Air-sea fluxes of momentum, heat and CO₂, associated micrometeorological and mean meteorological and ocean surface variables. Fluxes are derived from fast response (20 Hz) measurements of the 3-dimensional wind vector, temperature humidity and CO₂ using eddy covariance.
These are direct measurements of air sea exchange from sea-ice regions of the Arctic Ocean. They are key parameters in numerous processes, for example, air-sea gas transfer and determination of the surface energy balance.
The measurements are from instrumentation mounted on a 2-metre high mast adjacent to a sea-ice lead, approximately 1.5 km from icebreaker Oden’s location during the Arctic Ocean 2018 (AO2018, also referred to as MOCCHA-ACAS-ICE) expedition to the central Arctic Ocean in August and September 2018. Eddy covariance fluxes are determined on 30-minute intervals.
The instrumentation on the open lead mast consisted of a Metek uSonic-3 heated sonic anemometer, a LI-COR 7500 infrared gas analyser, a LI-COR 7200 infrared gas analyser and pump, a Heitronics KT15.IIp infrared temperature sensor, an aspirated TRH sensor, a TSI 3762 CPC, a GPS unit and a Pro-Oceanus CO2-Pro CV pCO₂ sensor. Power was provided by 12V batteries, exchanged daily.
The majority of the fast-response instrumentation measured at 20 Hz. Atmosphere-surface fluxes were determined from the fast-response measurements using eddy covariance. All wind measurements are ice-relative (no correction for ice-drift velocity). Anemometer winds have an aliasing correction applied prior to flux calculation, removing all signal above 5 Hz.
Condensation particle counter (CPC) particle number concentrations will be published in separate data sets and are not included here.
The surface through which the measured flux is occurring will depend on the wind direction and the (highly variable) dimensions of the open lead. Lead dimensions were measured throughout the expedition and flux footprint analysis will be published with a subsequent version of this dataset. Surface temperature measurements from the mast infrared sensor were primarily of the lead surface water (excluding periods when drifting ice was in the sensor field of view). Measurements of ice-surface temperature (from an infrared sensor mounted on Oden) are also included in this dataset for reference.
Quality control flagging follows Foken et al. (2012): Chapter 4 in Eddy Covariance: A practical guide to measurement and data analysis (eds. M. Aubinet, T. Vesala, D. Papale), Springer Atmospheric Sciences, and references therein: Foken and Wichura (1996) and Vickers and Mahrt (1997). Some of the code implementing these was adapted from the Eddycalc suite.
Data from the open-lead mast are combined into a cruise-length file. The data are time-averaged to both 1-minute and 30-minute intervals. Flux data are not included in the 1-minute files.
