Despite its status as a proverbial canary for global climatological change, the Arctic features a distinct lack of observational capability, particularly during the polar night. Trace gases play an important role in the energy balance of the region, particularly in relation to the prolonged periods of darkness and daylight. This interaction is especially important in the far- and mid-infrared spectrum, where the terrestrial emission is significant. In order to conduct these measurements, an Extended-range Atmospheric Emitted Radiance Interferometer (E-AERI) was installed at the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Canada (80°N, 86°W) in October 2008. The E-AERI is a moderate resolution (1 cm−1) Fourier Transform Infrared Spectrometer that measures the absolute downwelling infrared spectral radiance from the atmosphere between 400 and 3000 cm−1. Spectra are recorded every 7 minutes year-round, including during the four months of polar night.

I will discuss improvements to the monitoring capabilities at PEARL by inferring vertical profiles of carbon monoxide, nitrous oxide, methane, and ozone from E-AERI spectra. These are analyzed using an optimal-estimation-based retrieval algorithm, modified to allow for analysis of emission spectra, and including recent improvements to spectroscopy in modeling the emission contribution from the water vapour continuum in the far and mid-infrared. Validation is presented against several co-located observations at PEARL including against two instruments affiliated with the Network for the Detection of Atmospheric Composition Change (NDACC), a Bruker 125HR, and two UV-VIS Triax-180 ground based spectrometers (GBSs) during sunlit periods; weekly ozonesondes measurements are also compared with those from the E-AERI. Intra-annual variability and decadal trends in Eureka are also analyzed. Particular attention is given to the sensitivity of the E-AERI to Arctic springtime ozone depletion events (as in 2011 and 2020), and to CO as a tracer species of wildfire plumes.