic interactions are constant in space and time. To better inform the future development of these models across spatial scales, we call for accelerated collection of spatially and temporally explicit species data. Ideally, these data should be sampled to reflect variation in the underlying environment across large spatial extents, and at fine spatial resolution. Simplified ecosystems where there are relatively few interacting species and sometimes a wealth of existing ecosystem monitoring data (e.g. arctic, alpine or island habitats) offer settings where the development of modelling tools that account for biotic interactions may be less difficult than elsewhere.

Permafrost is warming at a global scale

Abstract: 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 Permafrost to evaluate temperature change across permafrost regions for the period since the International Polar Year (2007–2009). During the reference decade between 2007 and 2016, ground temperature near the depth of zero annual amplitude in the continuous permafrost zone increased by 0.39 ± 0.15 °C. Over the same period, discontinuous permafrost warmed by 0.20 ± 0.10 °C. Permafrost in mountains warmed by 0.19 ± 0.05 °C and in Antarctica by 0.37 ± 0.10 °C. Globally, permafrost temperature increased by 0.29 ± 0.12 °C. The observed trend follows the Arctic amplification of air temperature increase in the Northern Hemisphere. In the discontinuous zone, however, ground warming occurred due to increased snow thickness while air temperature remained statistically unchanged.