Pan-Arctic Precipitation Isotope (δ18O & δ2H) Characteristics and Processes.

The Arctic water cycle is changing dramatically as evidenced by marked shifts in Arctic seaice conditions, atmospheric processes, and hydrological regimes. Understanding thesecomplex interactions across a wide spatial and temporal scale is necessary to assess how thewhole Arctic water cycle is responding to changes today and in the future, including itspotential to feedback into the global climate system. Yet, an empirical and process-basedunderstanding of the interactions between these individual components is currently lacking inthe Arctic and further limits our ability to respond, adapt and develop resilient communitiesin the future. Measurements of oxygen and hydrogen stable isotopes in precipitation (δ18O, δ2H,d-excess) are a valuable and increasingly applied tool for tracing hydrological processes. Weare using a new coordinated network of 20 EU-INTERACT stations across the Arctic tocollect, analyze, and synthesize how precipitation isotope geochemistry varies in space andtime across the north. These new event-based data are combined with observed andmodelled analyses of storm tracks, cyclones, and sea ice traits to determine howisotopic variability is controlled by synoptic-scale atmospheric processes and sea icepatterns. Our goal is to produce weekly maps of precipitation δ18O and δ2H values across theArctic (e.g., "Isoscapes") that will provide a coherent framework to the communityfor understanding both modern and past changes in the Arctic water cycle. Forexample, initial δ18O and δ2H data from summer 2018 show that divergent stormtracks along the west coast of Greenland can lead to distinct isotopic gradients withlatitude. During mid-July we observed a 10 ‰ depletion in δ18O over a 1500 kmlatitudinal span (64˚ N to 76˚ N) at our stations in Nuuk (SW), Disko Island, andThule (NW), from -11‰ -16‰ to -21‰ respectively. This south to north depletingδ18O trend can be reversed within weeks depending upon the prevailing synopticatmospheric circulation pattern. These precipitation isotope fractionation processesalong Greenland’s west coast occur when relatively enriched moisture is transportedinto the Arctic from the North Atlantic; the reverse trend occur when moisture istransported south from the Arctic Basin into the lower latitudes along the west coast ofGreenland. This is the first coordinated network to quantify the spatial patterns of isotopes inprecipitation, simultaneously, across the entire Arctic, and our process-level studies willinform us about atmospheric transport processes within the Arctic, and between the Arcticand mid-latitude regions. [ABSTRACT FROM AUTHOR]