Four Years of CARVE-FTS Observations of CO2, CH4, and CO in the Alaskan Arctic: Status Quo and Comparison with Satellite Measurements

Abstract:

The end of 2015 marks the conclusion of the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE), a four-year aircraft-based Earth Venture 1 mission to study the carbon balance of the Alaskan Arctic ecosystem, with a particular focus on carbon release from melting permafrost. Operating from its base in Fairbanks, AK, the CARVE aircraft covers a range of principle flight paths in the Alaskan interior, the Yukon River valley, and the northern Alaska coast around Barrow and Dead Horse. Flight paths are chosen to maximize ecosystem variability and cover burn-recovery/regrowth sequences. CARVE observations cover the Arctic Spring/Summer/Fall seasons, with multiple flights per season and principle flight path. Science operations started in 05/2012 and will conclude in 11/2015.

The CARVE suite of instruments includes flask measurements, in situ gas analyzers for CO₂, CH₄ and CO observations, and a three-band polarizing Fourier Transform Spectrometer (FTS) for column measurements of CO₂, CH₄, CO, their interfering species (e.g., H₂O), and O₂. The FTS covers the spectral regions of 4,200-4,900 cm^-1 (CH₄, CO), 5,800-6,400 cm^-1 (CO₂), and 12,900-13,200 cm^-1 (O₂), with a spectral resolution of 0.2 cm^-1. Aircraft-based FTS science observations in Alaska have been performed since 23-05-2012. First-version data products from all CARVE instruments derived from observations during the 2012 campaign were publicly released earlier in 2013.

The FTS has performed well during flight conditions. A recent overhaul of the retrieval algorithm has led to improvements in FTS data quality. We present results from FTS column observations of CO₂, CH₄, and CO, obtained over the entire CARVE observation record from 2012 to 2015, including comparisons of CARVE FTS measurements with satellite observations of GOSAT CO₂ and CH₄ retrieved by NIES, GOSAT CO₂ from JPL/ACOS, MOPITT CO, and CO₂ from OCO-2. The comparisons emphasize coincident CARVE/OCO-2 observations over Alaska during the 2015 CARVE flights.