Seasonal hydrology and geochemistry of two small high Arctic catchments, Axel Heiberg Island, Northwest Territories

This study examines hydrological and geochemical processes in a continuous permafrost setting in the Canadian High Arctic on Axel Heiberg Island (79°25 \u27 N; 90°45 \u27 W) with the following objective: to identify spatial and seasonal variation in hydrology and geochemistry of the East Inflow (EIF) and West Inflow (WIF) sub basins draining into Colour Lake and relate them to processes operating in the basins. Field work in the catchment was carried out between 20 May to 16 August 1991 and 23 July to 20 August 1992. Surface flow and suprapermafrost groundwater in the active layer were monitored to assess seasonal changes in flowpaths of water. Water samples were taken from streams, suprapermafrost groundwaters and precipitation and analyzed for total dissolved solids (TDS), pH and major cations and anions. Hydrological and chemical processes are examined in three periods 1. snowmelt (1-12 June) 2. period of active layer development (12 June to 2 August) and 3. the rainstorm (2 August to 10 August). Results show that several processes are responsible for the observed spatial and temporal changes in the hydrology and chemistry of the streams. In the WIF/W, a large proportion of snowmelt water refreezes on boulders of the felsenmeer forming ground ice. Three results identify the melting of ground ice as an important stream flow generating factor in the WIF/W during the period of active layer development: 1. diurnal cycles in discharge 2. a positive significant correlation between air temperature and discharge 3. TDS are inversely correlated with discharge. The hydrological regime of the WIF/W, which shows the characteristics of a proglacial regime is therefore best described as melting ground ice regime . In the EIF, geomorphological characteristics of the basin result in a higher proportion of water travelling through the active layer, thus the response of discharge to high air temperatures is significantly lagged for 2 days ( modified melting ground ice regime). Chemical differences of the two streams are related to geological sources. Seasonal changes of ions in the EIF are related to two hydrological and chemical different source areas within the EIF basin. The seasonally increasing concentrations of ions during the third period of active layer development in both streams are explained by two processes: 1. increasing contribution of suprapermafrost groundwater to the stream runoff as a result of higher storage capacities of the active layer towards the end of the summer and 2. seasonally increasing ion concentrations of suprapermafrost groundwater with a longer residence time of water in the soil. Sulphate is the ion with the highest export rate for all streams. ln the EIF, the sum of Ca^2+ and SO4^2- is more than 90% of the total TDS exported. In the WIF/W, the percentage of Ca^2+ and SO4^2- exported is seasonally increasing from 83 to 90%. Overall, the rainstorm is the dominating event in both streams in terms of total export of TDS

A study of the large-scale climatic effects of a possible disappearance of high-latitude inland water surfaces during the 21st centurys

This study evaluates the climatic impact of possible future changes in high-latitude inland water surface (IWS) area. We carried out a set of climate-change experiments with an atmospheric general circulation model in which different scenarios of future changes of IWS extent were prescribed. The simulations are based on the SRES-A1B greenhouse gas emission scenario and represent the transient climatic state at the end of the 21st century.Our results indicate that the impact of a reduction in IWS extent depends on the season considered: the total disappearance of IWS would lead to cooling during cold seasons and to warming in summer. In the annual mean, the cooling effect would be dominant. In an experiment in which the future change of prescribed IWS extent is prescribed as a function of the simulated changes of permafrost extent, we find that these changes are self-consistent in the sense that their effects on the simulated temperature and precipitation patterns would not be contradictory to the underlying scenario of changes in IWS extent. In this best guess simulation, the projected changes in IWS extent would reduce future nearsurface warming over large parts of northern Eurasia by about 20% during the cold season, while the impact in North America and during summer is less clear. As a whole, the direct climatic impact of future IWS changes is likely to be moderate

Water Body Distributions Across Scales: A Remote Sensing Based Comparison of Three Arctic Tundra Wetlands

