LowPerm outputs from the team

Andrew Jonathan Hodson, Aga Nowak, Kelly Robert Redeker, Erik S. Holmlund, Hanne Hvidtfeldt Christiansen and Alexandra V. Turchyn, 2019. Seasonal Dynamics of Methane and Carbon Dioxide Evasion From an Open System Pingo: Lagoon Pingo, Svalbard Frontiers in Earth Science, doi.org/10.3389/feart.2019.00030

The processes associated with the release of CH4 and CO2 from sub-permafrost groundwaters are considered through a year-long monitoring investigation at a terrestrial seepage site in West Spitsbergen. The site is an open system pingo thought to be associated with the uplift of a former sea-floor pockmark in response to marked isostatic recovery of the coastline following local ice sheet loss over the last 10,000 years. We find that locally significant emissions of CH4 and (less so) CO2 to the atmosphere result from a seepage <1 L s−1 that occurs all year. Hydrological and meteorological conditions strongly regulate the emissions, resulting in periodic outbursts of gas-rich fluids following ice fracture events in winter, and significant dilution of the fluids in early summer by meltwater. Evasion of both gases from a pond that forms during the 100 days summer (45.6 ± 10.0 gCH4-C m−2 and 768 ± 211 gCO2-C m−2) constitute between roughly 20 and 40% of the total annual emissions (223 gCH4-C m−2 a−1 and 2,040 gCO2-C m−2 a−1). Seasonal maximum dissolved CH4 concentrations (up to 14.5 mg L−1 CH4) are observed in the fluids that accumulate beneath the winter ice layer. However, seasonal maximum dissolved CO2 levels (up to 233 mg L−1) occur during late summer. Differences between the δ13C-CH4 composition of the winter samples [average 58.2 ± 8.01‰ (s.d.)] and the late summer samples [average 66.9 ± 5.75‰ (s.d.)] suggest minor oxidation during temporary storage beneath the winter ice lid, although a seasonal change in the methane source could also be responsible. However, this isotopic composition is strongly indicative of predominantly biogenic methane production in the marine sediments that lie beneath the thin coastal permafrost layer. Small hotpots of methane emission from sub-permafrost groundwater seepages therefore deserve careful monitoring for an understanding of seasonal methane emissions from permafrost landscapes.

Gilbert, G.L., O'Neill, H.B., Nemec, W., Thiel, C., Christiansen, H.H., Buylaert, P., 2018. Late Quaternary sedimentation and permafrost developmentin a Svalbard fjord-valley, Norwegian high Arctic. Sedimentology, doi: 10.1111/sed.12476

The infilling history of the Adventdalen fjord-valley in central Spitsbergen isreconstructed, with a focus on permafrost development, based on sedimento-logical and cryostratigraphic evidence from drilling cores. The techniques ofoptically stimulated luminescence and radiocarbon accelerator mass-spec-trometry dating were used to establish sediment chronology. The fjord-fill sed-imentary succession includes the fjord-bottom late Weichselian subglacial tillof the Last Glacial Maximum, the early Holocene muddy glaciomarine depos-its with ice-rafted debris formed during the fjord deglaciation, and the youngerHolocene deposits of a fjord-head Gilbert-type delta of which the fluvial dis-tributary plain shows raised alluvial terraces hosting aeolian sedimentation.This sedimentary record of the last glaciation/deglaciation cycle is interpretedin terms of sequence stratigraphy. Zones of epigenetic and syngenetic perma-frost are recognized from the vertical distribution of cryofacies, with a conclu-sion that the formation of permafrost commenced and extended down-fjord asthe fluvio-deltaic fjord-fill was gradually reaching subaerial exposure. Theupwards-grown syngenetic permafrost and the top part of downwards-grownepigenetic permafrost below contain excess ice in a suite of cryofacies indicat-ing ground-ice segregation and segregative intrusion. The deeper epigeneticpermafrost is ice-poor and contains cryofacies formed solely by segregationprocesses. This case study may serve as an analogue for other similar Arcticfjord-valleys where the fjord-head shoreline was established during the post-Weichselian deglaciation.

O'Neill, H.B., Christiansen, H.H., 2018. Detection of Late Quaternary sedimentation and permafrost developmentin a Svalbard fjord-valley, Norwegian high Arcticce Wedge Cracking in Permafrost Using Miniature Accelerometers. Journal of Geophysical Research: Earth Surface, doi: 10.1002/2017JF004343

