del Rocio Tenorio Sánchez, Sandy Elizabeth; Verdugo, Josefa; Sanzana, Karen; Krock, Bernd: Dissolved methane and nitrous oxide in Patagonian fjords and channels of the Magellanic region during the M179/2 FjordFlux cruise (2022) [dataset]. PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.995733 (dataset in review)

The southern Patagonian Cold Estuarine System (PCES; -54 °S), is one of the largest fjord and channel systems in the Southern Hemisphere, strongly influenced by glacier meltwater, continental runoff and subantarctic oceanic waters. This region pays and important role in the regional carbon cycling and air-sea greenhouse gas exchange. Dissolved methane (CH4) and nitrous oxide (N2O), were sampled during the M179/2 FjordFlux cruise, conducted aboard the German research vessel METEOR, between January 14th and February 14th, 2022. PCES, which include Almirantazgo Sound, Garibaldi Fjord and Beagle Channel were covered. From a total of 41 stations, we present data from 27 stations around the Icefield Darwin. These stations include vertical profiles of gases such methane (CH4) and nitrous oxide (N2O). Vertical profiles of temperature and salinity were obtained with a CTD profiler SBE3 and SBE4 respectively, only at 0m, la T and S were obtained with a Salinometer YSI 30. Water samples at different depths were collected using Niskin bottles attached to a rosette for gas determination (CH4 and N2O); 20 mL of water were taken in triplicate in a glass vials, and 50 μL of saturated HgCl2 were added to preserve them. The vials were carefully sealed with rub and aluminum caps to avoid contamination with the atmosphere, then stored in darkness until analysis in the laboratory. N2O and CH4 were analyzed manually using the phase equilibrium method (McAuliffe, 1963) by creating a 5 mL headspace of ultrapure helium and equilibrating for 1h at 30°C. Mesurements were carried out through gas chromatography using an Electron Capture Detector (Shimadzu 17A) and Flame Ionization Detector (Agilent technologies 6850), respectively. A Restek Rt-QS- Bond column (30 m length, 0.53 mm inner diameter, 20 μm film thickness) was employed, maintained at a temperature of 30 °C with a flow of 2.6 mL min−1 using N2 as an ultra- pure gas carrier. For both gasses, a 4-point calibration curve was developed: He (as ~0 value) and four standard gas mixtures (Scott Mini-Mix, from Air Liquide) concentrations of 0.35, 0.55 and 1 ppm for N2O and 2.5, 5, and 10 ppm concentrations for CH4. The uncertainty of the measurements was calculated from the standard deviation of the triplicate measurements by depth. Samples with a variation coefficient above 10% were not considered. The solubility equations based on the in situ T and S of Wiesenburg and Guinasso (1979) and (Weiss and Price, 1980), were used to calculate N2O and CH4 concentrations.