Bjarne Holm Jakobsen

Soil and plant community characteristics and dynamics at Zackenberg

Arctic soils hold large amounts of nutrients in the weatherable minerals and the soil organic matter, which slowly decompose. The decomposition processes release nutrients to the plant-available nutrient pool as well as greenhouse gases to the atmosphere. Changes in climatic conditions, for example, changes in the distribution of snow, water balance and the length of the growing season, are likely to affect the complex interactions between plants, abiotic and biotic soil processes as well as the composition of soil micro- and macro-fauna and thereby the overall decomposition rates. These interactions, in turn, will influence soil-plant functioning and vegetation composition in the short as well as in the long term. In this chapter, we report on soils and. plant communities and their distribution patterns in the valley Zackenbergdalen and focus on the detailed investigations within five dominating plant communities. These five communities are located along an ecological gradient in the landscape and are closely related to differences in water availability. They are therefore indirectly formed as a result of the distribution of landforms, redistribution of snow and drainage conditions. Each of the plant communities is closely related to specific nutrient levels and degree of soil development including soil element accumulation and translocation, for example, organic carbon. Results presented here show that different parts of the landscape have responded quite differently to the same overall climate changes the last 10 years and thus, most likely in the future too. Fens represent the wettest sites holding large reactive buried carbon stocks. A warmer climate will cause a permafrost degradation, which most likely will result in anoxic decomposition and increasing methane emissions. However, the net gas emissions at fen sites are sensitive to long-term changes in the water table level. Indeed, increasing maximum active layer depth at fen sites has been recorded together with a decreasing water level at Zackenberg. This is in line with the first signs of increasing extension of grasslands at the expense of fens. In contrast, the most exposed and dry areas have less soil carbon, and decomposition processes are periodically water limited. Here, an increase in air temperatures may increase active layer depth more than at fen sites, but water availability will be critical in determining nutrient cycling and plant production. Field manipulation experiments of increasing temperature, water supply and nutrient addition show that soil-plant interactions are sensitive to these variables. However, additional plant-specific investigations are needed before net effects of climate changes on different landscape and plant communities can be integrated in a landscape context and used to assess the net ecosystem effect of future climate scenarios.

Influence of Vegetation, Temperature, and Water Content on Soil Carbon Distribution and Mineralization in Four High Arctic Soils

Abstract Soil organic matter distributions, reservoirs, and mineralization rates in tundra soils are important factors for understanding biogeochemical carbon cycling. This study focuses on spatial trends and environmental controls of soil carbon distribution and microbial soil respiration in 4 tundra vegetation communities in an arctic valley in NE-Greenland (74°N), including Dryas and Cassiope heaths, Salix snow bed, and fen vegetation. Measured total soil organic carbon in the upper 50 cm averaged (±SD) 11.0 ± 1.5 kg C m−2 with spatial variations strongly affected by vegetation, hydrology, and buried organic layers. Observed soil CO2 concentrations and effluxes were simulated with a steady-state diffusion model using laboratory measured CO2 productions as input. Simulated CO2 profiles and CO2 effluxes (up to 3 μmol CO2 m−2 s−1) agreed with field observations and revealed the importance of both vegetation- and depth-specific CO2 production and CO2 diffusion for understanding the spatial variation in near-surface soil CO2 gas dynamics. These results confirm that molecular diffusion dominates gas transport in the studied soils; but also that the complexity of CO2 production/transport coupled to soil heterogeneity (in particular the litter layer) complicates the application of soil-diffusion models to estimate seasonal trends of soil gas effluxes.

Soil resources and soil erosion in the Norse settlement area of østerbygden in southern Greenland

Sammendrag Jordbundsundersogelser i nordboernes Osterbygden i Sydgronland viser, at der i perioder er foregaet omfattende jorderosion. Erosionen har isaer ramt de taet bebyggede dele at nordbosamfundet, i indlandet. Detaljerede jordprofilstudier og 14C‐dateringer af storre traekulfragmenter fra forskellige lag i jorden er foretagede, ligesom jordenes erosionsresistens er undersogt. Undersogelserne viser, at de meget let eroderbare jorde har vaeret stabile gennem Holocaen frem til det tidspunkt, hvor nordboerne gjorde landnam i omradet. I nordboperioden (c. 1000–1450) og igen i det 20. arhundrede, hvor den moderne fareavl startede, foregik omfattende og katastrofal jorderosion i storre omrader. Det staerkt erosive klima i samspil med de let eroderbare jorde udloser jorderosion i befaeerdede omrader lang tid for omradets generelle frodighed overbelastes. En manglede analyse af okosystemets egentlige achilleshaael og en fokusering pa en skonnet samlet graesningskapacitet gor det vanskeligt at undga en fremtidig degra...