Determining the exact timing of ice wedge cracking in permafrost is challenging. Five miniature accelerometers were installed near the ground surface in the trough of a primary ice wedge within a network of low‐centered polygons in Adventdalen, Svalbard, to test whether these instruments could be used to detect dynamics of thermal contraction cracking. Data from 2003 to 2013 were analyzed to characterize cryoseismic signals in the ice wedge trough. High‐magnitude accelerations (from 5 g to at least 100 g) were typically registered in late winter, when the top of permafrost had cooled to about −10°C; these likely correspond to ice wedge cracking in permafrost. Tensile stresses calculated from temperatures measured in the ice wedge trough are near laboratory strengths reported for ice and mineral active layer sediments, supporting the interpretation that large accelerations are caused by thermal contraction cracking. Lower magnitude accelerations occurred throughout the freezing season, usually coinciding with rapid cooling at the ground surface. These small accelerations may be associated with (i) the initiation of small cracks in the active layer of the trough or (ii) the horizontal and vertical propagation of existing ice wedge cracks. The results of this investigation indicate that miniature accelerometers are an effective, inexpensive, and simple method to determine the timing of ice wedge cracking and rates of crack propagation along ice wedge troughs.

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Betlem, P., Senger, K., Hodson, A. 2018. 3D thermobaric modelling of the gas hydrate stability zone onshore central Spitsbergen, Arctic Norway. Marine and Petroleum Geology, doi.org/10.1016/j.marpetgeo.2018.10.050

Dissociation of onshore natural gas hydrates (NGHs) could lead to the release of methane directly to the atmosphere, especially in Arctic regions such as Svalbard, where enhanced climate warming has the capacity to promote rapid methane evasion to the atmosphere following the decay of permafrost and glacier ice. Here we present the first assessment of the NGH stability zone (GHSZ) in central Spitsbergen, a climate-sensitive part of Svalbard where thermobaric conditions appear favourable for onshore NGH formation. We developed an approach incorporating regionally constrained 3-dimensional parameterisation of temperature, pressure and phase boundary (93% methane, 7% ethane, 35 ppt salinity) to define the GHSZ. This resulted in an up to 650 m thick (mean: 308 m) GHSZ covering 74.8% of the study area, thickening significantly in the east where the climate is colder. Perturbation of the base case parameters was undertaken to quantify the sensitivity of the GHSZ to the variation in environmental conditions across the study area. We present 26 examples of these deterministic scenarios and show that the largest changes in the GHSZ were observed when either the ethane content (to 20%) or the regional pore water pressure (to 125% hydrostatic) were increased. The GHSZ also increased markedly when the geothermal gradient was reduced from 33 to 26 °C km−1, but was almost completely inhibited by a dry gas (100% methane), greater salinity (50 ppt), or exposure to an increase in surface temperatures relative to the mean annual air temperature (e.g., by 2 °C). Most parameters affected both the upper and the lower stability boundary of the GHSZ, with the exception of the geothermal gradient, which impacted primarily upon the latter. Given that Svalbard is host to a proven petroleum system, we conclude that NGHs almost certainly exist onshore Svalbard.

*Hodson et al., 2017. Climatically sensitive transfer of iron to maritime Antarctic ecosystems by surface runoff. Nature Communcations, DOI:10.1038/ncomms14499

Iron supplied by glacial weathering results in pronounced hotspots of biological production in an otherwise iron-limited Southern Ocean Ecosystem. However, glacial iron inputs are thought to be dominated by icebergs. Here we show that surface runoff from three island groups of the maritime Antarctic exports more filterable (<0.45 μm) iron (6–81 kg km−2 a−1) than icebergs (0.0–1.2 kg km−2 a−1). Glacier-fed streams also export more acid-soluble iron (27.0–18,500 kg km−2 a−1) associated with suspended sediment than icebergs (0–241 kg km−2 a−1). Significant fluxes of filterable and sediment-derived iron (1–10 Gg a−1 and 100–1,000 Gg a−1, respectively) are therefore likely to be delivered by runoff from the Antarctic continent. Although estuarine removal processes will greatly reduce their availability to coastal ecosystems, our results clearly indicate that riverine iron fluxes need to be accounted for as the volume of Antarctic melt increases in response to 21st century climate change.

*O'Neill et al., 2017. Near-surface ground ice variation in ice-wedge polygons in Adventdalen, Svalbard. Arctic Science Summit Week 2017 (Poster), Prague, Czech Republic

Near-surface ground ice is a characteristic feature of permafrsot, and its thaw may lead to ground subsidence, which can damage infrastructure and change landscape hydrology and ecology. The thaw of upper permafrost also mobilizes previously-frozen organic carbon. Little data exist on the distribution of ground ice in the top of permafrost in the high Arcitc archipelago of Svalbard. Polygonal terrain is widely distibuted on Svalbard, and hosts both wedge ice and segregated ice in fine-grained sediment. Here we present early results from part of the LowPerm project, which broadly seeks to understand nutrient transport in permafrost landscapes that may lead to changes in GHG produciton and fertilization of the Arctic Ocean.

