Geoelectric observations of the degradation of nearshore submarine permafrost at Barrow (Alaskan Beaufort Sea)

Overduin, Paul; Westermann, Sebastian; Yoshikawa, Kenji; Haberlau, Thomas; Romanovsky, V. E.; Wetterich, Sebastian

doi:10.1029/2011jf002088

Cited by 46 publications

(68 citation statements)

References 34 publications

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“…Sediment drilling was conducted just offshore of the eastern coast of Buor Khaya Bay in the central Laptev Sea (71°25′20.3″N, 132°05′05.3″E; Figure c), southeast of the Lena Delta, in April–May 2012 [ Günther et al , ]. Following measurements similar to Overduin et al [], a geophysical site survey was carried out in 2011 [ Wetterich et al , ]. Based on this reconnaissance field work, we were assured of encountering ice‐bonded permafrost undergoing degradation at the drill site.…”

Section: Methodsmentioning

confidence: 99%

Methane oxidation following submarine permafrost degradation: Measurements from a central Laptev Sea shelf borehole

Overduin

Liebner

Knoblauch

et al. 2015

J. Geophys. Res. Biogeosci.

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Submarine permafrost degradation has been invoked as a cause for recent observations of methane emissions from the seabed to the water column and atmosphere of the East Siberian shelf. Sediment drilled 52 m down from the sea ice in Buor Khaya Bay, central Laptev Sea revealed unfrozen sediment overlying ice-bonded permafrost. Methane concentrations in the overlying unfrozen sediment were low (mean 20 μM) but higher in the underlying ice-bonded submarine permafrost (mean 380 μM). In contrast, sulfate concentrations were substantially higher in the unfrozen sediment (mean 2.5 mM) than in the underlying submarine permafrost (mean 0.1 mM). Using deduced permafrost degradation rates, we calculate potential mean methane efflux from degrading permafrost of 120 mg m À2 yr À1 at this site.However, a drop of methane concentrations from 190 μM to 19 μM and a concomitant increase of methane δ 13 C from À63‰ to À35‰ directly above the ice-bonded permafrost suggest that methane is effectively oxidized within the overlying unfrozen sediment before it reaches the water column. High rates of methane ebullition into the water column observed elsewhere are thus unlikely to have ice-bonded permafrost as their source.

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Section: Methodsmentioning

confidence: 99%

Methane oxidation following submarine permafrost degradation: Measurements from a central Laptev Sea shelf borehole

Overduin

Liebner

Knoblauch

et al. 2015

J. Geophys. Res. Biogeosci.

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“…Laboratory measurements of saline silty and sandy sediment, similar in grain size distribution to those at Muostakh Island, show that ice is present in the sediment for bulk resistivities over 10 m , although the boundary between ice-free and ice-bonded sediment may not be sharply defined, so that resistivity changes gradually with depth. We consider that any sand-silt mixture that is ice-bonded with fresh porewater, as is the case here based on the porewater concentrations from the drilling samples, and consistent with previous observations of submarine permafrost in the Laptev Sea, will have a resistivity not lower than 10 m, and probably higher than 100 m. This assumption is also based on laboratory measurements of bulk resistivity as a function of temperature and salinity for marine sediments which show that the change in bulk sediment resistivity from an unfrozen seawater-saturated sediment to a frozen ice-saturated sediment corresponds to a jump in resistivity from less than 10 to over 100 m (Frolov, 1998;King et al, 1988;Overduin et al, 2012). Uncertainties in IBP depth estimated from resistivity profiles thus correspond to the depth range of the bulk sediment resistivity increase from 10 to 100 m. Mean submarine permafrost degradation rate was calculated as the quotient of the depth to IBP (z pf ) and the time of erosion (t 0 ; time of inundation).…”

Section: Electrical Resistivity and Time Of Inundationmentioning

confidence: 98%

Coastal dynamics and submarine permafrost in shallow water of the central Laptev Sea, East Siberia

