ALBERT

Description: In permafrost regions, there is a strong coupling between a soil’s moisture content and its thermal dynamics. However, dynamic changes in soil moisture have not been given much attention in permafrost monitoring, partially due to a previous shortage of observations. The questions hence arises: can novel remotely-sensed soil moisture estimates improve permafrost monitoring? Data assimilation seems a promising avenue, as it can improve the predicted temperatures and soil moisture by exploiting their complex, model-predicted coupling while accounting for uncertainties in both modelled and observed soil moisture. To explore its potential benefit, we conduct synthetic and real-world (Radarsat-2 soil moisture estimates over the Mackenzie River Delta Uplands, Canada) data assimilation experiments. We use an Ensemble Kalman Filter to ingest surface soil moisture into the state-of-the art CryoGrid-3 permafrost model, which has a flexible two-layer hydrology scheme. We address two questions. 1) Where can surface soil moisture information improve modelled temperatures? We find that it mainly does so for porous, organic soils, but not for mineral soils. As organic soils dry, the cooling effect by the insulating soil wins out over the competing warming effect induced by decreasing evaporation. Surface soil moisture observations thus provide valuable information on deeper soil temperatures, a finding that is largely consistent with field observations. In mineral soils, by contrast, the thermal conductivity decreases much less upon drying,and surface soil moisture provides little information on deeper soil temperatures. 2) How big are the improvements in organic soils? In our synthetic experiments, we find that estimates of the active layer thickness improve by up to a factor of two (down to 10 cm) upon assimilation, even when soil moisture observations are of limited precision. The modelled soil temperatures improve throughout the entire profile, with the largest improvements below 10 cm. We will compare those synthetic results with the Radarsat-2 observations. We conclude that satellite soil moisture information can help to reduce one major uncertainty in permafrost monitoring. We predict that advances in remote sensing and models will improve our knowledge of active layer and permafrost dynamics, not just of the water and energy balance, but also of ecological and biogeochemical processes.

Description: During the last decade the Arctic has experienced increasing human development while many native communities continue to live a subsistence lifestyle. Off-road winter tundra travel for resource exploration is most cost effective and least environmentally damaging during winter when the tundra is frozen and snow covered. Climate warming, which is occurring at an amplified rate in the Arctic, likely changes the period when access to the off-road tundra travel is possible. There currently exists, however, large uncertainty as to how climate change will impact the low-cost winter travel access across the tundra. Here we defined safe tundra access when soil temperatures are below a soil type dependent freezing temperature and snow cover is at least 20 cm. Our analysis is based on the simulated soil temperatures and snow depths of Land Surface Models (LSMs) contributing to “The Inter-Sectoral Impact Model Intercomparison Project” (ISIMIP). ISIMIP simulations are based on a common protocol, the same input data, the same spatial (0.5°) and temporal resolution (daily modeling output), and span over the period 1861-2100. The LSMs are forced by four different bias-corrected global circulation models (IPSL-CM5A-LR, GFDL-ESM2M, MIROC5, HadGEM2-ES) and three different future conditions (represented via representative concentration pathways (RCP) 2.6, 6.0, 8.5). The simulation results of our model ensemble (60 model combinations) show consistent permafrost warming and changing snow cover patterns at 60°N. Annual off-road tundra travel is considerably reduced (〉50%) under future climate change scenarios, especially under the RCP8.5. The main reduction can be observed in the spring and autumn (〉30%). The results of the multi-model ensemble differ in magnitude, however, their overall trend is consistent. Our results suggest a high vulnerability and substantial changes to the (subsistence) livelihoods of native communities and increasing costs for off-road resource exploration.

Description: The ESA DUE Permafrost project (2009-2011) is developing a suite of parameters indicative of the subsurface phenomenon permafrost using satellite remote sensing: Land Surface Temperature (LST), Surface Soil Moisture (SSM), Surface Frozen and Thawed State (Freeze/Thaw), Terrain, Land Cover (LC), and Surface Water (SW). Snow parameters (Snow Extent and Snow Water Equivalent) are being developed through the DUE GlobSnow project, Global Snow Monitoring for Climate Research (2008-2011). The final DUE Permafrost remote sensing products cover the years 2007 to 2011 with a circumpolar coverage that will soon be released (early 2012), and then be used to analyze the temporal dynamics and map the spatial patterns of indicators. Further information is available at www.ipf.tuwien.ac.at/ permafrost. Since the beginning, scientific stakeholders and the International Permafrost Association (IPA) have been involved in the science and implementation plan. Interactive international user workshops took place in 2010 at the Technical University of Vienna, Vienna (AT), and in 2011 at the International Arctic Research Center (IARC), Fairbanks, Alaska (US). This involvement and the ongoing evaluation of the indicators derived from remote sensing for the high-latitude permafrost regions make the DUE Permafrost products trustworthy for the permafrost and the climate research community. The adaption of the remote sensing products for the permafrost and climate modelling is experimental and highly dependent on the users’ involvement. For a few years already, the Geophysical Institute Permafrost Laboratory (GIPL), University of Alaska Fairbanks, US, (http://www.gi.alaska.edu/research/snowicepermafrost/Permafrost) has successfully demonstrated the value of using LST derived from remote sensing data for driving its permafrost models. Further experimental testing of the DUE Permafrost products for use by the modeling community (permafrost and climate) will range from (i) the evaluation of external data of the models, with modifying or providing new external data (e.g. tundra land cover, surface water ratio, soil distribution), to (ii) new drivers for regional models derived from remote sensing (e.g., LST), to (iii) the evaluation of the output data from the models (e.g. spatial patterns of moisture and temperature).