*Bak et al., 2017. Electron acceptor-based regulation of microbial greenhouse gas production from thawing permafrost. EGU 2017 (Poster), Vienna, Austria

Permafrost contains about 35% of the global soil organic carbon (0-3 m depth). As a consequence of global warming, the active layer thickness is steadily increasing and its organic carbon is becoming available for degradation, causing a concomitant release of CO2 and CH4. The climate forcing feedbacks of permafrost thaw are determined by the rate of organic carbon degradation and to which degree it is released as CO2 or CH4. Methane is produced under anoxic conditions, but the factors that regulate its production are poorly constrained.

*Jones et al., 2017. Redox and biogeochemical processes inferred from permafrost porewater extractions. EGU 2017 (Poster), Vienna, Austria

Climate change is causing permafrost to thaw in the Arctic coastal lowlands. The resulting release of stored organic carbon and nutrients leads to increased greenhouse gas (GHG) emissions in Arctic wetlands.
• In Svalbard (fig. 1), isostatic rebound during the last 10,000 years has created coastal wetlands by exposing more land area.
• The redox evolution of these wetlands influences methane release, as methanogenesis occurs once alternative electron acceptors for the microbial oxidation of organic matter have been depleted.
• It is crucial to understand the redox evolution of these environments in order to accurately predict the timing and magnitude of methane release.

*Hodson et al., 2015. Glacial and periglacial floodplain sediments regulate hydrologic transfer of reactive iron to a high arctic fjord. Hydrological Processes, DOI: 10.1002/hyp.10701

The transport of reactive iron (i.e. colloidal and dissolved) by a glacier-fed stream system draining a high relief periglacial landscape in the high Arctic archipelago of Svalbard is described. A negative, non-linear relationship between discharge and iron concentration is found, indicative of increased iron acquisition along baseflow pathways. Because the glaciers are cold-based and there are no intra- or sub-permafrost groundwater springs, baseflow is principally supplied by the active layer and the colluvial and alluvial sediments in the lower valley. Collectively, these environments increase the flux of iron in the stream by 40% over a floodplain length of just 8 km, resulting in 6 kg Fe km2a1 of reactive iron export for a 20% glacierized watershed. We show that pyrite oxidation in shallow-groundwater flowpaths of the floodplain is the most important source of reactive iron, although it is far less influential in the upper parts of the catchment where other sources are significant (including ironstone and secondary oxide coatings). Microbial catalysis of the pyrite oxidation occurs in the floodplain, enabling rapid, hyporheic water exchange to enhance the iron fluxes at high discharge and cause the non-linear relationship between discharge and reactive iron concentrations. Furthermore, because the pyrite oxidation is tightly coupled to carbonate and silicate mineral weathering, other nutrients such as base cations and silica are also released to the stream system. Our work therefore shows that high Arctic floodplains should be regarded as critically important regulators of terrestrial nutrient fluxes to coastal ecosystems from glacial and periglacial sources.

*Mallon et al., 2015. LowPerm: quantifying thaw-driven biogas production and nutrient export from Eurasian Arctic lowlands. Arctic Science Conference 2015 (Poster), Sheffield, UK

The surface energy budget of coastal lowlands in the Eurasian Arctic is very sensitive to atmospheric and oceanic warming, prompting the early onset of permafrost thaw, increased active layer thickness, and enhanced microbial metabolism. Although Arctic permafrost holds vast amounts of carbon, we still lack the tools to accurately forecast how changes in these processes influence permafrost biogeochemistry and feedback to climate change. Here we present early progress from the LowPerm project and describe a key site established in an ice-wedged polygonal landscape in Adventdalen, Svalbard. The environmental history of the site is explained and in situ data describing the hydrological and biogeochemical conditions during active layer development in 2015 are shown.

Nowak et al., 2015. On the biogeochemical response of a glacierized High Arctic watershed to climate change: revealing patterns, processes and heterogeneity among micro-catchments. Hydrological Processes, 29, 1588-1603

Our novel study examines landscape biogeochemical evolution following deglaciation and permafrost change in Svalbard by looking at the productivity of various micro-catchments existing within one watershed. It also sheds light on how moraine, talus and soil environments contribute to solute export from the entire watershed into the downstream marine ecosystem. We find that solute dynamics in different micro-catchments are sensitive to abiotic factors such as runoff volume, water temperature, geology, geomorphological controls upon hydrological flowpaths and landscape evolution following sea level and glacial changes. Biotic factors influence the anionic composition of runoff because of the importance of microbial SO42 and NO3 production. The legacy of glaciation and its impact upon sea level changes is shown to influence local hydrochemistry, allowing Cl to be used as a tracer of thawing permafrost that has marine origins. However, we show that a ‘glacial signal’ dominates solute export from the watershed. Therefore, although climatically driven change in the proglacial area has an influence on local ecosystems, the biogeochemical response of the entire watershed is dominated by glacially derived products of rapid chemical weathering. Consequently, only the study of micro-catchments existing within watersheds can uncover the landscape response to contemporary climate change.