Climatic conditions at the Mittivakkat Glacier catchment (1994–2006), Ammassalik Island, SE Greenland, and in a 109-year perspective (1898–2006)

Abstract Geografisk Tidsskrift, Danish Journal of Geography 108(1):51–72, 2008 The present-day climate in the Mittivakkat Glacier catchment (65°N), Southeast Greenland, is investigated spatiotemporally based on time series (13 years, 1994–2006) and standard synoptic climate data from the meteorological station in Tasiilaq (Ammasslik), covering 109 years (1898–2006). Within the catchment, meteorological conditions are monitored at the coast (Station Coast, 25 m a.s.l.) for the period 1998–2006 and in the glacier area (Station Nunatak 515 m a.s.l.)for 1994–2006. During this 13-year period, solar radiation shows increasing values, averaging 0.5 W m−2 y−1, at the nunatak and decreasing values, averaging 1.4 Wm−2 y−1, at the coast. The mean annual solar radiation at Station Coast is 102 Wm−2y−1, which is about 10% lower than at Station Nunatak, and is probably caused by increasing and higher percentages of dense clouds and sea fog in the coastal area. The mean annual air temperature is increasing by 0.10.°C y−1 at the nunatak and by 0.05°C y−1 at the coast, extending the thawing periods by about 50 days and 5 days, respectively. A snow-free period of 64 days is observed at the nunatak. The coastal area is highly dominated by air temperature inversion and sea breezes during spring and summer, strongly controlling the lapse rates within the catchments. The glacier area is highly dominated by katabatic fall winds, resulting in an almost total lack of calm periods. The wind speed is highest during winter, with mean average values around 6.0 m s−1, and gusts up to 35.0 m s−1. The total annual precipitation varies from 1,851 mm w.eq. y−1 at the nunatak (solid precipitation: 80%, mixed: 6%, and liquid: 14%) to 1,428 mm w.eq. y−1 at the coast (53%, 31%, and 16%), covering an average positive orographic effect for solid precipitation during winter (113 mm w.eq. 100 m−1) and a negative effect for liquid precipitation during summer (-52 mm w.eq. 100 m−1). Over the last 109 years (1898–2006) precipitation in the catchment has increased about 85 mm w.eq., covering two significant precipitation-rich periods: 1901–1914 (1,560 mm w.eq. y−1) and 1963–1978 (1,563 mm w.eq. y−1). Mean annual air temperature in the catchment has generally increased 0.2°C through the 109-year period, most significantly ∼2.7°C within the last 25 years. The warmest 10-year period since 1898 was 1938–1947, showing an annual average of -1.83°C, while 1997–2006 was the warmest 10- year period within the last 60 years, with an annual average of—2.10°C.

Soil solution pH measurements using in-line chambers with tension lysimeters.

During soil water extraction, pH can change as a result of atmospheric gas exchange. The pH change is important for monitoring soil acidification and determination of mineralogic controls on the solution composition. As part of a global change programme in Greenland for monitoring long-term changes in Arctic soil solutions we observed that the pH of extracted soil solutions increased in the order of a half pH unit during traditional sampling and handling of the soil solution. CO2 degassing is often considered the most important factor causing such a pH increase. Thus, traditional as well as in-line pH measurements were performed during the summers 1997 and 1998. The in-line method was designed to eliminate atmospheric contact with soil solutions prior to pH measurements. The time-dependent pH error was quantified based on laboratory experiments with soil solution under controlled temperatures and CO2 partial pressures. Equilibrium speciation modelling was used to predict pH values observed in the field an...

Holocene changes in climate and vegetation in the Ammassalik area, East Greenland, recorded in lake sediments and soil profiles

Abstract Geografisk Tidsskrift, Danish Journal of Geography 108(1):21–50, 2008 Holocene climatic, vegetational and environmental changes on the Ammassalik Island in SE Greenland (65.5 N and 37.5 W) have been studied in lake sediments and soil profiles. Based on the stratigraphy of sediments, geobiochemical characteristics, pollen and other biological proxies, a history of the land is outlined. The overall and continued climatic cooling during the Holocene basically seems to be orbitally controlled and due to both decreasing annual and summer insulations. The very early Holocene, concurrent with and following the final postglacial melting of glaciers in the landscape, appears to have experienced the warmest Holocene summer conditions, ice-free seas and limited snow covers. The climate situation seems to have been to a considerable extent based on internal regional meteorological processes and largely without strong and regular cyclonic impacts from lower latitudes. Generally decreasing insulation, a still colder landscape and near coastal sea, potentially further cooled by the negative albedo feedback from snow and ice, generally increase a gradient driven circulation of heat and moisture northwards in the western part of the North Atlantic. Counteracting this southerly influx of heat and moisture, will be the blocking effect of a snow and ice-covered region, resulting in decreasing precipitation and probably slightly increasing net radiation in landscapes. A framework and a climatic system are created to characterize the environmental changes of the latest 4–5 millennia. There has presumably been a continuous cooling trend interrupted by both spells and somewhat longer periods of renewed and stronger southerly influxes, relatively warmer conditions, higher precipitation and less sea ice.

