Water Isotope measurements contribute to the understanding of atmospheric, sea ice, ocean interactions during the ArtofMelt expedition, Fram Strait, spring 2023

Transitions periods between seasons in the Arctic are phases when the atmosphere-sea ice-ocean interactions are heightened, especially during these periods of exceptional warming.  These transition periods may be accompanied by shifts in atmospheric transport patterns, the distribution of sea ice and extreme events, such as atmospheric rivers.  Atmospheric Rivers may act as accelerants of sea ice melt and its redistribution, leading to spatial complexity in ice-ocean-atmosphere exchanges of mass and energy.

As part of an interdisciplinary team aboard the I/B Oden from early May to mid-June, four main water isotope measurement packages were collected to maximize collaborations and to resolve nuisances of the Arctic System throughout the cruise track between Svalbard and NE Greenland (Figure 1).  First, in order to delineate longitudinal distribution of the warm and salty W Svalbard current compared to the cold and fresh E Greenland current, we continuously measured the near surface water δ¹⁸O, δ²H and d-excess values. Second, in order to source water vapor and moisture sources from the warm, moist, and isotopically enriched subpolar & N Atlantic, compared to cold, dry and isotopically depleted Arctic air, we also continuously measured the δ¹⁸O, δ²H and d-excess values of water vapor collected from the ship’s, bow-mounted, eddy covariance tower. Third, in order to understand the horizontal and altitudinal patterns of water vapor parcels that surround the ship; in-situ water vapor isotopes were measured during fHeliPod flight lines that extended up to 30 km N-S-E-W of the Oden and from ~ 50 m above the sea ice and open water to over 2k in altitude.  Fourth, in order to delineate the source of moisture (sea water vs. meteoric water) throughout the sea ice core profiles and the patterns and sources of moisture in the snow pack profiles; ice cores and snow pits were collected (drilled) and dug at ~10 different locations and water isotope samples were analyzed for δ¹⁸O, δ²H and d-excess values back in the laboratory.

Four major discoveries will be presented: A) mixing of the surface W Svalbard and NE Greenland current is found to be farther east than previously reported and the surface water masses may differ by up to 5 ‰ δ¹⁸O during spring; B) water vapor isotopes responded at hourly time scales as moisture sources during Atmospheric River events begin with northward fluxes of warm, moist air masses but passing cyclones deliver N-S cold-dry, isotopically depleted water vapor in extreme Arctic-sourced storm events lasting a day or more; C) Horizontal and vertical transects during Heliopod flights captured horizontal and altitudinal variation in water vapor isotopes during periods when the weather of the ship was dominated by cold-dry Arctic air, interrupted by periods when the ship was experiencing pulses of warm, moist, and high humidity conditions; D) ice cores and snow packs exhibit vertical isotopic variation indicative of different moisture sources and morphogenesis processes.