Detecting a methane rush over the Arctic seas

The Arctic is warming twice as fast compared to the rest of the World. The Arctic ocean contains gigatons of organic carbon and methane hydrates. Warming may induce liberation of this methane into the atmosphere.

This greenhouse gas would start a positive feed-back: the warmer water – the faster methane emission, the higher concentration the warmer water, and so on. Satellite data help to understand processes of methane emission and allow predictions of what can be expected in the near future.

Presence of methane sources at the seafloor is not sufficient for the significant methane flux. The gas must be transported through the seawater column of hundreds of meters thick. It is especially difficult in summer, when the water is not well-mixed.

Only in November this stability breaks down and methane enters the atmosphere if the sea surface is ice-free (Fig. 1).

In Kara Sea (Fig. 2) methane encounters another barrier – sea ice. Ice degradation during last 17 years makes this barrier more and more penetrable. Growing methane flux over the Kara Sea is explained by fast growth of ice-free surface area. During a coming decade a further growth of methane flux is expected even for stable underwater sources.

Fig. 1. Seasonal cycle of methane anomaly (red) compared to Mixed Layer Depth (blue), SW of Svalbard [1].
Fig. 2. Amplitude of methane seasonal cycle for N. Kara Sea (red) compared to that for Norwegian Sea (blue), and Fraction of open water (black, 100% – ice concentration)

Original source:

  1. Yurganov L., Muller-Karger F., Leifer I. Methane increase over the Barents and Kara Seas after the autumn pycnocline breakdown: satellite observations. Adv. Polar Sci. 2019, 30(4): 382-390. doi: 10.13679/j.advps.2019.0024.
  2. Yurganov L. Degradation of sea ice in the Western Arctic facilitates methane transport from sub- seabed sediments to atmosphere: satellite data for 2003 – 2019. submitted to “Ice and Snow”, 2020.

Front photo: REUTERS/PAULINE ASKIN

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