Hydrology and Transport of Sediment and Solutes at Zackenberg

Publisher Summary This chapter focuses on the hydrology together with sediment and solute transport in the Zackenberg area in relation to climate variability during 1995–2005. The hydrology of the Zackenberg catchment area has certain distinct characteristics that determine the distribution of water and the timing of runoff. Sediment and solute transport is strongly related to the surface runoff because the water erodes bed and banks along the watercourses and acts as a transport medium for both sediment and solutes. Sediment is made available for transport by mechanical erosion of frost action, by glacial erosion, and erosion by running water on surfaces and in stream beds and banks. Sediment sinks in the catchment are alluvial cones, inland deltas, and lake basins. The chapter discusses the amount and distribution of precipitation relevant to runoff. Point measurements of precipitation at the Zackenberg Research Station in the period 1995–2005 show a slight but significant decrease in the annual amounts. Elements of the water balance—such as precipitation and snowmelt, evapotranspiration, storage, and runoff—are discussed in the chapter.

Preliminary Studies of Soils in North-East Greenland between 74° and 75° Northern Latitude

Jakobsen, Bjarne Holm: Preliminary Studies of Soils in North- East Greenland between 74° and 75° Northern Latitude. Geografisk Tidsskrift 92:111–115. Copenhagen 1992. The geography of soils has been studied in north-east Greenland between latitudes 74° and 75° N. The study ranges from the outer coast to the interior of the ice-free land area. Well-drained soils show a characteristic sequence determined by the east-west climatic gradient. Fossil soil characteristics and secondary formed features supply information on the palaeoclimate.

Geomorphology and Sedimentary Record of Three Cuspate Forelands as Indicators of Late Holocene Relative Sea-level Changes, Disko, West Greenland.

Abstract Geografisk Tidsskrift, Danish Journal of Geography 97: 33–46, 1997. The coastal geomorphology of three cuspate forelands at Saqqarliit Ilorliit, western Disko, West Greenland is described, sediment core data from salt marshes and lagoons are presented, an emergence curve is constructed, and data are discussed in relation to late Holocene relative sea-level (RSL) changes. On western Disko, falling RSL in early-middle Holocene was followed by rising RSL in late Holocene. Emergence continued until c. 2.5 ka BP. The coastal geomorphology at Saqqarliit Ilorliit suggest transgression early in the interval 2.5—1.0 ka BP and between 0.7 ka BP and the present. The first transgression resulted in formation of an intertidal platform and coastal cliffs. Washover ridges and lagoons developed during the transgression after 0.7 ka BP. Based on the core data it is suggested that the transgression after 0.7 ka BP might have consisted of three transgression phases separated by periods with stable or slightly regre...

Geochemistry of groundwater in front of a warm-based glacier in Southeast Greenland

Abstract Groundwater in front of warm‐based glaciers is likely to become a more integrated part of the future proglacial hydrological system at high latitudes due to global warming. Here, we present the first monitoring results of shallow groundwater chemistry and geochemical fingerprinting of glacier meltwater in front of a warm‐based glacier in outheast reenland (ittivakkat letscher, 65° 41′ , 37° 48′ ). The groundwater temperature, electrical conductivity and pressure head were monitored from ugust 2009 to ugust 2011, and water samples were collected in 2009 and analyzed for major ions and water isotopes (δD, δ18O). The 2-yrs of monitoring revealed that major outbursts of glacier water during the ablation season flushed the proglacial aquifer and determined the groundwater quality for the next 2–8 weeks until stable chemical conditions were reached again. Water isotope composition shows that isotopic fractionation occurs in both groundwater and glacier meltwater, but fractionation due to evaporation from near‐surface soil moisture prior to infiltration has the most significant effect. This study shows that groundwater in ow rctic reenland is likely to possess a combined geochemical and isotopic composition, which is distinguishable from other water sources in the proglacial environment. However, the shallow groundwater composition at a given time is highly dependent on major outbursts of glacier water in the previous months.