Mauna Loa, Hawaii and Sunnyvale, CA, USA – Climate scientists from the University of Colorado and the University of New Mexico studying the water cycle have successfully deployed a Picarro precision water isotope analyzer at a remote monitoring station near the top of Mauna Loa, Hawaii. Sampling water vapor at this extreme altitude (11,000 feet above sea level) is notoriously difficult because the water concentration can drop as low a few hundred parts per million. Yet the Picarro G1102-i, which utilizes WS-CRDS (wavelength scanned cavity ring down spectroscopy), is directly sampling the outside air at this location and providing simultaneous measurement of both δD and δ18O every ten seconds. The absolute calibration is checked with liquid water standards every few hours, which confirms that the instrument has virtually no drift over a six day period. During this extended period the standard deviation of all measurements has been 0.650/00 for δD and 0.080/00 for δ18O – levels of absolute precision comparable to laboratory methods using an IRMS (isotope ratio mass spectrometry) instrument.
Dr. David Noone of the University of Colorado explains, "While much attention has been focused on the role of CO2 in driving global warming, changes in the water cycle and the amount of water vapor in the air also have a significant impact. Simply stated, we need more water field data, both concentration and isotope ratios. But before the advent of portable isotope analyzers, obtaining water isotope data from a remote site required capturing samples and chemically processing these before separately analyzing them for deuterium and oxygen-18 in two separate mass spectrometers. Until now, this has precluded continuous real-time isotope monitoring." He notes that the preliminary Mauna Loa data for δD and δ18O are consistent with expected values, and the high frequency variability seen with the G1102-i reveals a richness in the isotope data that could only have been dreamed of only a few years ago.
Dr. Joe Galewsky, University of New Mexico Department of Earth and Planetary Sciences, in an interview with Nature added, "Real time isotope tracking could be a new way of detecting fundamental changes in Earth's atmospheric circulation," He points out that Mauna Loa was the obvious place to conduct the experiment because of its high elevation and its location in the subtropics, which is influenced by both tropical and northerly atmospheric currents.
Michael Woelk, CEO of Picarro states, "We recognize that continued research and monitoring of GHGs (greenhouse gases) must occur on many fronts before a complete picture, and ultimately a comprehensive solution, can be developed. This will include a combination of both field and laboratory studies. For this reason, we have designed all of our WS-CRDS gas and isotope analyzers to deliver the same combination of high performance and automated ease of use in both the laboratory and extremely demanding field settings. As such, we are pleased to participate in this landmark study and gratified to see the preliminary data validate our approach."