Enhancing our Understanding of the Arctic Atmospheric Hydrological Cycle using Observations from an International Arctic Water Vapor Isotope Network

Monday, 15 December 2014
Valérie Masson-Delmotte, Institut Pierre Simon Laplace, Paris, France, Hans Christian Steen-Larsen, LSCE Laboratoire des Sciences du Climat et de l'Environnement, Gif-Sur-Yvette Cedex, France and Martin Werner, Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Bremerhaven, Bremerhaven, Germany
Due to the role of water vapor and clouds in positive feedback mechanisms, water vapor is a key player in the future of Arctic climate. Ecosystems and human societies are vulnerable to climate change through even minor changes in precipitation patterns, including the occurrence of extreme events. It is therefore essential to monitor, understand and model correctly the mechanisms of transport of moisture, at the regional scale.

Water isotopes – the relative abundance of heavy and light water in the atmosphere – hold the key to understanding the physical processes influencing future Arctic climate. Water isotope observations in the atmosphere are a modern analog to the Rosetta Stone for understanding the processes involved in evaporation, moisture transport, cloud formation and to track moisture origin.

Indeed, technological progress now allows continuous, in situ or remote sensing monitoring of water isotopic composition. In parallel, a growing number of atmospheric circulation models are equipped with the explicit modeling of water stable isotopes, allowing evaluation at the process scale.

We present here data obtained through national or bi-national initiatives from stations onboard an icebreaker and land based stations in Greenland, Iceland, Svalbard, and Siberia – together forming an emerging international Arctic water vapor isotope network. Using water tagging and back trajectories we show water vapor of Arctic origin to have a high d-excess fingerprint. This show the potential of using water vapor isotopes as tracer for changes in the Arctic hydrological cycle. Using the network of monitoring stations we quantify using the isotopes advection of air masses and the key processes affecting the water vapor en-route between stations. We have successfully used the obtained atmospheric water vapor isotope observations to benchmark isotope-enabled general circulation models. This comparison allows us to address key processes of the atmospheric hydrological cycle for which their representation in the models should be improved.