Understanding formation of ice wedges and origin of trapped greenhouse gas at Zyryanka, Northeastern Siberia&amp;#160;

Nayeon Ko,Alexander Fedorov,Go Iwahana,Jinho Ahn,Hyejung Jung,Hansu Park

doi:10.5194/egusphere-egu22-6669

Abstract

&lt;p&gt;Multiple geochemical analyses may help us better constrain the ice-wedge formation and in-situ greenhouse gas (GHG) production mechanisms. Here we present new results from ice-wedge ice sampled at Zyryanka, Northeastern Siberia (65&amp;#176;93&amp;#8217;N, 150&amp;#176;89&amp;#8217;E). The plant remains and CO&lt;sub&gt;2&lt;/sub&gt; gas were analyzed for &lt;sup&gt;14&lt;/sup&gt;C dating, and we obtained from 810 to 1750 years before 1950 CE for the Zyryanka ice wedge. &amp;#948;(N&lt;sub&gt;2&lt;/sub&gt;/Ar) of the ice wedges ranges from -17.51 to -3.53 % with regard to modern air, indicating that the Zyryanka ice wedge was formed by both liquid water and dry snow. On the other hand, the &amp;#948;(O&lt;sub&gt;2&lt;/sub&gt;/Ar) value of the Zyryanka ice wedges ranges from -72.88 to -37.58 % with regard to modern air, implying oxygen gas was consumed considerably by respiration of microorganisms in the ice-wedge ice. We also observed correlations among the three greenhouse gas species and oxygen gas concentrations. N&lt;sub&gt;2&lt;/sub&gt;O and CO&lt;sub&gt;2&lt;/sub&gt; concentrations show a strong positive correlation (r&lt;em&gt; &lt;/em&gt;= 0.94, p=0.01). We also found that the melting fraction (estimated from N&lt;sub&gt;2&lt;/sub&gt;/Ar) is positively correlated with CO2 (r=0.81, p=0.01) and CH&lt;sub&gt;4&lt;/sub&gt; (r=0.87, p&lt;0.05). Furthermore, O&lt;sub&gt;2&lt;/sub&gt; concentration is negatively correlated with the CH&lt;sub&gt;4&lt;/sub&gt; concentrations (r = -0.41, p&lt;0.05) which may imply that CH&lt;sub&gt;4&lt;/sub&gt; production is associated with biological oxygen consumption. The &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O of ice melt ranges from -28.6 to -19.1 &amp;#8240; for the ice wedge and adjacent soil samples, showing a symmetric structure with low &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O values in the ice wedge parts and high in the adjacent soils. Comparing with the &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O value of modern precipitation in the Zyryanka region, it can be inferred that the ice wedge was mainly formed by filling with cold seasonal precipitation. Our study shows that the gas mixing ratios in ice wedges and water stable isotope analysis may help better understanding the biogeochemical environments during and after the formation of ice wedges.&lt;/p&gt;

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