Invaluable insights into the dynamics and water-vapor isotopes of the planetary boundary layer above the Greenland Ice Sheet from fixed-wing uncrewed aircraft samplings.

Abstract

The chemistry and aerosols in ice core records are used as proxy data for the past climate. Traditional interpretation of this recorded climate signal is that during formation snow captures a snapshot of the atmosphere. In recent years, observations have documented that the snow surface’s chemistry and isotopic composition change during the post-depositional interaction with the surface-near atmosphere. To more accurately interpret the climate signal in ice cores it is necessary to understand thesource of the water vapor in the planetary boundary layer (PBL), as well as the vertical mixing and transportation in the polar atmosphere. However, the dynamics in the polar PBL are poorly constrained in most climate models due to a lack of observations. Here we present insights from the first Arctic in-situ water-vapor isotope record both within and above the PBL up to 1500 meters above the Greenland Ice Sheet (GrIS) from the EastGRIP ice core camp 2022 field campaign. Flights were performed with a fixed-wing uncrewed aircraft recording high resolution atmospheric profiles. Moreover, air is sampled in glass flasks and brought to the surface for determination of δ18O and δDof water vapor. The observational set-up has been proven to guarantee reliable measurements of the isotopic composition of the atmospheric water vapor in remote locations and under extremely cold temperatures. Based on 105 observed temperature, humidity and isotopic profiles we identify different types of atmospheric structure above the GrIS. We evaluate the vertical atmospheric representation of the polar regional climate model MAR and the isotope-enabled global climate model ECHAM-wiso. Finally, from observations we estimate the height up to which the surface-near δ18O and δD isotopic values are affected by the atmosphere above.