Distribution of methane in the Lena Delta and Buor-Khaya Bay, Russia

Bussmann, Ingeborg

doi:10.5194/bg-10-4641-2013

Cited by 53 publications

(50 citation statements)

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“…The observed concentrations of CH 4 in the Lena River, delta and estuary vary considerably in magnitude and are observed to decrease from the river towards the open sea, probably due to outgassing from the supersaturated river water to the atmosphere Semiletov et al, 2011Semiletov et al, , 2012Bussmann, 2013). Hence, the role of riverine CH 4 loads for the CH 4 concentration in the Laptev Sea is unsolved, in particular if the permafrost in the catchment area of the Lena River thaws and large amounts of carbon reach the coastal zone.…”

Section: Discussionmentioning

confidence: 99%

“…Although the constant oxidation rate is a simplification, this approach was applied to investigate how different observed rates affect the seaÁair exchange. The concentration of CH 4 in the river water was set to 20 nmol L (1 , which is the upper limit from observations of Semiletov et al (2011), but the value is in the lower part observed by Bussmann (2013). The flux from the sediment was taken from Shakhova et al (2005) and the atmospheric pCH 4 values were downloaded data from the National Oceanic and atmospheric Administration (NOAA), Point Barrow, Alaska http://www.esrl.noaa.gov/gmd/ dv/iadv/graph.php?code0BRW&program0ccgg&type0ts (Dlugokencky et al, 2012).…”

Section: Sensitivity Experimentsmentioning

confidence: 99%

“…The observed concentrations of CH 4 in the Lena River, delta and estuary vary from 5 up to over 600 nmol L (1 and decrease downstream Semiletov et al, 2011Semiletov et al, , 2012Bussmann, 2013). To examine the effect of observed CH 4 concentration in the river discharge on the seaÁair exchange as well as possible increases due to potential permafrost thaw, three cases with different concentrations in the river runoff (5, 60 and 540 nmol L (1 ) are compared with the 20 nmol L (1 in the standard case.…”

mentioning

confidence: 97%

“…Measured CH 4 concentrations in this area vary considerably. For instance, Bussmann (2013) observed CH 4 concentrations of up to 1854 nmol L (1 in 2010 in a creek draining from the permafrost soil into the Lena River.…”

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confidence: 99%

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A model sensitivity study for the sea–air exchange of methane in the Laptev Sea, Arctic Ocean

Wåhlström

Meier

2014

Tellus B: Chemical and Physical Meteorology

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A B S T R A C T The ocean's sinks and sources determine the concentration of methane in the water column and by that regulating the emission of methane to the atmosphere. In this study, we investigate how sensitive the seaÁair exchange of methane is to increasing/decreasing sinks and sources as well as changes of different drivers with a time-dependent biogeochemical budget model for one of the shallow shelf sea in the Siberian Arctic, the Laptev Sea. The applied changes are: increased air temperature, river discharge, wind, atmospheric methane, concentration of nutrients in the river runoff or flux of methane from the sediment. Furthermore, simulations are performed to examine how the large range in observations for methane concentration in the Lena River as well as the rate of oxidation affects the net seaÁair exchange. In addition, a simulation with five of these changes applied together was carried out to simulate expected climate change at the end of this century. The result indicates that none of the simulations changed the seawater to becoming a net sink for atmospheric methane and all simulations except three increased the outgassing to the atmosphere. The three exceptions were: doubling the atmospheric methane, decreasing the rivers' concentration of methane and increasing the oxidation rate where the latter is one of the key mechanisms controlling emission of methane to the atmosphere.

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Section: Discussionmentioning

confidence: 99%

Section: Sensitivity Experimentsmentioning

confidence: 99%

mentioning

confidence: 97%

mentioning

confidence: 99%

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A model sensitivity study for the sea–air exchange of methane in the Laptev Sea, Arctic Ocean

Wåhlström

Meier

2014

Tellus B: Chemical and Physical Meteorology

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“…But while coastal erosion and fluvial transports of particulate as well as dissolved organic carbon into the Buor-Khaya Gulf (Charkin et al, 2011) are normal processes, the expected increase in discharge resulting from permafrost thaw is also likely to lead to a considerable increase in delivery of inorganic nutrients (Nowinski et al, 2008), terrigenous dissolved organic carbon (DOC) and particulate organic carbon (POC) as well as methane to coastal waters (Finlay et al, 2006;Bussmann, 2013). Changes in these parameters could also have profound consequences for the resident phytoplankton communities.…”

