Aquatic sources and sinks of CO2 and CH4 in the polar regions

The highest concentration and greatest seasonal amplitudes of atmospheric CO2 and CH4 occur at 60 degrees-70 degrees N, outside the 30 degrees-60 degrees N band where the main sources of anthropogenic CO2 and CH4 are located, indicating that the northern environment is a source of these gases. Based on the author's onshore and offshore arctic experimental results and literature data, an attempt was made to identify the main northern sources and sinks for atmospheric CH4 and CO2. The CH4 efflux from limnic environments in the north plays a significant role in the CH4 regional budget, whereas the role of the adjacent arctic adjacent seas in regional CH4 emission is small. This agrees with the aircraft data, which show a 10%-15% increase of CH4 over land when aircraft fly southward from the Arctic Basin. Offshore permafrost might add some CH4 into the atmosphere, although the preliminary data are not sufficient to estimate the effect. Evolution of the northern lakes might be considered as an important component of the climatic system. All-season data obtained in the delta system of the Lena River and typical northern lakes show that the freshwaters are supersaturated by CO2 with a drastic increase in the CO2 value during wintertime. The arctic and antarctic CO2 data presented here may be used to develop understanding of the processes controlling CO2 flux in the polar seas. It is shown that Arctic seas are a sink for atmospheric CO2 though supersaturation by CO2 is obtained in areas influenced by riverine output and in coastal sites. The pCO(2) difference between the surface of the Southern Ocean and atmosphere observed in the austral autumn shows that the area east of 7 degrees W might be considered a source of CO2 into the atmosphere, whereas the area west of 7 degrees W is a net sink of CO2. This is corroborated with literature data that indicate an overestimate of the role of antarctic waters as a sink for atmospheric CO2.