Description: The focus of this research has been on detecting changes in lakes vegetation, land surface temperatures, and snow cover, using data from remote sensing. The study area covers the main (central) part of the Lena River catchment in the Yakutia Region of Siberia (Russia) where continuous permafrost coverage’s is up to 90%. The remote sensing analyses are based on MODIS (NASA) and Landsat (USGS) satellite data. Time series of remote sensing products of MODIS land surface temperature were produced for the study region between 61°N and 65°N, and between 117.5°E and 131.5°E. The MODIS Land Surface Temperature level 3 product, MOD11C3 are configured on a 0.05° latitude/longitude MODIS Climate Model Grid (CMG) raster. The LST product is a monthly composited average and represents clear-sky LST values. The monthly land surface temperature were analyzed over the eleven year interval from May 2000 to April 2011. Linear trend calculations for the 11 year temperature measurement interval were performed separately for each two month interval, in each pixel, using the least squares method. Water bodies were extracted using the Landsat Short Wave Infrared SWIR band 5. Within the study region's 315,000 sq. km, the total area covered by lakes increased by 17.5% between 2002 and 2009. The amount of lake increase differs between 42-11% depending on the region. The overall trend in land surface temperature is around 0.15°C/year, but with seasonal warming trends in April-May of up to 0.45°C/year in some areas and cooling of -0.2 to -0.3°C/year in July-August in other areas. These regional differences and potential causes of the land surface temperature changes will be discussed with respect to land cover changes.

Description: The Lena River Delta in Northern Yakutia forms one of the largest deltas in the Arctic and its catchment area (2 430 000 km2) is one of the largest in the whole of Eurasia. The Lena River distributes water and sediment in four main channels before discharging in total about 30 km3 of water through the delta into the Arctic Ocean every year and its discharge has been observed to be increasing. The goal of this presentation is to characterize the hydrologic processes that are strongly affected by a transient climate component- the permafrost. Permafrost plays a major role for storage and release of water to rivers and surface and subsurface water bodies. Conversely, the coupled water and heat fluxes in the atmosphere and below ground have a marked influence on the permafrost’s thermal regime. Our study site, the Lena River Delta, is also one of the coldest and driest places on Earth, with mean annual air temperatures of about -13 °C, a large annual air temperature range of about 44 °C and summer precipitation usually less than 150 mm. Very cold continuous permafrost of about −8.6 °C (11 m depth) underlays the area between about 400 and 600 m below surface and since 2006 the permafrost has warmed than 1 °C at 10.7 m. Roughly half of the land surface is dominated by wet surfaces, such as polygons, ponds and thermokarst lakes. This contribution summarizes past and ongoing research on hydrologic processes across spatial scales, from microtopographic processes of polygonal tundra to regional scale deltaic processes to assess short and long term changes in water fluxes. We quantify unfrozen water in soils, streams and river discharges and water bodies’ storage at larger scales. Water bodies were mapped using optical and radar satellite data with resolutions of 4 m or better, Landsat-5 TM at 30 m and the MODIS water mask at 250 m resolution. Ponds, i. e. water bodies with surface are smaller than 104 m, make over 95 % of the total number of water bodies and are not resolved in Landsat-scale land cover classifications. Ponds are generally well mixed and experience high water temperatures up to 23 °C during the summer and are, therefore, hotspots for biological activity and CO2 emission. The ponds in the study area freeze completely in winter, whereas the deeper thermokarst lakes do not freeze to the bottom, with implications for coupling of the permafrost to the atmosphere. These deep thermokarst lakes are thermally stratified during winter and reach maximum water temperatures of up to 19 °C during summer. The summer water balance at the catchment scale was found to be mainly controlled by vertical fluxes (precipitation and evapotranspiration). On the other hand, redistribution of storage water due to lateral fluxes takes place within the microtopography of polygonal tundra. The long-term summer storage (precipitation minus evapotranspiration) from 1958-2011 indicates a reasonably balance on the polygonal tundra with an average surplus of 5 mm, but it is also characterized by high interannual variability due to precipitation input. During negative water balance years where evapotranspiration exceeds precipitation, shallower water bodies dry out. The extent of wetlands and water bodies will shift with changes in vertical water fluxes as well as permafrost warming and thaw. Thus, water bodies can serve as sentinels of environmental change and we present applicable remote-sensing observations and upscaling methods