Section: Introductionmentioning

confidence: 99%

Phytoplankton community structure in the Lena Delta (Siberia, Russia) in relation to hydrography

et al. 2013

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Abstract. The Lena Delta in Northern Siberia is one of the largest river deltas in the world. During peak discharge, after the ice melt in spring, it delivers between 60-8000 m 3 s −1 of water and sediment into the Arctic Ocean. The Lena Delta and the Laptev Sea coast also constitute a continuous permafrost region. Ongoing climate change, which is particularly pronounced in the Arctic, is leading to increased rates of permafrost thaw. This has already profoundly altered the discharge rates of the Lena River. But the chemistry of the river waters which are discharged into the coastal Laptev Sea have also been hypothesized to undergo considerable compositional changes, e.g. by increasing concentrations of inorganic nutrients such as dissolved organic carbon (DOC) and methane. These physical and chemical changes will also affect the composition of the phytoplankton communities. However, before potential consequences of climate change for coastal arctic phytoplankton communities can be judged, the inherent status of the diversity and food web interactions within the delta have to be established. In 2010, as part of the AWI Lena Delta programme, the phyto-and microzooplankton community in three river channels of the delta (Trofimov, Bykov and Olenek) as well as four coastal transects were investigated to capture the typical river phytoplankton communities and the transitional zone of brackish/marine conditions. Most CTD profiles from 23 coastal stations showed very strong stratification. The only exception to this was a small, shallow and mixed area running from the outflow of Bykov channel in a northerly direction parallel to the shore. Of the five stations in this area, three had a salinity of close to zero. Two further stations had salinities of around 2 and 5 throughout the water column. In the remaining transects, on the other hand, salinities varied between 5 and 30 with depth. Phytoplankton counts from the outflow from the Lena were dominated by diatoms (Aulacoseira species) cyanobacteria (Aphanizomenon, Pseudanabaena) and chlorophytes. In contrast, in the stratified stations the plankton was mostly dominated by dinoflagellates, ciliates and nanoflagellates, with only an insignificant diatom component from the genera Chaetoceros and Thalassiosira (brackish as opposed to freshwater species). Ciliate abundance was significantly coupled with the abundance of total flagellates. A pronounced partitioning in the phytoplankton community was also discernible with depth, with a different community composition and abundance above and below the thermocline in the stratified sites. This work is a first analysis of the phytoplankton community structure in the region where Lena River discharge enters the Laptev Sea.

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Impact of increasing inflow of warm Atlantic water on the sea‐air exchange of carbon dioxide and methane in the Laptev Sea

et al. 2016

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The Laptev Sea is generally a sink for atmospheric carbon dioxide and a source of methane to the atmosphere. We investigate how sensitive the net sea-air exchange of carbon dioxide and methane in the Laptev Sea are to observed changes in the inflow of Atlantic water into the Arctic Ocean and in atmospheric conditions occurring after 1990. Using a time-dependent coupled physical-biogeochemical column model, both the physical and biogeochemical effects are investigated in a series of sensitivity experiments. The forcing functions are kept constant at 40 year climatological values except successively selected drivers that vary in time. Their effects are examined by comparing two periods, 1971-1989 and 1991-2009. We find that the flux of carbon dioxide is more sensitive to the increased Atlantic water inflow than the methane exchange. The increased volume transport of water in the Atlantic layer increases the ocean net uptake of carbon dioxide more than the warming of the incoming bottom water as the vertical advection is enhanced in the first case. The methane cycling is mainly affected by the increase in temperature, irrespective of whether the warming originates from the atmosphere or the incoming bottom water, causing increased outgassing to the atmosphere. In summary, our results suggest that the observed changes in the atmosphere and ocean potentially had a substantial impact on carbon dioxide uptake on the Siberian Shelf. However, the results suggest that the impact on the outgassing of methane might have been relatively modest compared to the interannual variability of sea-air fluxes of methane.

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Distribution of methane in the Lena Delta and Buor-Khaya Bay, Russia

Cited by 53 publications

References 54 publications

A model sensitivity study for the sea–air exchange of methane in the Laptev Sea, Arctic Ocean

A model sensitivity study for the sea–air exchange of methane in the Laptev Sea, Arctic Ocean

Phytoplankton community structure in the Lena Delta (Siberia, Russia) in relation to hydrography

Impact of increasing inflow of warm Atlantic water on the sea‐air exchange of carbon dioxide and methane in the Laptev Sea

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