Water bodies are ubiquitous features in Arctic wetlands. Ponds, i.e., waters with a surface area smaller than 104 m2, have been recognized as hotspots of biological activity and greenhouse gas emissions but are not well inventoried. This study aimed to identify common characteristics of three Arctic wetlands including water body size and abundance for different spatial resolutions, and the potential of Landsat-5 TM satellite data to show the subpixel fraction of water cover (SWC) via the surface albedo. Water bodies were mapped using optical and radar satellite data with resolutions of 4mor better, Landsat-5 TM at 30mand the MODIS water mask (MOD44W) at 250m resolution. Study sites showed similar properties regarding water body distributions and scaling issues. Abundance-size distributions showed a curved pattern on a log-log scale with a flattened lower tail and an upper tail that appeared Paretian. Ponds represented 95% of the total water body number. Total number of water bodies decreased with coarser spatial resolutions. However, clusters of small water bodies were merged into single larger water bodies leading to local overestimation of water surface area. To assess the uncertainty of coarse-scale products, both surface water fraction and the water body size distribution should therefore be considered. Using Landsat surface albedo to estimate SWC across different terrain types including polygonal terrain and drained thermokarst basins proved to be a robust approach. However, the albedo–SWC relationship is site specific and needs to be tested in other Arctic regions. These findings present a baseline to better represent small water bodies of Arctic wet tundra environments in regional as well as global ecosystem and climate models

Importance of the Webb, Pearman, and Leuning (WPL) correction for the measurement of small CO2 fluxes

The WPL (Webb, Pearman, and Leuning) correction is fully accepted to correct trace gas fluxes like CO2 for density fluctuations due to water vapour and temperature fluctuations for open-path gas analysers. It is known that this additive correction can be on the order of magnitude of the actual flux. However, this is hardly ever included in the analysis of data quality. An example from the Arctic shows the problems, because the size of the correction is a multiple of the actual flux. As a general result, we examined and tabulated the magnitude of the WPL correction for carbon dioxide flux as a function of sensible and latent heat flux. Furthermore, we propose a parameter to better estimate possible deficits in data quality and recommend integrating the quality flag derived with this parameter into the general study of small carbon dioxide fluxes

An 18-year record (1998-2016) of permafrost soil temperature, soil water content, and meteorological data from a high Arctic permafrost site Bayelva (Svalbard)

Since 1998 we record hourly data from the Bayelva site close to Ny-Alesund, on Spitsbergen Island in the Svalbard archipelago (78°551 N, 11°571 E), where continuous permafrost underlies the un- glaciated coastal areas. The West Spitsbergen Ocean Current, a branch of the North Atlantic Current, warms this area to an average air temperature of about −13 °C in January and +5 °C in July, and provides about 400 mm of precipitation annually, falling mostly as snow between September and May. Significant warming of air temperatures has been detected since 1960, which is generally attributed to changes in the radiation budget and in atmospheric circulation. This warming is also reflected in the permafrost temperatures, as recorded from boreholes as well as increased active layer thaw depths. The scientific goal is to establish a long term- permafrost observational site to investigate the observed warming of permafrost and potential causes. At the site, weather components (radiation components, temperature, humidity, wind speed and direction, snow) and soil temperature and moisture in the seasonally thawing surface layer. In 2007, additional instruments were added: an eddy covariance system and a 10 m permafrost temperature profile. In 2012, this site was equipped with a 220 V power supply and data transfer cables that are buried in the soil. Data are transferred hourly to Potsdam and loggers and sensors can be accessed and programmed remotely from AWI. Due to this major improvement, we obtained a data record without gaps since 2012. Thus, this site is included as validation site in satellite missions, for example in NASA’s soil moisture active passive mission (SMAP). We give an overview of the available data, as well as the processing and cleaning routines that are applied

Vegetation map of Trail Valley Creek, Northwest Territories, Canada

The vegetation map distinguishes between five tundra vegetation types, trees, and open water at the forest–tundra transition north of Inuvik, Northwest Territories, Canada. The area is underlain by continuous permafrost. Vegetation types were distinguished based on vegetation height derived from airborne laser scanning, airborne orthophotos and observations from the field site. A detailed description of the data sources and processing steps is included

