CO₂ and CH₄ in sea ice from a subarctic fjord (original) (raw)

We present CH 4 concentration [CH 4 ] and the partial pressure of CO 2 (pCO 2) in bulk sea ice from subarctic, land-fast sea ice in the Kapisillit fjord, Greenland. The bulk ice [CH 4 ] ranged from 1.8 to 12.1 nmol L −1 , which corresponds to a partial pressure range of 3 to 28 ppmv. This is markedly higher than the average atmospheric methane content of 1.9 ppmv. Most of the trapped methane within the sea ice was evidently contained inside bubbles, and only a minor portion was dissolved in the brine. The bulk ice pCO 2 ranged from 60 to 330 ppmv showing that sea ice at temperatures above −4 • C is under-saturated compared to the atmosphere (390 ppmv). Our study adds to the few existing studies of CH 4 and CO 2 in sea ice and concludes that sub-arctic sea can be a sink for atmospheric CO 2 , while being a net source of CH 4. Processes related to the freezing and melting of sea ice represents large unknowns to the exchange of CO 2 but also CH 4. It is therefore imperative to assess the consequences of these unknowns through further field campaigns and targeted research under other sea ice conditions at both hemispheres. BGD 11, 4047-4083, 2014 CO 2 and CH 4 in sea ice from a subarctic fjord O. Crabeck et al.