Accurate measurements of atmospheric carbon dioxide and methane mole fractions at the Siberian coastal site Ambarchik

Abstract

Abstract. Sparse data coverage in the Arctic hampers our understanding of its carbon cycle dynamics and our predictions of the fate of its vast carbon reservoirs in a changing climate. In this paper, we present accurate measurements of atmospheric carbon dioxide (CO2) and methane (CH4) dry air mole fractions at the new atmospheric carbon observation station Ambarchik, which closes a large gap in the atmospheric trace gas monitoring network in northeastern Siberia. The site, which has been operational since August 2014, is located near the delta of the Kolyma River at the coast of the Arctic Ocean. Data quality control of CO2 and CH4 measurements includes frequent calibrations traced to World Meteorological Organization (WMO) scales, employment of a novel water vapor correction, an algorithm to detect the influence of local polluters, and meteorological measurements that enable data selection. The available CO2 and CH4 record was characterized in comparison with in situ data from Barrow, Alaska. A footprint analysis reveals that the station is sensitive to signals from the East Siberian Sea, as well as the northeast Siberian tundra and taiga regions. This makes data from Ambarchik highly valuable for inverse modeling studies aimed at constraining carbon budgets within the pan-Arctic domain, as well as for regional studies focusing on Siberia and the adjacent shelf areas of the Arctic Ocean.

Continuous CO2 and CH4 Observations in the Coastal Arctic Atmosphere of the Western Taimyr Peninsula, Siberia: The First Results from a New Measurement Station in Dikson

“…Like elsewhere, e.g., [32,[52][53][54], the annual amplitude of atmospheric CO 2 demonstrates a seasonal pattern (Figure 9a,b) and for the study area could be mostly related to local climate conditions and proximity to the Arctic Ocean.…”

“…After water correction and implemented calibration coefficients, prior to hourly averaging of the values, invalid data were removed using a set of filters: for bad analyzer status diagnostics, flushing of measurement lines prior and after probing reference air tanks, the timing of calibration and maintenance procedures, and spikes appeared due to contamination from local polluters. The criteria for the spike detection algorithm were based on [32,50] and tuned according to our measurements. The data passed through a set of strict filters for background conditions; in particular, the intra-hour variability of the data records was set as σ(CO 2 ) < 0.2 ppm and σ(CH 4 ) < 4 ppb [32], while the hour-to-hour variability in CO 2 was defined as 0.25 ppm [50].…”

“…The criteria for the spike detection algorithm were based on [32,50] and tuned according to our measurements. The data passed through a set of strict filters for background conditions; in particular, the intra-hour variability of the data records was set as σ(CO 2 ) < 0.2 ppm and σ(CH 4 ) < 4 ppb [32], while the hour-to-hour variability in CO 2 was defined as 0.25 ppm [50]. Since large CH 4 spikes are frequently matched with CO 2 spikes, both corresponding CO 2 and CH 4 spikes were flagged, even though this could remove some unpolluted CH 4 signals.…”

“…data records was set as σ(CO2) < 0.2 ppm and σ(CH4) < 4 ppb [32], while the hour-to-hour variability in CO2 was defined as 0.25 ppm [50]. Since large CH4 spikes are frequently matched with CO2 spikes, both corresponding CO2 and CH4 spikes were flagged, even though this could remove some unpolluted CH4 signals.…”

“…Atmospheric observations of CO 2 and CH 4 mole fractions at masts or towers have been previously utilized for studying their releases and trends in the northern latitudes [29][30][31][32]. Such measurements deal with a large area of influence ("footprint") as of hundreds to thousands of kilometers [33], in contrast to eddy covariance towers for carbon flux measurements, representing the local ecosystem-scale domain of a few hectares [34], or dynamic chamber technique measurements primarily used to capture homogeneous ecosystem patches (~1 m 2 ) or individual plant communities [35].…”