Sediment respiration drives circulation and production of CO2 in ice‐covered Alaskan arctic lakes

The goals of our study were to (1) quantify production of CO2 during winter ice‐cover in arctic lakes, (2) develop methodologies which would enable prediction of CO2 production from readily measured variables, and (3) improve understanding of under‐ice circulation as it influences the distribution of dissolved gases under the ice. To that end, we combined in situ measurements with profile data. CO2 production averaged 20 mg C m−2 d−1 in a 3 m deep lake and ∼ 45 mg C m−2 d−1 in four larger lakes, similar to experimental observations at temperatures below 4°C. CO2 production was predicted by the initial rate of loss of oxygen near the sediments at ice‐on and by the full water column loss of oxygen throughout the winter. The time series data also showed the lake‐size and time dependent contribution of sediment respiration to under‐ice circulation and the decreased near‐bottom flows enabling anoxia and CH4 accumulation.