| Summary: | From the western Arctic Ocean, we present the first continuous and simultaneous ocean water and boundary layer water vapor isotope data. We show that evaporative fractionation of isotopes in the Arctic Ocean can exceed 20‰ for δ18O (delta-O-18) and 160‰ for δ2H (delta deuterium). Greater sea ice melt freshwater contributions influence evaporative fractionation and can result in water vapor values more depleted in heavier isotopes. Sea surface water isotopes vary between the shallower continental Chukchi Shelf and deeper Chukchi Borderlands (basin) waters. The Chukchi Borderlands surface waters are less saline than the Chukchi Shelf, as it is influenced by greater sea ice extent and contribution of sea ice melt to the surface freshwater component. This greater contribution of sea ice melt results in lower d-excess surface water values in the deeper Chukchi Borderlands than on the shallower Chukchi Shelf. Additionally, the sea ice melt contribution to freshwater decreases, and total freshwater also decreases, substantially below 70 meters depth. Observed water isotope values provide the foundation for a remote sensing based creation of water isotope maps (isoscapes) that reveal unprecedented insight into the complexity of water isotopes. We also show how a strengthened East Siberian Current can lead to bidirectional flow through the Bering Strait and push high (low) d-excess (δ18O) surface waters south into the central Bering Sea. These new Arctic Ocean geochemical attributes are important for understanding the past, present, and future global water cycle as the Arctic experiences rapid changes that transport waters beyond the Arctic basin.
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