Development, Aircraft Integration, and Field Deployment of a CO2 Herriott Cell to Measure Arctic Carbon Fluxes

Abstract

The warming of the Arctic, as mediated by climate change, will precipitate a feedback effect. Should the carbon in soil be processed and emitted as the greenhouse gases CO2 and CH4, the feedback effect will be positive; if, however, increased plant growth draws down sufficient atmospheric CO2 to overwhelm emission mechanisms, the feedback will be negative. High resolution measurements of CO2 and CH4 emissions are critical to understanding how the changing Arctic biome will respond to, and, in turn, influence climate change. Yet the sparsity of infrastructure and population in the Arctic precludes widespread monitoring of carbon emissions and uptake in the Arctic, hindering understanding of the mechanisms which control the feedback effects of a warming Arctic. In response to these issues, we present a new CO2 Herriott Cell that operates in conjunction with a NOAA Best Air Turbulence probe on a lightweight DA-42 aircraft. The CO2 Herriott cell employs a tunable mid-IR Quantum Cascade Laser to measure CO2 and its isotopologues via direct absorption in a Herriott Cell. The CO2 Herriott cell demonstrates in-laboratory precision of 1ppmv (1 sec). We describe the development of the instrument, as well as our calibration and precision assessment protocols in the laboratory, in detail. In chapter 2, we report on the field deployment of the instrument suite in the North Slope of Alaska in August of 2013. Owing to differences between field deployment conditions and laboratory conditions, our instrument did not perform to specification in the field. Thus, in chapter 3, we examine the sources of instrument performance deterioration in the field. We provide as well corrections to field data carried out in the laboratory after the mission, and the subsequent recovered 12CO2 data from five flights of the field campaign, demonstrating proof-of-concept of the CO2 Herriott instrument. Finally, we offer suggested instrument augmentations to ensure the capacity to measure fluxes in-situ during future field deployments.