Description: Deciduous larch is a weak competitor when growing in mixed stands with evergreen taxa but is dominant in many boreal forest areas of Eastern Siberia. However, it is hypothesized that certain factors such as a shallow active layer thickness and high fire frequency favor larch dominance. Our aim is to understand how thermohydrological interactions between vegetation, permafrost, and atmosphere stabilize the larch forests and the underlying permafrost in Eastern Siberia. A tailored version of a one-dimensional land surface model (CryoGrid) is adapted for the application in vegetated areas and used to reproduce the energy transfer and thermal regime of permafrost ground in typical boreal larch stands. In order to simulate the responds of Arctic trees to local climate and permafrost conditions we have implemented a multilayer canopy parameterization originally developed for the Community Land Model (CLM-ml_v0). The coupled model is capable of calculating the full energy balance above, within and below the canopy including the radiation budget, the turbulent fluxes and the heat budget of the permafrost ground under several forcing scenarios. We will present first results of simulations performed for different study sites in larch-dominated forests of Eastern Siberia and Mongolia under current and future climate conditions. Model performance is thoroughly evaluated based on comprehensive in-situ soil temperature and radiation measurements at our study sites.

Description: Field observations from a range of permafrost landscapes convincingly show that melting of ground ice can lead to modifications of the drainage regime so that soil moisture conditions can radically change in short time. This not only leads to significant changes in the carbon turnover, but can also trigger further permafrost thaw through complicated feedback loops. Representation of small-scale interactions between hydrology and ground thermal state are a crucial prerequisite for credible projections on a future permafrost carbon feedback. However, the present generation of Earth System Models, based on single column ground models representing coarse grid cells, can not account for such processes, although spatial heterogeneity is to a certain extent represented by means of tiling. Aiming for structural changes to overcome these challenges, we present the concept of “interacting tiles” developed in the Permanor, COUP and PermaRisk projects: by coupling tiles through lateral fluxes of heat, water and snow, it becomes possible to explicitly represent changes of microtopography, drainage regime and soil watercontents triggered by melting ground ice. Simulations with the CryoGrid permafrost model and the Noah-MP land surface scheme suggest that “interacting tiles” is capable of representing a range of thaw phenomena in strongly different permafrost landscapes, ranging from lateral erosion of peat plateaus (sporadic permafrost) to formation of thermokarst ponds and ice-wedge degradation in polygonal tundra (continuous permafrost). Using field observations from permafrost landscapes, we discuss prospects and challenges for application in coupled circulation models, focusing on model architecture and possibilities for model calibration/validation with field and remote sensing data sets.

Description: Palaeotemperature reconstructions are valuable palaeoclimate indicators and important tools for the understanding of interactions in the climate system. They form a basis for models identifying the impact of various processes within the past and future climate system. Siberia is a region with large organic carbon reserves stored in permafrost (perennially frozen ground). Temperatures in this region are thus important as a driver for a positive feedback to the global climate. Local temperature histories in the ice-rich permafrost areas of the Russian Arctic are either sparse or based on proxy data with potential seasonal biases. Borehole temperature reconstructions are sensitive to the temperature signal throughout the year and available in regions for which no other records exist. This study used two inversion methods, particle swarm optimization and a least squares technique, to retrieve temperature histories of the last 200-300 years in the Laptev Sea region from two permafrost borehole temperature records. The retrieved histories were compared to larger scale reconstructions from the region. Distinct differences in the histories between the Lena Delta and western Laptev Sea sites were found, notably a one-century delay of warming and a three decade delay in peak warming in the western Laptev Sea. The local permafrost surface temperatures at Sardakh Island (central Lena Delta) resembled the circum-Arctic regional average trends. At Mamontov Klyk (western Laptev Sea) this was the case only for the most recent decade. In contrast, the Mamontov Klyk history was more similar to northern hemispheric mean trends. A rapid recent warming of synoptic scale was consistently observed at both sites. Differences in the past temperature trends between the sites may be caused by regionally differing environmental influences, such as atmospheric circulation and sea ice coverage. The re-constructed magnitude of temperature changes is consistent with warming greater than mean Arctic temperature trends. In conclusion, reconstruction from shallow permafrost boreholes provides short-scale temperature histories in the coastal tundra of the remote Arctic (resolved at annual to multi-decadal scale). As local differences from the circum-Arctic average – including later warming and higher warming magnitude – were shown to exist in this region, our results provide a basis for local surface temperature record parameterization of climate models and of permafrost models in particular-