In-situ measurements of sediment temperature under shallow water bodies in Arctic environments

The thermal regime under lakes, ponds, and shallow near shore zones in permafrost zones in the Arctic is predominantly determined by the temperature of the overlying water body throughout the year. Where the temperatures of the water are warmer than the air, unfrozen zones within the permafrost, called taliks, can form below the water bodies. However, the presence of bottom-fast ice can decrease the mean annual bed temperature in shallow water bodies and significantly slow down the thawing or even refreeze the lake or sea bed in winter. Small changes in water level have the potential to drastically alter the sub-bed thermal regime between permafrost-thawing and permafrost-forming. The temperature regime of lake sediments is a determining factor in the microbial activity that makes their taliks hot spots of methane gas emission. Measurements of the sediment temperature below shallow water bodies are scarce, and single temperature-chains in boreholes are not sufficient to map spatial variability. We present a new device to measure in-situ temperature-depth profiles in saturated soils or sediments, adapting the functionality of classic Lister-type heat flow probes to the special requirements of the Arctic. The measurement setup consists of 30 equally spaced (5cm) digital temperature sensors housed in a 1.5 m stainless steel lance. The lance is portable and can be pushed into the sediment by hand either from a wading position, a small boat or through a hole in the ice during the winter. Measurements are taken continuously and 15 minutes in the sediment are sufficient to acquire in-situ temperatures within the accuracy of the sensors (0.01K after calibration at 0°C). The spacing of the sensors yield a detailed temperature-depth-profile of the near-surface sediments, where small-scale changes in the bottom water changes dominate the temperature field of the sediment. The short time needed for a single measurement allows for fine-meshed surveys of the sediment in areas of interest, such as the transition zone from bottom-fast to free water. Test campaigns in the Canadian Arctic and on Svalbard have proven the device to be robust in a range of environments. We present data acquired during winter and summer, covering non-permafrost, thermokarst lake and offshore measurements

In-situ measurements of sediment temperature under shallow water bodies in Arctic environments

The thermal regime under lakes, ponds, and shallow near shore zones in permafrost zones in the Arctic is predominantly determined by the temperature of the overlying water body throughout the year. Where the temperatures of the water are warmer than the air, unfrozen zones within the permafrost, called taliks, can form below the water bodies. However, the presence of bottom-fast ice can decrease the mean annual bed temperature in shallow water bodies and significantly slow down the thawing or even refreeze the lake or sea bed in winter. Small changes in water level have the potential to drastically alter the sub-bed thermal regime between permafrost-thawing and permafrost-forming. The temperature regime of lake sediments is a determining factor in the microbial activity that makes their taliks hot spots of methane gas emission. Measurements of the sediment temperature below shallow water bodies are scarce, and single temperature-chains in boreholes are not sufficient to map spatial variability. We present a new device to measure in-situ temperature-depth profiles in saturated soils or sediments, adapting the functionality of classic Lister-type heat flow probes to the special requirements of the Arctic. The measurement setup consists of 30 equally spaced (5cm) digital temperature sensors housed in a 1.5 m stainless steel lance. The lance is portable and can be pushed into the sediment by hand either from a wading position, a small boat or through a hole in the ice during the winter. Measurements are taken continuously and 15 minutes in the sediment are sufficient to acquire in-situ temperatures within the accuracy of the sensors (0.01K after calibration at 0°C). The spacing of the sensors yield a detailed temperature-depth-profile of the near-surface sediments, where small-scale changes in the bottom water changes dominate the temperature field of the sediment. The short time needed for a single measurement allows for fine-meshed surveys of the sediment in areas of interest, such as the transition zone from bottom-fast to free water. Test campaigns in the Canadian Arctic and on Svalbard have proven the device to be robust in a range of environments. We present data acquired during winter and summer, covering non-permafrost, thermokarst lake and offshore measurements