Air‐lake exchange of methane during the open water season in Syowa Oasis, East Antarctica

Abstract

[1] Dissolved methane (DM) concentrations were measured in 17 lakes as part of the operations of the 45th Japanese Antarctic Research Expedition in ice-free rocky areas along the eastern coast of Lützow-Holm Bay (Syowa Oasis) in East Antarctica in the summer of [2003][2004]. DM at the surfaces of 14 lakes ranged from the atmospheric equilibrium concentration (about 4 nmol L −1 for freshwater) to 385 nmol L −1 . Relatively low DM of less than 50 nmol L −1 were observed in about 60% of the lakes. Many of the lakes (area fraction of 85%) were supersaturated and are thus sources of methane to the atmosphere. The exchange coefficient was calculated using wind speed data at Syowa Station. Area fraction frequency distributions with four surface DM ranges were applied to all lakes at Syowa Oasis (110 lakes, total lake area of 9 km 2 ). Extrapolation to the whole Syowa Oasis gives an estimate of total emission of about 1 t CH 4 yr. This is the first estimation of methane flux from the surfaces of thawed lakes to the atmosphere in Antarctica. Since a methane efflux of about 2 t CH 4 yr −1 was estimated in our previous study from frozen bubbles in lake ice, a total amount of 3 t CH 4 yr −1 would be released to the atmosphere from the lakes during the ice melting season (December-January) at Syowa Oasis.

Diffusive summer methane flux from lakes to the atmosphere in the Alaskan arctic zone

“…Sasaki et al, (2009Sasaki et al, ( , 2010 reported that approximately two-times larger flux from frozen bubbles (ebullition) in lake ice than diffusive methane flux during the open water season is released in Syowa Oasis, east Antarctica. Bastiviken et al, (2004) also reported that estimated total methane flux (ebullition + diffusion + storage) from all Swedish lakes (95,762) was 105 Gg CH 4 yr -1 and that the flux corresponded to 5~10% of total flux from wetlands.…”

“…The procedure used for water sampling in 2008 was the same as that described in our previous paper (Sasaki et al, 2010). The water samples were gently poured in 500 mL glass vials, which were first washed by strong shaking with 100~200 mL of sampled water.…”

Exchanges of Methane between Lakes and the Atmosphere in Hokkaido, Subarctic Climate Region, Japan

“…The result of A-N analysis is shown in Table 2. Total area of all (1,269) lakes in Hokkaido is 809 km 2 . Average lake to land area ratio is 1.03%, which is about 1/3 of global average (2.8% estimated by Downing et al [9]).…”

“…[10]). And this average flux density is about five times greater than that from lakes in Syowa Oasis, in East Antarctica [2],…”

“…Lakes are significant source of methane to the atmosphere. In the previous work [1] [2], it was reported that the anomalous dissolved methane concentrations (DM) were frequently found even in Antarctica. In a subarctic climate zone, Hokkaido, the northernmost island in Japan, because of higher ambient and water temperatures and thicker organic sediments on the lake floors than those in Antarctica, it is expected that more active methanogenesis must be observed.…”