et al. 2016

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Abstract. Coastal erosion and flooding transform terrestrial landscapes into marine environments. In the Arctic, these processes inundate terrestrial permafrost with seawater and create submarine permafrost. Permafrost begins to warm under marine conditions, which can destabilize the sea floor and may release greenhouse gases. We report on the transition of terrestrial to submarine permafrost at a site where the timing of inundation can be inferred from the rate of coastline retreat. On Muostakh Island in the central Laptev Sea, East Siberia, changes in annual coastline position have been measured for decades and vary highly spatially. We hypothesize that these rates are inversely related to the inclination of the upper surface of submarine ice-bonded permafrost (IBP) based on the consequent duration of inundation with increasing distance from the shoreline. We compared rapidly eroding and stable coastal sections of Muostakh Island and find permafrost-table inclinations, determined using direct current resistivity, of 1 and 5 %, respectively. Determinations of submarine IBP depth from a drilling transect in the early 1980s were compared to resistivity profiles from 2011. Based on borehole observations, the thickness of unfrozen sediment overlying the IBP increased from 0 to 14 m below sea level with increasing distance from the shoreline. The geoelectrical profiles showed thickening of the unfrozen sediment overlying ice-bonded permafrost over the 28 years since drilling took place. We use geoelectrical estimates of IBP depth to estimate permafrost degradation rates since inundation. Degradation rates decreased from over 0.4 m a −1 following inundation to around 0.1 m a −1 at the latest after 60 to 110 years and remained constant at this level as the duration of inundation increased to 250 years. We suggest that long-term rates are lower than these values, as the depth to the IBP increases and thermal and porewater solute concentration gradients over depth decrease. For the study region, recent increases in coastal erosion rate and changes in benthic temperature and salinity regimes are expected to affect the depth to submarine permafrost, leading to coastal regions with shallower IBP.

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“…In the ocean, the two major sources of methane are ongoing biogenic production by microbes in anoxic sediment (Formolo, 2010;Reeburgh, 2007;Whiticar, 1999) and release of fossil methane from geological storage (summarized by Kvenvolden and Rogers, 2005;Saunois et al, 2016). Other sources include release from permafrost, river runoff, submarine groundwater discharge (Lecher et al, 2016;Overduin et al, 2012), and production from methylated substrates under aerobic conditions (Damm et al, 2010;Karl et al, 2008;Repeta et al, 2016). More than 90 % of the methane sourced in the seabed is oxidized within the sediment by anaerobic and aerobic oxidation (Barnes and Goldberg, 1976;Boetius and Wenzhöfer, 2013;Knittel and Boetius, 2009;Reeburgh, 1976).…”

Section: Introductionmentioning

confidence: 99%

Methane-oxidizing seawater microbial communities from an Arctic shelf

et al. 2018

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Abstract. Marine microbial communities can consume dissolved methane before it can escape to the atmosphere and contribute to global warming. Seawater over the shallow Arctic shelf is characterized by excess methane compared to atmospheric equilibrium. This methane originates in sediment, permafrost, and hydrate. Particularly high concentrations are found beneath sea ice. We studied the structure and methane oxidation potential of the microbial communities from seawater collected close to Utqiagvik, Alaska, in April 2016. The in situ methane concentrations were 16.3 ± 7.2 nmol L −1 , approximately 4.8 times oversaturated relative to atmospheric equilibrium. The group of methaneoxidizing bacteria (MOB) in the natural seawater and incubated seawater was > 97 % dominated by Methylococcales (γ -Proteobacteria). Incubations of seawater under a range of methane concentrations led to loss of diversity in the bacterial community. The abundance of MOB was low with maximal fractions of 2.5 % at 200 times elevated methane concentration, while sequence reads of non-MOB methylotrophs were 4 times more abundant than MOB in most incubations. The abundances of MOB as well as non-MOB methylotroph sequences correlated tightly with the rate constant (k ox ) for methane oxidation, indicating that non-MOB methylotrophs might be coupled to MOB and involved in community methane oxidation. In sea ice, where methane concentrations of 82 ± 35.8 nmol kg −1 were found, Methylobacterium (α-Proteobacteria) was the dominant MOB with a relative abundance of 80 %. Total MOB abundances were very low in sea ice, with maximal fractions found at the icesnow interface (0.1 %), while non-MOB methylotrophs were present in abundances similar to natural seawater communities. The dissimilarities in MOB taxa, methane concentrations, and stable isotope ratios between the sea ice and water column point toward different methane dynamics in the two environments.

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Geoelectric observations of the degradation of nearshore submarine permafrost at Barrow (Alaskan Beaufort Sea)

Cited by 46 publications

References 34 publications

Methane oxidation following submarine permafrost degradation: Measurements from a central Laptev Sea shelf borehole

Methane oxidation following submarine permafrost degradation: Measurements from a central Laptev Sea shelf borehole

Coastal dynamics and submarine permafrost in shallow water of the central Laptev Sea, East Siberia

Methane-oxidizing seawater microbial communities from an Arctic shelf

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