Continuous Arctic Ocean Water Vapor Isotope Ratio (δ18O and δ2H) Measurements During a Summer Icebreaker Expedition

Abstract:

Warming in the Arctic is reducing sea ice, which may result in changes to the water cycle through increased atmospheric humidity. Here we present the first continuous record of water vapor isotope ratio (δ¹⁸O, δ²H, d-excess) measurements from the sub-Arctic and Arctic Ocean during ship transit through both open water and sea ice. As water vapor isotopes were collected across a spectrum of sea ice conditions, the influence of sea ice and availability of open water moisture sources on Arctic Ocean water vapor isotope values (particularly d-excess) is examined. Isotope values reveal characteristics about water availability at vapor sources, as influenced by presence of sea ice (e.g., ice covered arid or open water humid sources), and air parcel trajectory. Higher d-excess values were generally associated with more northern Arctic, ice covered, and arid vapor sources. Conversely, lower d-excess values were related to more southern, open water, and humid vapor sources. Additionally, water vapor isotopes while sea ice was present were generally characterized by more depleted δ¹⁸O and δ²H and higher d-excess values, relative to open water values. These water vapor isotope values also present information about potential shifts in moisture sources in an increasingly ice free Arctic Ocean. Understanding these shifts is important to learning about both modern and past patterns of Arctic atmospheric water movement and distribution.