Atmospheric carbon dioxide and its stable isotope ratios, methane, carbon monoxide, nitrous oxide and hydrogen from Shetland Isles

Abstract

Since November 1992, 0.5 l glass flasks have been filled approximately monthly with dry marine air from Shetland Isles, Scotland (60.2°N, 1.2°W) and transported to CSIRO, Australia for analyses. The Shetland site is part of a CSIRO global flask network with 10–12 sites, anchored to continuous high precision in situ measurements made at the Australian Cape Grim Baseline Station (40.7°S, 144.7°E), a primary station in the Global Atmosphere Watch programme (GAW) coordinated by the World Meteorological Organisation. The methodology is summarised, and Shetland results for CO 2, CH 4, N 2O, CO, H 2 and δ 13C, δ 18O of CO 2 presented for the period 1992–1996. We compare data to available results from surrounding stations of the NOAA cooperative network (in particular Mace Head, Ireland, 53.3°N, 9.9°W), and address issues of both trace species intercalibration and atmospheric spatial gradients. While considerable uniformity of trace-gas composition is evident in oceanic air over a 13° range of latitude, nevertheless anomalies in CO 2 concentration and isotopic composition are suggested in samples representing air to the west of Shetland. The potential for remotely monitoring integrated emissions from northern Europe is also identified.